Ampullae of Lorenzini
Ampullae were initially described by Marcello Malpighi and later given an exact description by the Italian physician and ichthyologist Stefano Lorenzini in 1679, though their function was unknown.
[7] Ampullae of Lorenzini are present in cartilaginous fishes (sharks, rays, and chimaeras), lungfishes, bichirs, coelacanths, sturgeons, paddlefishes, aquatic salamanders, and caecilians.
Ampullae of Lorenzini appear to have been lost early in the evolution of bony fishes and tetrapods, though the evidence for absence in many groups is incomplete and unsatisfactory.
Cartilaginous fishes Coelacanths Lungfish (aquatic salamanders, caecilians) Other tetrapods bichirs, reedfishes sturgeons, paddlefishes Most bony fishes Each ampulla is a bundle of sensory cells containing multiple nerve fibres in a sensory bulb (the endampulle) in a collagen sheath, and a gel-filled canal (the ampullengang) which opens to the surface by a pore in the skin.
[8][3][9] Pores are concentrated in the skin around the snout and mouth of sharks and rays, as well as the anterior nasal flap, barbel, circumnarial fold and lower labial furrow.
Non-pored canals do not interact with external fluid movement but serve a function as a tactile receptor to prevent interferences with foreign particles.
Because the basal membranes of the receptor cells have a lower resistance, most of the voltage is dropped across the excitable apical faces which are poised at the threshold.
The collagen jelly, a hydrogel, that fills the ampullae canals has one of the highest proton conductivity capabilities of any biological material.
A study from 2004 shows this magnetoreception by cartilaginous fish as they respond to artificially generated magnetic fields in association with food rewards.
These top predators can help keep the primary consumer populations in check, and when they migrate, they in turn help to cycle and redistribute nutrients to other ecosystems.
[21] The question remained open,[22] and in 2023 it was predicted that the ampullae of Lorenzini in sharks would be able to detect a temperature difference of 0.001 Kelvin (a thousandth of a degree).
