The True Sixth Sense: Electroreception

Electroreception is the biological ability to perceive natural electrical stimuli. In simpler words, it’s an animal’s ability to perceive the world via electricity. There are two forms of electroreception, active and passive. In active electroreception, the animal senses its surrounding environment by generating electric fields and detecting distortions in these fields using electroreceptor organs. This electric field is generated by means of a specialized electric organ consisting of modified muscle or nerves. In passive electroreception, the animal senses the weak bioelectric fields generated by other animals and uses it to locate them. These electric fields are generated by all animals due to the activity of their nerves and muscles.

Electroreception is quite common among aquatic or amphibious animals, considering water is a much more effective conductor than air. Some examples include sharks, rays, and the electric eel.

But what about mammals?

With recent estimates stating that there are nearly 5400 mammalian species, there has to be a few species possessing this ability, right? A few there are indeed! From what we know, the only mammals that possess the ability of electroreception are the platypus (Ornithorhynchus anatinus), echidnas (Tachyglossidae), and the Guiana dolphin (Sotalia guianensis).

Platypus & Echidnas (Monotremes)

Monotremes are very bizarre animals. They are mammals and yet, they lay eggs! The only surviving monotremes today are the platypus and four different species of echidnas. These momotremes possess the sixth sense of electrorecption!

Between the two, the duck-billed platypus by far has the most acute electrical sense. The platypus has about 40,000 electroreceptors striped along it’s bill. This allows it to catch large amounts of prey in the murky water at night. They swim with their eyes, ears, and nostrils closed, making electroreception a very useful trait.

Guiana dolphin

Although aquatic, this mammal was just recently discovered to also have electroreceptors and can sense electrical fields. On the snout of the dolphin, there are rows of little holes called hairless vibrissal crypts. Inside these crypts the dolphins have electroreceptors, capable of electroreception as low as to detect small fish.

There definitely may be more aquatic mammals that have this amazing ability, yet they have yet to be discovered.

Downfalls?

Although electroreception is an amazing ability, electrofishing may have deleterious consequences. Higher amounts of electroreceptors lower these mammal’s electrical impedance and make them vulnerable to the intense current generated by electrofishing devices. Direct observations show that these mammals were immobilized in the vicinity of the probe. This stressor, which makes these species particularly vulnerable, often causes death within hours of capture without rescue. It is important that we, as humans, are attentive when entering the homes of these mammals.

References:
Czech-Damal, N. U., Liebschner, A., Miersch, L., Klauer, G., Hanke, F. D., Marshall, C., Dehnhardt, G., & Hanke, W. 2012. Electroreception in the Guiana dolphin (Sotalia guianensis). Proceedings. Biological sciences / The Royal Society, 279 (1729), 663-8.

Pettigrew, J. D. 1999. Electroreception in monotremes. The Journal of experimental biology, 202, 1447-1454.

Scheich, H., Langner, G., Tidemann, C., Coles, R., & Guppy, A. 1986. Electroreception and electrolocation in platypus Nature, 319 (6052), 401-402.

Photo Credit:
Joel Sartore, National Geographic.

Manger, P.R. and Pettigrew, J.D., 1995. Electroreception and the feeding behaviour of platypus (Ornithorhynchus anatinus: Monotremata: Mammalia). Philosophical Transactions of the Royal Society B: Biological Sciences, 347(1322), 359-381.

Marcos Santos, WDC

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