tag:blogger.com,1999:blog-50722722408135560472024-03-13T09:59:11.653-07:00Invertebrate EmbryologySvetlana Maslakovahttp://www.blogger.com/profile/14967342545576469632noreply@blogger.comBlogger129125tag:blogger.com,1999:blog-5072272240813556047.post-21566036084268330572013-06-17T13:18:00.000-07:002013-06-17T14:09:51.409-07:00The life cycle of the Olympia oyster, Ostrea lurida<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCEALZJgqu5wuP0WeiWCNeo8eoCqGwjM57Krc_stDuoICANJqCimnLijSc9rr54Z0xUOk2JeR_Uw-SNmqQZqF53biJFi_C2ljHmuzgXtdzeGz3lGN59nuhakg2dGde_0ziFp-dwVfGDbo/s1600/O_lurida_adult.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="166" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCEALZJgqu5wuP0WeiWCNeo8eoCqGwjM57Krc_stDuoICANJqCimnLijSc9rr54Z0xUOk2JeR_Uw-SNmqQZqF53biJFi_C2ljHmuzgXtdzeGz3lGN59nuhakg2dGde_0ziFp-dwVfGDbo/s200/O_lurida_adult.jpg" width="200" /></a></div>
Coos Bay is home to two different species of oysters: <i>Crassostrea gigas</i>, a large species (typically up to 20 cm in shell height) which is native to Japan but reared commercially all over the world, and <i>Ostrea lurida</i>, a much smaller species (up to 6 cm in shell height), which is the only oyster native to the west coast of the United States (pictured here). Both oysters are sequential hermaphrodites, although they differ in the regularity and seasonality of their sex changes.<i> C. gigas</i> is a broadcast spawner whose eggs are fertilized externally, while functionally-female <i>O. lurida</i> adults filter sperm from the water column and fertilize their eggs internally. While<i> C. gigas</i> larvae develop entirely in the plankton, <i>O. lurida</i> larvae are brooded in the adult’s mantle cavity until they reach an early veliger stage (which takes roughly ten days) and are then released into the plankton (Strathmann et al. 1987, and references therein).<br />
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Larvae at this stage are known as D-stage veligers because their flat-hinged shells look like a capital letter D. In this picture the larva has extended its velum, the ciliated structure used for swimming and feeding. A green algal cell is visible in the larval gut. <i>O. lurida</i> veligers swim and feed in the plankton for a period ranging from one week to one month, depending largely on temperature. As the larva grows, it loses its resemblance to a capital D because the umbo becomes more prominent and triangular. The larva eventually develops an eyespot and is considered competent to settle and metamorphose when its shell measures about 0.3 mm.<br />
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<i>O. lurida</i> were harvested for a burgeoning West Coast market beginning in the late 19th century, but commercial stocks were depleted by the early 20th century. Habitat degradation and, in some cases, predation by introduced species and disease further contributed to the decline of this estuarine species (Polson et al. 2009). Many estuarine scientists are interested in restoring the species along the West Coast, as oyster beds provide habitat for a variety of other species and help stabilize the estuarine shoreline (e.g. Jackson et al. 2001, Ruesink et al. 2005).<br />
<br />
Jackson, J. B. C., Kirby, M. X., Berger, W. H., Bjorndal, K. A., Botsford, L. W., Bourque, B. J., Bradbury, R. H., Cooke, R., Erlandson, J., Estes, J.A., Hughes, T. P., Kidwell, S., Lange, C. B., Lenihan, H. S., Pandolfi, J. M., Peterson, C. H., Steneck, R. S., Tegner, M. J., and Warner, R. R. 2001. Historical overfishing and the recent collapse of coastal ecosystems. <i>Science</i> 293:629-638.<br />
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Polson, M. and Zacherl, D. 2009. Geographic distribution and intertidal population status for the Olympia oyster. <i>Journal of Shellfish Res</i> 28: 51-58. <br />
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Ruesink, J. L., Lenihan, H.S., Trimble, A.C., Heiman, K.W., Micheli, F., Byers, J.E., and Kay, M.C. 2005. Introduction of non-native oysters: Ecosystem effects and restoration implications. <i>Ann Rev Ecol Evol Syst</i> 36:643-689.<br />
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Strathmann, M.F., Kabat, A.R. and O’Foighil, D. 1987. Phylum Mollusca, Class Bivalvia. In Reproduction and Development of Marine Invertebrates of the Northern Pacific Coast: Data and Methods for the Study of Eggs, Embryos, and Larvae. Strathmann, M. F. University of Washington Press. Seattle and London. Rose Rimlerhttp://www.blogger.com/profile/00261528155118970273noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-88629177347288631062013-06-14T15:03:00.000-07:002013-06-14T15:29:32.336-07:00Gravity tells no liesHaven't
you ever wondered how larval invertebrates in the ocean orient
themselves? The answer often lies in a small balance organ called the
statocyst. A statocyst is a fluid-filled spherical capsule containing
a small stone, or statolith, and sensory cells that detect the
position of the statolith. Statocysts tell the organism which way is
up, and, in some cases, how fast it is moving.
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvLQBqEb5hIA0ZNkNVLflYVWC_rhlYYxQzHMW5Y80HTSJOsCuL1yew4NniWORjtHMocn4VC0QRW8QV6FUNoJ8tS_qSNO7ZPq0CJ01aLk0LLsyou9fAUVdL2879ZggHMSRTqmwYlwLZ4GI/s1600/20130523_095242.15_L.tiff" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><br /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQYJ-x6Q2YQFj36qoiuT89hKT25z8gtPC0-0Wz7m15qUSUJA8kjeYEBqlo8Hjv8bgix3QUf2vHsC3q-QV2FzqREhgFOA5JyIzfriaOkMUakQCoFku1ZYpERWnAMYc4M3cw-EuXnNacHNM/s1600/20130529_122943.71_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQYJ-x6Q2YQFj36qoiuT89hKT25z8gtPC0-0Wz7m15qUSUJA8kjeYEBqlo8Hjv8bgix3QUf2vHsC3q-QV2FzqREhgFOA5JyIzfriaOkMUakQCoFku1ZYpERWnAMYc4M3cw-EuXnNacHNM/s200/20130529_122943.71_L.tiff" width="132" /></a>
This is a recently hatched juvenile of the ctenophore
(comb jelly) <i>Beroe </i>sp. At
the aboral pole (up, opposite the mouth) there is a dome made of cilia
- the equivalent of the statocyst capsule. Inside this dome you will
note an aggregate of small marbles - that is the statolith. This
aboral sense organ detects gravity and controls the movement of comb
rows (ctenes) and the ctenophore’s orientation. The statolith rests on
four tufts of support cilia, connected via ciliary grooves to the ctene
rows. Tilting changes the gravitational pressure of the statolith on
the support cilia, which ultimately controls the beating rate of of
the ctenes. Differentially beating ctenes on one side allows the
animal to turn and return to vertical position (Hyman 1940).
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This is a veliger larva of the nudibranch <i>Diaulula sandiegensis</i> (which
hatched in the lab after we collected the egg mass off a dock in the
Charleston marina about a month ago). At the anterior end (up) you
will note a ciliated appendage - the velum, with which the larva
swims. Below it there are two statocysts. Each contains a single
statolith. Statocysts form during intracapsular development, in the
late trochophore and early veliger stages in gastropod mollusks
(Hyman 1967). </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKPJAA8npAkrdgT7U7U8TwasyhMRzhHt7UWEPBp8yR6E93bAVnC-j78-_93xGcpXJFQI2Bd58IaU_RL5e0hFdSfgKdEZBLkYtyGtKCD_k6tJ3-YIROeZrMlZpHYOOHnXCPF8p_Z8fLqqw/s1600/Distaplia+accidentalis.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="113" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKPJAA8npAkrdgT7U7U8TwasyhMRzhHt7UWEPBp8yR6E93bAVnC-j78-_93xGcpXJFQI2Bd58IaU_RL5e0hFdSfgKdEZBLkYtyGtKCD_k6tJ3-YIROeZrMlZpHYOOHnXCPF8p_Z8fLqqw/s200/Distaplia+accidentalis.jpg" width="200" /></a>
Here is another kind of balance organ in an ascidian
tadpole larva. This tadpole was released by the colonial ascidian
<i>Distaplia
occidentalis</i>. In ascidian tadpoles the balance organ is called a statocyte, and
occupies the bottom of a sensory vesicle, which also contains a light
sensing organ - the ocellus or eye (Cloney et al. 2001). The
statocyte contains a single melanin granule, the statolith. Both the
statolith and the ocellus are visible on this picture. The ocellus is
the black crescent shape, while the statolith is the black round
shape underneath. These two organs are involved in the perception of environmental cues that drive ascidian tadpole behavior (Zega et al. 2006).
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<div style="font-family: Georgia,"Times New Roman",serif;">
Cloney RA, Young
CM, Svane I. (2001) Phylum Chordata: Urochordata. In:Atlas of Marine
Invertebrate Larvae. Academic Press. New York. P. 567.<br />
<br /></div>
Hyman,
L.H. (1940) Protozoa through Ctenophora. The Invertebrates. Vol 1.
McGraw-Hill, New York. P. 665-8.
<br />
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<div style="font-family: Georgia,"Times New Roman",serif;">
Hyman,
L. H. (1967) Mollusca. The Invertebrates. Vol VI. McGraw-Hill, New
York. P. 471, 548, 583.<br />
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<div style="font-family: Georgia,"Times New Roman",serif;">
Zega G, Thorndyke MC, Brown ER (2006) Development of swimming behaviour in the larva of the ascidian <i>Ciona intestinalis</i>. <i> J Exp Biol</i> 209: 3405-12. </div>
Jonathan Giengerhttp://www.blogger.com/profile/16836233600359675194noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-29220904215332791002013-06-12T13:14:00.000-07:002013-06-12T13:14:31.970-07:00Brooding in cheilostome bryozoans<div style="font-family: Georgia,"Times New Roman",serif;">
Bryozoa is a phylum of miniature, sessile, colonial invertebrates characterized by a crown of tentacles called the lophophore that facilitates ciliated filter feeding. You can see several individual zooids with extended lophophores in the picture below. Most bryozoans brood their embryos, but where and how they brood varies. </div>
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<i>Bugula pacifica</i>, a cheilostome commonly known as the spiral bryozoan, broods one embryo at a time inside shallow ovicells; specialized calcified brood chambers visible here as semi-circular structures attached to maternal zooids. The ovicell is produced jointly by the two neighboring zooids - the maternal zooid and the next distal zooid (Giese et al. 1947).</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgx59c4I5eyCGQWylWtLvs4c7O8_qmIksgVTdVGTBnLNeZAm1ejyq9oV-S_EaBWzzGnXx24tLX5CZ7vWP8PuFx7xVN2eKS6DWz5mcLrIcTdoirQiGrwRZXQWVZW9755XUtXRJ6H_hjn8C4g/s1600/Blog+2.2.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgx59c4I5eyCGQWylWtLvs4c7O8_qmIksgVTdVGTBnLNeZAm1ejyq9oV-S_EaBWzzGnXx24tLX5CZ7vWP8PuFx7xVN2eKS6DWz5mcLrIcTdoirQiGrwRZXQWVZW9755XUtXRJ6H_hjn8C4g/s200/Blog+2.2.tiff" width="150" /></a>This is a close up view of a maternal zooid and an ovicell in <i>Bugula pacifica</i>. What looks like the head of a bird above the ovicell is a specialized zooid for defense called an avicularium. Ovicell and avicularium morphology vary within the genus, and can be used to key out species. <i>B. pacifica</i> has reduced ovicells, so reduced that a well developed embryo cannot be contained and bulges into the maternal zooid (Giese et al. 1947). Developing embryos in <i>Bugula</i> apparently receive extraembryonic nutrition from the maternal zooid (Giese et al. 1947). Ovicells of cheilostome bryozoans vary in morphology and development which suggests that they may have evolved independently many times in this group (Giese et al. 1947).</div>
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<i>Schizoporella japonica</i> pictured here, is another cheilostome bryozoan. It is often found encrusting mussel shells and other substrata in NE Pacific marinas. The ovicells are visible as small bumps on the surface of the colony, some with embryos (an orange mass inside) and some empty. <i>S. japonica</i>’s ovicells aren’t as intimate with the maternal zooids as in <i>Bugula</i>, and the embryos develop without the aid of extra-embryonic nutrition (Strathmann et al. 1987). See a <a href="http://invert-embryo.blogspot.com/2012/04/coronate-larva-of-crisia-sp.html">blog post</a> by Dylan Cottrell about brooding of multiple genetically identical embryos (polyembryony) inside gonozooids in <i>Crisia</i> sp., a local stenolaemate.</div>
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<div style="font-family: Georgia,"Times New Roman",serif;">
Arthur Charles Giese, John S. Pearse, Vicki Pearse 1974. Phylum Bryozoa. In: Reproduction of Marine Invertebrates. Academic Press, University of California. Pp. 494-510</div>
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<div style="font-family: Georgia,"Times New Roman",serif;">
Megumi F. Strathmann 1987. Chapter 3: Bryzoa. In: Reproduction and Development of Marine Invertebrates of the Northern Pacific Coast. University of Washington Press. Pp. 116-158</div>
Anders B. Hansenhttp://www.blogger.com/profile/03958497655520340582noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-37940345586269453372013-06-09T06:29:00.000-07:002013-06-10T12:24:21.888-07:00Hemigrapsus nudus: brooding mothers and their zoea<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhE7LYlSBWyI7JSb1KtavV3PVUMzTzPa-K3mOYUvZkx998qUN3eSrEzsNEzen4uDdyOg07HLyIYMSCDbLjEwefQTQb-f83LYN8Q1HzK7IsLRHXjF3YbThUekp6aLYWwvLXyHogrXNvDLA/s1600/hemigrapsus.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><span style="font-family: Georgia, Times New Roman, serif;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhE7LYlSBWyI7JSb1KtavV3PVUMzTzPa-K3mOYUvZkx998qUN3eSrEzsNEzen4uDdyOg07HLyIYMSCDbLjEwefQTQb-f83LYN8Q1HzK7IsLRHXjF3YbThUekp6aLYWwvLXyHogrXNvDLA/s1600/hemigrapsus.jpg" height="162" width="200" /></span></a></div>
<span style="font-family: Georgia, Times New Roman, serif;">Adult <i>Hemigrapsus nudus </i>can be found under rocks and in crevices of the mid-intertidal on the open coast and in estuaries, here found on the Portside rocks in the South Slough. This purple shore crab is distinctive for the spots on its chelae, or claws.</span> <br />
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<span style="font-family: Georgia, 'Times New Roman', serif;">The female on the left measures 17 mm (11/16 in.) across. She is "in berry", in other words, carrying an egg mass. Crabs brood their eggs under the abdominal flap. As eggs emerge from the gonopore, they are inseminated by stored sperm from a prior encounter with a male. The eggs are attached to the setae (bristles) covering her pleopods, the abdominal appendages used for swimming during the final stage of the crab's pelagic larval life. Her broad abdominal flap forms a protective enclosure for the eggs. The female cares for the eggs, cleaning and aerating them, for up to four and one half months before they hatch as zoea larvae.</span><br />
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<span style="font-family: Georgia, Times New Roman, serif;">This <i>H. nudus</i> zoea hatched six days ago to swim and feed in the plankton and go through several larval molts before metamorphosing into a benthic juvenile. Two compound eyes look out with a multi-faceted view of its surroundings, the mosaic of images from many ommatidia, or eye-lets. A distinctive dorsal spine projects from the top of its carapace, and a rostral spine is located anterior to the eyes. These spines may discourage predation. Note a thin-walled sac at the base of the dorsal spine, the zoea's beating heart. The segmented abdomen ends in forked telson.</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqu1vIrD05F-CvpTihD3YLpgYSrFxFA016mmyiq4JXsbXKPAeM5sGGTvoypL4t5iUhIkGmgR7kHjJjOrky4zUcR4yAcEVSvc_J_Wpjb8cpPFZ2-1ehS5bmmDD7m-RfilkqgNxPcjBliA/s1600/nine+day+old.+full+size.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><span style="font-family: Georgia, Times New Roman, serif;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqu1vIrD05F-CvpTihD3YLpgYSrFxFA016mmyiq4JXsbXKPAeM5sGGTvoypL4t5iUhIkGmgR7kHjJjOrky4zUcR4yAcEVSvc_J_Wpjb8cpPFZ2-1ehS5bmmDD7m-RfilkqgNxPcjBliA/s1600/nine+day+old.+full+size.jpg" height="193" width="200" /></span></a></div>
<span style="font-family: Georgia, Times New Roman, serif;">At nine days old, this crab zoea is close to undergoing a molt. The process of molting, called ecdysis, is characteristic of a large clade of animals (including arthropods and nematodes) known as the Ecdysozoa. A hard exoskeleton covering the body of these animals must be shed to accommodate growth. During successive molts of zoea, the abdomen adds new segments, and pleopods bud from them. Setae develop on the telson and the maxillipeds, the thoracic appendages present in newly hatched zoea. <i>Hemigrapsus</i> passes through five zoeal stages before becoming a megalopa. This stage resembles the adult form with stalked eyes and five pairs of pereopods (walking legs). The next ecdysis will take the megalopa to the juvenile stage and a benthic existence for the rest of its life.</span>Lorne Curranhttp://www.blogger.com/profile/03102500361525960558noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-73686096769054270372013-06-08T08:03:00.000-07:002013-06-08T08:03:14.759-07:00Planula of Proboscidactyla flavicirrata<div class="separator" style="clear: both; text-align: center;">
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<span style="font-size: small;"><span style="font-family: Georgia,"Times New Roman",serif;">The life cycle of the hydrozoan medusa, <i>Proboscidactyla flavicirrata,</i> is one that is typical of the hydrozoans, with full alternation of generations - i.e. with a fully developed medusa and polyp (see Ashley Choi's blog post, <a href="http://invert-embryo.blogspot.com/2011/05/obelia-medusa.html" target="_blank">Life cycle of hydrozoan <i>Obelia</i> sp.</a>). Freshly collected medusae readily release eggs or sperm (sexes are separate) in early morning the day after being collected. Fertilized eggs develop into planula larvae, depicted below.</span></span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-T4AUD4vhyphenhypheneW_OJ2wKYY8L9bhcgkqi9xwsrvWq0jquqZ3Xh_-U4tWd4O_xmX9iIVvuCMDPzSX4CdeSoi8Wm4_YR2M-hzKCyqn7dl5Vy5HJYWe56h7q67gJBkC1qCWFrKmrUkKu8XtJXc/s1600/Proboscidactyla3crop.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-T4AUD4vhyphenhypheneW_OJ2wKYY8L9bhcgkqi9xwsrvWq0jquqZ3Xh_-U4tWd4O_xmX9iIVvuCMDPzSX4CdeSoi8Wm4_YR2M-hzKCyqn7dl5Vy5HJYWe56h7q67gJBkC1qCWFrKmrUkKu8XtJXc/s200/Proboscidactyla3crop.tiff" width="156" /></a></div>
<span style="font-size: small;"><span style="font-family: Georgia,"Times New Roman",serif;">This is a picture of the 5-day old planula larva of <i>P. flavicirrata</i>. As in other hydrozoans and scyphozoans, the planulae of <i>P. flavicirrata</i> are lecithotrophic - they are non-feeding, rather they depend on yolk reserves to reach metamorphosis. Planulae are ovoid in shape and uniformly ciliated. Many hydrozoan planulae develop muscles only after metamorphosis (S. Maslakova, pers. com.), but in my culture, planulae of <i>P. flavicirrata</i> were clearly contractile!</span></span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFIM-tUdpn_8hkvDHLNvpQ1b8FqcsljT2Bee8kxSGJV5pOK_J4dYS9mnIDGgn6MNgWsYeV_H9a0BIVqss0L5gqA8TxGuefwxN3QM9KKtFF5v2YGvxF4D9TYUDr8Bt3fIUMxmhyc9-dxWI/s1600/ProbosLong2.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="155" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFIM-tUdpn_8hkvDHLNvpQ1b8FqcsljT2Bee8kxSGJV5pOK_J4dYS9mnIDGgn6MNgWsYeV_H9a0BIVqss0L5gqA8TxGuefwxN3QM9KKtFF5v2YGvxF4D9TYUDr8Bt3fIUMxmhyc9-dxWI/s200/ProbosLong2.tiff" width="200" /></a></div>
<span style="font-size: small;"><span style="font-family: Georgia,"Times New Roman",serif;">Believe it or not, this is the same individual as shown above. It has used its muscles to elongate. Hydrozoan planulae have two types of epithelial muscle cells that are separated by mesoglea (Gröger 2001).</span></span><br />
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<span style="font-size: small;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4DGonwnBHUeohEnQJWo-fxJnKUMSye2NenU1VQ6LbaQ2M3sAeA7OXEJr_t5kIjpt9raUgNCPp4PlkjvUnSwjhbrZdtDkb9rTUlY1JT6RYqco6E75GH5i9-R8hz59ZJMOttbw-7-sJBgw/s1600/ProbosClose.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="149" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4DGonwnBHUeohEnQJWo-fxJnKUMSye2NenU1VQ6LbaQ2M3sAeA7OXEJr_t5kIjpt9raUgNCPp4PlkjvUnSwjhbrZdtDkb9rTUlY1JT6RYqco6E75GH5i9-R8hz59ZJMOttbw-7-sJBgw/s200/ProbosClose.tiff" width="200" /></a></span></div>
<span style="font-size: small;">A close up view of the same individual shows the two cell layers: the outer ectodermis and the inner endodermis, separated by a thin extracellular layer of mesoglea. Myoepithelial cells in ectodermis and endodermis have muscle fibers (not detectable without special staining) that run along the mesoglea.</span><br />
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<span style="font-size: small;"><span style="font-family: Georgia,"Times New Roman",serif;">Gröger, H and V. Schmidt. 2001. Larval Development in Cnidaria: A Connection to Bilateria? gensis 29 (3):110-114.</span></span><br />
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<span style="font-size: small;"><span style="font-family: Georgia,"Times New Roman",serif;">Mills, C.E. and J.T. Rees. 2007. Key to the Hydromedusae. In "The Light and Smith Manual Intertidal Invertebrates from Central California to Oregon". Edited by J.T. Carlton. University of California press. Los Angeles. Pp. 137-150.</span></span><br />
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<span style="font-size: small;"><span style="font-family: Georgia,"Times New Roman",serif;">Wrobel, David and Claudia Mills. 1998. Pacific Coast Pelagic Invertebrates A Guide to the Common Gelatinous Animals. Monterey Bay Aquarium and Sea Challengers: California.</span></span><br />
<span style="font-family: Georgia,"Times New Roman",serif;"></span><br />Anonymoushttp://www.blogger.com/profile/01391891386105855973noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-2971428263441019452013-06-06T19:20:00.000-07:002013-06-07T12:02:57.379-07:00Ascidian tadpole larvae: settlement and metamorphosisAscidians (class Ascidiacea), commonly known as sea-squirts, are a class of sessile, filter-feeding chordates who live solitarily or colonially inside an extracellular “tunic.” Although the adults have no overt chordate features, their free-swimming tadpole-like larvae have a tail supported by a notochord, homologous to the spinal cord in vertebrates, and a hollow nerve cord like that of other chordates (Sasakura et al. 2012). The following pictures detail the process of larval settlement and metamorphosis in a colonial ascidian <i>Distaplia occidentalis</i>, a fouling organism on floating docks in NE Pacific marinas.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEit9UWAvk5Z1BE-HLfYranCgcrHB59ZmB4QTfXmU06Ivv8z33wXpA1I3OLX_dWLtct4bJk8uWfIvjt3bUa1ECXzKifTZt-r1KmRLHhjLYi3Zotw1rrlq6sZEHL9p-gxhOR8HE9K5pUHTTaG/s1600/good+tadpole2+.5X_4X.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEit9UWAvk5Z1BE-HLfYranCgcrHB59ZmB4QTfXmU06Ivv8z33wXpA1I3OLX_dWLtct4bJk8uWfIvjt3bUa1ECXzKifTZt-r1KmRLHhjLYi3Zotw1rrlq6sZEHL9p-gxhOR8HE9K5pUHTTaG/s200/good+tadpole2+.5X_4X.jpg" width="200" /></a></div>
This is a lateral view of a recently released tadpole larva. Almost all colonial ascidians brood their larvae, and release them for a brief planktonic period (minutes to hours). The dark spot near the base of the notochord is the sensory vesicle, which contains both a light-sensing ocellus, and gravity-sensing organ called a statocyst (both pigmented). At the anterior end of the tadpole’s trunk (to the right) one can see two bulbous structures just under the tadpole’s epidermis. They are called adhesive papillae. They are everted at settlement to initially adhere the tadpole to the substratum.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgADqrWY7zCEc2kWrZDqa3oCTEE-SdqJ7tXOR5G8OflHXYAf-WEJgKkBzuPFbMEJuJPem68tHEC1Wh0YMsbBXs5YEwZwwf_8H376e9LNiVn8CgJavteLbkgoOz0s7zJANqe8EQjFXy4HIuS/s1600/early+metamorphosis+tadpole+%2528papillae+close-up%2529+.5X%253A20X.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgADqrWY7zCEc2kWrZDqa3oCTEE-SdqJ7tXOR5G8OflHXYAf-WEJgKkBzuPFbMEJuJPem68tHEC1Wh0YMsbBXs5YEwZwwf_8H376e9LNiVn8CgJavteLbkgoOz0s7zJANqe8EQjFXy4HIuS/s200/early+metamorphosis+tadpole+%2528papillae+close-up%2529+.5X%253A20X.jpg" width="200" /></a></div>
Upon contact with whatever substratum the larva deems suitable for settlement, the tadpole rapidly (< 1 min) everts its papillae, the tips of which secrete an adhesive substance. This picture shows eversion of the adhesive papillae. A <i>Distaplia</i> tadpole has three adhesive papillae, and two are in focus here. The adhesive filamentous material seen radiating from the base of the papillae is secreted by the epidermal cells of the everted papillae (Cloney 1978, and previous studies by the same author cited therein). A study by Flores and Faulkes (2008) suggests that ascidian tadpoles may be able to differentiate between different types of surfaces on which to settle (e.g. smooth vs. sandblasted), possibly due to the presence of mechanoreceptors in those epidermal cells.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqHae4QnVDWSi7Zlr_fk2fde3wHNibAn8Hemg0cJF4z38ApDLA2j-7HaUw0wYSQDnJg9b0Ld49xxg319QeuIDdUXcofCEdwoCaBxmJ6BbUCUZFYOzUYsAN1mYs4j7CMQr5i3V230adCHCP/s1600/settled+larva+second+chamber+.5X_10X.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqHae4QnVDWSi7Zlr_fk2fde3wHNibAn8Hemg0cJF4z38ApDLA2j-7HaUw0wYSQDnJg9b0Ld49xxg319QeuIDdUXcofCEdwoCaBxmJ6BbUCUZFYOzUYsAN1mYs4j7CMQr5i3V230adCHCP/s200/settled+larva+second+chamber+.5X_10X.jpg" width="200" /></a></div>
After eversion of the papillae, the ampullae, large adhesive lobes which create a more permanent hold to the substratum, are everted. The ascidian begins to reabsorb its axial complex (the notochord, nerve cord, and associated musculature of the tail) and develops the respiratory and feeding structures that characterize the adult. This picture shows a recently metamorphosed juvenile, its ampullae (short root-like structures) attached to the substratum (the side of glass slide). The tail is reabsorbed within a few hours after settlement. The large dark shape inside is the remnant of the larval axial complex plus the developing branchial basket of the juvenile. The little dark spot at upper right of the dark shape is the degenerating sensory vesicle. Immediately above the sensory vesicle one can see one of the two developing siphons, through which the adult ascidian pumps water to breathe and feed.<br />
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Cloney, R. A. (1978). Ascidian metamorphosis: review and analysis. In: Settlement and metamorphosis of marine invertebrate larvae. Chia, F.-S. and Rice, M.E. (eds). Elsevier. New York. pp. 255-282. <br />
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Flores, A. R. and Faulkes, Z. (2008). Texture preferences of ascidian tadpole larvae during settlement. Marine and Freshwater Behaviour and Physiology. 41(3): 155-159. <br />
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Sasakura, Y., Mita, K., Ogura, Y., and Horie, T. (2012). Ascidians as excellent chordate models for studying the development of the nervous system during embryogenesis and metamorphosis. Development, Growth, and Differentiation. 54(3): 420-437.Anonymoushttp://www.blogger.com/profile/02634149187264793802noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-78407508996294140552013-06-06T15:07:00.001-07:002013-06-07T11:58:11.670-07:00Development of the hydrozoan Clytia gregaria<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2nA3fAJCOk0S2eBGaEY5L8KQYbIfC9Io248pzYzOI3nOcrh5AWQYW1DuyYcEW_pVQZ5rbYreB7DH8XT8eqqWQoplUW8Vab48buj9_mgvSsVNatAlTfGUM-K51TNFvgWLPb-YtD7ErSts/s1600/Clytia+ADULT.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="133" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2nA3fAJCOk0S2eBGaEY5L8KQYbIfC9Io248pzYzOI3nOcrh5AWQYW1DuyYcEW_pVQZ5rbYreB7DH8XT8eqqWQoplUW8Vab48buj9_mgvSsVNatAlTfGUM-K51TNFvgWLPb-YtD7ErSts/s200/Clytia+ADULT.jpg" width="200" /></a></div>
<o:p><span style="font-family: Calibri;"><span style="font-family: Georgia, "Times New Roman", serif;">This is <i>Clytia gregaria</i>, formerly known as <i>Phialidium
gregarium</i>. The instructor of our Embryology class collected many adult
individuals of this hydromedusa from the plankton off F-dock in the Charleston
Marina Complex. I like cnidarians and I wanted to follow the development in
this species.<o:p></o:p></span></span></o:p><br />
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<span style="font-family: Calibri;"><span style="font-family: Georgia, "Times New Roman", serif;">Adult <i>C. gregaria</i> is about 2 cm in diameter, and can be
identified by its ruffled manubrium located in the center of the subumbrella
(the underside of the bell). The four gonads are located along the radial
canals of the digestive system (the thick white lines radially arranged on the underside of the bell). <i>C.
gregaria</i> hydromedusae are present in the plankton from late spring to early fall.<span style="mso-spacerun: yes;"> </span>Recently collected hydromedusae of
this species readily release eggs and sperm (typically, at the crack of dawn
the day after collection), fertilization and embryonic development is
external.<o:p></o:p></span></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEio3U9dFTEuPTSZs0yMyc-QWt-MpW6w6oV7SES130CCK__ocIUOqGQEOWwdPL6cwQgWwzoZ7wKvDz5voQszuGE9V02-K1HLoY1_jBGsId4kRKE5Gb-itY9ZOtLJvZP3gU_sW6m8795HCYc/s1600/4cell_clytia_bal.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEio3U9dFTEuPTSZs0yMyc-QWt-MpW6w6oV7SES130CCK__ocIUOqGQEOWwdPL6cwQgWwzoZ7wKvDz5voQszuGE9V02-K1HLoY1_jBGsId4kRKE5Gb-itY9ZOtLJvZP3gU_sW6m8795HCYc/s200/4cell_clytia_bal.jpg" width="200" /></a></div>
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<span style="font-family: Georgia, "Times New Roman", serif;">This is a 4-cell stage. As you can see the
cells are all the same size, so the cleavage is equal.<span style="mso-spacerun: yes;"> </span><i>Clytia</i>, like many hydromedusae, have
transparent eggs which makes them convenient embryological study objects. The
four little spheres (one inside each cell) in this picture are the cell nuclei,
visible thanks to the clear cytoplasm of these eggs.<o:p></o:p></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2PZrx4OpqtKYXW2izmNqElagaN9HjbdkMY_F6i7gt5ZcXSNLzA3imtbd0YHP9sJSLk5KMeTnfKFzIeCyuVd1vTOinMK32VjWN7f6LgXz2BZJN1Ik95G27yH6GXnx5l6EiniCNqQdVnzA/s1600/16cell_clytia.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="184" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2PZrx4OpqtKYXW2izmNqElagaN9HjbdkMY_F6i7gt5ZcXSNLzA3imtbd0YHP9sJSLk5KMeTnfKFzIeCyuVd1vTOinMK32VjWN7f6LgXz2BZJN1Ik95G27yH6GXnx5l6EiniCNqQdVnzA/s200/16cell_clytia.jpg" width="200" /></a></div>
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</span><span style="font-family: Georgia, "Times New Roman", serif;">Cnidarians (and ctenophores) exhibit an
unusual type of cell division illustrated here. It is called unilateral
cleavage, and means that cleavage furrow forms at one pole of the cell and
progresses to the other pole, so the cells appear heart-shaped in mid-cleavage,
as you can clearly see on this picture of a ~16-celled embryo. The site of
initiation of first embryonic cleavage defines the oral end of the developing
embryo.<o:p></o:p></span></div>
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<span style="font-family: Georgia, "Times New Roman", serif;">The embryo develops into a planktonic planula
larva shown here. The planula larva is characteristic of most cnidarians. The
hydrozoan planula is uniformly ciliated, oval-shaped, usually somewhat opaque,
and lacking any appendages or defined gut (they do not feed). Hydrozoan
planulae usually spend a short period in the plankton (days), then settle and
undergo metamorphosis into a benthic polyp stage, the asexual generation in the
<a href="http://invert-embryo.blogspot.com/2011/05/obelia-medusa.html">life cycle</a> of a hydrozoan.</span> <o:p></o:p></div>
</span>Susan Brushhttp://www.blogger.com/profile/12309371503051112009noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-39527581345746251432013-06-06T13:12:00.000-07:002013-06-07T11:11:12.793-07:00Gastrulation and early actinotroch of Phoronopsis harmeri<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTI9aSoyxI72oYdzGwJ-Br7Nf77OfJGJ-DBZKNlsDY7y4kb6XLd2hnqvi_f-HphTnA0KjtUgnHZC-YuH7ptvquCkrwRsrtCnbuqO-453lQjW0zdtW7ASRRajqwmyfO6hxu7J93TipWmg1C/s1600/Image+1.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTI9aSoyxI72oYdzGwJ-Br7Nf77OfJGJ-DBZKNlsDY7y4kb6XLd2hnqvi_f-HphTnA0KjtUgnHZC-YuH7ptvquCkrwRsrtCnbuqO-453lQjW0zdtW7ASRRajqwmyfO6hxu7J93TipWmg1C/s200/Image+1.jpg" width="150" /></a></div>
<span style="font-family: Georgia, Times New Roman, serif;">This is a side view of a blastula of the phoronid, a.k.a. horseshoe worm, <i>Phoronopsis harmeri</i>. It is about 22 hours after egg release (developing at ambient sea temperature). Eggs in this species are fertilized inside the body cavity, but initiate their development after spawning (or being dissected, as is the case here). Note the spacious cavity called blastocoel inside the blastula. The surface of the blastula is ciliated, each cell bearing a single cilium. Longer cilia at the animal pole (up) indicate position of the future apical sensory organ. </span><br />
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<span style="font-family: Georgia, Times New Roman, serif;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEdF66F3cAdiBlQl8hymhtRhu_rNT9_AdX9Zyb0BeK6TXGSIKedsraBQ-fZUejcqdnZAvZw-9GexGlzSvmsPYDV0w4tAqDHaxVounHLZub7DFCkBsuz4miP5SPQsL4FQrTNILNbkIAGeof/s1600/Image+2.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEdF66F3cAdiBlQl8hymhtRhu_rNT9_AdX9Zyb0BeK6TXGSIKedsraBQ-fZUejcqdnZAvZw-9GexGlzSvmsPYDV0w4tAqDHaxVounHLZub7DFCkBsuz4miP5SPQsL4FQrTNILNbkIAGeof/s200/Image+2.jpg" width="200" /></a></span></div>
<span style="font-family: Georgia, Times New Roman, serif;">This is a gastrula stage. It is 24 hours old. The circle of cells inside the blastocoel is the developing gut of the embryo, otherwise known as the archenteron. The archenteron opens to the outside via the blastopore which will later develop into the mouth. Cells clustered at one end of the archenteron are the mesoderm cells which will form the muscles and coelomic sacs in the larva. </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiN_sDtw0yBmPLzUYxWUYbUBaZhyphenhyphenGAJuNEwVxu1ZN5Re0tc80s8ei3kpZSxCBNq0HxHM9wPXSEtrB5c8MlzfOfMa9UAXBP2d0JD03FEfIBo1Up5hvxHfu9X1T5gjtyCdCC4do4yKv0KiyjU/s1600/Image+3.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiN_sDtw0yBmPLzUYxWUYbUBaZhyphenhyphenGAJuNEwVxu1ZN5Re0tc80s8ei3kpZSxCBNq0HxHM9wPXSEtrB5c8MlzfOfMa9UAXBP2d0JD03FEfIBo1Up5hvxHfu9X1T5gjtyCdCC4do4yKv0KiyjU/s200/Image+3.jpg" width="200" /></a></div>
<span style="font-family: Georgia, Times New Roman, serif;">This is a young actinotroch larva that is ready to feed on microscopic algae. It has a complete gut with mouth and anus. The mouth opens under the anterior hood and leads into a spacious vestibule, which leads into the gut. Note a thickened region of epidermis directly overlaying the vestibule - this is the apical sense organ. Sandwiched between the apical sense organ and the vestibule is a thin-walled sac - this is the anterior coelomic cavity, the protocoel. The gut proper has two distinct compartments - the stomach, which occupies most of the actinotroch’s body, and the short hindgut that opens via an anus at the posterior end. The actinotroch will later develop a crown of tentacles posterior to the mouth which will assist in capturing food. </span><br />
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Anonymoushttp://www.blogger.com/profile/10904933891047373610noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-49706058982707643822013-06-06T13:02:00.000-07:002013-06-07T11:10:55.180-07:00Procuring gametes from echinoderms<span style="font-family: Georgia, Times New Roman, serif;">Echinoderms, sea urchins and sea stars in particular, are classical objects of embryological studies because it is relatively easy to obtain their gametes. Here I will describe two standard techniques used to obtain embryonic cultures of echinoids, exemplified by the sand dollar <i>Dendraster excentricus</i>, and asteroids, exemplified by the ochre sea star <i>Pisaster ochraceus</i>.</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6o7klyRdX9Rx3-q2eJyNjKtV-UO3ZNSkWn4uYlGZ99tPWfPwGGJOeMb2jZQWyGyL8GMU4RCR1CithTHT4Htj84nWrTZaY89DEsMvZZcQKh_oR09q7xbVpl-SMKk1mA5Hmc79CTnHYTRn1/s1600/Image+1.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><span style="font-family: Georgia, Times New Roman, serif;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6o7klyRdX9Rx3-q2eJyNjKtV-UO3ZNSkWn4uYlGZ99tPWfPwGGJOeMb2jZQWyGyL8GMU4RCR1CithTHT4Htj84nWrTZaY89DEsMvZZcQKh_oR09q7xbVpl-SMKk1mA5Hmc79CTnHYTRn1/s200/Image+1.jpg" width="200" /></span></a></div>
<span style="font-family: Georgia, Times New Roman, serif;">Here you can see how we collect sperm from a spawning male of the sand dollar. Injection of ~1 ml of 0.5M KCl into the body cavity of the sand dollar induces spawning by causing strong contractions of the gonad. </span>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiiCXiqxMpRo24vnr3C50dVcUxTDm67xMtda875acup2zvTKoJJmqnR3pBdrczy4BLVcVrpT-bFRbLe-x7HcMmXMDVQODu5x9bdWUUK9XL2NcYxsur01Vg1tBgGfM7xaljQVS_-l5JTCOeu/s1600/Image+2.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><span style="font-family: Georgia, Times New Roman, serif;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiiCXiqxMpRo24vnr3C50dVcUxTDm67xMtda875acup2zvTKoJJmqnR3pBdrczy4BLVcVrpT-bFRbLe-x7HcMmXMDVQODu5x9bdWUUK9XL2NcYxsur01Vg1tBgGfM7xaljQVS_-l5JTCOeu/s200/Image+2.jpg" width="200" /></span></a></div>
<span style="font-family: Georgia, Times New Roman, serif;">If the specimen has ripe gonads, after a few moments gametes (sperm or eggs) begin to emerge from the five small openings called gonopores on the aboral (opposite side from the mouth) surface. Sperm is cream colored, and eggs are pink. To collect eggs, we inverted a spawning female (oral end up) over a beaker full of filtered seawater. The eggs collect at the bottom of the beaker. </span><br />
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<span style="font-family: Georgia, Times New Roman, serif;">There are several ways to get fertilizable oocytes from sea stars. One way is to inject the body cavity with 1-methyl adenine (1-MA) solution (about 1 ml of 100 </span><span class="Apple-style-span" style="font-family: Symbol;"><span class="Apple-style-span" style="font-size: 15px; line-height: 17px;">μ</span></span><span style="font-family: Georgia, 'Times New Roman', serif;">M 1-MA in distilled water per 100 ml of body volume). 1-MA, also known as maturation-inducing substance, stimulates spawning, ovulation (release of oocytes from follicles), and oocyte maturation (completion of meiosis) in sea stars. The advantage of this method is that the adult remains intact. The disadvantage is that it will have completely spawned out, and won’t be useful for future embryological experiments for at least a few months. In order to use the same individual several times, one can take advantage of the sea star’s regenerative abilities. Instead of injecting 1-MA into the body of the intact individual, dissection of just a piece of ovary or testis is sufficient. For example, </span><i style="font-family: Georgia, 'Times New Roman', serif;">Patiria miniata</i><span style="font-family: Georgia, 'Times New Roman', serif;">, the bat star, tolerates biopsy very well, then promptly heals, so one can re-use the same individual many times. One can use a biopsy tool to cut a small window at the base of an arm, and pull a small piece of gonad out. However, some species, like </span><i style="font-family: Georgia, 'Times New Roman', serif;">Pisaster ochraceus</i><span style="font-family: Georgia, 'Times New Roman', serif;"> do not heal well after biopsy, and heal much better if an entire ray is severed to remove gonads (apparently, the cutting of the radial nerve stimulates regeneration).</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgc1RNVjTQGW6uoRcYVJS0GnAfZGHD-61iSEdXEay-GNn9DiMQOYG9fsrht2Hkx3RBYNKrnT_W1UIPqyrltKj1tfCC4BCTdm0vxpSAD5IwBHMI_B-XXEqcrE6-zDsC3DnWj6n8tka73Ds6O/s1600/Image+5.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><span style="font-family: Georgia, Times New Roman, serif;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgc1RNVjTQGW6uoRcYVJS0GnAfZGHD-61iSEdXEay-GNn9DiMQOYG9fsrht2Hkx3RBYNKrnT_W1UIPqyrltKj1tfCC4BCTdm0vxpSAD5IwBHMI_B-XXEqcrE6-zDsC3DnWj6n8tka73Ds6O/s200/Image+5.jpg" width="200" /></span></a></div>
<span style="font-family: Georgia, Times New Roman, serif;">As shown here, one can use a razor blade to cut the ray and reveal paired gonads within the body cavity. Ovaries in <i>P. ochraceus</i> are pink or orange-ish, while testes are creamy white. Some oocytes thus dissected complete meiosis spontaneously and can be fertilized, however, most need some help in the form of 1-MA. Incubation of dissected ovaries with 1 </span><span class="Apple-style-span" style="font-family: Symbol;"><span class="Apple-style-span" style="font-size: 15px; line-height: 17px;">μ</span></span><span style="font-family: Georgia, 'Times New Roman', serif;">M of 1-MA in filtered sea water for about an hour stimulates ovulation and oocyte maturation.</span>Anonymoushttp://www.blogger.com/profile/10904933891047373610noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-39945280251535181932013-06-06T07:49:00.001-07:002013-06-07T11:54:10.721-07:00Development of the ctenophore Beroe<div style="font-family: Georgia,"Times New Roman",serif;">
Below are pictures of early embryos of the ctenophore <i>Beroe </i>sp. Three adults were collected around Charleston docks near OIMB in mid-May and shed strings of ~ 220 µm eggs in the lab. </div>
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Ctenophore embryos are beautifully clear, and possess a unique type of development. Like cnidarians, ctenophores have unilateral cleavage, which means that the cleavage furrow cuts in from one pole of the egg and gradually proceeds to the other side (see a <a href="http://gvondassow.com/Research_Site/Video_-_Beroe_cleavage_and_gastrulation.html">video</a> of cleaveage in another species of <i>Beroe</i> by George von Dassow). Ctenophore cleavage is stereotypical (all embryos exhibit the same series of highly ordered divisions), and the same cells consistently give rise to certain structures in the adult. Ctenophores exemplify mosaic development, which means that cell fates are determined early in development by inheritance of different regions of the egg’s cytoplasm which possess different properties. As a result, with few exceptions, when specific blastomeres are damaged, they are not replaced; and the embryo lacks the structures these blastomeres normally give rise to (Martindale & Henry 1999). </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgb54bkwPSZZWspg6GAQ8AeLIdXtUvMROJKHFRV4-ao0LYTtmmY5X7nxdQAeayca_ZHHms7zj0eXa-HLj_OMISxOe_ezPmcQtMRmdUUw_HhIWU_kTnu2HcQht2hSdYTf7OvjYsy5dpR/s1600/20130522_110504.65_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="168" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgb54bkwPSZZWspg6GAQ8AeLIdXtUvMROJKHFRV4-ao0LYTtmmY5X7nxdQAeayca_ZHHms7zj0eXa-HLj_OMISxOe_ezPmcQtMRmdUUw_HhIWU_kTnu2HcQht2hSdYTf7OvjYsy5dpR/s1600/20130522_110504.65_L.tiff" width="200" /></a>
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This is a gastrula of the same species of <i>Beroe</i>. Ctenophores undergo gastrulation by a variety of mechanisms simultaneously, including epiboly, delamination, invagination, and involution. At the end of gastrulation large cells, called macromeres, end up surrounded by small cells called micromeres (see another <a href="http://gvondassow.com/Research_Site/Video_-_Pleurobrachia.html">video</a> by George von Dassow)<span style="font: 12px 'Times New Roman';">.</span> </div>
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These embryos developed into little juvenile <i>Beroe,</i> pictured here, with beautiful red pigment granules in the epidermis. Another curious fact about the development of <i>Beroe </i>is that apparently, at least one species, <i>Beroe ovata, </i>can tolerate naturally occurring polyspermy (Carré & Sardet 1984). Polyspermy is a condition in which more than one sperm enter the egg. In most animals polyspermic embryos develop abnormally. However, Carre & Sardet (1984) demonstrated that in <i>Beroe ovata</i> the female pronucleus appears to preferentially select a sperm pronucleus with which to bind. The female pronucleus visits each sperm pronucleus, returning to the site of formation of polar bodies in between visits, and finally fuses with one of them (see <a href="http://intrabiodev.obs-vlfr.fr/recherche/biomarcell/ctenophores/Video/choix%20noyaux.mpg">video</a> on Christian Sardet's website). The other male pronuclei are destroyed and do not participate in development which proceeds normally. </div>
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Carré, D., Sardet, C. (1984). Fertilization and Early Development in <i>Beroe ovata. </i>Developmental Biology 105: 188-195. </div>
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Martindale, M.Q., Henry, J.Q. (1999). Intracellular fate mapping in a basal metazoan, the ctenophore <i>Mnemiopsis leidyi</i>, reveals the origins of mesoderm and existence of indeterminate cell lineages. Developmental Biology 214: 243-257.</div>
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Anonymoushttp://www.blogger.com/profile/14580208261540896682noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-79890763972247216052013-06-04T11:07:00.000-07:002013-06-04T11:07:10.373-07:00Brachiolaria larva of the seastar Mediaster aequalis <div class="MsoNormal">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEim8eNkdy6hUgkxuwH8hKApaOPAktBoYhf8E_ExaaIS42NMKy9qE9KEp_TsSk6xx87QOCy_9Zti2Z7WKFWK8Q3R3ct8nkvNq4u0xDmKKSbhMpJ8irC3KiKPdBHTFUwm6tKrIKHgGgGS6nQ/s1600/Mediaster+Pic.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="198" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEim8eNkdy6hUgkxuwH8hKApaOPAktBoYhf8E_ExaaIS42NMKy9qE9KEp_TsSk6xx87QOCy_9Zti2Z7WKFWK8Q3R3ct8nkvNq4u0xDmKKSbhMpJ8irC3KiKPdBHTFUwm6tKrIKHgGgGS6nQ/s200/Mediaster+Pic.JPG" width="200" /></a><i style="font-family: Georgia,'Times New Roman',serif;">Mediaster aequalis</i><span style="font-family: Georgia,'Times New Roman',serif;"></span><span style="font-family: Georgia, 'Times New Roman', serif;"> is a bright red asteroid, three to seven inches in diameter, found subtidally off the coast of Oregon. </span><i style="font-family: Georgia,'Times New Roman',serif;">M. aequalis</i><span style="font-family: Georgia, 'Times New Roman', serif;"> has a breeding season from late March through May and spawns large (~1.2mm) yolky
oocytes that are opaque and bright orange (Birkeland et al. 1971). In order to
get the oocytes and sperm out we biopsied adult </span><i style="font-family: Georgia,'Times New Roman',serif;">M. aequalis</i><span style="font-family: Georgia, 'Times New Roman', serif;">. Pieces of dissected ovary were placed into a solution of 1-methyl adenine (1-MA) for an hour to induce oocyte maturation. Oocytes were then fertilized with a dilute suspension of sperm. Several of the fertilized eggs developed.</span><br />
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<span style="font-family: Georgia, Times New Roman, serif;">I took some pictures of 35-day old brachiolaria
larvae. As in other species of seastars with large yolky eggs, <i>Mediaster </i> lacks a feeding</span> <a href="http://invert-embryo.blogspot.com/2010/05/asteroid-bipinnaria-larva.html">bipinnaria larva</a><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">, and develops via a non-feeding pelagic brachiolaria. As you can see here these yolky non-feeding
brachiolariae have three brachiolar arms (stubby appendages at upper right).
These are used for attachment to substratum during metamorphosis. The juvenile seastar
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<span style="font-family: Georgia, 'Times New Roman', serif;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2ciqX8ltnE92Uw3W5gLCpad4fqj1TSnff_63Jly5sASJhHI5hEu7hAnl_rxLV9zk8OXXRToYmOC4yCtgn60OcLXCJwcltFQDQQ9y6MbHsBygZNnUUdSc8FRNP-Q2kPoje8Rt5D3dCnYY/s1600/Juvenile+Rudiment.tif" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="181" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2ciqX8ltnE92Uw3W5gLCpad4fqj1TSnff_63Jly5sASJhHI5hEu7hAnl_rxLV9zk8OXXRToYmOC4yCtgn60OcLXCJwcltFQDQQ9y6MbHsBygZNnUUdSc8FRNP-Q2kPoje8Rt5D3dCnYY/s200/Juvenile+Rudiment.tif" width="200" /></a></span></div>
<span style="font-family: Georgia, 'Times New Roman', serif;">The many small bumps
(clearly visible in the bottom picture) cover the juvenile rudiment and develop
into adult spines. The larger bumps of the juvenile rudiment are the developing
rays of the seastar. Once the juvenile rudiment and the brachiolar arms are
formed (which may be as early as 9-10</span><b style="font-family: Georgia,'Times New Roman',serif;"> </b><span style="font-family: Georgia, 'Times New Roman', serif;">days)
the larva is capable of metamorphosing. </span><i style="font-family: Georgia,'Times New Roman',serif;">M. aequalis</i><span style="font-family: Georgia, 'Times New Roman', serif;">
will only settle and metamorphose on a suitable substratum, such as a tube of
the annelid </span><i style="font-family: Georgia,'Times New Roman',serif;">Phyllochaetopterus</i><span style="font-family: Georgia, 'Times New Roman', serif;">. If
no suitable substratum is available, larvae can delay metamorphosis for as long as
14 months (Birkeland et al. 1971). </span>
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<span style="font-family: Georgia, Times New Roman, serif;"><span lang="ES-MX">Birkeland, C., Chia, F-S., Strathmann, R.R. 1971. </span>Development,
substratum selection, delay of metamorphosis and growth in the seastar, <i>Mediaster aequalis</i> stimpson. <i>Biological Bulletin</i>. 141:1, 99-108.</span><o:p></o:p></div>
Anonymoushttp://www.blogger.com/profile/13629418435325677324noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-81405400596785250342013-06-01T13:18:00.000-07:002013-06-03T11:46:20.990-07:00Planktonic larvae of the polychaetes Nephtys and Capitella<div style="font-family: Georgia,"Times New Roman",serif;">
I collected the two polychaete larvae pictured here from a plankton sample taken off a dock in Charleston, OR on May 8, 2013. The thing that caught my eye was the deep blue color in the lining of the gut of the larva shown immediately below. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyAsFx5nkPLJEC2ivbXcIXK8Xvq-Db3lphPdKSntCo01f0ibQdis5Flj08g7q8pnWMmNvV8xD2ITWU1AedcpaamAxfOXQM9qEhFuX7_FwqPr2Tf8Y_GIGY2f1zd5Xw4WVdoFUAukIrY1g/s1600/2.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyAsFx5nkPLJEC2ivbXcIXK8Xvq-Db3lphPdKSntCo01f0ibQdis5Flj08g7q8pnWMmNvV8xD2ITWU1AedcpaamAxfOXQM9qEhFuX7_FwqPr2Tf8Y_GIGY2f1zd5Xw4WVdoFUAukIrY1g/s200/2.tiff" style="cursor: move;" width="200" /></a></div>
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This blue pigmentation along with a dome shaped episphere, a pair of eyes, and two transverse ciliary bands (anterior prototroch and posterior telotroch) separated by 10 body segments suggests that this larva (called metatrochophore) belongs to a polychaete from the family Nephtyidae, likely the genus <i>Nephtys</i>. Twelve species of nephtyids are reported from the NE Pacific, but the larval development has been described only for one of them, <i>Nephtys caeca</i> (Crumrine 2001). </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLtTAOzJeI4uLHum3QIYkar0oXV3d7dGS3eCx801XwNnm1aVlyWmr9sYXFlt6vrfYXIY1imdIBk4yhL75G3DBxFIWNytEeSoTW3KwvlwxUnXPW_hJd0nrb1GnL5WjhhebCSjzSVPPnPvs/s1600/6.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLtTAOzJeI4uLHum3QIYkar0oXV3d7dGS3eCx801XwNnm1aVlyWmr9sYXFlt6vrfYXIY1imdIBk4yhL75G3DBxFIWNytEeSoTW3KwvlwxUnXPW_hJd0nrb1GnL5WjhhebCSjzSVPPnPvs/s200/6.tiff" width="200" /></a> Jay Bowles, a student in the Molecular Marine Biology class at the OIMB, matched a similar-looking larva to the genus <i>Nephtys</i> using DNA sequence data (see blog post <a href="http://invert-embryo.blogspot.com/2012/12/confirmed-identity-of-wild-caught.html" target="_blank">Confirmed identity of wild-caught planktonic larvae</a> by Terra Hiebert). <i>Nephtys</i> larvae like this one are planktotrophic, their gut has a spacious lumen, and one can sometimes see diatoms and other food particles inside (S. A. Maslakova, pers. comm.).</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6kIBvFy4iBpsptS-YAiCVBWA9Gai2wxkhLUajTqzehJhjy-TUQ-lw4fk5ovNnddDa45GUIEyNrGkf2G7f1HlwuH8xq2x8Vc0Du7RU2HLJzwifDiT1L4qJhN7W1Q90kQ9RH8vuT03ZAv0/s1600/3.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="125" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6kIBvFy4iBpsptS-YAiCVBWA9Gai2wxkhLUajTqzehJhjy-TUQ-lw4fk5ovNnddDa45GUIEyNrGkf2G7f1HlwuH8xq2x8Vc0Du7RU2HLJzwifDiT1L4qJhN7W1Q90kQ9RH8vuT03ZAv0/s200/3.tiff" width="200" /></a>The morphology of this other larva suggests that it belongs to the polychaete family Capitellidae, likely the genus <i>Capitella</i>.
There are eight species of capitellids in the NE Pacific, but the
development is described only for two of them. Although this larva fits the brief description of larval <i>Capitella capitata</i> in Crumrine (2001), it may also belong to another capitellid species whose development has not been described. This larva, like the one pictured above, is also propelled by two transverse ciliary bands, the anterior prototroch and posterior telotroch. There are several segments bearing developing chaetae (none protrude at this stage) between the two ciliary bands. The segment posterior to the telotroch, called pygidium is covered with short cilia. The two eyes are at the same level as the prototroch. The shiny marbles inside are the lipid droplets filling the cells of the gut. These lipid droplets are likely inherited from the egg, - i.e. this larva is likely non-feeding (lecithotrophic). See my other blog post about <a href="http://invert-embryo.blogspot.com/2013/05/planktotrophy-versus-lecithotrophy.html" target="_blank">lecithotrophy vs. planktotrophy</a>. <br />
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<div style="font-family: Georgia,"Times New Roman",serif;">
<span style="font-family: Georgia,"Times New Roman",serif;">Crumrine, L. 2001. Polychaeta. In: An Identification Guide to the Larval Marine Invertebrates of the Pacific Northwest. Edited by Alan Shanks. OSU Press, Corvallis.</span></div>
Jonathan Giengerhttp://www.blogger.com/profile/16836233600359675194noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-31936336970959297642013-06-01T09:02:00.000-07:002013-06-02T06:10:28.703-07:00Mass spawning of beached hoplonemertean Nipponnemertes bimaculata<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJ8Xxt3ICjYIh9RonvpYEZnJVh0Oe7s7NCICT5RiNs1ieoOb3ROJQfEvx_d7dKruKxF87Zma-h1Yz_1BvZAgImmzZlPyAm_AyduBZSeJRbGP9aR6VW4AzdGfzwJYYrO-vExYD8bkrpLyYt/s1600/photo.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJ8Xxt3ICjYIh9RonvpYEZnJVh0Oe7s7NCICT5RiNs1ieoOb3ROJQfEvx_d7dKruKxF87Zma-h1Yz_1BvZAgImmzZlPyAm_AyduBZSeJRbGP9aR6VW4AzdGfzwJYYrO-vExYD8bkrpLyYt/s200/photo.jpg" width="200" /></a></div>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The tide was low at 6 am on May 8th as our Embryology class descended into South cove at Cape Arago, OR. As we made our way to the tide pools we noticed a few live <i>Nipponnemertes bimaculata</i>, bright orange ribbon worms (nemerteans), laying among the floatsam and kelp washed up onto the sandy beach of the cove. The two characteristic brown spots on the head are responsible for the specific epithet (“bimaculata” means “two spots”). Svetlana, our instructor and an expert on the biology of nemerteans, thought it strange; these are usually subtidal and are only occasionally found under rocks intertidally, but are not generally known to get stranded on sandy beaches. Puzzled, we continued on to the tide pools to collect bryozoans (our study subjects that day). </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgD9O7U9MWIe2c94fF1sW4vXMfRY5Xg36hKUm1HxDAmz1mCNCzi6IZKMNQ-vb_UdFSOziav9NMUmBcElwm2v4TnWhwmq18bX84ln2p3jmNJ0pbgR-Y9qF7vGE4NRXHdeyizy0DXK0tkLM3j/s1600/2013-05-08+08.47.56.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgD9O7U9MWIe2c94fF1sW4vXMfRY5Xg36hKUm1HxDAmz1mCNCzi6IZKMNQ-vb_UdFSOziav9NMUmBcElwm2v4TnWhwmq18bX84ln2p3jmNJ0pbgR-Y9qF7vGE4NRXHdeyizy0DXK0tkLM3j/s200/2013-05-08+08.47.56.jpg" width="150" /></span></a><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">When we made our way back to the sandy beach at about 9 am we found the beach littered with stranded <i>N. bimaculata</i>. We soon realized that most of them were releasing gametes! Hundreds of these worms got stranded in an unheard-of, for hoplonemerteans, mass spawning event. <i>N. bimaculata</i> and other members of the family Cratenemertidae are unusual among monostiliferan hoplonemerteans because they can swim by undulating their body. Svetlana hypothesized that the worms (normally benthic) were swimming and spawning <i>en mass</i>, when the change in tide and currents got them stranded. </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhXLMLAhw2AWuo_YDdQ9rXmd9DVw4iFeyKaoLcluJ9dNm7hs8KICcBRIXwb8MhrOtagnXpr8so3A9nasbmP0f1vmxxjIukJ8ImX-FmG2_skZetA11kxf6nxG9bCawf0CZTZDsRnJCc4iiGM/s1600/2013-05-08+08-1.44.24.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhXLMLAhw2AWuo_YDdQ9rXmd9DVw4iFeyKaoLcluJ9dNm7hs8KICcBRIXwb8MhrOtagnXpr8so3A9nasbmP0f1vmxxjIukJ8ImX-FmG2_skZetA11kxf6nxG9bCawf0CZTZDsRnJCc4iiGM/s200/2013-05-08+08-1.44.24.jpg" width="200" /></span></a><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">We collected several of the worms of each gender, placing males and females in separate bags as well as in a bag together in order to observe embryonic and larval development, which has not been previoulsy described. The males were rather orange and released white sperm, while the females were somewhat darker (brownish or greenish) due to the color of the eggs inside them, You can see both males and females on this picture. Sexes cannot be easily distinguished once the worms release gametes. On our way back to OIMB we checked the sandy beaches of Middle cove at Cape Arago, and the nearby Sunset Bay, but they were devoid of nemerteans. This may be either because the suitable adult habitat is lacking (e.g. kelp holdfasts) or because the hydrodynamics are different in these coves.</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihZg-uWyq4NoxOaQWU-LpZUZXueWFHpAGydruKGQJwj_XVwhbqhqxQLJ1-N-i4LHK2d64UWpTmfo_8bbuSuchjQ2a5xh-HtGIFwGB0zdajCmQ9Uhbl0cRJnQRA0cPNn0BzpNLHbstXPLso/s1600/planuliforn+nipponnemertes+bimaculatus.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihZg-uWyq4NoxOaQWU-LpZUZXueWFHpAGydruKGQJwj_XVwhbqhqxQLJ1-N-i4LHK2d64UWpTmfo_8bbuSuchjQ2a5xh-HtGIFwGB0zdajCmQ9Uhbl0cRJnQRA0cPNn0BzpNLHbstXPLso/s200/planuliforn+nipponnemertes+bimaculatus.tiff" width="200" /></span></a></div>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The greenish </span><span class="Apple-style-span" style="color: #333333;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">~ 265</span></span><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"> micron eggs are loosely connected by jelly when released, are very delicate despite the protection of the chorion, and easily rupture when handled. Most of the eggs in our culture disintegrated after the first few days, but a few developed into planktonic planuliform larvae, one of which is depicted here - a week and two days after fertilization. Note the two large reddish eyes and conspicuous lipid droplets. Most hoplonemertean larvae have several pairs of relatively smaller eyes (e.g. see blog posts by <a href="http://invert-embryo.blogspot.com/2012/05/hoplonemertean-embryo-and-larva.html"> Jenna Valley</a> and<a href="http://invert-embryo.blogspot.com/2013/03/development-of-hoplonemertean.html"> Kirstin Meyer</a>). The larva depicted here is 460 micron long.</span>Anonymoushttp://www.blogger.com/profile/05567124010386714862noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-17616198998698710532013-06-01T08:56:00.000-07:002013-06-04T11:31:04.479-07:00Brooding copepods<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAQVtSctr2_6GCDgL308dxMpIiNaaoi9rU7IWYrvVrkid18eopyVTFsiRQ36aDGhBHsepfQ-76L-cSWbaL0YnwvJCGgK00z0SQCNTAELlin8QPYakdyOQD0fYkcaBhgAzH2LwM5pCxiHlT/s1600/adjusted+copepod.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAQVtSctr2_6GCDgL308dxMpIiNaaoi9rU7IWYrvVrkid18eopyVTFsiRQ36aDGhBHsepfQ-76L-cSWbaL0YnwvJCGgK00z0SQCNTAELlin8QPYakdyOQD0fYkcaBhgAzH2LwM5pCxiHlT/s200/adjusted+copepod.tiff" width="150" /></a></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Copepoda, with approximately 12,000
described species, is one of largest taxa of crustaceans and a large
contributor in most plankton samples. This is particularly true of calanoid
copepods, as most species in this group live entirely planktonic lifestyles. I collected the brooding calanoid copepod
pictured here from a plankton sample taken in the Charleston boat basin. The
anterior-most and longest appendages (first antennae) extend out of the frame
of this picture. Some copepods release eggs into the plankton, but, as is the
case here, many species carry their eggs in sacks attached to the abdomen. Note
the two ovisacs laterally along the abdomen (the narrow posterior portion of
the body) posterior to the thorax (the broad portion of the body) and anterior
to the caudal ramus (the forked tail). </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhH7uND0uhCFCXz-w3b3b8m2JWEwg0OXhJMlTI2eezpbR_ZKYCs3S-UhUesygzif26gOgNjr0Bz6oh6gjREqVpAVLuH1RE91yE5IsM_ARnQkLhY5Y3ClsweJbs3yvZaWShG2ahS2HcACd4L/s1600/brood.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhH7uND0uhCFCXz-w3b3b8m2JWEwg0OXhJMlTI2eezpbR_ZKYCs3S-UhUesygzif26gOgNjr0Bz6oh6gjREqVpAVLuH1RE91yE5IsM_ARnQkLhY5Y3ClsweJbs3yvZaWShG2ahS2HcACd4L/s200/brood.tiff" width="150" /></a></div>
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<span style="font-family: Georgia, Times New Roman, serif;">The second picture shows a close up view
of the ovisacs. Inside the very thin transparent membrane of each ovisac
(barely visible here) are 15-25 large eggs (each 70-80μm in diameter). The ovisacs are secreted
by the epithelial cells lining the oviducts and are attached to the genital
segment (the 6<sup>th</sup> thoracic segment fused to the 1<sup>st</sup>
abdominal segment). Copepods in general are dioecious (meaning that they have
separate sexes). During copulation males release spermatophores (sperm
packages) and glue them to the female abdomen. Spermatozoa from the
spermatophores then move into the female reproductive tracts and are stored
there until they are needed. The eggs are fertilized internally on their way to
the ovisacs where they will be brooded until they hatch as nauplii. </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7_MqDqslctHvkiARrQlqbucCB01ci8sGvFhvkeHR39sPWEmebCIAPzAoq7N7TdXpWaUiub74n6wWrYHZ8dJ922PfR4dJvjfTXxEyIhDLnpf_wT7m237oGdizIwVQvOYTxgwJL_AwzX9qT/s1600/20130517_134331.24_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7_MqDqslctHvkiARrQlqbucCB01ci8sGvFhvkeHR39sPWEmebCIAPzAoq7N7TdXpWaUiub74n6wWrYHZ8dJ922PfR4dJvjfTXxEyIhDLnpf_wT7m237oGdizIwVQvOYTxgwJL_AwzX9qT/s200/20130517_134331.24_L.tiff" width="150" /></a></div>
<span style="font-family: Georgia, Times New Roman, serif;">The
nauplius larva pictured here hatched from just such a brood. It is about 270μm
long. The nauplius hatches and swims using three pairs of head appendages: the
first and second antennae, and the mandibles (from anterior to posterior
respectively). The reddish blotch between the two first antennae is the
naupliar eye. Copepod larvae go through six naupliar stages followed by five
copepodid larval stages, molting between each stage. The mature adult no longer
molts, and thus cannot grow. </span><o:p></o:p></div>
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<!--EndFragment-->Susanna DeBellhttp://www.blogger.com/profile/07275057172378205719noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-55692459107820892622013-05-30T17:30:00.000-07:002013-05-31T17:14:32.735-07:00Two types of Aeolidia papillosa larvae<div style="text-align: left;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGndzEbNNxVoV3mpxcSB0Yh6vOddl7VoN-3o-CtydDz7B3i86hVW82y3zyaTrY8Ojg6xnvDqKvSBic2ahZ5CerL8GnDiAF9ZcgQ01jL0qQYJs6_xVHNTBDbQE27h0KwJUOhl3EZLNH/s1600/DSCN2263.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="170" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGndzEbNNxVoV3mpxcSB0Yh6vOddl7VoN-3o-CtydDz7B3i86hVW82y3zyaTrY8Ojg6xnvDqKvSBic2ahZ5CerL8GnDiAF9ZcgQ01jL0qQYJs6_xVHNTBDbQE27h0KwJUOhl3EZLNH/s1600/DSCN2263.JPG" width="200" /></a><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">This is a picture of an adult nudibranch <i>Aeolidia papillosa</i>, found on the Charleston docks near OIMB. As with many other nudibranchs, <i>A. papillosa</i> package their eggs a few per egg capsule, the capsules embedded in a gelatinous ribbon, which are deposited as egg masses (pictured below). Early development is encapsulated, and embryos begin to move inside the capsule, before they hatch as shelled veligers (bottom picture).</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLIFfr-lzGnrxhBe9H2sOqRaMREiXD3_iTiFL0qQ9if7_DKf1I5_VpIOA2Uai1cjLoovRF4CCiMGir_5amrhH7smHMKbEsci_cLE9WR5MZfB21yt9V2dJGqPUB5UJkLNlKT35h97Oy/s1600/DSCN2259.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLIFfr-lzGnrxhBe9H2sOqRaMREiXD3_iTiFL0qQ9if7_DKf1I5_VpIOA2Uai1cjLoovRF4CCiMGir_5amrhH7smHMKbEsci_cLE9WR5MZfB21yt9V2dJGqPUB5UJkLNlKT35h97Oy/s1600/DSCN2259.JPG" width="200" /></a>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Many marine invertebrates are characterized by a particular type of development e.g. either lecithotrophic or planktotrophic (see Jon Gienger's blog post, <a href="http://invert-embryo.blogspot.com/2013/05/planktotrophy-versus-lecithotrophy.html">Planktotrophy versus lecithotrophy</a>). Interestingly, <i>Aeolidia papillosa</i> veligers hatching from the same egg capsule can be polytypic: some released as yolk-laden lecithotrophic larvae, and others as yolk-free planktotrophic larvae (Williams, 1980). Williams (1980) also noted that larvae that hatched without yolk reserves were, paradoxically, larger than those released with yolk reserves, although both types of larvae developed from uniformly small eggs. A simple explanation might be that because these two types of larvae develop within the same egg capsule, it is possible that the yolk-laden (slower developing) larvae are prematurely released from the egg capsule by their yolk-free (faster-developing) siblings. However, yolk-laden larvae hatched from egg capsules that did not contain any yolk-free larvae. What’s more, smaller larvae were apparently less likely to feed on unicellular algae (e.g. <i>Chlorella</i>, <i>Dunaliella</i>) than their larger siblings. Both yolk-free and yolk-laden veligers were present in the egg masses I looked at, in addition to yolk-laden trochophores, indicating that larvae were still developing. </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_CgauwTOuLXp_l5XkgTqvVxsJhXfTVrVPE_YP9cu-lzd_elEU7DaVd474CmUd4hyphenhyphenQK9z-yC8aqM4lR1W_jDQyj8d40EhgsZFtsH8fddvB4IP2ti-WWkfcq28GEBHwuvbTs-9II__E/s1600/20130426_130830.64_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="191" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_CgauwTOuLXp_l5XkgTqvVxsJhXfTVrVPE_YP9cu-lzd_elEU7DaVd474CmUd4hyphenhyphenQK9z-yC8aqM4lR1W_jDQyj8d40EhgsZFtsH8fddvB4IP2ti-WWkfcq28GEBHwuvbTs-9II__E/s1600/20130426_130830.64_L.tiff" width="200" /></a><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"></span>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">One possible explanation for this polytypic development may be bet-hedging (varying strategy to increase the overall chances of offspring survival and success). Lecithotrophic larvae are expected to survive to metamorphosis better than the planktotrophic under conditions of scarce food, whereas planktotrophic larvae may be more successful when phytoplakton is abundant. Producing both types of larvae may be advantageous when phytoplankton has spatially and temporally patchy distribution (Williams, 1980).</span><br />
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<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Williams, L.G. (1980). Development and feeding of the larvae of the nudibranch gastropods <i>Hermissenda crassicornis</i> and <i>Aeolidia papillosa</i>. Malacologia 20:99–116.</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDUXy03QSH-q6DCOT8iJKavWf1hQ0KlvvEvuVT086MN_gWN73vAfGmSYU6Z0y4gxbTkQsuw4tfvwk3jJnMBm1m1uRjhlAHDnYnlBihioY8KI_XzpaYC_DLfv1bLy72j3_AEIIRq01u/s1600/20130405_132540.9asdf2_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="171" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDUXy03QSH-q6DCOT8iJKavWf1hQ0KlvvEvuVT086MN_gWN73vAfGmSYU6Z0y4gxbTkQsuw4tfvwk3jJnMBm1m1uRjhlAHDnYnlBihioY8KI_XzpaYC_DLfv1bLy72j3_AEIIRq01u/s1600/20130405_132540.9asdf2_L.tiff" width="200" /></a></div>
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This is a marine rotifer from the genus <i>Synchaeta </i>(according to a key in Wallace & Snell 2010). Rotifers are a phylum of small, mostly fresh-water invertebrates. This adult individual is 0.7 mm long. When I found it in the plankton sample, it was carrying two egg capsules attached to its foot (a little stalk at posterior end of the organism-see photo). While I watched it, one of the egg cases ruptured, releasing a fully formed and seemingly completely functional miniature (~ half a millimeter long) rotifer. The empty case remained attached to the foot of the adult, while the newly hatched rotifer (shown below) began swimming immediately. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh71_BMzvlToXI3nDz9Yts5o_C2mIEjLPdIM9PFHVegBnU1ypbHMyBXMof9PikdwDwmkkL7aSrygbXQVIKB8yoI8hfyR4mCMK4aYP8Gqzu9NkZR1T0zDDqTYMoznJTe_uHuc7e1lWvI/s1600/20130424_162907.07asdf_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="183" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh71_BMzvlToXI3nDz9Yts5o_C2mIEjLPdIM9PFHVegBnU1ypbHMyBXMof9PikdwDwmkkL7aSrygbXQVIKB8yoI8hfyR4mCMK4aYP8Gqzu9NkZR1T0zDDqTYMoznJTe_uHuc7e1lWvI/s1600/20130424_162907.07asdf_L.tiff" width="200" /></a>Interestingly, rotifers can reproduce both sexually and asexually. One class, Bdelloidea, appears to lack males altogether (Wallace & Snell 1991). Sexes are separate in the Class Monogononta, to which the marine genus <i>Synchaeta</i> belongs. For the majority of the year, females produce offspring asexually by generating diploid embryos that develop without fertilization into females. Under certain conditions though, females produce haploid eggs. As in certain social insects (e.g. bees), if these eggs remain unfertilized, they develop into haploid males. If fertilized, diploid eggs can remain in a diapause (resting state) for up to 20 years (Fradkin 2007), and eventually develop into females who feed and grow before becoming sexually mature (Ricci & Melone 1998). These resting eggs allow the population to outlive adverse conditions (e.g. desiccation, freezing etc.). Haploid males are sexually mature at birth, do not feed and live a short life (usually about half as long as females) with the apparent sole purpose of fertilizing females via hypodermic insemination (Ricci & Melone 1998). Another fascinating fact is that most rotifers have constant cell numbers as adults (~ 1000) (Fradkin 2007). In other words, no cell divisions take place after embryogenesis is completed, and growth is accomplished solely by enlarging existing cells. In contrast, humans start out as one cell, but end up with trillions in the adult b<span class="Apple-style-span" style="font-family: inherit;">ody, <span class="Apple-style-span" style="border-collapse: collapse; color: #222222;">the vast majority of which are born post-embryonically</span></span>. Additionally, in some asexually reproducing rotifer genera, generational clones have progressively shorter life spans (i.e. daughters live a shorter life than their mothers, grand-daughters live even shorter, and so on), which eventually leads to extinction of the line (see King 1969 for a review).<br />
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A dearth of information about development, distribution, and ecology in NE Pacific rotifers leave members of this phylum prime candidates for future research.<br />
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Fradkin, S.C. (2007). Rotifera. Light's manual; intertidal invertebrates of the central California coast. 4th ed. pp 280-282. J.T. Carlton (ed.). University of California Press.<br />
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King, C.E. (1969). Experimental studies of aging in rotifers. Experimental Gerontology 4: 69-79.<br />
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Wallace, R.L., Snell T.W. (2010). Rotifera. In: Ecology and classification of North American freshwater invertebrates. 1st ed. pp 173-235. J.H. Throp and A.P. Covich, eds. Academic Press.<br />
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Ricci, C., Melone, G. (1998). Dwarf males in monogonont rotifers. Aquatic Ecology 32: 361-365.Anonymoushttp://www.blogger.com/profile/14580208261540896682noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-89814895787888226642013-05-29T19:52:00.000-07:002013-05-30T10:40:42.926-07:00Early development and spermatophore of the phoronid Phoronopsis harmeri<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggOCrjTcnRhSMdjFSdk7F_qRDKpKMRTxikzkcE_ze09wNA879O6M1dtJvaXXip6GWhxxiOtLRVk-x7qwMFnHH7J61c44VXR5GJEWzfkqsPDguGzn6eZgtAhyphenhyphengf0h7SRRFOXnLmUAp8ocU/s1600/P_harmeri_spermatophore_10.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="149" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggOCrjTcnRhSMdjFSdk7F_qRDKpKMRTxikzkcE_ze09wNA879O6M1dtJvaXXip6GWhxxiOtLRVk-x7qwMFnHH7J61c44VXR5GJEWzfkqsPDguGzn6eZgtAhyphenhyphengf0h7SRRFOXnLmUAp8ocU/s200/P_harmeri_spermatophore_10.tiff" width="200" /></a><i>Phoronopsis harmeri</i> is a member of Phoronida, a relatively small phylum of sessile, tube-building marine worms. Phoronids release sperm in packets called spermatophores, which probably drift in water currents before landing on the lophophore of another individual. In <i>P. harmeri</i> and some other species, these spermatophores are equipped with a mucoid spiral “sail” (Zimmer 1997). The spermatophore of <i>P. harmeri</i>, sail included, is pictured here. </div>
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There is some controversy regarding the early cleavage pattern of phoronids. While some researchers have reported radial cleavage, others have reported spiral cleavage, biradial cleavage, and “derived spiral” cleavage (reviewed by Pennerstorfer and Scholtz, 2012). In spiral cleavage, the blastomeres of the early embryo divide along a plane that is oblique to the animal-vegetal (A/V) axis, and the cells are not stacked directly on top of each other but are offset from one another. In contrast, blastomeres undergoing typical radial cleavage divide either parallel or perpendicular to the A/V axis, and the cells stack directly on top of one another (Ruppert et al. 2004). Pennerstorfer and Scholtz (2012) quantified the number of embryos exhibiting spiral-like cleavage in <i>Phoronis muelleri</i> and the degree of tilt of the plane of division. They concluded that, beginning with the third cleavage, early cell division in <i>P. muelleri</i> tends to occur in a spiral pattern, although there is a high amount of variability among embryos of this species. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizhx3C5k5mhAORHVhvIuX1mAlEghMK1oEG_LZQ2PWJ4uSPZwoa5f8efMNhGYyrZ7_Ix8mNdGlWpi42HhZwVULv16yJR-1AlFfQWAVOHDjMA1TYlHRpaeAS0ob3U0NnS5yltQOHjN5k2n0/s1600/P_harmeri_8-cell_3.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="178" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizhx3C5k5mhAORHVhvIuX1mAlEghMK1oEG_LZQ2PWJ4uSPZwoa5f8efMNhGYyrZ7_Ix8mNdGlWpi42HhZwVULv16yJR-1AlFfQWAVOHDjMA1TYlHRpaeAS0ob3U0NnS5yltQOHjN5k2n0/s200/P_harmeri_8-cell_3.jpg" width="200" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinAkeMGxCVZpCkw9z-H4jnRhZupXXj5VTmxyUHR9DyDZIEJE_PhKNoeKg-N65iTGRWeFySs7Wzc09Ej3M8AVQucaf77PgWkhISX1b2AiFvDwC6rbTPNLwZxh-PvW8jTLF_wfHy1mcKr9o/s1600/P_harmeri_16-cell_.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinAkeMGxCVZpCkw9z-H4jnRhZupXXj5VTmxyUHR9DyDZIEJE_PhKNoeKg-N65iTGRWeFySs7Wzc09Ej3M8AVQucaf77PgWkhISX1b2AiFvDwC6rbTPNLwZxh-PvW8jTLF_wfHy1mcKr9o/s200/P_harmeri_16-cell_.jpg" width="198" /></a><span id="goog_1545914216"></span>Pictured at left are examples of the 8-cell and 16-cell stage of <i>P. harmeri</i>, whose early development I observed while taking the Embryology course at OIMB. The sister cells in the 8-cell embryo (side view) appear to be nearly on top of one another, so the third cleavage (at least in some embryos) of this species is not obviously spiral. However, the four polar blastomeres in the 16-cell stage pictured here are noticeably offset from their four sisters, though not every embryo in our class culture looked like this at the 16-cell stage. At least some embryos in this culture exhibited alternating (dextral vs. sinistral) divisions (S. Maslakova, pers. comm.), as in
typical spiralians. Is early development in <i>P. harmeri</i> also somewhat spiral?
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Pennerstorfer. M. and Scholtz, G. 2012. Early cleavage in <i>Phoronis muelleri</i> (Phoronida) displays spiral features.Evolution and Development. 14(6): 484-500.<br />
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Rupert, E., Fox, R., and Barnes, R. 2004. Invertebrate Zoology: A Functional Evolutionary Approach. 7 ed. Brooks/Cole.<br />
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Zimmer, R. 1997. Phoronids, Brachiopods, and Bryozoans: The Lophophorates. In Embryology: Constructing the Organism. Gilbert, S. and Raunio, A. Eds. Sinauer Associates, Inc. Sunderland, MA. </div>
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Rose Rimlerhttp://www.blogger.com/profile/00261528155118970273noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-18442795056283618352013-05-25T18:09:00.000-07:002013-05-28T22:24:10.715-07:00Development of Trimusculus, a limpet-like marine snail <span style="font-family: Georgia, "Times New Roman", serif;"><span style="font-family: Georgia, "Times New Roman", serif;"><i>Trimusculus reticulatus,</i></span> or the button-snail, is an unusual marine gastropod that looks like a
limpet (i.e. a member of the Patellogastropoda) but is not. It is, in fact, a
pulmonate gastropod (it has a lung) - a relative of the common garden snail. Pulmonate species are
generally terrestrial or live in fresh water, but some are marine like <i style="mso-bidi-font-style: normal;">T. reticulatus</i>. The adults of <span style="font-family: "Calibri Italic","serif";"><span style="font-family: Georgia, "Times New Roman", serif;"><i>T. reticulatus</i></span> </span>are found in
the high intertidal underneath the overhangs of boulders or on the roofs of sea
caves.
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<span style="font-family: Georgia, "Times New Roman", serif;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEha_ojaXNdGxQHEripdKnmQj2VkYIwoju6HgmO1SHhkRSZlGLisd0YlAwrkoBuiOjbwhQY6WI5fhjXIRCSa14Ai4rXoFRyfj-ljOOGo_KW657w1Th8cfs1IqmJ8WaBD4aPbnuKisG53hxI/s1600/AdultSM.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="112" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEha_ojaXNdGxQHEripdKnmQj2VkYIwoju6HgmO1SHhkRSZlGLisd0YlAwrkoBuiOjbwhQY6WI5fhjXIRCSa14Ai4rXoFRyfj-ljOOGo_KW657w1Th8cfs1IqmJ8WaBD4aPbnuKisG53hxI/s200/AdultSM.jpg" width="200" /></a></span></div>
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I collected the specimen pictured here from Strawberry
Hill, Oregon. As shown, the shell of adult <span style="font-family: "Calibri Italic","serif";"><span style="font-family: Georgia, "Times New Roman", serif;"><i>T. reticulatus</i></span> </span>is about the
size of a penny.<span style="mso-spacerun: yes;"> </span>The shell is shallow
and uncoiled, like that of a true limpet, but unlike shells of most other
gastropods.
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</span><span style="font-family: "Calibri Italic","serif";"><span style="font-family: Georgia, "Times New Roman", serif;"><i>T. reticulatus</i></span></span> lays its
eggs in petal-like gelatinous masses around itself (Johnson 1968). These
“petals” were detached during collection. Each “petal” is about 5-10 mm in
diameter and contains dozens of embryos; the picture has a 5 mm scale bar. The
color is indicative of “petal’s” age.<span style="mso-spacerun: yes;">
</span>The whitish masses contain embryos in earlier stages of development. In
light brown masses the veliger larvae are about to hatch.<span style="mso-spacerun: yes;"> </span>The “petals” pictured here were produced
sequentially by a single individual. <br />
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This is an embryo from one of
the whitish ”petals”.<span style="mso-spacerun: yes;"> </span>Note the two polar
bodies (at four o'clock) trapped inside the oval egg capsule.<span style="mso-spacerun: yes;"> </span>Polar bodies mark the animal pole of the
embryo.<span style="mso-spacerun: yes;"> </span>This embryo is gastrulating
(forming the primary gut). The indentation at the opposite (vegetal) pole is
the blastopore – the opening of the primary gut, which will become the mouth of
the larva. <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6gDCvStPP1ipZ-jFfMSSV3DOFZtlcFdm3HTQT4Ch3nsjRTPzZKp9q4HkbFwBOrzoxGTthpaqhBmCsbwZe4JgkP0XaI0KFf4oTt6ioqFmSKrYqcCSpcqkMS3PX9gwjdMx2rs0TPg1gSXg/s1600/VeligerSM.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6gDCvStPP1ipZ-jFfMSSV3DOFZtlcFdm3HTQT4Ch3nsjRTPzZKp9q4HkbFwBOrzoxGTthpaqhBmCsbwZe4JgkP0XaI0KFf4oTt6ioqFmSKrYqcCSpcqkMS3PX9gwjdMx2rs0TPg1gSXg/s200/VeligerSM.tiff" width="183" /></a></div>
This is a hatched veliger larva.<span style="mso-spacerun: yes;"> </span>Unlike the adult, the larva has a typical
coiled shell – a vestige from the evolutionary past. One can also see the velum
– the ciliated larval appendage used for swimming – pulled into the shell, the
foot with an operculum, and the statocyst – a paired larval balance organ – that
looks like a little marble inside a spherical capsule. <br />
<br />
Johnson, K.J. (1968)
Studies on the feeding, movement, and respiration of the pulmonate limpet <i style="mso-bidi-font-style: normal;">Trimusculus (Gadinia) reticulatus</i>
(Sowerby) with notes on general morphology, egg masses, and veliger larva.
Unpubl. student paper (abstract). Marine Science Center, Newport, Oregon<span style="font-family: "Calibri Italic","serif";"><o:p></o:p></span></span><br />Anonymoushttp://www.blogger.com/profile/01391891386105855973noreply@blogger.com1tag:blogger.com,1999:blog-5072272240813556047.post-53369326821638112602013-05-22T15:49:00.000-07:002013-05-23T10:32:04.211-07:00Unidentified wild-caught Müller’s larva<br />
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<span style="font-family: Georgia, Times New Roman, serif;"><span style="background: none repeat scroll 0% 0% white;">On April 17,
2013 I took a plankton tow off a dock in Charleston, OR. While sorting plankton
I found a Müller’s larva (pictured here). The Müller’s larva is found in
free-living marine flatworms from the order Polycladida (class Turbellaria),
both in suborder Cotylea and Acotylea (Smith et al 2002). When a Müller’s larva
hatches from the egg it usually has 8 lobes, though larvae of some local
species have only 6 lobes (e.g. <i>Pesudoceros canadensis</i>). The entire larval body is covered in cilia, but the lobes
usually bear longer cilia. Müller’s larvae may be either transparent or opaque
and are often brown, mine was greenish. They normally have three eyes to begin
with, two subepidermal and associated with the brain and a third, epidermal eye
(Smith et al 2002). The two subepidermal eyes can be seen in this picture near
the anterior end (upper right). The eye spots often increase in number after
metamorphosis (Martín-Durán et al 2012). The larval lobes are reabsorbed during
metamorphosis. </span></span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEibv24KA1OoJSlj4FgiafPQcuwe-gvyS5HIt8eyp7eoF_gNk4YBQN-PxWrNKrAkripNZVWqyRVjPEJWhZIOMzagonkuwMOzGAo_nLP4Y9lLlilGk3vER_S3rS0C9GQe3j-h_Fab2M28Wlk/s1600/M%25C3%25BCller%2527s+Lobes.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEibv24KA1OoJSlj4FgiafPQcuwe-gvyS5HIt8eyp7eoF_gNk4YBQN-PxWrNKrAkripNZVWqyRVjPEJWhZIOMzagonkuwMOzGAo_nLP4Y9lLlilGk3vER_S3rS0C9GQe3j-h_Fab2M28Wlk/s200/M%25C3%25BCller%2527s+Lobes.tiff" width="151" /></a></div>
<span style="font-family: Georgia, Times New Roman, serif;"><span style="background: none repeat scroll 0% 0% white;">My larva had at least 4 lobes, more likely 6 (two
ventro-lateral, two dorsal-lateral, and two unpaired). One can see clearly two
of the lobes in focus in these pictures. The lobes are often retracted or
flattened when the larva is under the coverglass. Note the dark green branched
gut inside the larva. Polyclads, in general, are characterized by a multilobed
gut. Many Müller’s larvae apparently require food in order to reach metamorphosis but only a few species have been observed to feed in the
laboratory on microscopic algae </span><span style="background: none repeat scroll 0% 0% white;">(</span>Rawlinson<span style="background: none repeat scroll 0% 0% white;"> 2010 and
references therein).</span></span></div>
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<span style="background: none repeat scroll 0% 0% white;">Martín- Durán,
J. M. and Egger, B. 2012. Developmental diversity in free-living flatworms. <i>EvoDevo</i>, 3:7.<o:p></o:p></span></div>
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<div class="MsoNormal" style="color: black; font-family: Georgia,"Times New Roman",serif;">
<span style="background: none repeat scroll 0% 0% white;">Rawlinson, K. 2010. </span>Embryonic
and post-embryonic development of the polyclad flatworm Maritigrella crozieri;
implications for the evolution of spiralian life history traits. Frontiers in
Zoology 7: 12.<o:p></o:p></div>
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<span style="background: none repeat scroll 0% 0% white; color: #333333;"><span style="color: black; font-family: Georgia,"Times New Roman",serif;">Smith NF,
Johnson KB and Young, CY. 2002. Platyhelminthes. In: Atlas of Marine
Invertebrate Larvae. Edited by C. M. Young. Academic Press. New York.</span><o:p></o:p></span></div>
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Anonymoushttp://www.blogger.com/profile/13629418435325677324noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-68460678616031428702013-05-22T12:57:00.000-07:002013-05-30T10:52:48.595-07:00Bowling for Calliostoma<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><i>Calliostoma ligatum</i></span><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"> is a gastropod found on the rocky intertidal of the Pacific coast. </span><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><i>Calliostoma</i></span><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"> are dioecous (i.e. have separate sexes) and, like most other archaeogastropods, free-spawn their gametes. Conveniently, </span><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><i>C. ligatum</i></span><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"> can be easily induced to spawn in the lab if mildly harassed. </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgva9ze070Razrt3qruL_3qAqrRdKxP1wx70CbVtm-B4fXroGcYu4m0IKML-4N1uljzEg9BKC5VXJ4xNgNuoxNQ7w-xltvA5NnlAYdMggo0BfA1iDANCIHscyAIBXsNZRoOylwb3zntK-jB/s1600/male.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgva9ze070Razrt3qruL_3qAqrRdKxP1wx70CbVtm-B4fXroGcYu4m0IKML-4N1uljzEg9BKC5VXJ4xNgNuoxNQ7w-xltvA5NnlAYdMggo0BfA1iDANCIHscyAIBXsNZRoOylwb3zntK-jB/s200/male.JPG" width="200" /></a></div>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The two individuals pictured here were collected intertidally at the South Cove of Cape Arago near Charleston, OR. I placed them out at room temperature in small bowls filled with sea water, set the bowls on my desk to allow the water to warm up, and flipped the snails upside-down. When they regained their footing (takes about a minute or two) I would flip them again. I repeated this for about fifty minutes (it usually only takes as little as half an hour) after which the snails began to spawn. The first picture shows a male actively releasing sperm, hence the cloudy water in the bowl.</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiYJqeMMrnidvx0z9D8ZsELWMnNSBGfAzguJ40BmrLni5DySGEBD9Lq3mkaY5in6z4Fn-_aYTSNV3h5xHVDUnE-LTG6w80_gWWA3ckjOc7uORHlAB27LAn7BlrDA3z7rNxvbX-hzby7_tck/s1600/goodmom.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiYJqeMMrnidvx0z9D8ZsELWMnNSBGfAzguJ40BmrLni5DySGEBD9Lq3mkaY5in6z4Fn-_aYTSNV3h5xHVDUnE-LTG6w80_gWWA3ckjOc7uORHlAB27LAn7BlrDA3z7rNxvbX-hzby7_tck/s200/goodmom.JPG" width="200" /></a></div>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">This is a female which has recently released a mass of large 220 µm greenish eggs loosely connected by a jelly. She is flipped on her back, so one can see the bright orange foot rimmed with brown, the operculum, two cephalic tentacles and four pairs of epipodal tentacles. </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1qo4OvF73zI0UsYo0TxdpDMe3IILFHcfKFSI9Cm78VRZhbwDem8INtVqeT6xm1ufNiiwmRNF9-6V-h47DTqKSh4LRzm0tCvg1Opw14dSlSThkOcMxb7KvP_TytJk3EoeAVwYdfDlCXvaF/s1600/fertilization.tif.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1qo4OvF73zI0UsYo0TxdpDMe3IILFHcfKFSI9Cm78VRZhbwDem8INtVqeT6xm1ufNiiwmRNF9-6V-h47DTqKSh4LRzm0tCvg1Opw14dSlSThkOcMxb7KvP_TytJk3EoeAVwYdfDlCXvaF/s200/fertilization.tif.tiff" width="200" /></a></div>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The third picture shows an egg two hours after fertilization. You can see here that <i>C. ligatum</i> eggs are surrounded by an egg envelope (a distinct membrane near the surface of the egg), and a thick bilayered jelly coat. Note the two tiny clear cells (at 6 o’clock) trapped inside the egg envelope. These are polar bodies, the tiny sister cells of the oocyte, which contain the DNA discarded during meiosis. As in many other marine invertebrates meiosis in <i>Calliostoma</i> is completed after fertilization. Presence of the polar bodies is a sure sign of fertilization. Note a single needle-like spermatozoan still trapped in the inner layer of the egg jelly (at about 1 o'clock). Clearly it did not make it!</span>Anonymoushttp://www.blogger.com/profile/05567124010386714862noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-59598638468624002682013-05-22T12:53:00.001-07:002013-05-26T16:06:06.091-07:00Planktotrophy versus lecithotrophy <span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><span style="color: black;">Many marine invertebrates undergo indirect development, a kind of life history that includes a larval stage distinct from the adult. Two types of larval development are distinguished based on the source of larval nutrition. Lecithotrophy, meaning “feeding on yolk”, refers to development with a non-feeding larva, which depends on the egg’s yolk reserve supplied by the mother. Planktotrophy, meaning “feeding on plankton” refers to development via a larva that must feed in the plankton in order to develop to metamorphosis. </span></span></span><span style="font-family: Georgia,"Times New Roman",serif;"><span style="color: black; font-size: small;"><span style="background: none repeat scroll 0% 0% transparent;"><span style="color: black;"><span style="text-decoration: none;"><span lang="en-US"><span style="background: none repeat scroll 0% 0% transparent;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipUQsdi1aduQ71JreU9fARfhOfCfsx-7fVTHs94-8qRl3U9k8vy8yRZY8OQ3hxKa3Xg3-DxbAArzFDhK6RSBfkPgv5zAv-ndxqD2sv3sumt5ufxghOgh7xIVrTCO2FZkoO4ZPQ7NXtyJA/s1600/Screen+shot+2013-04-19+at+12.46.23+PM.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="100" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipUQsdi1aduQ71JreU9fARfhOfCfsx-7fVTHs94-8qRl3U9k8vy8yRZY8OQ3hxKa3Xg3-DxbAArzFDhK6RSBfkPgv5zAv-ndxqD2sv3sumt5ufxghOgh7xIVrTCO2FZkoO4ZPQ7NXtyJA/s200/Screen+shot+2013-04-19+at+12.46.23+PM.png" width="200" /></a><span style="font-family: Georgia,"Times New Roman",serif;"><span style="color: black; font-size: small;"><span style="background: none repeat scroll 0% 0% transparent;"><span style="color: black;"><span style="text-decoration: none;"><span lang="en-US"><span style="background: none repeat scroll 0% 0% transparent;"> </span></span></span></span></span></span></span><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><span style="color: black;">Species with planktotrophic development produce many small energy-poor eggs with adequate nutrient reserves for the development of a feeding larva. These larvae must begin to feed immediately upon acquisition of feeding structures since they rapidly deplete their relatively insignificant yolk stores. Lecithotrophic species, on the other hand, produce fewer but larger eggs. These large yolky eggs develop into non-feeding larvae which usually lack feeding structures (e.g. mouth, gut, ciliary bands for capture of food particles). Lecithotrophic larvae spend comparatively less time in the plankton, and begin to feed after metamorphosis. Here, I pictured eggs of two sea star species with contrasting development. The opaque orange egg on the left (~1.2 mm in diameter) belongs to <i>Mediaster aequalis</i>, a lecithotroph, while the relatively transparent oocyte on the right (~150 µm) belongs to <i>Pisaster ochraceus</i>, a planktotroph. </span></span></span><br />
<span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><span style="color: black;"> </span></span></span>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGw_ZZ-JYeOsXT4ebeehRmkoJnBe8NCGIrxDneYrawcEbHqBRunOsQFB7ku5seCdQdYbSUusljcOl0-u7_eMfRbK4Jeo2b0eUD_VeC0teFqp9Ppw9-vIyA1YQ_jF2oPPU7GSsgLAXA9sU/s1600/dendraster+jg+blog.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGw_ZZ-JYeOsXT4ebeehRmkoJnBe8NCGIrxDneYrawcEbHqBRunOsQFB7ku5seCdQdYbSUusljcOl0-u7_eMfRbK4Jeo2b0eUD_VeC0teFqp9Ppw9-vIyA1YQ_jF2oPPU7GSsgLAXA9sU/s200/dendraster+jg+blog.tiff" width="200" /></a><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><span style="color: black;"> This picture depicts a 3-week old pluteus larva of <i>Dendraster excentricus</i> (sand dollar) which develops from a 125 µm egg and exemplifies planktotrophic development. Planktotrophic larvae, like this pluteus, have a functional gut, and one can often see food in their stomachs. Note several green single-celled algae (<i>Dunaliella</i>) inside the larval stomach. Feeding larvae typically spend weeks to months in the plankton before metamorphosis. This larva has begun to form the juvenile rudiment - an unpaired sack-like structure visible between two of the larval arms on the left side of the image. This is also the left side of the larva, which is viewed from the dorsal side (anterior at upper left). With plenty of food <i>Dendraster</i> plutei may reach metamorphopsis after 3-4 weeks at ambient sea temperature.</span></span></span>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgaAQYwvRApEC2CDJ5cef6JU6P1_elLrpWPr6H_Q5QZ7MJJ0aaKhA4Z7HB5yShOUfG4B9dmwtf8WKfQoHwY_fYmxTvjJXBSfNUd4SODDSD5yFiXmfZCLB86xY-8PXqyAItuYaS6ETYe6Nk/s1600/cucumaria+miniata+jg+4.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgaAQYwvRApEC2CDJ5cef6JU6P1_elLrpWPr6H_Q5QZ7MJJ0aaKhA4Z7HB5yShOUfG4B9dmwtf8WKfQoHwY_fYmxTvjJXBSfNUd4SODDSD5yFiXmfZCLB86xY-8PXqyAItuYaS6ETYe6Nk/s200/cucumaria+miniata+jg+4.tiff" width="200" /></a><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"> <span style="color: black;">The last picture depicts a wild-caught lecithotrophic doliolaria larva of <i>Cucumaria miniata</i> a local species of sea cucumber, that develops from large yolky eggs (~ 500 µm). Its planktonic development lasts only about two weeks and the larvae lack the capacity (and the need) to feed.</span></span></span>
Jonathan Giengerhttp://www.blogger.com/profile/16836233600359675194noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-15967086076331605082013-05-20T10:33:00.000-07:002013-05-20T10:33:42.291-07:00Early cleavage in echinoderms<!--[if gte mso 9]><xml>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSKE7PvMPDyJc4kUdM_kgdPrbzHMUAcr0kYPHhrGFfTAEz75DGLysGFcftq8TkpN3HBC5IvcuBPcDLXSPqLCJKAK-I6MlTHnW-3oZvIPUqjRfJ7Hnh4R0IN9r3xQanhVdxLQz7BFdvqPPC/s1600/P.o.20130419_234500.00_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSKE7PvMPDyJc4kUdM_kgdPrbzHMUAcr0kYPHhrGFfTAEz75DGLysGFcftq8TkpN3HBC5IvcuBPcDLXSPqLCJKAK-I6MlTHnW-3oZvIPUqjRfJ7Hnh4R0IN9r3xQanhVdxLQz7BFdvqPPC/s200/P.o.20130419_234500.00_L.tiff" width="162" /></a></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Early development in echinoderm embryos follows a regular
and predictable pattern. The first and second cleavages are equal and
meridional (cut along the animal-vegetal axis of the egg). The third cleavage
is equal and equatorial, i.e. perpendicular to the plane of the first two
divisions, resulting in two tiers of 4 equal-sized cells. The nature of the
fourth cleavage (from 8 to 16 cells) differs between echinoids and asteroids.</span></div>
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<span style="font-family: Georgia, 'Times New Roman', serif;"><br /></span></div>
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<span style="font-family: Georgia, 'Times New Roman', serif;">The first picture shows a side view of a 16-cell stage of
the sea star </span><i style="font-family: Georgia,'Times New Roman',serif;">Pisaster ochraceus </i><span style="font-family: Georgia, 'Times New Roman', serif;">(animal
pole, marked by the two polar bodies, is at about two o’clock). As you can see
here, all cells (12 of 16 are visible in this focal plane) are equal in size.</span></div>
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<span style="font-family: Georgia, 'Times New Roman', serif;"><br /></span></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinOiWNEMKM92p1XALDapHOX1mKAbzOD9QtIMcvtPqjQKHN3Unv6npqpMSymt5rkdtzIzWgELW3YOjAvtppFwjk-JAtrdklPBLv_oV352jwx4d7ZynZpB3nd43wpxWAqvHNNX4E2rL85XlT/s1600/D.e.3pma.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinOiWNEMKM92p1XALDapHOX1mKAbzOD9QtIMcvtPqjQKHN3Unv6npqpMSymt5rkdtzIzWgELW3YOjAvtppFwjk-JAtrdklPBLv_oV352jwx4d7ZynZpB3nd43wpxWAqvHNNX4E2rL85XlT/s200/D.e.3pma.tiff" width="162" /></a></div>
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<span style="font-family: Georgia, 'Times New Roman', serif;">The second picture shows a side view of a 16-celled embryo
of the sand dollar </span><i style="font-family: Georgia,'Times New Roman',serif;">Dendraster excentricus
</i><span style="font-family: Georgia, 'Times New Roman', serif;">(animal pole up). As in most other echinoids, the four cells of the animal
pole tier divided equally and meridionally, producing a tier of eight equal-sized
cells (called mesomeres). Four mesomeres are clearly visible in this focal
plane. The blastomeres of the vegetal tier divided equatorially and unequally
producing four smaller cells at the vegetal pole, called micromeres (two are
visible), and four larger cells called macromeres (two are in focus). The
micromeres of echinoids give rise to the larval skeletogenic cells. In
comparison, asteroids, have no micromeres and no larval skeletal spicules (see a
</span><a href="http://invert-embryo.blogspot.com/2011/05/spicules-or-no-spicules.html" style="font-family: Georgia,'Times New Roman',serif;">post by Nick Hayman</a><span style="font-family: Georgia, 'Times New Roman', serif;">).</span></div>
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<span style="font-family: Georgia, 'Times New Roman', serif;"><br /></span></div>
<div class="MsoNormal">
<span style="font-family: Georgia, 'Times New Roman', serif;">Other differences in early development of the two classes
are also apparent here. In the asteroids</span><i style="font-family: Georgia,'Times New Roman',serif;">, </i><span style="font-family: Georgia, 'Times New Roman', serif;">developing
oocytes in the adult ovary are arrested at prophase I. Meiosis is normally completed
after fertilization (which traps the polar bodies inside the fertilization
envelope). This is why you can see the polar bodies in the top picture. On the
other hand, in echinoids oocytes complete meiosis in the ovary (prior to
fertilization), thus no polar bodies can be seen inside the fertilization envelope. </span></div>
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<o:p></o:p></div>
<!--EndFragment-->Susanna DeBellhttp://www.blogger.com/profile/07275057172378205719noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-12753121523020557472013-05-17T10:28:00.000-07:002013-05-21T21:57:44.889-07:00Development of the nudibranch Janolus fuscus<br />
<div style="font-family: Georgia,"Times New Roman",serif;">
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJXK38ayp5rzdifpv3lz06ptGKk4LqucroQcijWYJ_D-UmW9KuAsB8_8GjczRP8g1XMc3DNIquDqKcUv30xsZO3ATQO5Ok0gyynepysjQxdHMav-45MLDGAqiU_P815XUAMWp-m-bFEKk/s1600/Janolus.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="136" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJXK38ayp5rzdifpv3lz06ptGKk4LqucroQcijWYJ_D-UmW9KuAsB8_8GjczRP8g1XMc3DNIquDqKcUv30xsZO3ATQO5Ok0gyynepysjQxdHMav-45MLDGAqiU_P815XUAMWp-m-bFEKk/s200/Janolus.jpg" width="200" /></a></div>
Nudibranchs are arguably some of the most flamboyant animals of the Pacific coast. <i>Janolus fuscus</i> (shown here), a sub-tidal species that is commonly found on the floating docks in Oregon, is no exception. Surprisingly, it’s brilliant and delicate morphology is a beautiful display of camouflage. <i>Janolus fuscus</i> is remarkably difficult to spot when it is on its primary food source, the bryzoan <i>Bugula pacifica</i>. Its distinctly lined cerata break up the nudibranch's outline, making the body less conspicuous. Its translucent flesh allows the nudibranch to blend in. The two characteristics seem gaudy until the nudibranch is viewed in it’s native habitat, where they act as a veil. Often, the egg masses of <i>J. fuscus</i> are more visible than the adults. <br />
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Nudibranchs are simultaneous hermaphrodites, so a mature adult can mate with any other mature adult of the species. Nudibranchs deposit eggs in characteristic gelatinous masses. An egg mass of <i>J. fuscus</i> depicted here is a cylindrical, jelly-filled cord with egg capsules <br />
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arranged in a single row, resembling white beads on a string.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbmHSc2FOtEp1yE5hHgzHQugcrMpaz-B-Kf5MQz_rCnW6hlCnoR1p0OWC5ss8BOiUj9ljVf2nYnt1WmeBYtOAz4_awwmPkvF77S4IwonXhYlxpLS99xQ5wUDkPkIcoGywudZl91MnTLr8/s1600/Nudibranch+egg+dissecting.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbmHSc2FOtEp1yE5hHgzHQugcrMpaz-B-Kf5MQz_rCnW6hlCnoR1p0OWC5ss8BOiUj9ljVf2nYnt1WmeBYtOAz4_awwmPkvF77S4IwonXhYlxpLS99xQ5wUDkPkIcoGywudZl91MnTLr8/s200/Nudibranch+egg+dissecting.tiff" width="200" /></a>As you can see, each capsule contains numerous embryos. The embryos undergo spiral cleavage and develop into trochophore larvae at around the forth day after egg deposition. <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjV070OhswnNtP6dTwVPB5zxaW1_DhroVNz_voHrKje1rLdqIWCJCTfVPYzWV4Y9h9QML04yzIbQcELg0fwdPkBb0X8yTW2Rpv0Nc8jtI8RpN69ClHM_xFz03m1u1Vne7aNIu9xHWwwXZvy/s1600/veliger.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjV070OhswnNtP6dTwVPB5zxaW1_DhroVNz_voHrKje1rLdqIWCJCTfVPYzWV4Y9h9QML04yzIbQcELg0fwdPkBb0X8yTW2Rpv0Nc8jtI8RpN69ClHM_xFz03m1u1Vne7aNIu9xHWwwXZvy/s200/veliger.tiff" style="cursor: move;" width="200" /></a>Two days later, the trochophores develop into veligers, with a shell and velum. Veligers hatch after about two weeks of development, and spend about six weeks in the plankton feeding on unicellular algae. Then the larvae settle on a bryzoan (preferably <i>Bugula pacifica</i>) and undergo meta-morphosis to become a juvenile (e.g. loose the shell and become elongated). Unlike the larvae, the juveniles feed on bryzoan lophophores. The juveniles grow into mature adults, all the while camouflaged by the bryzoan upon which they depend.<br />
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M. Wolf. 2012. The reproductive ecology of a northeastern Pacific nudibranch, <i>Janolus fuscus</i>, with an examination of its endoparasitic copepod, <i>Ismaila belciki</i>, Biol. Bull. 222: 137–149.</div>
Anders B. Hansenhttp://www.blogger.com/profile/03958497655520340582noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-61211996205303118252013-05-14T10:22:00.000-07:002013-05-30T16:17:44.270-07:00Egg capsule and larva of the intertidal snail Littorina scutulata<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwIR0JVUVfQd55EO_zNr9YGYiGKLzkn7Rxb00_WaFIrI2R4IZ7xyvnZJlPGAIZZU3r262OP2FfSmVCM-9WIkB3RzrB9MsGefmgS7K8jvcH25W5JvDYfGh_wQmc263-_st6BgN3_QwCuoc/s1600/L_scutulata_adult.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="198" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwIR0JVUVfQd55EO_zNr9YGYiGKLzkn7Rxb00_WaFIrI2R4IZ7xyvnZJlPGAIZZU3r262OP2FfSmVCM-9WIkB3RzrB9MsGefmgS7K8jvcH25W5JvDYfGh_wQmc263-_st6BgN3_QwCuoc/s200/L_scutulata_adult.tiff" width="200" /></a></div>
Pictured here is the adult, egg case, and veliger larva of <i>Littorina scutulata. L. scutulata</i> is a small (up to 1.5 cm shell height) gastropod, common in the mid- to high-intertidal of the west coast of North America (Kozloff and Price 1996, Reid 2007). The shape of the penis, tentacle pattern, and characteristics of the egg capsule distinguish <i>L. scutulata</i> from its co-occurring sister species, <i>L. plena</i>.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_L5UU355Bv2onDRZnb9oeN_395X7NTGo6BvN6y-nidNeIHQUZr2DxObyIA2iyzCmjmPGuDfCChFTSg9rP1ebZG_PE3OKf1u4-N7J2fcRO353duH7yHwnKJfPvsOtOtEV0MCvkF8mNdPM/s1600/image0034.tif" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="156" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_L5UU355Bv2onDRZnb9oeN_395X7NTGo6BvN6y-nidNeIHQUZr2DxObyIA2iyzCmjmPGuDfCChFTSg9rP1ebZG_PE3OKf1u4-N7J2fcRO353duH7yHwnKJfPvsOtOtEV0MCvkF8mNdPM/s200/image0034.tif" width="200" /></a></div>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCFoycemyC0OIFABib7ooyaSOCoy4As8ZdiNhA8CbygvGdk5H4bsTyhUmKXpz11MdaPkg2lKHqJ0bIcsA0ExBSJlcsIEvVCPVESC5Qe0oUls189M-_vxdx5AISnYGbC6QEOqUYSa9LDig/s1600/egg_case_2_cropped.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="191" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCFoycemyC0OIFABib7ooyaSOCoy4As8ZdiNhA8CbygvGdk5H4bsTyhUmKXpz11MdaPkg2lKHqJ0bIcsA0ExBSJlcsIEvVCPVESC5Qe0oUls189M-_vxdx5AISnYGbC6QEOqUYSa9LDig/s200/egg_case_2_cropped.jpg" width="200" /></a><i>L. scutulata</i> females typically lay transparent egg capsules shaped like a stack of two unequally sized disks. The egg capsules of <i>L. plena</i> females look similar, except that the upper and lower disk are equal in diameter (Hohenlohe 2002). The upper picture shows a side view of the <i>L. scutulata</i> egg capsule, in which the distinctive shape is evident. The lower picture focuses on the embryos, each of which develops in its own membrane (Buckland-Nicks <i>et al.</i> 1972). <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtiNp9Y-H9u0FskPoJt35c3qu8-I_g-rEAc6BwAHLcDVuQRIl2liqiUSAfQR73s2rJfzsxPFBXAcW3v-ZCjokzgxsI1-uI_GDGnfsdDXRt2RGSxuSVIMJ29XWjZSx_eBfqmRSz5QxYpV8/s1600/L_scutulata8.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtiNp9Y-H9u0FskPoJt35c3qu8-I_g-rEAc6BwAHLcDVuQRIl2liqiUSAfQR73s2rJfzsxPFBXAcW3v-ZCjokzgxsI1-uI_GDGnfsdDXRt2RGSxuSVIMJ29XWjZSx_eBfqmRSz5QxYpV8/s200/L_scutulata8.jpg" width="185" /></a></div>
The veligers hatch from the egg capsule about a week after egg laying, and measure about 160 micrometers long. They are competent to settle after spending four weeks in the plankton and reaching about 300-360 micrometers in length. The veliger shown here is about 210 microns long. One can see the velum and its two ciliary bands (the more prominent and more anterior prototroch, and the less prominent metatroch). Note also the larva’s paired eyes and statocysts. The statocyst is a balance organ that looks like a round vesicle with a marble inside. <br />
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<br />
Reid, D. 2007. Littorina. In: Intertidal Invertebrates from Central California to Oregon. Carlton, James T. ed. University of California Press. Berkeley and Los Angeles, California. 2007.<br />
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Kozloff, E. N. and Price, L. H. 1996. Phylum Mollusca: Class Gastropoda. In: Marine Invertebrates of the Pacific Northwest. Kozloff, E.N. ed. University of Washington Press. Seattle and London.<br />
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Buckland-Nicks, J., Chia, F-S, and Behrens, S. 1972. Oviposition and development of two intertidal snails, <i>Littorina sitkana</i> and <i>Littorina scutulata</i>. Canadian Journal of Zoology. 51: 359-365<br />
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Hohenlohe, P. A. 2002. Life history of <i>Littorina scutulata</i> and <i>Littorina plena</i>, sibling gastropod species with planktonic larvae. Invertebrate Biology. 12 (1): 25-37.Rose Rimlerhttp://www.blogger.com/profile/00261528155118970273noreply@blogger.com0tag:blogger.com,1999:blog-5072272240813556047.post-24557432179570618362013-05-14T08:33:00.000-07:002013-05-14T08:33:18.740-07:00Filopodia of mesenchymal cells in gastrulating echinoderms<span style="font-family: Georgia, "Times New Roman", serif;">These pictures show gastrulating echinoderm embryos.<span style="mso-spacerun: yes;"> </span>I was fascinated by the role filopodial
processes (small-thread-like-extensions) of mesenchymal cells play during
echinoderm gastrulation. <o:p></o:p></span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhchBUxti7An_sC-rite2u81ux_if1QX31gb8R2X71Az1RSb2kA2v40kMS4D3f05yaz4qpht9R1-pPDHVbtQL7xJDfIktvXahqfgSchYE4dMMMIt_ISBfo-h3I9V1nJWLsNFISXAOc5foI/s1600/20130420_170443.77_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhchBUxti7An_sC-rite2u81ux_if1QX31gb8R2X71Az1RSb2kA2v40kMS4D3f05yaz4qpht9R1-pPDHVbtQL7xJDfIktvXahqfgSchYE4dMMMIt_ISBfo-h3I9V1nJWLsNFISXAOc5foI/s200/20130420_170443.77_L.tiff" width="200" /></a></div>
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<span style="font-family: Georgia, "Times New Roman", serif;">The first two pictures show a 30-hour old gastrula of the sand dollar <span style="font-family: "Calibri Italic","serif";"><span style="font-family: Georgia, "Times New Roman", serif;"><i>Dendraster
excentricus</i></span></span>. During echinoid gastrulation the first cells to enter the
blastocoel (the spatial gel-filled cavity inside the embryo) are called primary
mesenchyme cells. Then, the archenteron (the primary gut) buckles in
(invaginates). Through a series of cell rearrangements called convergence and
extension, the archenteron (a large tube visible here inside the embryo)
elongates and extends towards the roof of the blastocoel. In the meantime the
primary mesenchyme cells form two groups and begin to secrete calcareous larval
spicules (two tri-radiate spicules are visible here on either side of the
archenteron). Approximately two thirds of the way up, a second group of cells
ingress into the blastocoel from the roof of the archenteron.<span style="mso-spacerun: yes;"> </span>This is where the filopodia come in.<o:p></o:p></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_i9vdNNZHt4vq7Lu7ukmymrhNQoQ98BPUVILvJ3ytyVi9JvzuBCfjpV4K31a60fBfqjtBFzd5LC0GEtHitxa0cfg_jIlNylrZqnE613TpfeZz3iEEHUTeB9uSs8z6bog7hNjlugrGpgU/s1600/20130420_170851.67_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_i9vdNNZHt4vq7Lu7ukmymrhNQoQ98BPUVILvJ3ytyVi9JvzuBCfjpV4K31a60fBfqjtBFzd5LC0GEtHitxa0cfg_jIlNylrZqnE613TpfeZz3iEEHUTeB9uSs8z6bog7hNjlugrGpgU/s200/20130420_170851.67_L.tiff" width="200" /></a></div>
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<span style="font-family: Georgia, "Times New Roman", serif;">This image is a close up view of the tip of the archenteron, showing a secondary mesenchyme cell with a long conical projection reaching
toward the roof of the blastocoel. These processes attach to the roof of the
blastocoel and aid in the final extension of the archenteron.<span style="font-family: "Times New Roman","serif"; font-size: 12pt; mso-bidi-font-family: "Times New Roman"; mso-bidi-font-size: 11.0pt; mso-bidi-theme-font: minor-bidi; mso-fareast-font-family: "Times New Roman";"> <o:p></o:p></span></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh60xPFTvmlO2FYDac1FzMWtt8j30HtHGOOtWjI_3Cqeb6r44bxurk2W37a4N4OBqOhjkyjatysvjpNoXuH2HCbtjWVX5iB06HArTJRIkQZeY4IK66liUXVx7OxQI20kIh2GCh-J3C1y6k/s1600/20130422_073819.36_L.tiff" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh60xPFTvmlO2FYDac1FzMWtt8j30HtHGOOtWjI_3Cqeb6r44bxurk2W37a4N4OBqOhjkyjatysvjpNoXuH2HCbtjWVX5iB06HArTJRIkQZeY4IK66liUXVx7OxQI20kIh2GCh-J3C1y6k/s200/20130422_073819.36_L.tiff" width="200" /></a></div>
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<span style="font-family: Georgia, "Times New Roman", serif;">This picture shows a 62 hour old gastrula of
a sea star <span style="font-family: "Calibri Italic","serif";"><span style="font-family: Georgia, "Times New Roman", serif;"><i>Pisaster
ochraceous</i></span>. </span>Asteroids lack the primary mesenchyme cells, so the
mesenchyme cells that ingress at the tip of the archenteron are the only
mesenchyme they have. Note the lack of primary mesenchyme cells in the
blastocoel and the numerous branched filopodia on the mesenchyme cells at the
tip of the archenteron.</span><span style="mso-spacerun: yes;"><span style="font-family: Calibri;"> </span></span><span style="font-family: Calibri;"><o:p></o:p></span></div>
Susan Brushhttp://www.blogger.com/profile/12309371503051112009noreply@blogger.com0