Wednesday, October 12, 2005

Arachnids faking it during sex

I've always had a fascination with the way that spiders decide to mate with one another. Being heavily armed predators by having webs, a bad temper and a nasty bite, mating is a very dicey affair at the best of times. Male spiders pretty much face an up-hill battle as the female is usually bigger, meaner and hungrier than he is. Worse, many species of spiders are almost blind or their eyesight isn't the best meaning males have an even harder time. This has resulted in males often having odd mating behaviours or very elaborate dances so that they avoid being eaten.

A recent paper published online in Biology Letters discusses the mating behaviour of Pisaura mirabilis males. These spiders use a strategy where the male attempts to distract the female by giving her a 'nupital gift', which consists of an insect he's caught and wrapped up in silk. While she dines on his gift, he sneaks in to mate and then gets away as quick as he can. Unfortunately, this strategy doesn't always work and instead of going for the tasty gift, she decides the male would be a more tasty snack!

The clever male however has a devious way of getting around this problem, he falls into thanatosis (plays dead) putting her attention back on the gift and not him. When she moves on to dine on the snack, he slowly gets up and proceeds to sneak in a mating while she isn't paying attention. This strategy works remarkably well as most males succeed in mating by doing this. Of course, the male sacrifices any form of defence he may have previously had and is more open to being cannabalised than he was originally. Additionally, the male also doesn't get as long to mate with his rather bossy mate as one who succeeds in the original courting.

Interestingly, playing dead is a relatively uncommon strategy among spiders and many other invertebrates as well. This is probably due to the large amount of risk that is involved, particularly as it does leave the male utterly defenseless and with some predatory insects it might not be overly much of a defence (female would attack anyway). Overall, it's yet another file to add in the kinky sex files of spiders.

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Quite cute! (Picture found here, which also has pictures of other spiders as well. The site is in German though).