Influence of the Eyes and Pineal Gland on Locomotor Activity Patterns of Channel Catfish Ictalurus punctatus

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Abstract
The influence of the eyes and pineal gland on locomotor activity rhythms of channel catfish, Ictalurus punctatus, and the extent to which varying light intensity altered these activity rhythms were evaluated. Locomotor activity was measured in normal, blinded, pinealectomized, and pinealectomized-blinded channel catfish exposed to a 12:12 light/dark photoperiod of decreasing light intensities (7,500, 175, and 0.7 lx). Normal, blinded, and pinealectomized fish exhibited nocturnal activity patterns which corresponded with the exogenous photoperiod. Fish without lateral eyes and pineal gland did not entrain to the photoperiod but had arrhythmic activity patterns. Neither treatment nor light intensity affected total locomotor activity. Blinding or pinealectomy decreased the level of dark-period activity at low light intensities, but the effect of light intensity was not observed in normal and pinealectomized-blinded fish. Normal and blinded fish under constant light or constant dark exhibited arrhythmic activity. The pineal gland functions as an extraretinal light receptor in channel catfish.