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BOB HIRSHON (host):
Brainy legs. I’m Bob Hirshon and this is Science Update.
Some spiders’ brains are so big they spill over into their legs. This according to evolutionary biologist William Eberhard of the Smithsonian Tropical Research Insitute. He and his colleagues at the University of Costa Rica discovered this while studying a variety of Central American spiders.
WILLIAM EBERHARD (Smithsonian Tropical Research Institute):
In both young individuals of larger species and in adults of very small species, the brain extends into the bases of their legs and also bulges out of the lower part of their body, so they have what looks like a slightly bulging tummy, which houses almost pure brain as far as we can see. And this has also been found in very small insects, that they have brains that go all the way back into their abdomen, some species.
Eberhard notes that smaller creatures generally have big brains relative to their body size. But the spiders are a particularly extreme case. I’m Bob Hirshon for AAAS, the Science Society.