Activity of long-wavelength cones under scotopic conditions in the cyprinid fish Danio aequipinnatus |
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Authors: | P van Roessel A G Palacios T H Goldsmith |
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Institution: | (1) Department of Molecular, Cellular, and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA Tel.: +1-203 432-3494; Fax: +1-203 432-6161 e-mail: timothy.goldsmith@yale.edu, US |
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Abstract: | 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.
Accepted: 14 June 1997 |
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Keywords: | Rod-cone interaction Scotopic spectral sensitivity Cyprinid fish Danio aequipinnatus |
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