A circadian rhythm of locomotor activity in newly emerged Ceratophyllus sciurorum

Circadian rhythm in newly emerged individuals of the Red Squirrel (Scuirus vulgaris) flea C.s.sciurorum was studied in a constant environment, using an insect activity monitor. Trials were run over 7 days using two start times (08.00 and 17.00 hours). The results show that, regardless of start time, the fleas display a 24 h activity rhythm. The presence of a rhythm under constant conditions gives a strong indication that C.s.sciurorum has a self-sustaining clock which is started by disturbance and is most likely to be linked to host activity patterns.