In a first, scientists observe actions spiders use to escape sexual cannibalism

In the animal world, there are examples of creatures that use extremely fast speeds to capture prey – or avoid being captured.

Now, for the first time, scientists have observed the use of ultra-fast action in a very specific scenario: as a means of escaping sexual cannibalism.

Scientists have discovered male spiders of the species Philoponella prominens can survive encounters with aggressive females due to its unique ability to catapult itself. This is facilitated by a newly identified ability described Monday in the journal Current Biology.

Through the use of high-resolution video cameras, scientists have discovered that these spiders initiate their catapult maneuver by folding their front legs against the female. When they break free of this fold, the ensuing release of hydraulic pressure causes the legs to expand rapidly, sending the males hovering clockwise.

During these catapults, the spiders accelerate so quickly that the action cannot be captured in detail by ordinary cameras. During this parade, males can spin up to 175 times per second during flight.

Shichang Zhang, a professor at Hubei University in China and first author of the study, said he first observed this catapult when observing these spiders in the wild, and wanted to examine how the action was associated with sexual conflict (when two sexes have conflicting reproductive strategies).

This type of spider is also unusual because it lives in groups of up to 300 individuals. They live together in a mass of linked webs, while maintaining their own individual webs within this complex.

“It’s a common spider, which is not common in nature,” Zhang said. “Most web-building spiders build solitary webs.”

In his lab, Zhang and his team observed that 152 of 155 successful spider matings ended in a male catapult. Males that did not jump were killed and eaten. This escape doesn’t happen if the men “don’t sense the approaching danger, or if they’re exhausted,” Zhang said.

Escaped males often return to the scene to try again. Some males end up catapulting several times after their 30-second dates.

To examine the importance of catapulting, the scientists stopped 30 male spiders from catapulting themselves by placing a thin brush on the spiders’ backs. All of these spiders were then killed and eaten by the female.

This made it clear that catapulting was essential for survival. To understand how this happens, the team then conducted a series of experiments involving the spiders’ legs. For example, when removing the spiders’ first pair of front legs, the male spiders still approached the females, but were unable to mate. When the scientists removed one or two more legs, mating and catapulting continued as usual.

Further examination with cameras revealed that catapultation is possible because the male spider bends his first pair of forelegs against the female spider’s body, and the ensuing rapid extension allows him to pounce.

“This is a well-conducted study presenting a fascinating example of a male trait that most likely evolved as a result of sexual conflict due to sexual cannibalism,” said Jutta Schneider, unit leader of research in behavioral biology at the University of Hamburg in Germany. and who was not part of the new study.

Although sexual cannibalism is generally rare, it is common in spiders and scorpions. In turn, a number of male spiders have evolved different means of escape. For example, Schneider found that males of the orb-weaving spider Fenestrated Trichonephila “sacrificing their front legs during mating to keep the female busy,” Schneider said.

Overall, sexual canniblism in spiders can occur before, during, or after mating. Female spiders benefit from eating their mates as it eliminates unfit males or prevents the best males from mating with other females. Schneider explained that in these cases, the female may just as well eat the male as allow him to live – although the meal is considered a small meal.

“Female cannibalism of males is common in many species of spiders,” said Eileen Hebets, a professor at the University of Nebraska-Lincoln who has studied mating preferences in spiders.

“There are all sorts of great stories of strategies that male spiders have invented to escape being devoured by their mates,” Hebets said. “Some males may induce acquiescence from their female partner – for example, knocking her unconscious – to escape. Others tie females with silk. Others come with gifts, such as prey wrapped in silk , to presumably occupy the female while she attempts to mate.

In this case, it is theorized that the male Philoponella prominens may jump because of the evolutionary pressures imposed on them by sexual canniblism. That’s still certain, but it’s possible that the female spiders reacted in turn – and are now using the catapult as a means of judging the male’s fitness.

When Zhang is out in the field observing spiders, people come to ask him what he and his team are up to. When they reveal that they collect spiders, “most of them will look at us like we’re monsters,” Zhang said. This attitude, according to him, is a mistake. We can learn a lot from spiders, especially when it comes to understanding the relationship between evolution and sex.

“Spiders aren’t horrible at all,” Zhang said. “If you know them, you will love them.”