PP - Shark electroreception

The Ampullae of Lorenzini are electrorecepting organs found on the snout of shark. These tiny pores enter into a mucus filled canal, fillled with glucopolysaccharides, which aids in directing the electrical signal down to the base of the canal where the sensory cells are found. The receptor cells innervate at cranial nerve 7, along with the lateral line systems fish use to detect current flow of water. Rather than sensing its environment, a shark uses it electroreception to pinpoint prey it cannot see. This is especially important due to the positioning of the eyes on the shark. They are on the side of the sharks head. Therefore, when a fish is directly in front of the shark, it cannot see it. Thus, the shark relies its ability to detect electric fields to sense what is directly in front of it.

The Ampullae of Lorenzini are extremely sensitive organs and can detect charges down to a billionth of a volt. This means that the shark can detect cell depolarizations, such as those that occur during the contraction of a muscle. However the voltage of cell depolarizations is actually a much higher voltage than what the ampullae can detect. Rather, these electroreceptors are fine tuned to be able to detect the ions flowing through the gills of other fish. So as long as a fish is alive, moving and breathing, a shark can sense it.