Ampullae of Lorenzini
Named after the 17th-century anatomist who first described them, these skin
pores stipple the head and body of sharks. They connect to long, jelly-filled
tubes ending in blind sacs called ampullae, which contain sensory cells and
nerves connecting to the brain. The cells enable sharks to home in on hidden
prey, which, like all animals, give off weak electric fields. Sharks can also
detect the presence of ocean currents and make long migrations by sensing the
seabed's local geomagnetic signature. The smooth dogfish, for one, can detect a
change in direction of intensity of five billionths of a volt per centimeter.
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