Locomotor Activity Rhythms in the Bluegill Sunfish, Lepomis macrochirus

Abstract

Locomotor activity of bluegill sunfish was monitored electronically as the fish moved between the chambers of an experimental tank. Phototransistors and associated circuitry permitted the fish to control water temperature and/or lights independently along 2 axes, with no prior training; alternatively, these variables could be exogenously controlled by thermostats and timers. The fish exhibited an endogenous, diurnal (60-75% of total 24 h activity), locomotor activity pattern which persisted in the absence of an exogenous light cycle (DD), or when the fish controlled the lights, and was unaffected by temperature (17 or 31 C). The diurnal activity pattern persisted when fish controlled the water temperature (mean = 31 C both day and night), indicating that thermoregulatory movements at night did not disrupt the rhythm seen at constant fixed temperatures.