how does female cannibalizing the male fit into darwin evolution theory ?
that evolution should make reproducing less efficient, either the male is dead before he finish reproducing with the female or at least, he is not able to reproduce with other females.
Yet it seems to be working just fine with other species of octopuses where the male get eaten.
With preying mantis and black widow it seemed, as their names suggest, very common for the female to eat the male after being boinked. However, it turns out that in the lab setting with a small closed environment, probably lots of lights and weird sounds, the female was freaked out, which led to her getting the first meal she could find, that being the male. In the wild, it does happen but as a last resort if food is scarce.
The orb spider figured out a hack: he ejects his member in to her after sex which keeps inseminating her from that point forward. Sure he dies, but he reproduces from beyond the grave!
Wow obvious good point. Even if it was "preying mantis", plenty of creatures prey on prey without coital cannibalism. Other spiders, insects, and even snakes do similar but lack the name to warn the male of his danger.
What if one specific mutation of orb spider is really nice but he was killed and its "member" is in a single female orb spider limiting the greatness of a good mutation I suppose which can feel counter to evolution to me I suppose.
> What if one specific mutation of orb spider is really nice but he was killed and its "member" is in a single female orb spider limiting the greatness of a good mutation
That's a very soft limit; a spider lays dozens (hundreds?) of eggs after mating once. Mortality is extremely high, so there's tons of room for "really nice" mutations to spread quickly.
It's important to say that evolution isn't versioned, and what we're observing isn't finished. We may be looking at an evolutionary dead-end. Which is to say that if eating the male is an evolutionary development, it might a poor one.
There is no logic to evolution. No decisions are being made. Evolution is reactive, and the surviving lineages may only be responding effectively to some of the external forces. Evolution doesn't happen at a species level, it happens at the individual level and has downstream effects on the species.
We're seeing evolution in action. Tragically, we (individually) won't be around long enough to observe the changes in another 100 or 200 or 1000 generations.
THIS. The life expectancy of an octopus is extremely low - https://en.wikipedia.org/wiki/Octopus#Lifespan - and they're all-in on the "extreme number of offspring, microscopic survival rate" strategy. So for a male - it's a fairly reasonable tactic to end up as a big, nourishing meal for the female that will go all-in on producing the eggs of your decedents.
Presumably the female acquires calories with which to grow her brood.
"Unable to reproduce with other females" is probably relevant. The relative size of different genders has a lot to do with if a species is polygamous or monogamous. Larger males the former and larger females the latter.
Yes, although the fact that the male has evolved this venomous defense seems to indicate that benefit of maintaining diversity in the gene pool (maybe good genes even, if he had to compete to mate) might outweigh the benefit of being a quick snack for a post-coital hungry female.
The effect of natural selection is that the genes that propagate most are the ones that maximize the probability of that gene appearing future generations. There is no direct evolutionary pressure for an individual to behave in ways that benefit the species in general.
Yes, because there is no concept of "species" in nature, species is an arbitrary grouping we humans apply to the individuals and genetic lines that are actually involved in natural selection.
The female's genes are most likely to get passed down many generations if the males she mates with have genes that enable her male children to survive long enough to reproduce. Once a species gets into a state where females make a habit of eating the males during copulation, it can't readily evolve out of that state, because a female that is less aggressive will mate with males who can't succeed at mating with other females, leading to that line dying out. Sexual cannibalism is a local maximum.
So if at any point in the past there were evolutionary pressure that made cannibalism beneficial to the genes, we would expect to see it stick around until there's sufficient pressure against cannibalism to allow selection away from that local maximum.
> "a female that is less aggressive will mate with males who can't succeed at mating with other females"
That premise is the fundamental point that your argument hinges on and I see no reason to just assume it would be true, and can create plenty of plausible arguments (that I think are fairly self evident) for why it would be untrue.
But that is true regardless of whether a male is fit enough to survive a cannibalistic female, which means that pacifist females do not have an advantage in natural selection:
As long as there are enough males in circulation that can succeed in fertilizing before being eaten, then there's no pressure on females to drop the cannibalistic strategy. Any male that cannot win the cannibalism game can only fertilize pacifist females, but a male that can win the cannibalism game has genes that can be passed on to both cannibalistic and pacifist females. So the genes of cannibalistic females have broader reach within a species that has already gotten to majority-cannibalistic because her male offspring can fertilize both types of female rather than just one type.
Again, to GP's point, just because non-cannibalism would be more beneficial to the species as a whole doesn't mean that evolutionary pressure on individual genetic lines will select away from it. The individual line is often better off being selfish and selecting the strategy that gives them the broadest possible range of propagation (hence Richard Dawkins' title, The Selfish Gene), which in this case is cannibalism.
> either the male is dead before he finish reproducing with the female or at least, he is not able to reproduce with other females
In addition to the sibling comment's caveats, it's worth mentioning that the latter might actually be an advantage? If the male is able to continue reproducing with an unbounded number of females, and the females are limited by how often they can lay eggs (or how quickly they can after copulation), a mutation that causes females to prevent males from reproducing with other females could potentially drown out the ability of females without those mutations to reproduce (e.g. if those females were able to copulate with most males first, they'd be the only ones to produce offspring, and there could even be other adaptions or mutations that aid them in the "first to copulate" race).
that evolution should make reproducing less efficient, either the male is dead before he finish reproducing with the female or at least, he is not able to reproduce with other females.
Yet it seems to be working just fine with other species of octopuses where the male get eaten.