Effects of Ambient Temperature and Temperature Cycle on Locomotor Activity Rhythm in the Onion fly, Delia antiqua

Abstract

Abstract The phase of locomotor activity of the onion fly, Delia antiqua, in LD12:12 advanced at a low temperature (20°C) as compared with that at a high temperature (25°C). The free-running period (τ) in constant darkness (DD) at 20°C became shorter than that at 25°C, suggesting that the phase advance of locomotor activity in LD cycles at 20°C was caused by the decrease in τ. In constant light (LL), the locomotor activity was arrhythmic at a constant temperature. In both DD and LL, the locomotor activity was entrained to a 12 hr 25°C:12 hr 20°C temperature cycle; the activity occurred in the thermophase and its peak delayed with age. However, the delay in LL was smaller than that in DD. At a cycle of 12 hr cool (20°C) light and 12 hr warm (25°C) dark, the fly showed a similar activity pattern to that in LD 12:12 at a constant temperature (20°C or 25°C); the activity occurred in the light phase. This suggests that LD cycle is a stronger zeitgeber than a temperature cycle to entrain the locomotor activity ...