Monday, 23 June 2014 | MYT 6:45 PM

When spidey wants some sushi, spidey goes out fishin'!

Not content with their stereotyped image as bug-hunters, up to 24 species of spiders actually go fishing — one even snatches unsuspecting goldfish from garden ponds.

Researchers documented the spiders’ wide-ranging palate in a study detailing how at least two dozen species of spiders — on every continent but Antarctica — eat small freshwater fish that often exceed them in size.

Scientists have long known that some spiders consume fish, but the study — considered the first systematic review of the topic — showed that the practice is far more common and geographically widespread than previously thought.

“Fish may represent a ‘big-ticket item’ in the nutritional budget of semi-aquatic spiders,” said zoologist Martin Nyffeler, of the University of Basel in Switzerland, who led the study, which was published on June 18 in the scientific journal PLOS ONE.

“Fish meat is high-quality prey regarding protein content and caloric value,” Nyffeler said. “Feeding on fish may be particularly advantageous during the mating period when the elevated energy and protein requirements of gravid (pregnant) female spiders require increased food intake, or at times of limited availability of invertebrate prey.”

The spiders employ potent neurotoxins and enzymes to kill and digest fish. Semi-aquatic spiders — able to swim, dive and even walk on the water surface — lurk at the edges of shallow streams, lakes, ponds or swamps. They often anchor their hind legs to a stone or plant, with their front legs ready for the ambush on the water’s surface.

After the spider snares a fish, it drags it to a dry place like a rock or tree trunk to begin the feeding process: pumping digestive enzymes into the fish and sucking out the dissolved tissue like a milkshake. “It takes a spider usually many hours to devour a fish until nothing is left but bones and scales,” Nyffeler said.

Gone fishing: Dolomedes facetus, one of two dozen species of spiders that have been identified as fish-eaters is pictured above with dinner, a positively dead Xiphophorus, in a garden pond in Brisbane, Australia. Since spiders don't have teeth to chew their food, they have to wait around for a while for the enzymes they inject into their prey's body to liquefy their insides so they can suck it up like a smoothie. — Reuters

‘Adept predators’

Fish-catching is largely limited to warmer climates. The Florida wetlands and neighbouring regions are a particular hotspot, with mosquito fish in large numbers.

The researchers said at least 18 spider species from five families have been observed catching fish in the wild. Six more species, including some from three other families of spiders, have been documented doing it under laboratory conditions.

About 30 species of fish — ranging from just under 2cm to 6cm — have been observed being captured by spiders in the wild. In North America, the species Dolomedes triton frequently catches fish. In Australia, the species Dolomedes facetus steals goldfish from ponds in suburban gardens.

Fish are not the only small vertebrates that spiders include on the menu. Some have been known to eat frogs, toads, salamanders, lizards, snakes, mice, rats, bats and birds, Nyffeler said.

Brad Pusey of the University of Western Australia, who also worked on the study, noted: “Spiders are more adept predators than most give credit for.” – Reuters

Tags / Keywords: Lifestyle , Features , Science , Biology , Nature , spider , arachnids , fish , fishing , study , research , fish eating spider , aquatic spider


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