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Why the male dies after mating?

xarvh

Pygmy Octopus
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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?
 

DWhatley

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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
 

xarvh

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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.
 

monty

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

Females invariably become emaciated and die soon after hatching occurs. Males also die at about the same age, due to the same physical degradation as females: hormonally induced muscle catabolism, high amino acid levels in the blood, and consequent high metabolic rate (O'Dor & Wells 1978).

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.
 

DWhatley

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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.
 

xarvh

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monty;79998 said:
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.

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.
 

Architeuthoceras

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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?
 

xarvh

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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.
 

Nancy

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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
 

xarvh

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Nancy;80017 said:
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
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.
 

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