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L. Peichl, A. Vielma, M. Glösmann, A. G. Palacios, C. E. Schleich; Retinal Photoreceptors in Fossorial Tuco-Tucos (Rodentia, Ctenomys): Types, Topographies, and UV Sensitivity. Invest. Ophthalmol. Vis. Sci. 2010;51(13):896.
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Cone and rod populations in two fossorial (facultative subterranean) rodent species, Ctenomys talarum and C. magellanicus (tuco-tucos), were analyzed to elucidate whether their retinas are more adapted to their near-lightless burrows or to their occasional diurnal surface activity.
Paraformaldehyde-fixed retinas were dissected and prepared as flatmounts. Overall photoreceptor densities were assessed with differential interference contrast optics. Middle-to-longwave sensitive (L) cones and shortwave sensitive (S) cones were immunolabeled by opsin-specific antisera, and their numbers and retinal distributions determined. Genomic DNA was used to PCR-amplify and sequence the tuning-relevant part of the S opsin gene.
The eyes of Ctenomys have low rod densities, similar to those of other subterranean rodents (Nemec et al, BRB 75:356, 2008). However, their cone proportions are higher than those of strongly subterranean species. Avoiding predators and selecting food during the brief above-ground excursions may have exerted pressure to retain robust cone-based vision in Ctenomys. The UV tuning of the S pigment is shared by a number of rodents, while its adaptive advantage remains enigmatic.
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