Spectral sensitivities of short‐ and long‐wavelength sensitive cone mechanisms in the frog retina

Abstract

ERG mass photoreceptor responses were recorded across the isolated, aspartate‐perfused retina of the frog, Rana temporaria , in order to determine spectral sensitivities of cones. Cone responses were distinguished from rod responses by their faster kinetics, and responses from different cone types were isolated by selective background adaptation. Our main finding is that of a novel short‐wavelength sensitive cone population peaking at about 431 nm. Further, we find that the sensitivity spectrum of the dominant long‐wavelength sensitive cone population fully accounts for the most common type of photopic ganglion cell spectrum. Both can be described by a nomogram with λ max = 562 nm. This resolves a long‐standing apparent conflict between cone absorbance spectra and ganglion cell sensitivities. Including the 502 nm cones previously described by microspectrophotometry, the frog possesses a collection of cones that could support trichromatic photopic vision.