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Stomatopod Log Entry: Comparing Stomatopods to Cephalopods (Nov 16, 2000)

Contributor: Dr. Roy Caldwell

A few years ago at the meeting I gave a talk comparing the behavior of octopuses and stomatopods. I had a check sheet of about 25 characters where I compared them. Not surprisingly, the stomatopods came out way on top. Learning studies on stomatopods is roughly like training pigs - they are bright but never want to do what you want them to. If you use positive reward such as food, they quickly autoshape and start trying to eat the stimulus. If you punish them, they either refuse to play or attack.

The studies that Marshall and I have done show the ability to distinguish colors, polarization patterns, and shape. (My very first study was to train a stomatopod to distinguish between a right side up and up side down equilateral triangle.) We have also observed them learn to open unfamiliar shell morphologies and change the size of prey taken depending on the risk of foraging. Then there are the learning to recognize other individuals studies. Within the constraints of being able to manipulate objects, they appear to be able to do everything that large octopus can and then some. Memory wise, the longest ability to discriminate between two individuals I have documented is a month. I think that is similar to octopus.

Hemisquilla ensigera by Phillip Hookham

As for fights between octopus and stomatopods, it is hard to predict. Hall has some great footage of a Hemisquilla beating the hell out of an octopus. The stomatopod was smart enough to come out of its burrow and launch a swimming attack. Trapped in a burrow or cavity, bet on the octopus. One story to make a point. When I got my first blue-ring, I paid way too much for it and was trying to get all of the neat photos that I could. I decided that a picture of it capturing and eating a stomatopod would be nice. I posed the octopus and released into the tank a mantis shrimp that I thought would make a nice meal. The mantis shrimp looked at the octopus and launched a preemptive strike, stabbing the blue-ring right between the eyes killing it instantly. Most tropical octopus do very well catching and subduing stomatopods, but not always. I'm not sure I mentioned this before, but one of the things that we have been working on is stomatopods killing and eating blue-rings. The TTX (editor's note: a potent neurotoxin called tetradotoxin used by blue rings to capture and subdue prey),doesn't seem to faze them.

In general, squillids don't have much of a chance against cephalopods and are usually dead meat. However, against a large smasher - in the open - bet on the stomatopod.


 

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