Water enters the system through numerous pores on the animal's surface and flows along the tube past the neuromasts. Pressure of moving water bends the cupula causing an action potential in the hair cells. Provides information about the body's movement direction and velocity of water currents, and movements or vibrations caused by predators and prey. Sound waves are conducted through the skeleton of the head to the inner ear, this sets otoliths in motion, stimulating the hair cells. Some fish have a Weberian apparatus , a series of 3 bones which conducts vibrations from the swim bladder to the inner ear.
Fish can hear higher frequencies due to their inner ears.
In terrestrial amphibians, reptiles and birds, sound is conducted from the tympanic membrane to the inner ear by a single bone, the stapes. The body hairs of many insects vibrate in response to sound waves of specific frequencies. Fine hairs on the antennae of male mosquitoes detect the hum produced by a female's wings. Vibrating body hairs of some caterpillars detect predatory wasps.