Snout goo may help sharks sense prey

This ‘jelly’ relays the electric currents that are created as prey move

Tests of jelly extracted from a bonnethead shark (such as this one) and two rays show that it may help these fish sense their prey — even in murky conditions.

Loren Javier / Flickr (CC BY-NC-ND 2.0)

Sharks appear to have a sixth sense that helps them locate prey in murky ocean waters. These fish rely on special electricity-sensing pores on their heads and snouts. The pores were first described in 1678. Even now, however, scientists aren’t quite sure how they work. But new data have just brought them a step closer.

These pores are known as ampullae (AM-puh-lay) of Lorenzini. They connect to cells that sense electric fields. And that can be useful as the movement of nearby prey emit such fields.

Those pores are filled with what might best be thought of as shark jelly. It’s a mysterious goo that is thick but clear. Scientists had suspected the jelly might play some role in detecting prey, but they weren’t sure just how.

So Marco Rolandi of the University of California, Santa Cruz and his engineering colleagues have just analyzed this goo. They squeezed some of it from the pores of a bonnethead shark and two skates (the “big” and longnose species).

Protons are a type of positively charged subatomic particle. Their movement can create an electric current. Many good proton conductors occur in nature. (One, for instance, exists in squid skin.) Rolandi’s team investigated whether the shark jelly, too, could transmit protons.

And indeed it can, the scientists now report. Protons move well through the jelly and transmit an electric current. They shared their findings May 13 in Science Advances.

Shark jelly is, in fact, the living world’s best proton conductor. Engineers have come up with a synthetic compound that is 40-times better. But other than that material, known as Nafion, nothing comes close to the stuff sharks make. So it appears that shark jelly may allow these fish to sense very weak electric fields — picking up on teensy hints that lunch may be swimming nearby.

Physics writer Emily Conover studied physics at the University of Chicago. She loves physics for its ability to reveal the secret rules about how stuff works, from tiny atoms to the vast cosmos.

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