Visual Neuroscience



Cone contributions to the photopic spectral sensitivity of the zebrafish ERG


ALAN  HUGHES a1a2, SHANNON  SASZIK a1, JOSEPH  BILOTTA a1c1, PAUL J.  DEMARCO  JR. a2a3 and WARREN F.  PATTERSON  II a1
a1 Department of Psychology, Western Kentucky University, Bowling Green
a2 Department of Psychology, University of Louisville, Louisville
a3 Louisville VA Medical Center, Louisville

Abstract

Microspectrophotometry studies show that zebrafish (Danio rerio) possess four cone photopigments. The purpose of this study was to determine the cone contributions to the zebrafish photopic increment threshold spectral-sensitivity function. Electroretinogram (ERG) b-wave responses to monochromatic lights presented on a broadband or chromatic background were obtained. It was found that under the broadband background condition, the zebrafish spectral-sensitivity function showed several peaks that were narrower in sensitivity compared to the cone spectra. The spectral-sensitivity function was modeled with L − M and M − S opponent interactions and nonopponent S- and U-cone mechanisms. Using chromatic adaptation designed to suppress the contribution of the S-cones, a strong U-cone contribution to the spectral-sensitivity function was revealed, and the contributions of the S-cones to the M − S mechanism were reduced. These results show that the b-wave component of the ERG receives input from all four cone types and appears to reflect color opponent mechanisms. Thus, zebrafish may possess the fundamental properties necessary for color vision.

(Received July 28 1997)
(Accepted April 29 1998)


Key Words: Danio rerio; Electroretinogram; Color opponency; Ultraviolet cones.

Correspondence:
c1 Correspondence and reprint requests to: Joseph Bilotta, Department of Psychology, Western Kentucky University, 1 Big Red Way, Bowling Green, KY 42101, USA.