Tuesday, April 19, 2011

Regeneration in bipinnaria

The top picture on the left shows a bipinnaria larva of the starfish Pisaster ochraceus. One interesting characteristic of this organism, and the starfish in general, is its ability to regenerate missing body parts both as a larva and as an adult. I read that bisected starfish larvae have been observed to regenerate to form complete larvae within 12-14 days (Vickery and McClintock, 1998). I wanted to see it myself, so on April 13, 2011 I surgically bisected several bipinnarias across the middle, separating the anterior from the posterior portion. The two bottom pictures show the divorced anterior and posterior portions of the bisected larva. I took these pictures within 5 minutes of the surgery. If you look closely you can already see that each fragment is closing the wound! Amazing!

Cutting the larvae was difficult, because these bipinnarias keep swimming around. In addition to tracking and anticipating their movements, I had to be careful not to break the tip of the glass needle I used to make a cut. I pulled pipettes using a Sutter Micropipette Puller. They are so sharp, their ends so miniscule, that they cannot be seen with the naked eye. I broke 5 needles while cutting 15 individuals!

Finally, towards the end of the procedure, I started to get the hang of trapping the larva and cutting it without poking myself or breaking the needle! After the bisection, the two pieces of the larva swam away as if nothing had happened! I will follow the regeneration of these larvae, taking pictures as they develop.  I hope to witness organogenesis, the formation of organs, until the larvae are complete once again!

Vickery, MS and McClintock, JB. 1998. Regeneration in metazoan larvae. Nature. 394: 140

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