We all know how dangerous mating can be in the world of spiders, especially for the males. If he’s not risking his life to get one lucky shot at inseminating the female, he’s “castrating” himself to plug up the female so no further suitors can do the deed. But new research has documented how in one species, it seems that the female is the one getting the raw end of the deal during sex.
In a move to guarantee that he will be the sole father of all offspring, males of the spider Larinia jeskovi mutilate the external parts of the females’ genitalia, preventing her from mating with any other males afterwards. This drastic and direct method is thought to be the first time that males have been observed disfiguring the females’ sex organ after mating. Virgin females have what is called the “scapus,” an odd-shaped blob located above the genitalia. But after breeding, the scientists found this to be missing.
In order to fully understand what actually goes on during mating, the spiders needed to be observed actually having sex. But mating only goes on for a matter of seconds, so to catch them at it, the researchers decided to freeze them in the act, literally. Catching wild specimens, the scientists let them start mating and then blasted them with liquid nitrogen. This allowed them to then take the frozen spiders, still interlocked, and examine what exactly is going on under a micro-CT-scan.
They found that when a male comes in to mate, he grab the scapus to get a good hold of the female and then delivers his sperm using appendages found near his mouth. After he has deposited his seed and dismounts, he twists the scapus off. This means that no male after him can mount the female, ensuring that all the offspring are now his. The paper describing this behavior is published in Current Biology.
But it might not all be doom and gloom for the female, as there could actually be advantages to allowing the male to perform the snip. Female spiders are known to be able to store sperm from the same male for years, and so it might be that she could continue laying eggs for some time to come even though she’s only mated once. It might also mean that because she is now unavailable, she is less likely to be harassed by other males. With 80 species of spider known to have a scapus, the researchers suspect that this behavior might be surprisingly common.
Main image: A spider of the species Larinia minor, similar to the Larinia jeskovi looked at in this study. Carlos De Soto Molinari/Flickr CC BY-NC-ND 2.0