Effects of Pineal Shielding on the Thermoregulatory Behavior of the White Sucker Catostomus commersoni

Abstract

Examinations were made of the roles of pineal and extraretinal photoreceptors in determining the thermal preferences and thermoregulatory behaviors of a teleost fish, the white sucker Catostomus commersoni. Fish whose pineal regions were shielded from light spent significantly more time in the warmer and/or more illuminated portions of both horizontal thermal gradients and chambers maintained at constant temperatures. These shifts in thermal and light preferences could be reversed by removal of the pineal shields. Shifts in light and thermal preferences became completely developed over 3-5 days after shielding, suggesting immediate neural as well as long-term endocrine alterations. These data indicate that pineal and possibly other extraretinal photoreceptors of this teleost fish have a dosimetric function that is involved in sensing ambient illumination and mediating thermoregulatory behavior.