Tuesday, November 13, 2012

Dolphins can sense electric fields

Electric fields travel much farther through air than through which is why bony and cartilaginous fishes have exquisitely sensitive electroreceptors but most tetrapods have lost them. Known exceptions are some partially or fully aquatic tetrapods like some amphibians and monotremes. This research shows that dolphins can also be added to the list. The study found that the dolphins have little pits along their face called vibrissal crypts that resemble the ampullae that fish use for detecting electric fields. They also showed that the dolphins could detect electric fields by training them to respond to an electrical signal in the water. This is another example of convergent evolution because the vibrissal crypts are not homologous with the ectroreceptive organs of fish or even of the monotremes. Instead, they are equivalent to the pores that whiskers grow from in other animals. Whiskers are extremely sensitive sensory organs in many animal such as felines and rodents. It seems that in the course of dolphin evolution, the whiskers were lost but the sensory apparatus was retained and co-opted for a new purpose.

The vibrissal crypts (Proceedings of the Royal Society B
Electroreception in the Guiana dolphin (Sotalia guianensis
Proc. R. Soc. Bvol. 279 no. 1729 663-668