Now researchers have traced the origin of those electrosensory powers to the same type of embryonic cells that gives rise to many head and facial features in humans.

The discovery, reported by University of Florida scientists in the current edition of Evolution & Development, identifies neural crest cells, which are common in vertebrate development, as a source of sharks' electrical ESP.

It also fortifies the idea that before our early ancestors emerged from the sea, they too had the ability to detect electric fields.

"Sharks have a network of electrosensory cells that allows them to hunt by detecting electrical signals generated by prey," said Martin Cohn, a developmental biologist with the departments of zoology and anatomy and cell biology, and the UF Genetics Institute. "That doesn't mean they can only detect electric fish. They can sense electricity generated by a muscle twitch, even if it's the weak signal of a flounder buried under sand."

Likewise, sharks are widely thought to use the Earth's magnetic field for navigation, enabling them to swim in precise paths across large expanses of featureless ocean, Cohn said.

"If you think of this in the big picture of evolution of sensory systems, such as olfaction, hearing, vision and touch, this shows sharks took a pre-existing genetic program and used it to build yet another type of sensory system," Cohn said.

UF and University of Louisiana researchers analyzed electroreceptor development in the embryos of the lesser spotted catshark, an animal that is largely motionless during the day and hunts at night, mainly in the seagrass beds of the eastern Atlantic Ocean.

Using molecular tests, scientists found two independent genetic markers of neural crest cells in the animal's electricity-sensing organs. Analysis shows these cel
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Contact: John Pastor
jpastor@vpha.health.ufl.edu
352-273-5815
University of Florida
6-Feb-2006