The presence of a porphyropsin-based visual pigment in the juvenile lemon shark (Negaprion brevirostris).

The visual pigment from the juvenile lemon shark has been extracted and is a homogeneous vitamin A2-based porphyropsin with maximum absorption at 522 nm. This is the first report of a porphyropsin visual pigment extracted from the retina of an elasmobranch. In contrast, the visual pigment from the adult lemon shark yields a homogeneous vitamin A1-based rhodopsin with maximum absorption at 501 nm. We conclude that the porphyropsin of the juvenile lemon shark changes over to a rhodopsin as the animal matures.