| Abstract: | Abstract— An attempt was made to determine whether entrainment of the circadian rhythms of locomotor activity and ERG amplitude of the crayfish involved extraretinal photoreception. The results of a variety of experiments involving surgical lesions and localized illumination provided evidence that both rhythms can be entrained via an extraretinal pathway. The data also demonstrate that the caudal photoreceptor is unnecessary for entrainment. Our evidence to date suggests that the extraretinal photoreceptor is located in the supraesophageal ganglion; however, the possibility of photoreceptive input from other regions of the CNS, particularly the optic lobe, has not been eliminated. It is also tentatively concluded that the circadian oscillators for both the locomotor and the ERG amplitude rhythms are located within the supraesophageal ganglion, but more data are needed to confirm this conclusion. |
