NONPARAMETRIC EFFECTS OF MONOCHROMATIC LIGHT ON THE ACTIVITY RHYTHM OF JUVENILE CRAYFISH

The current study was carried out to test the influence of blue and re d monochromatic light upon the motor activity rhythm of juvenile crayf ish as well as determine whether this effect involves extraretinal pho toreception. Two groups of 46 juvenile instars were used: (1) intact c ontrol animals and (2) animals lacking retina and lamina ganglionaris. All animals were individually monitored with a motor activity recordi ng system for 30 days. For the first 10 days the animals were maintain ed and kept in constant darkness (DD) and then submitted to 24-h skele ton photoperiod cycles (SP) consisting of 30 min red or blue light sig nals calibrated to the same irradiance (25 Wm(-2)) during the next 10 days. Afterwards, they were left in DD for the last 10 days of the exp eriment. Activity was quantitatively and qualitatively analyzed. Resul ts show that all control intact animals synchronized to blue or red li ght exhibited shift advances or delays. These results indicate that bo th circadian responses to monochromatic light investigated in this stu dy are mediated by extraretinal photoreceptors.