The effects of temperature on the dark-adapted spectral sensitivity function of the adult zebrafish

In goldfish and other cold-blooded vertebrates, temperature can influence t he rhodopsin/ porphyropsin contributions to the rod photoreceptors. This st udy examined the effects of temperature on the spectral sensitivity functio n of the dark-adapted zebrafish. Zebrafish were housed in either a warm (28 -30 degrees C) or cold (22-25 degrees C) tank prior to testing. Fish were d ark-adapted for at least 1 h and electroretinogram (ERG) responses to 200 m s stimuli of various wavelengths and irradiances were obtained. Results sho w that water temperature affected the spectral sensitivity function of the ERG b-wave. Subjects housed in the warm temperatures had a spectral sensiti vity consistent with the rhodopsin absorption curve; however, fish housed i n the colder temperatures had a spectral sensitivity function that was the result of a rhodopsin/porphyropsin mixture. In addition, ultraviolet cones (lambda(max): 362 nm) contributed to the dark-adapted spectral sensitivity function under both temperature conditions. Consistent with the results fro m other fish, the dark-adapted visual system of the zebrafish can be influe nced by water temperature. The results of this study demonstrate the necess ity of maintaining a stable environment when examining the contributions of the photoreceptors to the visual response. (C) 1999 Elsevier Science Ltd. All rights reserved.