[The content of electrolytes (Na, K, Ca, Mg) in vertebrate otoliths and otoconia]

Na, K, Ca and Mg concentrations have been determined in the otoliths and otoconia of the lamprey, skate, guppy and hen. Lamprey otoliths sharply differ from the otoliths and otoconia of other animals with respect to their K and Ca content. In all the animals investigated excluding lamprey, only traces of K were found. Na concentration in the otilithic apparatus of the investigated animals varies within 0.475-1.04 mM/g. Na presumably is bound to proteins of the organic matrix and plays an important role in the growth of otoliths and otoconia. Concentration of Ca in the otoliths and otoconia of all animals excluding the lamprey was equal to 9.09-9.63 mM/g: organic substances constitute 4-10 per cent of their mass. In the lamprey, Ca concentration in the otoliths was found to be 5.33 mM/g, the content of organic matter amounting to more than 40 per cent. In constantly growing otoliths of fish, concentration of Mg was significantly lower than in otoconia of fish and other animals. This is presumably due to the fact that Mg inhibits crystalline growth of calcium salts.