Animals

Lateral Line

by Marcia Malory

The lateral line is a sense organ that is found in fish.

Some adult amphibians and most amphibian larvae also have lateral lines.

Lateral lines detect movement in the water.

Fish use their lateral lines to orient themselves in relation to the current, to find prey, and to avoid colliding with other fish.

Lateral lines look like two faint lines that run along the side of a fish's body, from its head to its tail.

A lateral line is made up of receptors known as neuromasts.

Each neuromast is made up of a group of hair cells that are surrounded by a gelatinous cap, which is known as a cupula.

The neuromasts constantly send out nerve impulses.

When something, such as another fish, moves in the water, it creates waves in the water.

This causes the cupulas to move and the hairs inside of them bend, which in turn causes the frequency of the nerve impulses to change.

The change in the frequency of the nerve impulses provide the fish with information about the moving object, such as its shape, size and the speed at which it is moving.

Hair cells in lateral lines resemble hair cells in the inner ears of vertebrates.

Fish can hear very low frequency sounds with their lateral lines.

Neuromasts are often found inside lateral line canals, where they are arranged in rows and form the lateral line system.

The neuromasts in the lateral line canals are linked to the external environment via canal pores.

Fish also have free neuromasts, which come into the direct contact with water, on the surfaces their bodies.

Sometimes small groups of neuromasts can be found together in pit organs, which are scattered all over a fish's body.

Electroreception in Fish

Cartilaginous fish, such as sharks, and some bony fish have modified neuromasts that are known ampullae of Lorenzini.

The ampullae of Lorenzini act as electroreceptors - sensory organs that detect electric fields in the water.

Some scientists think that fish that have ampullae of Lorenzini may also use them to detect magnetic fields, changes in temperature and changes in the salinity of water.