Scientists have discovered that a number of spider species catch and eat fish.
Spiders are traditionally viewed as predators of insects, but
a new study suggests that eating fish is widespread among species that
live near water.
In some cases, the arachnids used powerful poisons to kill fish that were much bigger than them.
Details of the study by a Swiss-Australian team appear in the academic journal Plos One.
Martin Nyffeler from the University of Basel in Switzerland
and Bradley Pusey from the University of Western Australia gathered and
documented numerous incidents of spiders catching fish.
Their review of the evidence shows that spiders from as many
as five families have been observed eating small fish in the wild and
three more families contain species that catch fish under laboratory
conditions.
These semi-aquatic spiders typically dwell at the fringes of shallow freshwater streams, ponds or swamps.
Some are capable of swimming, diving and walking on the water
surface. But they generally have powerful neurotoxins and enzymes
enabling them to kill and digest fish that are bigger and heavier than
them.
Fish caught by the spiders were, on average, about twice as long as their arachnid predators.
"Our evidence suggests that fish might be an occasional prey item of substantial nutritional importance," said Dr Nyffeler.
Fish eating by spiders has been reported from all continents
with the exception of Antarctica. Most incidents have been documented in
North America, especially in the wetlands of Florida.
Here, 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 is then dragged to a dry place before the feeding process can begin. This usually lasts several hours.
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