Electric dolphins: cetaceans with a seventh sense

Interesting article in New Scientist – how do mammals use an electric field? what implications does this have for up an coming therapies involving electrical stimulation?

One extra sense isn’t quite enough for Guiana dolphins. In addition to echolocation, they can sense the electric fields of their prey – the first time this has been seen in true mammals.

Wolf Hanke at the University of Rostock in Germany and colleagues were intrigued by thermal images showing intense physiological activity in the pits on the upper jaw of the dolphins, Sotalia guianensisFish, some amphibians and primitive egg-laying mammals such as the duck-billed platypus use similar pits to pick up electric fields generated by nearby animals.

By examining the structures in a dead dolphin, and training a live one to respond to an electric field comparable to that generated by a fish, the team showed that dolphins also have electro-sensory perception.

“Electroreception is good for sensing prey over short distances, where echolocation isn’t so effective,” says Hanke. Other species of dolphin, and even whales, may be similarly gifted, he says. “Most people don’t realise that whales also feed on the floor of the ocean, so it is possible that they also use electrosensing.”

Hanke points out that the electro-sensory organs are derived from whiskers in ancestral animals. These mechanoreceptor organs, like the hair cells in the human ear, mechanically transmit the stimulus of touch or sound waves. The adaptation in Guiana dolphins is fairly new, Hanke says, and he suspects that “it is relatively easy to evolve, to change mechanoreceptor organs into electroreceptors”.

Indeed, the finding suggests nearly all mammals have at least the potential to evolve it too.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2011.1127

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