Catapulting to safety

In the animal world, various mechanisms allow for extremely fast actions or reactions through storage of energy in elastic structures, followed by its instant release, resembling the function of a catapult. Many of these mechanisms are employed for prey capture or for predator avoidance, but so far, such superfast actions have not been known to dodge sexual cannibalism.


In a paper published online 25 April 2022 in the journal Current Biology (https://doi.org/10.1016/j.cub.2022.03.051), a group of scientists from China, Singapore and Slovenia describe the first such mechanism in the animal world. Males of the spider Philoponella prominens of the family Uloboridae undertake a split-second catapult action immediately after mating, thereby fleeing their cannibalistic partner (video).


Through a series of experiments, the authors demonstrate that males achieve their superfast action (up to 88.2 cm/s) by extending the tibia–metatarsus joint of their first leg pair via hydraulic pressure in a joint that is known to lack extensor muscles in spiders. This rapid expansion greatly reduces the likelihood of the male being killed and eaten by the female. The evolution of catapulting is likely a result of sexual conflict.


Among animals, numerous mechanisms allow for extremely fast actions or reactions via the slow storage of energy, typically in elastic structures, which is then nearly instantly released, similar to the operation of a catapult. Many of these mechanisms are employed for prey capture or for predator avoidance; however, such superfast actions have not yet been reported as a means to dodge sexual cannibalism. Here, we unveil a novel mechanism in a communal orb-weaving spider Philoponella prominens (Uloboridae), whereby males undertake a superfast (up to 88.2 cm/s) catapult action immediately after mating, thereby fleeing their partner. This rapid expansion greatly reduces the likelihood of the male being sexually cannibalized.


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