Seasonal changes in retinal function of the frog Rana Ridibunda.

The electroretinogram (ERG) of Rana ridibunda was recorded at different times of the year. The frogs exhibited distinct seasonal changes in various parameters of the ERG. The amplitudes of both the a- and the b-waves were greater in summer than in winter. With a luminance of 3000 cd/m(2) the mean amplitude of the a-wave ranged from minimal 30 μ V (February) to maximal 60 μ V (July), and that of the b-wave from 190 μ V (February) to maximal 550 μ V (June). Average latency was about 28 ms in winter and 14 ms in summer. The greatest difference was found in flicker-fusion frequency which averaged 29 Hz in July and 9 Hz in January. There was also a significant change in the average threshold for response to white light (0.011 cd/m(2) in March).