More likely, it's that they have a tendency to die shortly after mating. There's a lot of debate on the matter, and the reasons aren't fully understood, but in a large portion of octopus species, mating is usually followed soon after by death.
Also, they don't mate for life. That bit was a lie. Even though they die not terribly long after mating, most species are not monogamous and will mate with multiple partners that are deemed 'fit' before they kick the bucket.
The most logical reason for them dying shortly after mating is that they reach sexual maturity very close to the end of their natural lifespan. Basically, that they hit puberty in September and have died of old age by New Year's. And in some species, that's probably it almost literally, since some species only live for around six months. That said, some species can live for up to five years. That's still a remarkably short lifespan for such an intelligent animal, but it's still 10x better than six months.
For the females, there's another perfectly good reason why they often die shortly after mating, or more accurately after laying their eggs. Octopus moms are fiercely devoted. They're aggressive towards anything coming near their eggs and they never leave the eggs unguarded. And they don't eat while they're guarding the eggs. Like the male emperor penguin, most female octopuses will stand guard over their eggs and slowly starve. Unlike the male emperor penguin though, the octopus doesn't have a reserve of fat which they use to make it through the time until the eggs hatch. They just flat-out starve, while their body slowly consumes itself. By the time the eggs hatch, the starved female's body is so wasted away that even if she did start eating again, she would still likely die. The thing is, they usually don't start eating again after the eggs hatch, they basically give up on eating.
Now, there's a reason that covers both of those options, and it's outlined in a 1978 paper entitled Antigen-induced secretion in the optic gland of Octopus Vulgaris (the Common Octopus), written by D. Froesch. Unfortunately, I can't find a free copy of the article online, so I'll have to hope that Wikipedia's summary is accurate. Basically, the optic glands (which doesn't seem to have anything to do with vision, unless I'm misunderstanding the abstracts of the article) controls sexual development, appetite and senescence (old age). Once the optic glands have triggered the hormones for sexual maturity, it stops sending out the normal level of appetite controlling hormones, so the female stops feeling hungry. At a set time after mating, namely a time closely connected to the time it takes for the eggs to hatch, the optic glands start releasing the hormones related to dying of old age, which causes the animal to die shortly after. If the optic glands are removed after the eggs are laid, the octopus won't die of old age, but it will still eventually starve to death.
I should point out, once more just for clarity, not all octopuses die shortly after mating, but it is a species to species thing. It's not like the male gets off any easier than the female of any given species. If the female dies shortly after the eggs hatch, the males generally don't survive much beyond mating. If the male survives until another breeding season, generally the females do as well (assuming they don't get eaten while still weak after emerging from hatching the eggs).
In the world of many octopuses, like in 1980's slasher movies, having sex means you're going to die.
To lighten the mood from this sex = death, I present to you a funny little French animated short, entitled Oktapodi (2009 Oscar nominee for best animated short film).
Sources:
ScienceDaily.com article on octopus mating habits
Wikipedia article on the Octopus
TONMO.com forum thread concerning octopus death after mating
JSTOR preview of D. Froesch's article
Official site for Oktapodi
No comments:
Post a Comment