Spider spotted chaining wild crayfish with silk before devouring

7 October 2016

By Julianna Photopoulos

It was too late to escape the jaws of death. A fishing spider has been seen feasting on a young crayfish along the banks of Knox Creek in Buckhannon County in Virginia.

“We were all pretty excited when we stumbled across the event in the field — we had never seen a fishing spider feeding on a crayfish before,” says Zachary Loughman of West Liberty University in West Virginia. Indeed, no one has reported this behaviour in the wild, and similar records in captivity are rare, Loughman says.

He and his team were studying two endangered species of crayfish — the Big Sandy crayfish and the Guyandotte River crayfish — when they came across the event.

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While sampling a stream, they often take additional information and look for other critters. “We were flipping over boulders, looking for water snakes, when we found a crayfish caught in the spider’s fangs,” says Loughman.

A large female striped fishing spider (Dolomedes scriptus) was devouring a young spiny stream crayfish (Orconectes cristavarius). This semi-aquatic spider had ingested most of the crayfish’s abdomen and had used silk threads to anchor the crayfish under the rock, about half a metre from the stream, where a small amount of water had pooled.

Young crayfish are frequently encountered near the edges of streams, in shallow eddies, or shallow pools – locations where fishing spiders are known to hunt.
 

“We didn’t witness the actual predation event, but it’s highly likely that the fishing spider killed the crayfish, given the typical predatory behavior these spiders employ,” Loughman says. “The location of the spider was also conducive for it encountering a crayfish as prey.”

These spiders are opportunistic hunters that prey on small invertebrates and vertebrates. Rather than capturing their meal in a web, they extend their front legs onto the water’s surface and wait.

The slightest ripple can trigger an attack, and the spiders run across the water’s surface or even dive. Judging by the species’ usual strategy, the spider probably grasped the young crayfish from the back of the head, wrapped its legs around it and injected its lethal venom, avoiding the crayfish’s pincers.

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