Fish-eating spiders are everywhere (Wired UK)


A fish-eating spider from the Trechalea genus eating a characiform while sitting on a rock in middle of small river in central Colombia

Solimary Garcia Hernandez


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If you want to watch a spider eat a fish — and you know you do
— you need to think like a spider.

First, go where the water is still: a windless lake, or a bend
in a lazy stream. This is where fish wait for insects to fly close
to the surface. It’s a place where the fish feels comfortable. The
spider is comfortable, too: Its hind legs anchored on a stone or
branch while the front legs rest on the water’s surface. But
the spider is ready (and hopefully so are you, with your camera),
and the moment the fish’s dorsal fin breaks the surface and makes a
ripple, the spider will pounce.

This drama plays out every day, on every continent except
Antarctica, according to a paper
published today in PLoS ONE
by zoologist Martin Nyffeler the
University of Basel in Switzerland, who has made his career
studying spider behaviour.

Apparently, he also has a passion for giving the world more
nightmares, because recently his academic output has
focused on spiders that eat bats, earthworms,
snails, and now, fish. “A couple of years ago, I started to review
the entire spider ecology literature,” he said. “Everything.”

He compiled research from mainstream journals as well as those
too old, obscure, or foreign to make it into the arachnophilic
canon. After a while, he noticed that non-insect eating behaviours
seemed to be more common, and more widely spread, than most spider
biologists previously believed. “They all laughed at me and said
‘Spiders don’t eat slugs and snails’,” said Nyffeler. Then he
published his review, and the laughter stopped.

In addition to his massive literature review, Nyffeler combed
the internet and spoke to fish and spider biologists to gather
evidence of fish predation. He contacted the author of each
internet picture to make sure the photo wasn’t staged (otherwise he
excluded it from his analysis). He also took note which species
only caught fish in experiments staged by researchers in the lab or
in the field. He didn’t immediately discount these, but was careful
to annotate them as such. He also worked with fish
specialists, and recruited fish expert Bradley Pusey from
Australia’s Centre for Excellence in Natural Resource Management as
his co-author.

By the end, he confirmed 89 incidences of spiders hunting fish,
spread among 8 spider families. The most prolific were
the Dolomedes genus, commonly known as raft
spiders. According to the paper, spiders hunt fish most
frequently between 40 degrees north and south of the equator.
Nyffeler says this is probably because the water is warmer and less
oxygenated. Fewer organisms can live in such waters, so fish have
to get their food from insects near the surface.

But just because spiders may be hunting fish in a stream near
you doesn’t mean it’s easy to catch them in action. One of the
wildlife photographers Nyffeler spoke with told him that he had
spent over 300 hours taking pictures in the wetlands near Tampa,
Florida, and had only seen this behaviour about a half dozen
times.

Nyffeler says across all the fish-hunting spider species, the
kill was similar: After pouncing from a stable position, they bite
the fish and inject it with neurotoxins. After seconds, minutes, or
sometimes hours, the fish dies and the spider drags it somewhere
dry, and pumps it full of digestive enzymes. Once the fish’s
innards are turned into mush, the spider typically eats everything
but the bones. Fish soup, spider style. Yum.

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This article originally appeared on Wired.com

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19 June 2014 | 11:08 am – Source: wired.co.uk
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