Spectral sensitivity in the guppy (poecilia reticulata) measured using the dorsal light response

Abstract

Photopic spectral sensitivity was determined behaviourally, using the dorsal light response (DLR), for guppies (Poecilia reticulata) kept under 12L/12D light regimes at two light intensities: 0.184W/m2 and 3.18W/m2. Thresholds were measured at each of 11 wavelengths, from 407.5 nm to 624 nm, by presenting the monochromatic light to one eye and finding the intensity necessary to balance out the response to a standard tungsten light presented to the other eye. Sensitivity in both groups was greatest at the shortest wavelength used (407.5 nm), with a secondary maximum at about 500 nm and a possible further rise in sensitivity at the longest wavelength used (624 nm). The short wavelength maximum is probably due to short wavelength sensitive cones containing VP408, and the sensitivity around 500 nm may be due to the rods.