Visual pigment types and quantum-catch ratios: implications from three marine teleosts

Experimental data on photoreceptor cells and visual pigments are the basis for model calculations performed to assess photoreceptor quantum catches under disparate irradiance conditions. Three unrelated species of fish--black sea bass (Centropristis striata), sea raven (Hemitripterus americanus), and adult winter flounder (Pseudopleuronectes americanus)--are considered. In each case, receptor type quantum catches are compared for various water types and depths. By associating the habit and habitat of an organism with the physical properties of its photoreceptors, quantum-catch ratios are found as possible criteria in the selection of pigment peaks (lambda max). In addition to integrated ("total") quantum catches by the receptor types, rates of quantum catches are determined as a function of wavelength. The latter functions are replotted as pairwise difference spectra. These, in turn, are used to assess the ability of receptor types to participate in wavelength discrimination.