Absorbance spectra were recorded by microspectrophotometry
from 39 different rod and cone types representing amphibians,
reptiles, and fishes, with A1- or A2-based visual pigments
and λmax ranging from 357 to 620 nm. The
purpose was to investigate accuracy limits of putative
universal templates for visual pigment absorbance spectra,
and if possible to amend the templates to overcome the
limitations. It was found that (1) the absorbance spectrum
of frog rhodopsin extract very precisely parallels that
of rod outer segments from the same individual, with only
a slight hypsochromic shift in λmax, hence
templates based on extracts are valid for absorbance in
situ; (2) a template based on the bovine rhodopsin
extract data of Partridge and De Grip (1991) describes
the absorbance of amphibian rod outer segments excellently,
contrary to recent electrophysiological results; (3) the
λmax/λ invariance of spectral shape
fails for A1 pigments with small λmax and
for A2 pigments with large λmax, but the
deviations are systematic and can be readily incorporated
into, for example, the Lamb (1995) template. We thus propose
modified templates for the main “α-band”
of A1 and A2 pigments and show that these describe both
absorbance and spectral sensitivities of photoreceptors
over the whole range of λmax. Subtraction
of the α-band from the full absorbance spectrum leaves
a “β-band” described by a λmax-dependent
Gaussian. We conclude that the idea of universal templates
(one for A1- and one for A2-based visual pigments) remains
valid and useful at the present level of accuracy of data
on photoreceptor absorbance and sensitivity. The sum of
our expressions for the α- and β-band gives a good
description for visual pigment spectra with λmax
> 350 nm.