Question

What are neuromast organs of fishes? What is their function?

Answer 1

Hint:
There are certain organs that help a fish to detect movement, vibrations and pressure gradients of the surrounding water. They are sense organs that are part of the lateral line organs in a fish. It provides the fish with spatial orientation and the ability to navigate in unknown waters.

Complete answer:
Neuromast is a sensory organ with hair-like cells. It is a mechanoreceptive organ and is part of the lateral line organs.
The lateral line organs are a system of sensory organs that are present in aquatic vertebrates. These organs guide the fish in the water by helping them detect movements, vibrations and pressure gradients. The neuromast is a major component of the lateral line. The cells of the neuromast are hair-like and covered with a jellylike cupula. These cells possess afferent and efferent nerve fibres. The cells are modified epithelial cells and are receptive in nature. The presence of microvilli makes the cells function as mechanoreceptors.
There are two types of neuromasts – canal and superficial
CANAL NEUROMAST:
Canal neuromasts are located along the lateral line in sub-dermal and fluid-filled canals.
SUPERFICIAL NEUROMAST
Also called freestanding neuromasts, these are located on the external surface of the body.
The neuromast plays a key role in helping the fish with orientation, defence, behaviour and social schooling.

Note: The lateral line system is even found in amphibians.
The hair-like cells of these organs are similar to the morphology and function of the auditory and vestibular system in vertebrates.
The presence of a sensory organ like neuromast makes it easier for a fish to find its way about in unknown water.