Ampullae of Lorenzini
topic claimed by Megan Kirsch
The ampullae of Lorenzini is a subcutaneous, electroreceptive sensory system consisting of a network of jelly filled pores. These are found in cartilaginous fish such as sharks, rays, chimeras, reedfish, and sturgeons. Each ampulla consists of a visible pore on the skin that opens to a canal which leads to a cilia filled cavity. Within the ampulla is a gel substance made of glycoproteins that conducts electricity, allowing for the detection of nearby electric fields. Pores tend to be located on the underside of the head, snout, and nose of the organism. The ampullae canal lengths vary for each animal, but the distribution of the pores is the same for each species. In all species, there is a left-right symmetry of the distribution of pores.
Discovery
The ampullae were first discovered by Italian biologist Marcello Malpighi in 1663. The first studies on it however were done by Italian physician and icthyologist Stefano Lorenzini who published his findings in 1678. At first it was thought that the ampullae detected pressure and temperature, but in 1962 Dutch scientists Dijkgraaf and Kalmijn discovered its electroreceptive abilities. Today further research is being undergone to further understand the functions and specifics of the ampullae of Lorenzini.
Mechanism
The ampullae detects electric fields by detecting the difference between the voltage at the skin pore and the cavity. The internal electrochemical environment of an organism differs from the external environment. When a strong enough electric field is conducted through the canal, the change in potential difference is detected by the cilia in the cavity and alerts the organism to the electric field.
Function
All living creatures produce electric fields through muscle contractions. These fields are conducted through the salt water of the ocean to other organisms. If an organism with electroreceptive abilities is in close proximity to the generated electric field, it can sense the other organism even without it being visible. The more muscle contractions produce a stronger electric field, which makes it easier to be detected. Wounded animals tend to undergo much more muscles contractions, producing stronger electric fields, and becoming easy targets for predators with electroreceptive abilities. Also, if an animal is bleeding, the salt in its blood will make its surroundings an even more conductive medium, making it even easier to be detected. This is how sharks are such effective predators. Further studies are being done indicating the possibility of the ampullae being able to detect the magnetic field of the earth, giving the ampullae a navigational function as well.