Rod contributions to the electroretinogram of the dark-adapted developing zebrafish

Anatomical studies of the developing zebrafish retina have shown that rods approach maturity at about 15 days postfertilization (dpf). Past work has e xamined the photopic spectral sensitivity function of the developing zebraf ish, but not spectral sensitivity under dark-adapted conditions. This study examined rod contributions to the dark-adapted spectral sensitivity functi on of the ERG b-wave component in developing zebrafish. ERG responses to st imuli of various wavelengths and irradiances were obtained from dark-adapte d fish at 6-8, 13-15, 21-24, and 27-29 dpf. The results show that dark-adap ted spectral sensitivity varied with age. Spectral sensitivity functions of the 6-8 and 13-15 dpf groups appeared to be cone dominated and contained l ittle or no rod contributions. Spectral sensitivity functions of the 21-24 and 27-29 dpf groups appeared to have both rod and cone contributions. Even at the oldest age group tested, the dark-adapted spectral sensitivity func tion did not match the adult function. Thus, consistent with anatomical fin dings, the rod contributions to the ERG spectral sensitivity function appea r to develop with age; however, these contributions are still not adult-lik e by 29 dpf, which is contrary to anatomical work. These results illustrate that the zebrafish is an excellent model for visual development. (C) 2001 Wiley-Liss, Inc.