SCHLEICH Cristian Eric
congresos y reuniones científicas
THE EYES OF TWO SUBTERRANEAN TUCO-TUCO SPECIES (RODENTIA, CTENOMYS): HISTOLOGICAL CHARACTERISTICS AND RETINAL SPECTRAL SENSITIVITY
SCHLEICH, C.E.,; VIELMA, A.,; GLOSMANN, M.,; PALACIOS, A.,; PEICHL, L.
Congreso; International Mammalogical Congress; 2009
Although vision was thought to be useless for organisms living in dark underground habitats, recent studies have shown that some species of facultative subterranean rodents have retained their eyes and visual capabilities. Among these are the species of the genus Ctenomys, which present some surface activity. The objectives of this work were to determine the anatomy and function of the retina in two species of Ctenomys. C. talarum and C. magellanicus presented normally developed eyes with transparent lenses and corneas. The retinas were characterized by a low density of photoreceptors (110,000-170,000 mm-2), of which 69-85% were rods. Although rod-dominated, the retina of these subterranean rodents also contained a high density of cones (14-31 % of total retinal photoreceptors). The majority of cones expressed an LWS-opsin (19,000-47,500 mm-2). The densities of cones expressing SWS1-opsin ranged from 1,800-7,300 mm-2 (5.7-16.5% of all cones). No co-expression of LWS- and SWS1-opsin was observed in any cones. S-opsin gene sequencing revealed that these species possess key amino acids that have a crucial role in shifting the spectral sensitivity of the SWS1-pigment towards the UV range. Photopic spectral electroretinograms of these speciesshowed two relative main sensitivity peaks, which suggests the contributions of two cone mechanisms. However, a visual template consisting of the linear summation of three visual pigments produced the best fit. While the 373 and 509 nm peaks would correspond to the UV-sensitive SWS1-cones and the LWS-cones, an unexpected (third) sensitive mechanism with with a maximum of sensitivity close to 450 nm need to be clarify. These results show that the eyes of Ctenomys seem to be analogous to those of surface-dwelling rodents. Avoiding predators and selecting food items during brief above-ground excursions may have exerted strong selective pressures to retain normal visual capabilities in the subterranean rodent Ctenomys