Spiders from five different families prey on small fish in the wild, according to a systematic review recently published in the journal PLOS ONE.
Spiders are known to prey on insects, but in recent years researchers have become increasingly aware that spiders are not exclusively insectivorous, and that certain larger-sized species might supplement their insect diets by occasionally catching small vertebrate prey. Semi-aquatic spiders in particular — some of which swim, dive, and walk on the water’s surface — are equipped with powerful neurotoxins and enzymes that help them kill and digest fish that are larger than they are.
“Our finding of such a large diversity of spider families being engaged in fish predation is novel,” the authors wrote. “Semi-aquatic spiders captured fish whose body length exceeded the spiders’ body length (the captured fish being, on average, 2.2 times as long as the spiders).”
In the article, the researchers report that spiders preying on fish can be found on all continents except Antarctica, with most occurring in warmer climates, especially in the North American Florida wetlands and neighboring regions.
The authors found that other published evidence indicates that as many as eight spider families contain fish-catching species, which is a larger amount of diversity than previously known.
They report that naturally occurring fish predation has been witnessed in more than a dozen spider species from the superfamily Lycosoidea (families Pisauridae, Trechaleidae, and Lycosidae), in two species of the superfamily Ctenoidea (family Ctenidae), and in one species of the superfamily Corinnoidea (family Liocranidae).
The majority of reports on fish predation by spiders referred to pisaurid spiders of the genera Dolomedes and Nilus.
This video, which is not related to the PLOS ONE article, shows some fishing spiders in action:
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