The male dark fishing spider has a strange sense of romance; after choosing a mating partner, he will allow the female spider to mutilate his genitalia and then eat him.
The male dark fishing spider willingly sacrifices himself to ensure the health of his offspring, according to a study published recently in Biology Letters. The event is called monogyny, and scientists think this sexual cannibalism may provide an advantage. Researchers say a better-fed female will produce healthier offspring.
"It's almost like an extreme nuptial gift," study leader Steven K. Schwartz, a behavioral ecologist at the University of Nebraska-Lincoln, told National Geographic. "He is donating his body. That allows her to produce more offspring or better offspring."
Male fishing spiders will mate with any female, but they tend to prefer virgins. According to the study, females who mate with "only one male will bear only his offspring, thus eliminating any competition."
The cannibalism is not the only matting issue this particular breed of spiders face. According to National Geographic, the male spiders reportedly can die before mating "if they prematurely trigger one of their pedipalps, two feeler-like appendages near the mouth where sperm is stored. "
"It's a one-shot deal, and it triggers a cascade," said Schwartz, who's been studying the mating habits of the dark fishing spider for years, capturing wild specimens and then bringing them into the lab for tests. "There have been a few times I've been handling males, and their pedipalp got caught on some cotton, and they died."
Even if the male spiders manage to make it to a female with sperm intact, that doesn't mean she won't eat him before they mate. Males must reportedly engage in about 1.5 hours of abdomen jiggling and light caresses or the female will devour him.
"It's like a game," Schwartz told National Geographic. "If he doesn't behave properly, and just starts running around, the female will usually just jump."
If he manages to successfully "woos" the female into letting him the insert one of his pedipalps into her, he will release his sperm and die.
However, the male does not die instantly, as his heart can continue to beat for two hours. For the last moments of his life he will lie immobile and helpless.
Females take this opportunity to squirt out digestive enzymes onto the male for her consumption. This creates a "sloshy milkshake, and that's what gets sucked in," Schwartz said.
Read the full story on National Geographic's website here.
