Wednesday 24 January 2018

Spiders 'shoot web like Spider-Man'

A spider crossing a silk 'bridge', similar to how Spider-Man throws webs in order to leap skyscrapers
A spider crossing a silk 'bridge', similar to how Spider-Man throws webs in order to leap skyscrapers

Spider-Man has much in common with the male spiders whose powers he emulates, a study has found.

Like the comic book hero, male spiders of many forest species are adept at flinging out lines of silk that help them cross wide regions of empty space, according to the Spanish National Research Council. Its scientists studied the behaviours of 204 spiders from 13 species in wind tunnel conditions.

The same ability allows Spider-Man to leap between skyscrapers in New York with effortless ease, they said.

Scientists believe the acrobatics of male spiders can explain why they are so much smaller than the females.

Being small assists their superhero-like antics and those that are better at the technique - known as "bridging" - are more likely to find a female to mate with.

Natural selection therefore favours male spiders being small.

Study scientist Guadalupe Corcobado said: "In species where bridging is a very common mode of locomotion, small males, by being more efficient bridgers, will enjoy more mating opportunities and thus will be better at competition to reach receptive females. This may lead to selective pressure for smaller size."

In contrast, being big confers an advantage to female spiders by helping them produce offspring.

The findings are being published in the journal BMC Evolutionary Biology.

Ms Corcobado said: "Previous studies have suggested that female fecundity (fertility) was the main driver of extreme male and female size differences. However, fecundity alone could not explain why males may grow as large as giant females in some species but remain extremely small in others. A selective pressure against large male body size has been searched for by researchers since Darwin; the constraint on bridging seems to be such a selective pressure."

Press Association

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