Shark Snot Key to Following Bloody Trails

As Brown did, Fields and his team inserted two silver wires into the gel and heated or cooled one end of the wire's holder. Sure enough, this generated electricity, but Fields found out that the electricity was simply caused by an electrochemical reaction between the silver and the gel. When non-silver devices were heated or cooled, no electricity was generated by the gel.

"So the gel is nothing but a conductor that allows electrical signals to move from the membrane to the brain," Fields said.

The slimy substance plays a big role in hunting, however. It allows the fish to detect very faint electrical fields, which prey emit when they swim or bleed.

"Imagine that a shark is swimming between two points of a 1.5 volt battery, with one battery end dipped into Long Island Sound and the other located in the waters off of Jacksonville, Florida," Fields said. "Despite the incredible distance, the shark could easily determine if the battery was switched on and off. That's how sensitive its electroreception is."

Harold Zakon, a professor of neurobiology at the University of Texas, supports the new findings.

"Dr. Fields had every reason to be skeptical of Brown's results," Zakon told Discovery News. "The generation of voltages at metal-electrolyte interfaces is a bugaboo for electrophysiologists who take great care to ensure that such voltages do not obscure or mislead."

Now that the sharks' electricity detection process is better understood, Fields and his colleagues hope the information may one day lead to better shark repellent devices that he said could "decoy sharks away from swimmers."

Related Links:

Shark Week at Discovery

Jennifer Viegas' animals blog on Discovery News

The Shark Research Institute

International Shark Attack Files

All about electroreception