Neuromast

A neuromast is a mechanosensory organ found in fishes and aquatic amphibians that detects water movement and vibration. Neuromasts are the functional units of the lateral line system, a sensory network that provides information about nearby objects, flow patterns, and relative motion in the surrounding fluid environment.

Each neuromast typically contains a cluster of hair cells—sensory epithelial cells with bundles of stereocilia and a single kinocilium—surrounded by supporting cells. The hair cell bundles are embedded in a gelatinous structure called the cupula, which transmits deflections caused by water flow to the mechanosensitive hair bundles. Deflection of stereocilia opens mechanically gated ion channels, producing receptor potentials that are transmitted via afferent neurons to the brain.

Neuromasts occur in two main forms: superficial neuromasts, located on the skin surface and sensitive to slow, sustained flows; and canal neuromasts, enclosed within subepidermal canals that detect rapid pressure changes and higher-frequency stimuli. Their distribution along the head and body varies by species and life stage, reflecting ecological demands such as prey detection, schooling coordination, obstacle avoidance, and rheotaxis.

Neuromast hair cells share molecular and functional features with inner ear hair cells and can regenerate after injury in many fish species, making them a model for studying hair-cell repair and sensory regeneration. The lateral line and its neuromasts are absent in terrestrial adult vertebrates such as mammals.