Activity of long-wavelength cones under scotopic conditions in the cyprinid fish Danio aequipinnatus.
In carp (Cyprinus) and goldfish (Carassius), long-wavelength cones are reported to be active under scotopic conditions. Using the electroretinogram (ERG), we tested another cyprinid fish, Danio aequipinnatus, which contains A1-based visual pigments and for which we had previously measured the spectral sensitivities of individual cones. Dark adaptation curves show a rod/cone break at about 45 min. When thoroughly dark-adapted, the spectral sensitivity function is broader than can be accounted for by self-screening of rhodopsin, but it can be modeled by an additive combination of rods and the 560-nm cones. Dim, red background light causes adaptation of rods and a broadening of the spectral sensitivity function, which can be simulated by increasing the proportion of cones in the model. Brighter red backgrounds adapt the 560-nm cones. Because of the effect of red adapting lights, the ERG evidence for the participation of long-wavelength cones close to visual threshold appears to be different in Danio than in the goldfish Carassius.
van Roessel
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Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven 06520-8103, USA.
Palacios
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Goldsmith
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D000818:Animals; D003530:Cyprinidae / Q000502:physiology*; D003623:Dark Adaptation / Q000502:physiology*; D004596:Electroretinography; D006054:Goldfish / Q000502:physiology; D066298:In Vitro Techniques; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology; D012243:Rhodopsin / Q000502:physiology; D013045:Species Specificity
D012243:Rhodopsin