LIFE SCIENCE

Male spiders can escape their partner’s mouth with amazing catapults

On April 25, researchers reported in Cell Press’s journal Current Biology that the male Longxi fetter spider would soon flee after mating with a female. The male spider will use the joint between the tibia and metatarsals on the first pair of legs to catapult instantaneously, throwing himself away from his partner at an astonishing speed of tens of centimeters per second (the male spider is only about 2 mm long). This mechanism has never been described before.

Zhang Shichang, an associate professor at Hubei University’s School of Life Sciences, said: “We found that the mating of Longxi fetter spiders always ended with catapults, which was too fast for ordinary cameras to clearly record the details. ”

The male spider catapults himself for a simple reason: to avoid being eaten by the female during mating. The researchers found that the few males who did not eject were quickly captured, killed and eaten by the female spiders. When the researchers artificially prevented the male spiders from ejecting, they suffered the same fate.

Zhang Shichang and colleagues discovered this phenomenon while studying the spider’s sexual selection. Longxi femme spiders have a certain social nature, they each separately knotted the web, and then the web is connected to each other to form a large web, a large web of up to 300 spiders living together. The researchers found that of 155 successful mating experiments, 152 ended with male catapults. The males who catapulted all survived mating.

On the other hand, all 3 male spiders that did not eject were killed. Another 30 male spiders that were prevented from being ejected by the researchers were also killed and eaten by the females. The researchers say the findings clearly show that the ejection behavior is to avoid “sexual eating homogeneity.”

Using a high-speed HIGH-definition camera coupled with a macro camera head, the researchers captured a high-definition image of the male spider ejection, and then used Python software to calculate that the average peak speed of the spider’s ejection was about 65 cm/s, usually ranging from 30 cm/s to 90 cm/s. They also accelerate at an average speed of 200 m/s2. When flying in the air, they spin an average of 175 times per second.

Male spiders eject by folding their tibia-metatarsal joints, and the force of the ejection comes from the pressure of the fluid inside the spider’s legs.

“We observed that males who could not eject were eaten by females.” Zhang Shichang said. “This suggests that this behavior was evolved to counter the female’s sexual predatory counterpart under strong predatory pressure.”

“Females may use this behavior to judge the quality of males when mating.” He added, “If a male can’t eject, kill it; if a male catapults multiple times, accept its sperm.” ”

In future studies, the researchers hope to explore the relationship between ejection ability and male spider fitness. (Source: Science Network)

Related thesis information: https://dx.doi.org/10.1016/j.cub.2022.03.051

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