| MadSci Network: Zoology |
Hi Mike,
I hope you didn't make a bet with your pal, because if you did, you have to pay up! Or maybe not. It turns out that the most technically correct answer to the question "Will a seastar regenerate if cut in half?" is, "It depends on the seastar." I realize that's not a very satisfying answer, so let me explain.
Seastars are capable of amazing feats of regeneration. They can replace any part of a lost arm, and some portion of the central disc. In addition to these typical regeneration activities, some stars also reproduce asexually by splitting their bodies into two parts, each of which goes on to become a new star. In fact, there are species of the genus Linckia that routinely cast off an arm, which then regenerates the rest of the body (four arms + disc). These regenerating stars are called "comets" because they look like, well, comets. Here, you can see for yourself:
What Linckia does is what you would do if you could walk up to a door, grab the doorknob, then walk away from the door while leaving your arm attached to the knob. Your arm would grow a whole body (minus one arm, of course) and the main part of your body would simply regrow the missing arm. The net result would be two Mikes where before there was only one.
If you are interested in learning more about regeneration in seastars, this site from the National Museum of Natural History has a good article and photos of some freaky stars. And, of course, a textbook on invertebrate zoology will give you more detailed information. Two that I can recommend are:
Ruppert and Barnes, 1994. Invertebrate Zoology. Saunders
College Publishing
Pearse and Buchsbaum, 1987. Living Invertebrates. Blackwell
Scientific Publications, Inc.
Thanks for the question!
Allison J. Gong
Mad Scientist