Fish-eating spiders that eat prey twice their size discovered across the world

Zoologists from Switzerland and Australia have discovered a number of species that can catch and eat fish

Dolomedes facetus captured pond fish (genus Xiphophorus) in a garden pond near Brisbane, Queensland, Australia. The number of spiders who catch and eat fish is on the rise across the world, scientists believe. ( Peter Liley, Moffat Beach, Queensland)

A number of spiders who catch and eat fish have been discovered across the world by scientists.

A study has found that while they typically prey on insects, some larger species of spiders will supplement their diet with small fish that are sometimes twice their size.

Martin Nyffeler from the University of Basel, Switzerland and Bradley Pusey from the University of Western Australia gathered data showing spiders from as many as five families predating on small fish in the wild.

Three other families contained semi-aquatic species that also caught fish under laboratory conditions.

Their review of evidence found the semi-aquatic families usually dwell at the fringes of shallow freshwater streams, ponds or swamps and some are capable of swimming, diving and walking on the water surface.

In order to catch its prey, the spider will typically anchor its hind legs to a stone or a plant, with its front legs resting on the surface of the water, ready to ambush. Their catch will then be dragged to a dry place before the feeding process can begin - which usually lasts several hours.

The arachnids also have powerful neurotoxins and enzymes allowing them to kill and digest fish that are often bigger and heavier than their own body weight. The fish caught by spiders were, on average, twice as long as them.

“The finding of such a large diversity of spiders engaging in fish predation is novel. Our evidence suggests that fish might be an occasional prey item of substantial nutritional importance”, Dr Nyffeler said.

Reports of fish-eating spiders have been made in all continents except Antarctica, although the majority have been recorded in North America.

In Florida, semi-aquatic spiders have often been witnessed catching and eating small freshwater fish such as mosquitofish.

The results of the study ‘Fish Predation by Semi-Aquatic Spiders: A Global Pattern’ have been published in the journal PLOS ONE.