Essential for the formation of otoliths in the inner ear of developing larvae and for the perception of gravity and acceleration. May be one of the organic components of the ortholiths. Detected on otoliths and the apical surface of epithelial cells in the otic placode in larvae 24 hours after fertilization. Detected in the otic placode and the pineal gland in embryos 24 hours after fertilization. Detected in the sensory hair epithelium along the entire length of the lateral line organ in larvae 72 hours post fertilization. Restricted mainly to neuroepithelial patches in the ear of larvae 72 hours post fertilization. Otoliths are structures composed of proteins and calcium carbonate that are found in the fish inner ear in contact with the otic epithelium. They are essential for the perception of gravity and acceleration.