Lateral line
The lateral line is a system of sense organs found in fish, and not in land vertebrates. It detects movement and vibration in the surrounding water. Modified epithelial cells, known as hair cells, respond to changes around the fish. These turn the changes into electrical impulses which go to their central nervous system.
Lateral lines are used in schooling, predation, and orientation. For example, fish use their lateral line system to follow the vortices produced by fleeing prey. They are faint lines running lengthwise down each side, from the gill covers to the base of the tail.
In some species, the receptive organs of the lateral line have been modified to function as electroreceptors, which are organs used to detect electrical impulses. Most amphibian larvae and some fully aquatic adult amphibians have systems which work a bit like the lateral line.[1]
Lateral Line Media
Oblique view of a goldfish (Carassius auratus), showing pored scales of the lateral line system
Some scales of the lateral line of a Rutilus rutilus
A three-spined stickleback with stained neuromasts
Lateral line rate coding indicates direction and sometimes strength of stimulus. One neuromast shown.
The motion detection system in fish works despite "noise" created by the fish itself. The brain copies the efferent commands it gives to the swimming muscles to the lateral line, effectively suppressing swimming noise and revealing small signals from the environment, such as from prey.
The electroreceptive organs called ampullae of Lorenzini (red dots), illustrated here on the head of a shark, evolved from the mechanosensory lateral line organs (gray lines) of the last common ancestor of vertebrates.
Sea Lamprey (Petromyzon marinus). From female 12 5/8 inches long.
Illustration by Duane Raver
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