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Scientists have discovered a number of fish-eating spiders that can consume prey twice their size and weight.

A study by zoologists in Australia and Switzerland has found that while spiders typically prey on insects, some species will supplement their diet by catching small fish.

The spiders, some of which are capable of swimming, diving and walking on the water surface, have powerful neurotoxins and enzymes that enable them to kill and digest fish that often exceed them in size.

A study by zoologists in Australia and Switzerland has found that while spiders typically prey on insects, some species will supplement their diet by catching small fish

Martin Nyffeler from the University of Basel in Switzerland and Bradley Pusey from the University of Western Australia observed spiders from as many as five families predating on small fish in the wild across the world.

They also examined three more spider species catching fish under laboratory conditions.

These so called semi-aquatic spiders typically dwell at the fringes of shallow freshwater streams, ponds or swamps.

'The finding of such a large diversity of spiders engaging in fish predation is novel,' Mr Nyffeler said.

'Our evidence suggests that fish might be an occasional prey item of substantial nutritional importance.'

The spiders, some of which are capable of swimming, diving and walking on the water surface, have powerful neurotoxins and enzymes that enable them to kill and digest fish that often exceed them in size

Based on the results of the study, published by the academic journal Plos One, naturally occurring fish predation by spiders occurs right across the world expect for Antarctica.

Most incidents have been documented in North America, especially in the wetlands of Florida, where semi-aquatic spiders have often been witnessed catching and eating small freshwater fish such as mosquitofish.

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.

The fish will then be dragged to a dry place before the feeding process can begin which usually lasts several hours.

Martin Nyffeler from the University of Basel in Switzerland and Bradley Pusey from the University of Western Australia observed spiders from as many as five families predating on small fish in the wild across the world