Mammals use cold-sensitive ion channels to translate temperature into neural signals. Sharks possess an array of electrosensors — the ampullae of Lorenzini — that are sensitive to abrupt cooling and which are thought process temperature transduction signals by a different mechanism. In the January 30 Nature, Brandon R. Brown at the University of California at San Francisco, USA, show that the gel surrounding these electrosensors translates temperature into electrical information without the need for ion channels (Nature 421:495, January 30, 2003).

Brown measured the in vitro thermoelectric properties of the extracellular gel removed from the electrosensors of the black-tip reef shark (Carcharinus melanopterus) and the white shark (Carcharodon carcharias). He observed that this gel developed significant voltages in response to tiny abrupt temperature gradients (in the range of one tenth of one degree Celsius).

"This bulk property of the gel indicates that temperature...

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