Effect of the temperature upon ultradian and circadian ERG amplitude rhythms during ontogeny of crayfish Procambarus clarkii.

The purpose of this work was to investigate whether the ultradian rhythms that are present prior the electroretinogram (ERG) amplitude circadian rhythm, and are superimposed upon it, during the different stages of development of the crayfish Procambarus clarkii are temperature sensitive, as well as the circadian rhythm. Temperature sensitivity was investigated using ERG amplitude recordings in free running conditions at high and low temperature from juvenile instars of different ages. All recordings were submitted to two types of statistical tests: X2 periodogram and power spectrum analysis. Cycles detected by both methods were selected from periodogram and Q10 was computed. Selected ultradian periods (ranging between 1.7 to 17.5 hrs.) seem to show temperature insensitivity that could imply temperature compensation, a property apparently shared with the emerging circadian period. These results support the endogenous nature of the ultradian ERG rhythms as well as their probably functional interaction with the circadian rhythm.