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Brains of Tiny Spiders Fill Their Body Cavities and Legs

New research on tiny spiders has revealed that their brains are so large that they fill their body cavities and overflow into their legs, say a team of scientists at the Smithsonian Tropical Research Institute in Panama.

As part of ongoing research to understand how miniaturization affects brain size and behavior, the researchers measured the central nervous systems of nine species of spiders, from rainforest giants to spiders smaller than the head of a pin. As the spiders get smaller, their brains get proportionally larger, filling up more and more of their body cavities. The discovery was announced in the journal Arthropod Structure and Development.

“The smaller the animal, the more it has to invest in its brain, which means even very tiny spiders are able to weave a web and perform other fairly complex behaviors,” said William Wcislo, staff scientist at the Smithsonian Tropical Research Institute. “We discovered that the central nervous systems of the smallest spiders fill up almost 80 percent of their total body cavity, including about 25 percent of their legs.”

(Read More: Smithsonian Science)   (photo: Frank Starmer)

(Article: Quesada, Rosanette, Triana, Emilia, Vargas, Gloria, Douglass, John K., Seid, Marc A., Niven, Jeremy E., Eberhard, William G., Wcislo, William T. 2011. “The allometry of CNS size and consequences of miniaturization in orb-weaving and cleptoparasitic spiders.” 521-529, doi10.1016/j.asd.2011.07.002)