Pseudocyphonautes of Flustrellidra

These pictures are of the bryozoan Flustrellidra coniculata and its pseudocyphonautes larva. The pseudocyphonautes resembles the planktotrophic cyphonautes larva of some bryozoans in that it has a bivalve shell. But it is lecithotrophic (non-feeding) and is brooded. The top picture shows the bean-shaped pseudocyphonautes larva using a dark-field technique. One can distinguish the cilia of the corona ciliata along one edge of the larva. One can also see a ridge on the opposite side which corresponds to the shell margin. The clear outer coating is the shell that protects the larva’s interior structures.

The middle picture shows a small section of the colony (with zooid lophophores retracted). The three white oval shapes out of focus are the larvae which I have dissected. Just beneath the surface of the colony one can see a few yellowish-white masses. These are the ovicells, specialized zooids for brooding eggs and larvae. I extracted the pseudocyphonautes larvae by puncturing the ovicells with a pair of fine forceps and squeezing gently to push them through the hole.

The bottom picture shows a complete Flustrellidra colony, with my palm for scale. This is the largest upright bryozoan colony I have ever seen. It does not look like a bryozoan at all. In the field I would have easily mistook this animal for some sort of alga or a sponge!