Electroreceptor

Monotremes

The monotremes, including the semi-aquatic platypus and the terrestrial echidnas, are one of the only groups of mammals that have evolved electroreception. While the electroreceptors in fish and amphibians evolved from mechanosensory lateral line organs, those of monotremes are based on cutaneous glands innervated by trigeminal nerves. The electroreceptors of monotremes consist of free nerve endings located in the mucous glands of the snout. Among the monotremes, the platypus (Ornithorhynchus anatinus) has the most acute electric sense. The platypus localises its prey using almost 40,000 electroreceptors arranged in front-to-back stripes along the bill. The arrangement is highly directional, being most sensitive off to the sides and below. By making short quick head movements called saccades, platypuses accurately locate their prey. The platypus appears to use electroreception along with pressure sensors to determine the distance to prey from the delay between the arrival of electrical signals and pressure changes in water.