OTOLITH GROWTH IN FISHES

1. 1. The sagittal otoliths of teleosts rest in a groove in the base of the otic cleft resulting in restriction of growth along part of the ventral edge of the otolith. 2. 2. The rate of crystalline deposition of the otolith is low at the sulcus, increasingly higher along the sulcul surface rising to a maximum at the growing edge of the otolith. 3. 3. It is proposed that the gradient in growth of crystalline deposition between sulcus and otolith edge is maintained by a pH gradient resulting from high to low levels of metabolic activity. 4. 4. Decreasing crystal widths along sulcus to edge surface are in accordance with those predicted by the Ostwald-Lussac law of crystal size changes along solubility gradients. 5. 5. The metabolic basis driving the pH gradient makes it probable that check rings in the sulcul part of the otolith are caused by surges in metabolic activity, not age. © 1990.