1. dick says

    Somehow they maintain a little dignity in dying.

    That’s more than could be said for many people, at the ends of their lives. Thanks to stupid laws influenced by religious belief.

  2. F.O. says

    What is the evolutionary pressure that makes (most) cephalopods die after they spawn?
    Is the competition among adults really so fierce that if they don’t die then the new generation won’t be able to mature?
    I feel I’m missing something.

  3. Anton Mates says


    It’s not generally thought that the dying part is particularly adaptive for cephalopods and other semelparous organisms; they only die because they’ve committed every last ounce of effort to reproduction and offspring care, and there’s nothing left for survival. Their bodies aren’t even bothering to heal wounds and so forth.

    There are various models and explanations for semelparity, but the general idea is that these species benefit from producing and rearing as many offspring as they can, as quickly as they can, when they reach maturity. AFAIK, two of the life history factors that favor this strategy are rapid maturation of juveniles, and high adult mortality compared to juvenile mortality.

    Suppose you can either raise six offspring this year, take a break to recover, and then raise six offspring next year–or you can work yourself to death raising nine offspring right now. If adult mortality is high, then you probably won’t be around to reproduce next year anyway. And if your offspring mature quickly, then any extra kids from this year will already be having kids of their own next year, probably passing on more of your genes than you could have passed on yourself, even if you did survive to breed again. So natural selection favors the work-yourself-to-death option in this case.

    If you’ve heard of r-selected and K-selected species, semelparity is an extreme example of an r-selected trait.

  4. F.O. says

    Thanks Anton Mates, very clear explanation. =D
    No, I haven’t heard of K or r selection and I will be checking it presently.