This spider’s solution to sexual cannibalism? catapulting away

Throughout the animal world there are examples of creatures using extremely fast speeds to capture prey or avoid being captured.

Now, for the first time, scientists have observed the use of superfast action in a very specific scenario: as a way to escape sexual cannibalism.

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

Using high-resolution video cameras, the scientists found that these spiders initiate their catapult maneuver by folding their front legs against the female. When released from this fold, the ensuing release of hydraulic pressure causes the legs to rapidly expand, sending the males flying in a clockwise direction.

During these catapults, the spiders accelerate so fast that regular cameras can’t capture the action in detail. During this display, males can rotate up to 175 times per second during flight.

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

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

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

In his lab, Zhang and his team found that 152 of 155 successful spider matings ended with the male catapulting. The males that did not jump were killed and eaten. This escape doesn’t happen if the males “don’t sense approaching danger, or are exhausted,” Zhang said.

Leaping 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 prevented 30 male spiders from catapulting by placing a fine brush on the back of the spiders. All of these spiders were then killed and eaten by the female.

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

Further examination with cameras revealed that catapulting is possible because the male spider folds its first pair of front legs against the body of the female spider, and the rapid rear extension allows it to jump.

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

While sexual cannibalism is generally a rarity, it is common among spiders and scorpions. In turn, various male spiders have evolved different means of escape. For example, Schneider found that male golden orb-weaver spiders Trichonophila fenestrata “sacrificing their front legs during mating to keep the female busy,” Schneider said.

In general, sexual cannibalism in spiders can occur before, during, or after mating. Female spiders benefit from eating their mates because it eliminates unfit males or prevents the best males from mating with other females. Schneider explained that in these cases, the female may eat the male instead of allowing him to continue living, even though the meal is considered small.

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

“There are all sorts of great stories of strategies that male spiders have devised to escape being eaten by their mates,” Hebets said. “Some men may induce acquiescence in their female partner, for example by knocking her out, to escape. Others tie the females with silk. Others come bearing gifts, such as prey wrapped in silk, to presumably occupy the female while they attempt to mate.”

In this case, it is theorized that men Philoponella prominens they can jump due to evolutionary pressures placed on them through sexual cannibalism. It’s still safe, but it’s possible that the female spiders have responded in turn, and now use catapult as a way to judge the fitness of the male.

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

“Spiders are nothing horrible,” Zhang said. “If you know them, you will love them.”

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