The spider can hide underwater for 30 minutes

A species of tropical spider uses a “film” of air to hide underwater from predators for 30 minutes, according to faculty at Binghamton University.

Lindsey Swierk, research assistant professor of biological sciences, observed a large tropical spider (Trechalea extensa) fleeing from humans and hiding underwater; this species was not previously known to use water to escape. Swierk had previously observed a species of Costa Rican lizard capable of staying underwater for 16 minutes to hide from predators.

“For many species, getting wet and cold is almost as risky for survival as facing their predators to begin with,” Swierk said. “Trechalea spiders weren’t previously known to hide underwater from threats – and certainly not for that long.”

The spider spent about 30 minutes underwater. While submerged, it kept a “film” of air all over its body.

“The film of air surrounding the spider when underwater appears to be held in place by hydrophobic hairs covering the entire surface of the spider’s body,” Swierk said. “It’s so complete that the spider almost looks like it’s been dipped in silver. The film of air could serve to keep the breathing holes away from the water, since these spiders breathe air. The air film could also help to minimize heat loss in the cold stream water in which the spider immerses itself.

According to Swierk, this observation gives new insight into how species can cope with the problem of finding refuge underwater.

“These spiders, and any animal hiding from predators in general, have to do their best to manage the risk,” Swierk said. “Risk of predation, yes, but also risk of the costs they will incur by fleeing. For some species, this means leaving territory or mates unguarded, or perhaps expending stored energy in a sprint. In this species, potential risks from using an underwater refuge may include lack of respiration and loss of body heat. There are many other questions to explore from this first observation.

This observation, “Dive behavior in a neotropical spider (Trechalea extensa) as a potential antipredator tactic,” was published in Ethology.

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