Spectral sensitivities including the ultraviolet of the passeriform bird Leiothrix lutea

Abstract

Summary.Spectral sensitivity functions of a passeriform bird, the Red-billed Leiothrix Leiothrix lutea (Timalidae) were determined in a behavioural test under different background illuminations.1. With photopic illumination the spectral sensitivity of Leiothrix lutea covered the measured range from 320 nm to 680 nm. Four peaks of spectral sensitivity were found: a UV (370 nm), a blue (460 nm), a green (530 nm) and a red (620 nm) sensitivity peak. The spectral sensitivity was highest in the UV and decreased (over the blue and the green peak) towards the red sensitivity peak. The 4 peaks of spectral sensitivity point to 4 underlying cone mechanisms under photopic illumination and thus to a probably tetrachromatic colour vision of Leiothrix lutea.2. With mesopic illumination the bird's spectral sensitivity covered the measured range from 320 nm to 680 nm. Neural interactions between cone and rod sensitivities are likely to determine this function. The increased overall sensitivity and a dominant sensitivity peak at 500 nm point to a typical rhodopsin as the likely rod photopigment.3. Different aspects of the biological significance of the high UV sensitivity are discussed.

Microstructure Characteristics of the Cornea in Birds and Mammals

“…In contrast, most birds and the rat have UV vision because they possess a cone cell sensitive to UV in their retina [5,8,14,18]. The maximum absorbance of the shortest-wavelength pigment in many species has been examined using a microspectrophotometer [3,4,6,7,19,24,25,32]. The cornea of animals with UV vision may be exposed to UV rays more frequently than that in animals without UV vision.…”

The role of UV in crab spider signals: effects on perception by prey and predators

“…This detectability is due to two characteristics of photoreceptors. First, honeybees and most birds are more sensitive in the ultraviolet than in other spectral ranges (Helversen, 1972;Maier, 1992). Second, each type of photoreceptor is sensitive across a wide range of wavelengths, forming roughly a Gaussian function (Stavenga et al, 1993).…”

Ultraviolet sensitivity and colour vision in raptor foraging

“…Spatial summation can improve signal strength (signal-to-noise ratio) so that the limiting Weber fraction in each receptor mechanism can be estimated from Eqn4 where ω is the Weber fraction, v is the standard deviation of the noise in an individual cone of type i, and η is the number of this cone type per receptive field. The absolute noise levels of bird photoreceptors are not known but a Weber fraction of 0.1 in the LWS mechanism of the pekin robin (Leiothrix lutea) has been derived from behavioural data of photopic spectral sensitivity (Maier, 1992;. We thus used a Weber fraction of the LWS mechanism of 0.1 and the assumption that noise is independent of receptor type and proportional to the relative abundance of each receptor type in the retina (Eqn4).…”