Spiders that go fishing? They exist! And a new study finds they are more common than previously thought.
More than a dozen spider species have been found that catch and eat fish, and they've been observed on every continent on the planet, except for Antarctica, according to a report published this week in PLOS One.
If this abundance of fish-eating spiders is kind of shocking to you, you are in good company. Even Martin Nyffeler of the University of Basel in Switzerland admitted to being surprised by the findings, and he has been studying spiders that eat things like earthworms and slugs for more than a decade. (Last year, he published a paper describing 50 incidents of spiders eating bats.)
It wasn't the fact that spiders eat fish that stunned Nyffeler, rather it was how many spiders actually do it.
"I was very surprised that fish-catching behavior is so widespread geographically and taxonomically across several spider families," he told the Los Angeles Times.
In this new study, Nyffeler and his colleague Bradley Pusey of the University of Western Australia scoured scientific journals and the Internet to find as many records of spiders attacking and devouring fish as they could. Through their research, they unearthed 89 incidents of spiders eating fish.
More than half of those incidents were documented in the United States. Most of them occurred in the South, especially the Southeast (think Florida), but there were eight examples recorded in California as well.
There were also several incidents reported in South America and Australia, but comparatively few in Africa, Asia and Europe.
The researchers discerned a few patterns about fish-eating spiders from their survey. Spiders that eat fish are semi-aquatic and are usually found on the shores of freshwater ponds, streams, rivers and bayous. They are all hunting spiders, which means they do not use a web to catch their prey.
Instead, these spiders sit on the top of the water, with their hind legs anchored to a stone or a plant. When a small fish swims to the surface -- either to find its own insect snack or to breathe in more oxygenated air -- the spider pounces, and injects the fish with venom, usually at the base of its head. Then it drags it away to a dry spot to be eaten.
The fish captured by the spiders are generally between 0.8 and 2 inches in length and, on average, 2.2 times bigger than the spider.
The bulk of these fish-eating spiders' diet is still made up of insects, the researchers report. Fish to these spiders is just an occasional food. They also note that spiders that eat fish appear to live only in warmer climates -- in places within 40 degrees north or south of the equator.
If you are wondering how a spider eats a fish that is more than twice its size, the answer is as fascinating as it is gross. Once it has dragged the fish to a dry spot, it pumps a digestive enzyme into its prey, and then sucks the dissolved tissue through its mouth opening.
Isn't nature amazing?