Male Dark Fishing Spider Dies in Gruesome Way After Sex--And Loses 'Genitals' (Video)

Everyone knows that male Black Widow spiders are devoured by their female counterparts. But an even more gruesome fate awaits the dark fishing spider. Immediately after having sex, the male dark fishing spider dies--often after having his genitalia broken off inside the female.

It's actually relatively common for a male to die after mating with a female in the animal world. For example, the anglerfish actually absorbs the male's body into her own after he bites her in a type of weird cannibalism mating act. The praying mantis also sometimes kills a male after mating, biting off his head before consuming the rest of the body. In this case, though, the male dark fishing spider dies in order to give the female essential nutrients--from his own body.

"The act of sperm transfer is triggering this cascade of death," said Steven Schwartz, a behavioral ecologist at the University of Nebraska, in an interview with Wired. "Once that button is pushed, it's lights out."

 Like many spiders, female fishing spiders are much larger than the males. Spanning about three inches across, they're about 14 times heavier than the tiny males. Despite their size difference, though, the females don't actually kill the males during mating; the males just die.

So why is this? The male uses a pedipalp, an appendange-like organ near his mouth, to deposit sperm into the female. Before mating, though, he inflates something called a hematodochal bulb inside the pedipalp. While in most species of spiders this bulb can deflate, it remains permanently inflated in the dark fishing spider. This results in a sudden shift in blood pressure that leaves the male curled up and immobilized--stuck within the female but not dead.

That's when the female jumps in. She usually removes the male and then eats him while his tiny spider heart is still beating. During removal, though, the male's bulb often remains stuck inside the female. This creates the perfect "plug" to prevent other males from mating with her and ensures that the male's sperm will fertilize as many of the females eggs as possible.

Yet even if the female didn't show an interest in eating a male, he'd still die. The researchers removed the mated males from their partners in order to see what would happen. Although blood continued to pump in the male's circulatory system for about three hours after the deed, he still perished.

"Technically they're not dead, but they're on that trajectory and they're not coming back," said Schwartz in an interview with Wired.

On the bright side, at least these spiders get to have sex before they die in a horrific fashion.

The findings are published in the journal Biology Letters.

You can check out the morbid mating practices of this species in the video below, courtesy of YouTube.