Why the male dies after mating?

[xarvh]

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 (Octopus - Wikipedia) 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]

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]

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]

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]

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]

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:
Home
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]

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]

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]

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]

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.

 

[Nancy]

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

 

[sobhi]

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

 

[Steve O'Shea]

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?)

... 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.

 

[Neogonodactylus]

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

 

[monty]

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.