Cannibalism: Male spider flees after mating to avoid being eaten by female

When a small spider species mates, one partner needs a special move to survive the encounter.

Philoponella prominens are social spiders, meaning they live in groups, but right after mating, the male arachnid needs to jump quickly to avoid being eaten by his mate, new research shows.

The tiny spiders live in communities of up to 215 arachnids and build connecting webs, according to a study published in the journal Current Biology.

They make their homes in the forests of central China in places like Hubei, Hunan and Jiangxi provinces, according to study author Shichang Zhang, an associate professor at Hubei University in China.

Other spider species, such as the redback, practice sexual cannibalism, but this is the first report of a spider species using super-fast actions to escape being eaten by its partners.

The team analyzed 155 successful matings in a laboratory setting. In 152 of the matings, the male spiders were able to jump to safety, while the three male spiders that didn’t were eaten by their mates.

“Hazard detection capability is low, either they were exhausted during mating, or they just couldn’t make the jump,” Zhang said of the three spiders that didn’t jump to safety.

Using a high-speed camera to capture the acrobatic movements, the scientists determined that male spiders pressed their front legs against females, then pushed rapidly to release hydraulic pressure, and reached speeds of up to 88 centimeters per second to escape.

Arachnids can also spin up to 469 revolutions per second while jumping to avoid sexual cannibalism, according to the study.

“I think it’s mainly to escape the female, catapulting (jumping) and spinning makes it difficult for the females to catch her,” Zhang said.

If the researchers removed one or both of their front legs, male spiders courted potential mates but made no attempts to mate, meaning both legs were needed for successful mating, the study found.

When Zhang’s team prevented some male spiders from being able to catapult away, all of these spiders were eaten by their mates, which led the researchers to believe that jumping was a necessary survival skill.

Female spiders select sperm

Mating is terminated by the female spider, and once the male partner senses his counterpart’s aggression, it jumps to safety, Zhang said.

It’s not known why female Philoponella prominens try to eat male spiders after mating, but it could be a test of sexual selection to assess whether males are worthy reproductive partners, Zhang said.

Unlike mammals, a female spider has a sac in her reproductive tract called the spermatheca that contains the sperm and prevents it from finding an egg. After the male injects the sperm into her body, she keeps it there until she determines whether to use it, Zhang said.

If she wants to use it, she squeezes sperm from her spermatheca to fertilize her egg, he said. If she doesn’t want to, she can squeeze the sperm out of her body or change the spermatheca’s pH level to kill the sperm, Zhang added.

“Female can accept sperm from the male that she can catapult, but deplete sperm from the male that can easily be captured by her,” he said.

Suspended

In the communal web, females of Philoponella rarely come out, while males venture into other webs to mate and can copulate with one female spider up to six times before moving on to another, Zhang said.

Male spiders attached themselves to the end of a safety line of silk thread at the edge of a mate’s web before mating and also used it to help escape, the study found.

When the researchers cut the safety line during mating, they observed the males still jumping away, but they fell to the ground instead of climbing the safety line, according to the study.

Male spiders often repeat a mating behavior, jumping and crawling back to the same female to mate again, Zhang said.

In the future, Zhang would like to research whether there is a correlation between a male Philoponella prominens’ ability to catapult and his ability to successfully reproduce.