Cephalopodcast

Pucker and Bloat #3, Nerviscerate. © Jason Robertshaw

Whatever side you take in the Invertebrate Wars, both contenders have some interesting defense strategies. On the one side, many octopus and other cephalopods have the ability to eject an ink cloud to confuse their would-be predators (this should technically be coming out of Pucker’s funnel). I’ve also heard some researchers suggest that the volume and shape of the ink cloud is meant to mimic the departing cephalopod. Maybe it smells like the cephalopod too, thereby overwhelming two senses.

Sea cucumbers take a much different strategy. When they are disturbed, they can extrude sticky filaments called cuvierian tubules. It’s a rather extreme defense mechanism that requires the sea cucumber to tear a hole in its gut and expel the filaments through the new opening. You can see a short video of the process here. I am somewhat ambivalent about linking to it, since it demonstrates some rather poor behavior on the part of the divers. In fact, in the tradition of coining new Internet eponyms, I want to propose a new one for this occasion. When someone harasses marine life and it turns around to bite them in the arse (or hand, or nose or foot), that person has been MacPhersoned (with apologies to Rick, but he has a knack for pointing out these occurrences). It’s just too bad this sea cucumber can’t MacPherson these divers severely. And if the sea cucumber gets really stressed, it may even eject some of its internal organs as well. I’ve never seen that happen myself, but here’s a picture of what it looks like. Fortunately, the little bloaters are resilient and can rapidly regenerate this lost tissue. Indeed, I’ve read that they might do this intentionally as a way of clearing their system of parasites.

• TONMO: What Is Octopus Ink?
• Integrative and Comparative Biology: Biomechanics of Adhesion in Sea Cucumber Cuvierian Tubules (Echinodermata, Holothuroidea)
• pierre pouliquin: Le concombre et le crabe 1/7. A Flickr photoseries showing a sea cucumber versus a crab.
• hollyoeding: When pestered the sea cucmber spills her guts. This is a knitting project. No actual cukes were harmed in its making.

Next week: More carap about sea cucumbers