CRITICAL FLICKER FUSION FREQUENCY OF THE RIVER LAMPREY (LAMPETRA-FLUVIATILIS)

Enucleated eyes of the river lamprey (Lampetra fluviatilis) were investigated by flicker stimulation. The critical fusion frequencies (CFF's) of the ERG were determined at various intensities of the stimulating light. The relation between CFF and light intensity shows two phases. On the average, the shift between these two phases occurs at 9.8 Hz and -3.0 log units relative intensity (170 lux). The scotopic fusion frequencies are low compared to those of most other vertebrates hitherto investigated and may reflect an extraordinarily slow decay of the photoreceptor potentials in the river lamprey. The intensity at which the CFF phase-shift occurs indicates that the river lamprey retina takes an intermediate position between rod- and cone-dominated retinas with regard to the cone/rod ratio. The results agree with previous morphological findings and suggest a duplex organization of the river lamprey retina. © 1979.