noun, plural: otoliths
An otolith is a particle that is crystalline in structure due to its calcium carbonate composition. It is found in the inner ear of vertebrates. In particular, it adheres to the gelatinous membrane of the maculae of the utricle and the saccule. Saccule and utricle of the inner ear make the otolith organs in vertebrates. Thus, otoliths are associated with the sense of balance. Movement of otoliths (for instance, due to a change in the position), stimulates the sensory hair cells to send impulses to the brain. The otoliths are also a directional indicator. In higher aquatic and terrestrial vertebrates, the otoliths are involved in sound detection. The otoliths are also sensitive to gravity and linear acceleration.
The otoliths may also be used as an indication of the age of a fish. Counting the annual growth rings on the otoliths may provide an estimate of the age of a particular fish.
Word origin: Ancient Greek ōto, from oûs (“ear”) + líthos (“stone”)
- statolith (zoology)