For the first time, spiders have been observed escaping sexual cannibalism by flinging themselves away from females, reaching speeds of up to 88.2 centimetres per second
25 April 2022
To escape sexual cannibalism, some animals move stealthily to avoid detection or even play dead – but male orb-weaving spiders have developed another approach: after copulation, they rapidly catapult to safety. This is the first time catapulting to avoid being eaten by a mate has been reported.
Shichang Zhang at Hubei University in China and his team first noticed this behaviour while studying orb-weaving spiders in the mountains in Wuhan in October 2019.
The researchers decided to investigate things further in the lab. They used high-speed cameras to capture the behaviour of 155 mating pairs of an orb-weaving spider (Philoponella prominens). Only three of the males didn’t catapult after mating, and all were promptly captured, killed and eaten by their partners. All of the males that catapulted after mating survived.
To further test the necessity of this behaviour, the researchers put a small paintbrush behind the spiders that blocked the males from catapulting. They, too, were all killed and eaten.
The cameras revealed that the males launch themselves at remarkable speeds of up to 88.2 centimetres per second, which Zhang says is impressive for a spider only around 3 millimetres in length. That is as if a person 183 centimetres tall flung themselves 538 metres – the length of about five football fields – in 1 second.
William Brown at the State University of New York at Fredonia says this research contributes to our understanding of how sexually cannibalistic species continue to successfully mate. But he wonders if the escape strategy might also be used in response to other threats. “Have males co-opted a general anti-predator defence or is this uniquely an adaptation to reduce the risk of sexual cannibalism?”
Zhang and colleagues hypothesise that this behaviour evolved to signal fitness as mates. “If a male could not catapult, or the catapulting ability is not good, the female may deplete or eliminate its sperm, and accept other males’ courtship and sperm,” says Zhang.
Journal reference: Current Biology, DOI: 10.1016/j.cub.2022.03.051
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