Dammit Jim!

Spiders males are often cannibalized by their mates after sex. Spiders have two penis-like organs, called pedipalps, which usually break during sex meaning male spiders can only have sex twice. I wasn’t going to write about anymore spider sex but I came across a couple articles about the adaptations that can occur since males with no remaining pedipalps males are evolutionary useless. Often females help their mates find purpose by using the male as dinner. Scientists had thought that this was an example of competition between the sexes with the large female taking advantage of the undersized male (like the picture to the left). Sort of a male spiders are from Mars, female spiders are from Cannibal World Centauri 6. But in 1996 M. C. B. Andrade noticed that males of the redback spider actually perform a difficult somersault maneuver just to position their bodies in prime eating position (her video).

While I am in danger of feeding my reputation as sexually fixated, I did want to put up one more post about weird mating systems before moving onto other non-sexual types of biology. I was taking a quick look at the literature after the post about spider genital breakage and came across an interesting paper on mating in queenless ants (Dinoponera quadriceps). These ants are really interesting in and of themselves and I think I’ll write more about them later. But for now, they have a pretty curious way of mating that manages to one-up the spiders.

I was browsing journals the other day trying to figure out where to send a paper when I came across a paper called Genital damage in the orb-web spider increases paternity success. I guess I have a weird sense of curiosity because I had to take a look and see what they were talking about.

When females of a species mate with several males, evolution can develop some pretty weird adaptations in males competing to fertilize the egg. More numerous, faster or cooperative sperm can improve the chances of their sperm reaching the egg first. Another alternative is to try to prevent other males from mating with that female.

As a way to interfere with other males, many species develop sticky semen to form copulatory plugs blocking other sperm access to the egg. I had heard of this before but what I didn’t know was that some insects have taken this method to an extreme and actually leaves pieces of their genitals behind in the female. These pieces had been shown to protect the males’ sperm against competition by blocking rivals from mating with the female. Similar genital breakage had been observed in spiders but since spider females like to eat their mates and males have two penis-like organs, called pedipalps, scientists debated whether a spider sacrificing one of his genitalia could be a sort of quick release to allow the males to live another day and mate again.