The relationship between organic material and check rings in fish otoliths

Abstract

1. 1. Staining techniques used to reveal check ring patterns in otoliths owed their effect to the dissolution of otolith material caused by the low pH of the stain. 2. 2. Stains with higher pH values did not etch otoliths, but showed variable staining intensities in different parts of the otolith as well as between parts of micro- and macroincrements. 3. 3. Acid dissolution of sections of otoliths left deposits of protein with patterns similar to observed micro- and macroincrements. 4. 4. Comparisons of the patterns of low and high pH staining effects suggested that two acid insoluble matrix proteins may be present, one with S-C-N groupings similar to keratin; and that a third acid soluble protein is associated with the dark band of the microincrement resulting in etched grooves at the point where the microincrements become more narrow.