The role of the eyes and the pineal organ in the circadian rhythmicity in the catfish Silurus asotus.

Abstract

The role of the eyes and pineal organ in the circadian timing system of locomotor activity in catfish Silurus asotus was examined in continuous darkness (DD) and two different intensities of continuous light (dim LL and LL). Freerunning activity was present even after removal of the eyes or the pineal organ, indicating that these organs were not the driving oscillators. However, removal of these organs had different effects on circadian locomotor activity in each condition. (1) In DD, circadian period (τ) of pinealectomized fish were significantly different (p<0.05) from those of intact fish. (2) In LL, the τ of ophthalmectomized fish were significantly different from intact fish (p<0.01). (3) In dim LL, the τ of treated groups were not different from those of intact fish. These results indicate that the biological clock of catfish receives photic input from different photo-receptors separately and integrally depending on the quality of the stimulus. Eyes were presumed to be responsible for obedience to the modified Aschoff's rule in respect to the τ and total locomotor activity.