Review of the growth regulation processes of otolith daily incremet formation

摘要

Otolith growth is a complex phenomenon integrating vaious factors tat can be considered either as endogenous or exogenous, although they are always regulated by the physiology of the fish. Both types of factors may operate upon the anabolism and catabolism of the fish. and these proceses are reflected in the rhythmic deposition of the two main constituents of the otolith: the organic matrix and the paragonite layers. Both components reflect the endogenous process in their periodicity, and the exogenous process in the amount of materal laid down in the otolith, resulting in how and where the increments are formed. At the endogenous level, several morphological and functional aspects are relevant. The main one is the role of the otolith as a mechano-receptor in the inner ear. Thus, inner-ear anatomy and function regulate otolith growth and morphology, which in turn determine the daily growth rats. Environmental conditions, transmitted through the physiology of fish, affect the otolith growth rate (increment width) but increment periodicity may be disrupted only in extreme cases of physiological stress. The current state of the art is reviewed and the otolith growth paradigm is summarized. Relevant subjects not yet studied are pointed out for future research.