DIEL THERMOREGULATION OF THE CRAWFISH PROCAMBARUS-CLARKII (CRUSTACEA,CAMBARIDAE)

1. In a diel cycle Procambarus clarkii has two preferred temperatures: 24.0 +/- 0.15 SEM degrees C during the day and 26.7 +/- 0.13 SEM degr ees C at night. 2. The preferred temperatures are independent from the weight of the organisms. 3. In the photophase the animals are dispers ed, in the scotophase they congregate. 4. The crawfish seem to feed du ring the thermal interphases. 5. Animals in a constantly dark conditio n maintain a diel preferendum of temperature.