Spectral sensitivity of mollies: comparing surface- and cave-dwelling Atlantic mollies, Poecilia mexicana

The visual pigments of cones and rods in three species of mollies, Poecilia mexicana, Poecilia latipinna and their asexual hybrid Poecilia formosa, were examined using microspectrophotometry. In P. mexicana, populations from extreme photic habitats were used: one population originated from a clear water habitat, one from a milky water habitat and another from a completely dark cave. Ultraviolet-sensitive cones were found in all species. Differences in the lmax values of the visual pigments were small between species and among the three P. mexicana populations, but dark-reared cave fishes showed appreciably higher variance. The hybrid species P. formosa showed a highly variable long wavelength cone absorbance, ranging from 528!9 to 598!5 nm, suggesting multiple opsin expression or chromophore mixing. # 2006 The Authors