Despite lizards using a wide range of color signals, the limited variation in photoreceptor spectral sensitivities across lizards suggests only weak selection for species-specific, spectral tuning of photoreceptors. Some species, however, have enhanced short wavelength sensitivity, which likely helps with the detection of signals rich in ultraviolet and short wavelengths. In this study, we examined the visual system of Tiliqua rugosa, which has a UV/blue tongue, to gain insight into this species’ visual ecology. We used electroretinograms, opsin sequencing and immunohistochemical labelling to characterize whole eye spectral sensitivity and the elements that shape it. Our findings reveal that T. rugosa expresses all five opsins typically found in lizards (SWS1, SWS2, RH1, RH2 and LWS) but possesses greatly enhanced short wavelength sensitivity compared to other diurnal lizards. This enhanced short wavelength sensitivity is characterized by a broadening of the spectral sensitivity curve of the eye towards shorter wavelengths while the peak sensitivity of the eye at longer wavelengths (560 nm) remains similar to other diurnal lizards. While an increased abundance of SWS1 photoreceptors is thought to mediate elevated ultraviolet sensitivity in a couple of other lizard species, SWS1 photoreceptor abundance remains low in our species. Instead, our findings suggest that short-wavelength sensitivity is driven by multiple factors which include a potentially red-shifted SWS1 photoreceptor and the absence of short-wavelength absorbing oil droplets. Examining the coincidence of enhanced short-wavelength sensitivity with blue tongues among lizards of this genus will provide further insight into the co-evolution of conspecific signals and whole-eye spectral sensitivity.
Enhanced short-wavelength sensitivity in the blue-tongued skink, Tiliqua rugosa
- Award Group:
- Funder(s): Australian Research Council
- Award Id(s): FT110100528
- Funder(s):
Currently Viewing Accepted Manuscript - Newer Version Available
Nicolas Nagloo, Jessica K. Mountford, Ben J. Gundry, Nathan S. Hart, Wayne I. L. Davies, Shaun P. Collin, Jan M. Hemmi; Enhanced short-wavelength sensitivity in the blue-tongued skink, Tiliqua rugosa. J Exp Biol 2022; jeb.244317. doi: https://doi.org/10.1242/jeb.244317
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