A New Apparatus Used to Record the Locomotor Rhythms of Laboratory Reared Prawns and Shrimps

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Abstract
A new design of actograph with a high sensitivity is described, employing IR emitting diodes and detectors which can record the movements of small, aquatic animals. The actograph was used to record the locomotory activity of juvenile P. elegans and C. crangon reared under LD [light/dark] 12:12, LD 8:8 and LD-random L/D cycles. In LD 12:12 P. elegans and C. crangon displayed a daily rhythm, which in P. elegans had a weak endogenous component. In LD 8:8 both species were synchronized by the light regime, displaying rhythms with an 8 or 16 h component. These rhythms did not persist under constant conditions, and the test animals also were arrhythmic in the LD random regime. Some specimens of P. elegans which were reared in LD 8:8 and LD random displayed weak circadian rhythms under constant conditions.