Abstract
Although ultraviolet (UV) sensitivity is widespread among animals it is considered rare in mammals, being restricted to the few species that have a visual pigment maximally sensitive (λmax) below 400 nm. However, even animals without such a pigment will be UV-sensitive if they have ocular media that transmit these wavelengths, as all visual pigments absorb significant amounts of UV if the energy level is sufficient. Although it is known that lenses of diurnal sciurid rodents, tree shrews and primates prevent UV from reaching the retina, the degree of UV transmission by ocular media of most other mammals without a visual pigment with λmax in the UV is unknown. We examined lenses of 38 mammalian species from 25 families in nine orders and observed large diversity in the degree of short-wavelength transmission. All species whose lenses removed short wavelengths had retinae specialized for high spatial resolution and relatively high cone numbers, suggesting that UV removal is primarily linked to increased acuity. Other mammals, however, such as hedgehogs, dogs, cats, ferrets and okapis had lenses transmitting significant amounts of UVA (315–400 nm), suggesting that they will be UV-sensitive even without a specific UV visual pigment.
Highlights
The range of wavelengths an animal perceives depends on the spectrum available in the environment, the degree to which this is transmitted though the ocular media and the visual pigments within the retina
Many let through significant amounts of shortwave radiation, suggesting that a degree of UV sensitivity is widespread among mammals
Transmission at 700 nm was set to 100% and ocular media scanned at 1 nm intervals from 300 to 700 nm
Summary
The range of wavelengths an animal perceives depends on the spectrum available in the environment, the degree to which this is transmitted though the ocular media and the visual pigments within the retina. Among mammals, such UV-sensitive visual pigments are relatively rare and have only been described in some rodents [11 –18], a mole [19], several marsupials [20 –23] and some bats [24 –27] Such animals have lenses that, unlike those of humans, transmit short wavelengths well. All photoreceptors can potentially absorb significant amounts of UV and any animal with ocular media that are transparent to UV light will inevitably be sensitive to these wavelengths even if they do not possess a visual pigment with lmax in this part of the spectrum [9] (figure 1). Many let through significant amounts of shortwave radiation, suggesting that a degree of UV sensitivity is widespread among mammals
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