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Spiders Colonized A Remote Pacific Island By Flying There

author

Josh Davis

Staff Writer

clockDec 8 2016, 20:10 UTC
Ghost spider

Ghost spiders, such as this one (Anyphaena sp.) are found all around the world. Dann Thombs/Flickr CC BY-NC-ND 2.0

Bad news for arachnophobes: nowhere is safe from the eight-legged critters. If you think you might be able to escape them on a tropical island hundreds of kilometers off the coast of South America, then I’m sad to say you’d be wrong. It turns out that those spiders living on the beautifully idyllic Robinson Crusoe Island probably flew there. Yep, you read that right.

Named after the eponymous novel that is based on an 18th-century sailor stranded on the island, Robinson Crusoe is located 670 kilometers (416 miles) off the west coast of Chile. Formed from a volcanic eruption roughly 4 million years ago, it means that all life now living on the relatively young lump of rock has had to get there from somewhere else.

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For plants, some species have developed seeds that can withstand the harsh conditions of the ocean, while birds obviously have little issue crossing the expanse. But other land-based creatures usually need a helping hand, either hitching a ride on avian pioneers or sailing the seas on rafts of vegetation. But the ghost spiders of Robinson Crusoe had other ideas. They made the journey using kites made of silk, a behavior known as “ballooning”.

They’re not the only species of arachnid, or invertebrate for that matter, to use this method of locomotion, which is often employed by spiderlings as a way to disperse from the nest. But it seems that it certainly aided the spiders' ability to colonize the island where few other creatures lived. This meant that when the creepy crawlies arrived, they effectively had the run of the place, with little else in competition.

This, the researchers suspect, is the reason why there are so many species of ghost spiders present on Robinson Crusoe. When the team, from Argentina’s National Scientific and Technical Research Council, first started looking for the arachnids in 2011, they discovered four new species, and since have found another three, which are still yet to be named.

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But as if flying to the island from the mainland wasn’t weird enough, the scientists have also found another oddity among the spiders. It appears that the critters have unusually small genitals, too. The reasons for this are still unclear, but it is probably related to their fascinating mating ritual, the researchers suggest. After a little bit of leg stroking, the spiders then “interact with their mouths”.

Flying, kissing spiders, anyone?


natureNature
  • tag
  • spider,

  • arachnids,

  • South America,

  • colonization,

  • Pacific,

  • chili,

  • Robinson Crusoe Island