Spiders’ hydraulic legs save them from cannibalistic companions

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In the 2013 DreamWorks animated film Turbo (now streaming on Peacock), our titular hero dreams of being a NASCAR driver, but there’s only one problem: he’s a snail, an animal known for its notoriously slow pace. By chance involving a turbocharged car on the highway, Turbo achieves his dream of becoming the fastest snail in the world and competing in the Indy 500.

In the animal world, being quick can have a survival advantage for avoiding predators, capturing prey, or getting away from mates who tend to snack on their lovers after mating. For males of the species Philoponella prominens – a common orb spider native to Japan and Korea – the latter scenario is a constant concern. Balancing the desire to reproduce while avoiding becoming a post-coital meal requires adapting a quick escape strategy.

In a recent paper published in the journal Current Biology, Schichang Zhang of Hubei University’s Center for Behavioral Ecology and Evolution and colleagues described how these spiders use a hydraulic catapult maneuver to get out of the bed just in time.

P. prominens often lives in large communities with hundreds of spiders that have all set up their webs next to each other. These spider quarters make it easier to find a mate, but being near a female spider can be a deadly proposition for males.

“When we were studying the sexual behavior of this common spider in the field, we found that mating always ended in catapult,” Zhang told SYFY WIRE.

Immediately after mating, males of the species have been observed moving away from their partners at speeds of up to 88.2 centimeters per second. This equates to about two miles per hour. It may not seem fast, but males average 3 millimeters. Scaled to human sizes, it would be equivalent to sprinting at 1,200 miles per hour.

In order to capture the movements, the researchers set up high-speed cameras to act as technological voyeurs, observing the spiders’ mating behaviors, including rapid flight at around 1,500 frames per second.

“The locomotion of the spider’s legs relies on an internal hydraulic mechanism. In our study, we found that the area of ​​the tibia-metatarsus joint in the first part of the legs is significantly larger than that of any other joint,” Zhang said.

To escape, male spiders fold their forelimbs over their mates’ bodies like a closed fist and use them to launch themselves in the blink of an eye. Generally speaking, kicking your partner immediately after mating can be considered aggression, but for P. prominens there is little choice. Observations of the spiders’ mating habits have confirmed that a quick escape is crucial for the long-term survival of the males.

In a series of experiments, researchers prevented males from catapulting each other and found that they were quickly consumed by females. Unlike jumping spiders, which also use hydraulics to achieve rapid movements in pursuit of prey, P. prominens seems to have developed this specifically for sexual escapes. Zhang said he was not observed under any other circumstances.

“Only men can escape the sexual cannibalism of women,” Zhang said.

Additionally, an ability to perform this catapult maneuver appears to be necessary for males to mate successfully, whether or not they are able to escape afterwards. In cases where one or both first pairs of legs were damaged or removed, males have been observed courting females but failed to mate. This was not the case when one of the other legs was damaged or removed.

Dating isn’t easy no matter what species you are, but at least we don’t have land speed records just to survive having kids.

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