Why the male dies after mating?

Discussion in 'Physiology and Biology' started by xarvh, Sep 24, 2006.

  1. xarvh

    xarvh Pygmy Octopus Registered

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    I've been looking around the net a lot and searched the forum, but i could not find any complete explanation.

    My understanding of mating is that the male injects sperm with the penis into his hectocotylius and then uses the hectocotylius to put the sperm "inside the female" (directly inside the gonads? or if it is stored, how is this achieved and how the fertilization occours afterwards?)

    In the process, the hectocotylius may rupture and remain inside the female (or does this happen only to other cephalopods?)

    The question is double:
    1. what actually causes the male to die after the mating?
    This seems particularly strange to me because i've read (http://en.wikipedia.org/wiki/Octopus#Physiology) they can survive months after mating.

    2. Does this death give any reproductive advantage?
    In the female case, this is clear, yet i can't get what's worth the sacrifice of a healthy male that i would expect being able to mate again.
    If this is just a flaw, i would have expected evolution to fix this disadvantage in a quite ancent, successful, varied and spreaded group.

    Any clues?
     
  2. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    I am new to octopuses and have been pondering the question about mating and dieing as well. I find it even stranger that the spider, another 8 legged creature is also programmed to die after reproducing. The one thing that seems obvious in light of their superior intelligence is that octopuses would rule the sea if their genetic code didn't keep their lives short. Curious
     
  3. xarvh

    xarvh Pygmy Octopus Registered

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    The matter is a bit different.
    As far as i know the male spider dies only if killed by the female, and when this occours the male has anyway the advantage of indirectly feeding the eggs.
    On the contrary, the male octopus may survive for months after mating and i read nowhere about him being consumed by her or partecipating in any way to the breeding.
     
  4. monty

    monty Colossal Squid Staff Member Supporter

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    From Hanlon & Messenger p.110 (regarding octopuses):

    So it sounds like they're programmed to die off as their progeny hatches. I seem to remember reading somewhere that there is a particular lobe of the brain, which, if removed, will cause the animal to neither reach sexual maturity nor this programmed mortality. Unfortunately, I don't remember the details.
     
  5. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    Spider & octopus

    Actually, I was thinking about the female spider that dies in the fall after laying eggs. I think, but am not sure, that it is only the black widow that eats her mate. However, after some reading spider longevity varies considerably but it is notable that in some species the male dies shortly after reaching sexual maturity but the female lives years longer. The variation between spiders is so diverse, however, that a comparison really can't be drawn.
     
  6. xarvh

    xarvh Pygmy Octopus Registered

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    That's quite impressive, thanks!
    Programmed death does not seem a great advantage for the male...

    According to this:
    http://www.oum.ox.ac.uk/thezone/fossils/history/jurass01.htm
    octopuses appeared in the Cretaceous, that's at least 65M years ago.
    It's really weird that evolution didn't fix it in so much time.
    I guess that's such an intrinsic feature of coleoidea that it cannot be discarded easily.
     
  7. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    Both male and female Salmon die after spawning. Is there some kind of evolutionary advantage to this? To other animals it means more food but to the offspring?
     
  8. xarvh

    xarvh Pygmy Octopus Registered

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    Indeed.
    But they both die for the effort of reaching a convenient location for their offspring: they use up all their resources for the reproduction, just as the female octopus does.
    They cannot recover from such a straining process.

    The male octopus can live for months after the reproduction, so my guess is that for him the reproduction is not that straining: he is still able to recover.
    After mating he has no more role whatsoever in the breeding
    Since the reproduction process is not that straining for him, he could mate again.

    Not sure if i've been clear.
     
  9. Nancy

    Nancy Titanites Staff Member Moderator

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    I'm not sure that the old view that all female octos become emaciated and die right after the eggs hatch is still valid. I can't point you to an article, but I have heard of research on some species living on after reproduction.

    Even in the case of octos kept by our TONMO members, some refused food, and others continued to eat. I don't think we've had any females live more than 3 weeks after their eggs hatched, but this isn't something I've been tracking.

    Nancy
     
  10. xarvh

    xarvh Pygmy Octopus Registered

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    And what about the guys?

    Anyway, that's interesting: i'm no biologist, but i would say that the females are programmed to die as well: this may partly explain a faulty male biology.
    Entering the field of wild speculations, i'd wonder if this "programming" helps the female to perform the best during egg breeding, not unlike doped athletes that give the best for a short period but leave it completely ruined.

    Should you stumble again on those articles you mentioned, i'd love to read them.
     
  11. Nancy

    Nancy Titanites Staff Member Moderator

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    The males kept by Tonmo members have suffered a quick decline at the end of their lives (senility) and died within a few days.

    Nancy
     
  12. sobhi

    sobhi Larval Mass Registered

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    Male mating and life span

    In octopods, the male doesn't necessarily doesn't die after mating. The male simply enters senescence toward the end of its life span, and dies finally. It can mate almost till the middle or end of senescence. The female on the other hand, usually dies after spawning, since after all octopods are terminal spawners.

    As for spiders, males don't die after mating unless eaten or injured by the female. So they can continue onto mating with more females. However, in some species (like the redback I believe? The exact species' name escapes me now) the male is programmed to execute a 180 degree flip such that it lands between the jaws of the female. This ensures certain and painful death for the male, but it also almost always ensures that this male's sperm get to inseminate the eggs of this female etc etc.

    Hope this helps!
    Sobhi
    UT Austin - Marine Science Institute
     
  13. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    ... although not a question of yours (in the first post), this account of sperm(atophore) transfer isn't quite correct.
    The spermatophores are discharged from the male 'boy bit' into his mantle cavity, where they most likely travel down the side of his viscera and are directed to his funnel; he directs the funnel to the base of his third left or right arm, depending on which is hectocotylised in the species concerned; from here the spermatophores travel down a well-developed, quite deeply excavated (in many species) groove (spermatophoral groove) that extends the length of the hectocotylised arm, to the terminal structures, the calamus and ligula (these (most likely) play a role in insertion of spermatophores into the female).

    There is no 'injecting of sperm into the hectocotylus', strictly speaking; it all occurs outside the hectocotylus, along this spermatophoral groove.

    The only 'rupturing' of the hectocotylus that I am aware of occurs in a group of similar-looking pelagic species, the likes of Argonauta, Ocythoe, Tremoctopus and Haliphron (=Alloposus). It will not occur in benthic octopuses the likes of which you will be more familiar.
     
  14. Neogonodactylus

    Neogonodactylus Haliphron Atlanticus Staff Member Moderator

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    Don't fall into the trap of considering that an octopus is an octopus. There is quite a bit of variation in senescence across species and between males and females. A few deep water species and others such as O. chierchiae lay multiple clutchs (not much known about the males). In other species males appear to have some programmed senescence, but that may interact with age and size. Very little is known about the interaction between mating activity and death in any species. In blue-rings, we have mated males daily to several different females and they certainly did not drop dead. WIth more controlled experiements, we hope to clarify this a bit more.

    Roy
     
  15. monty

    monty Colossal Squid Staff Member Supporter

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    In some animals, programmed death is believed to free up resources for the offspring... if there is no parental support of the offspring, it may be more beneficial to the survival of the little ones not to have their parents around taking up food or whatever. It's not obvious to me that this applies in most modern ceph lifestyles, but perhaps there were environmental conditions that led to this being important at some early point in ceph history, and it became so engrained in the genetics that it's been conserved.
     
  16. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    This thread had started me wondering how many animals with the level of intelligence of the octopus naturally lives for such a short time. Does any one know of a good search engine for scientific research? The most popular produce more revenue sites than informational any more.
     
  17. monty

    monty Colossal Squid Staff Member Supporter

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    scholar.google.com is one of the better hardcore academic ones, but frequently points you at papers that you (or your school) have to have a paid subscription to read. Cephbase has a lot of articles on cephs specificially, too. There are a number that universities can subscribe to, but I'm not sure which ones are available to the public. There's not much gray area between "completely pop culture web" and "only academic, peer-reviewed papers," though, so I frequently find I have to look through all the junk in a broad google search to find things that are intelligent yet comprehensible to people without years of learning obscure terminology.
     
  18. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    Thanks, I "bookmarked" it. and did a quick search to see what kind of references it gave. I am glad Google is experimenting this way but their revenue generation stream may not get it past beta. I will be glad when online books are mainstream. I don't mind paying for information I want but I do mind paying just to see if an article contains information I need.
     
  19. main_board

    main_board Vampyroteuthis Supporter

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    Monty touched on this. To spawn, salmon migrate to rivers and streams that aren't exactly rich in food for the fry. By dying, the adults provide an initial food resource for the fry (and the surronding community). I don't mean to say that the fry hatch and start to pick at the dead bodies of their parents (I think hatching takes too long anyways), but I mean the decomposing salmon provide the starting point of a food web that will produce suitable food for the fry.

    Now in octopus, as it has been stated, there is a lot of grey area. I remember watching a documentary on GPO where the female denned up, failed to eat for months, and as a result died just around the hatching time for her brood. It was claimed that her death also provided an early food source for her brood, I'm not sure if directly or indirectly (as in the salmon example). Not all octopus act this way.

    Clearly, there are advantages to dying as an adult.

    The reason (or so I have read once) female octopus' die after laying eggs is that they generally don't eat while brooding. As a result, to sustain them selves (in some cases over months!) their body systematically digests itself, starting at the least important tissues. By the time the brood hatches, the female is beyond recuperation.

    Cheers!
     
  20. DHyslop

    DHyslop Architeuthis Supporter

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    Occasionally--in O. bimaculoides at least--the brooding female can even resort to eating a festoon of her own eggs. I suppose its worth it if it keeps her alive until the rest of the eggs hatch without having to leave to hunt.

    Dan
     

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