Circadian clock controlling arylalkylamine N-acetyltransferase-like activity in the cricket ( Gryllus bimaculatus) egg

When cricket ( Gryllus bimaculatus) eggs were incubated under a 12-h light/12-h dark (LD) cycle for 6 days after oviposition at 24–26°C and thereafter transferred to constant darkness (DD), arylalkylamine N-acetyltransferase (NAT)-like activity fluctuated in a circadian manner, peaking during the subjective dark period, and the rhythmic activity persisted during the 3rd day of incubation in DD. When the eggs were transferred from LD to a lighting regime in which the light and dark periods were reversed, the rhythm of NAT-like activity continued to oscillate in phase with the light/dark cycle. These data demonstrate that the cricket egg (probably the embryo) contains a circadian clock controlling NAT-like activity, and that the circadian clock entrains to environmental light/dark cycles.