FAQ
A contribution of The Cephalopod Page
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Hi, I have read the following curious claim in a book for children (titled '501 Incredible Facts To Boost Your Brainpower', published by Andromeda Oxford Limited, 1996): 'When an octopus becomes upset, it may eat itself.' I have tried to look for more info about this since I simply cannot imagine how an animal may eat itself. This is how I found your excellent Cephalopod Page and I think you might be the person to know details about this self-eating phenomenon, if it really exists at all. So could you please explain to me whether an octopus really can eat itself, and if yes, why and how on earth might this happen? Perhaps they meant that an octopus may eat one of its arms when the arm gets torn off, or something. Or is it just a mistake in the book? But I really don't know why someone would invent such nonsense. Would you please shed some light on this curiosity? Best wishes, Andras Szilagyi, Biophysicist Institute of Enzymology, Hungarian Academy of Sciences |
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| Andras,
Some species of octopuses are able to autotomize their arms. Autotomy is the breaking off of an arm at a specific point. Male Argonauts break off their reproductive arms while mating. (It is common to read that all male octopuses break off their reproductive arm during copulation, this is untrue). Another use for this behavior is as a decoy. The severed arm of an octopus can continue to flash colors, crawl around, etc. and makes a good distraction. For a land example, some lizards can autotomize their tails. You are asking about autophagy, a type of cannibalism where an animal eats part of it self. Yes, this can occur in octopuses and I'm sorry to say that I have observed it myself. The traditional explanation is that this behavior is caused by stress. A few years ago two octopuses were shipped to me and they took 8 days to arrive. Needles to say they were DOA. Both octopuses had eaten some of their arms. I've seen one of my deep-sea octopuses do this shortly after collection (catching an animal in a scallop trawl has got to be stressful!). I've also have had about 1/3 of a group of healthy 3 month old octopuses start doing this and this problem does seem more common in group cultures. Dr. Budelmann, at the University of Texas Medical Branch, believes that an infectious agent affect the octopuses nervous system and causes this behavior. I think it may be caused by any number of factors. So yes, this behavior really does exist. Is it adaptive i.e. does it benefit the animal? I have no idea because I'm not sure of the cause. If it is a virus, for example, the octopus's behavior may be beneficial to the virus at the expense of the octopus. Are octopuses the only animals that do this? No, rats for example, will eat parts of themselves if stressed. Dr. James Wood |