Hunting sharks have the remarkable ability to sense the electric energy generated by prey. Using special head organs, the predators can detect even the slightest muscle twitch of a flounder buried in sand.
But the cellular origin of sharks' electrical "ESP" has remained a mystery—until now.
Scientists at the University of Florida and the University of Louisiana have identified specialized cells as the sources of sharks' powers.
Embryonic neural crest cells have the ability to become many different structures. (Read an excerpt from a National Geographic magazine article on embryonic stem cells.)
In humans, for example, these cells give rise to head and facial features.
Using molecular tests of shark embryos, the researchers found genetic evidence of neural crest cells in the animals' electricity-sensing organs.
The findings support the idea that the common ancestor of all vertebrates (animals with spinal columns) also detected electric fields. But over time mammals, reptiles, and birds lost the ability, the theory goes.
"Our work is really the first demonstration of the embryonic origin of these organs, and it gives us some insight into how they arose during evolution," said Martin Cohn, a developmental biologist at the University of Florida Genetics Institute in Gainesville.
The discovery is reported in the current edition of the journal Evolution and Development.
Good Sense
Cohn, along with lead study author Renata Freitas, looked for genetic evidence of neural crest cells in embryos of the lesser spotted catshark, a species that mostly hunts at night. The team found indications of the cells in the embryos' electro-sensory organs.
The scientists believe that during development neural crest cells migrate from the sharks' brains into various regions of the head. There the cells create the framework for the electro-sensory system.
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