Chapter 41 - Electroreceptors and Magnetoreceptors

Many animals have the ability to detect electric and magnetic fields. Although many species respond and orient to magnetic stimuli, only recently were putative vertebrate receptor systems identified. All organisms generate weak electric fields in water, due to an uneven distribution of ions between the interior of the organism and the external aqueous environment. Ampullary electroreceptors are an ancestral vertebrate trait that allows for the passive detection of these electric fields, which is useful for detecting prey, predators and mates. Although ampullary electroreceptors were lost during vertebrate evolution, they subsequently re-evolved several times independently. In two groups of teleost fishes, both ampullary and tuberous electroreceptors evolved, the latter specialized for the detection of actively generated electric organ discharges, or EODs. These fish generate EODs to communicate in the electrosensory domain, as well as actively to sense their environment by detecting distortions in the self-generated EOD. Many physiological mechanisms involved in electrosensory processing are unique.