Differences in ocular media transmittance in classical frog and toad model species and its impact on visual sensitivity.

The transmittance properties of the cornea, lens and humours of vertebrates determine how much light across the visible spectrum reaches the retina, influencing sensitivity to visual stimuli. Amphibians are the only vertebrate class in which the light transmittance of these ocular media has not been thoroughly characterised, preventing large-scale comparative studies and precise quantification of visual stimuli in physiological and behavioural experiments. We measured the ocular media transmittance in some commonly used species of amphibians (the bufonids Bufo bufo and Rhinella ornate, and the ranids Lithobates catesbeianus and Rana temporaria) and found low transmittance of short wavelength light, with ranids having less transmissive ocular media than bufonids. Our analyses also show that these transmittance properties have a considerable impact on spectral sensitivity, highlighting the need to incorporate this type of measurement into the design of stimuli for experiments on visual function.