Electroretinograms and Retinal Ganglion Cell Responses in the Skipjack Tuna

Abstract

The ERG's and retinal ganglion cell responses were recorded from immobilized skipjack tuna, Katsuwonus pelamis. The light-adapted ERG's were characterized by a rather small a-wave and a distinct b-wave. During dark-adaptation, the b-wave grew larger and the sensitivity increased by 3 logarithmic units. Photopic and scotopic spectral sensitivity curves, based on the b-wave, were almost identical and, in addition, differed little from the Dartnall's nomogram cruve with its λ max at 490 nm. The simple photopic curve points to a single photopigment involved in the photopic vision, accordingly, color-blindness of the species. The retinal units revealed a similar spectral sensitivity and did not change their response patterns with the wavelength of the stimulus. This also suggests the absence of color-discriminating capacity by the fish. © 1973, The Japanese Society of Fisheries Science. All rights reserved.