supersensitive sharks

As if it’s not scary enough that sharks can smell a drop of blood in an Olympic-sized swimming pool, or that they can sense the electric field given off by a hidden prey’s heartbeat; it seems they can also detect temperature changes of a thousandth of a degree Celsius in seawater, according to a study reported in the Jan. 30 Nature. Sharks have gel-filled canals that connect skin pores to electrosensory organs called ampullae of Lorenzini. Brandon R. Brown, a physicist at the University of San Francisco, analyzed samples of this clear, protein-based gel that were taken from black-tip and white sharks. He found that temperature changes as small as .001 degree in the gel would induce a voltage large enough for the animal to detect. Brown thinks sharks evolved such a sensitive thermometer to help them locate thermal fronts in the ocean, areas where cold and warm water mix, and where many of their quarry feed.

This news brief appeared in the Random Data column of the Boston Globe’s Health/Science section on 2/11/2003.