Studies on the effects of bleaching amphibian rod pigments in situ: I. The absorbance spectra of axolotl and tiger salamander rhodopsin and porphyropsin

Spectrophotometric measurements on retinal folds of axolotl larvae show that the visual pigments of the red rods are rhodopsin with a λ_max of ca. 502 nm and porphyropsin with a λ_max of ca. 526 nm. The spectral changes associated with the bleaching products of these pigments are described. When the larvae metamorphose, following the addition of thyroxine to their water, more than two-thirds of the pigment in their rods is rhodopsin. The same appears to be true for the red rod pigments of naturally metamorphosed tiger salamanders.