Fish-Eating Spiders Are Everywhere

spider tarantula
A Chilean rose tarantula Henry Romero/Reuters

Arachnophobes, stop reading: Researchers have found fish-eating spiders on every continent in the world except Antarctica, they claim in a new PLOS ONE paper published Wednesday.

Historically, spiders have occasionally been found preying on fish and other small animals, including bats and birds. But study authors Martin Nyffeler, a zoologist from University of Basel, and Bradley Pusey, a fish expert from the University of Western Australia, have now "documented numerous incidents of spiders predating fish from all around the world," according to a statement about the study.

Nyffeler (who has studied bat-eating spiders in the past) and Pusey found up to five families of spiders preying on small fish in the wild. They have also observed species in three more spider families catching fish in a lab.

"The finding of such a large diversity of spiders engaging in fish predation is novel," Nyffeler says in the statement. "Our evidence suggests that fish might be an occasional prey item of substantial nutritional importance."

Following its long tradition of weird news ("Man throwing concrete at hotel says zombies were chasing him," for example), the Sunshine State plays a prominent part here: More fish-eating spiders were found in the Florida wetlands than anywhere else in the world.

The spiders are mostly "semi-aquatic." That is, they tend to live alongside "shallow freshwater streams, ponds or swamps," according to the statement. Many of these spiders can swim, dive and walk on the water—and some pack powerful poisons, both neurotoxins and other enzymes, enabling "them to kill and digest fish that often exceed them in size and weight."

These water spiders catch their prey by anchoring their hind legs on a stone or plant and placing their front legs on the surface, "ready to ambush," the researchers say. (Usually, the foreleg and hind leg distinction in spiders refers to the front two and back two pairs of the animal's limbs.) After the spider strikes, it drags the fish to dry land and gets ready to eat. The whole feeding process can take a few hours.

The prospect of a spider capable of killing a fish a lot bigger than it is will probably horrify a third of the population—one statistic for the number of arachnophobes in the country—but it's no cause for alarm. Despite what you might see in sci-fi tales, especially this Jeff Daniels movie, most spiders aren't harmful to humans.