THE ROLE OF VARIOUS ENVIRONMENTAL FACTORS AND THE PINEAL ORGAN ON THE PHYSIOLOGY OF TELEOST FISHES

The physiology of temperate zone teleost fishes is regulated in part by various fluctuating environmental parameters. Little is known, however, about how these environmental variations are translated into the regulation of physiological processes. The pineal organ in some fishes may be a photoreceptor or mediator of photoperiod information. This suggests that the pineal may be involved in physiological adjustments to photoperiod shifts. Since many physiological events in fishes are modulated by photoperiod, it was of interest to determine whether removal of this organ affected some of the various parameters known to be influenced by environmental lighting. Both reproductive activity and prolactin physiology in some fishes are known to be controlled, in part, by photoperiod. Thus, the effects of pinealectomy on pituitary prolactin levels, and on pituitary and plasma gonadotropin titres and gonadal development in fish exposed to various photoperiod-temperature regimes were examined