Electroreception

February 4, 2025

The Ampullae of Lorenzini are specialised pores capable of detecting very weak electric fields that are thought to have evolved from the lateral line system. They consist of a small chamber (the ampulla) and a sub-dermal canal which projects outward to the surface of the skin, the ampulla contains hundreds of sensory hair cells. The wall of the canal contains a double layer of connective tissue fibres and epithelial cells, which are tightly joined together to form a high electrical resistance between the inner and outer wall of the canal. The canal and ampulla themselves are filled with a high potassium low resistance gel that forms an electrical core conductor with a resistance equalling that of seawater.

Fish carry an electrical charge different to that of seawater and so a weak voltage is created (by the movement of positive and negative particles moving back and forth shifting electrons in an attempt to become stable). Because the salt in the water contains both sodium and chlorine ions which can move freely in the water the electricity itself is transported, and this is what the ampullae of lorenzini are able to detect.

Sharks also use their electrosensory system to detect other sharks of the same species and the earths magnetic fields. The detection range for naturally occurring weak electrical fields from prey etc is around 50 cm and less.