Unusual cone and rod properties in subterranean African mole-rats (Rodentia, Bathyergidae).
We have determined the presence of spectral cone types, and the population densities of cones and rods, in subterranean mole-rats of the rodent family Bathyergidae, for which light and vision seems of little importance. Most mammals have two spectral cone types, a majority of middle- to long-wave-sensitive (L-) cones, and a minority of short-wave-sensitive (S-)cones. We were interested to see whether the subterranean bathyergids show the same pattern. In three species, Ansell's mole-rat Cryptomys anselli, the giant mole-rat Cryptomys mechowi and the naked mole-rat Heterocephalus glaber, spectral cone types and rods were assessed immunocytochemically with opsin-specific antibodies. All three species had rod-dominated retinae but possessed significant cone populations. A quantitative assessment in C. anselli and C. mechowi revealed surprisingly low photoreceptor densities of 100 000-150 000/mm(2), and high cone proportions, approximately 10% (8000-15 000/mm(2)). In all three species, the vast majority of the cones were strongly S-opsin-immunoreactive; L-opsin immunoreactivity was much fainter. In C. anselli, approximately 20% of the cones showed exclusive S-opsin label, approximately 10% exclusive L-opsin label and approximately 70% strong S-opsin and faint L-opsin double label (potential dual-pigment cones). This is the first observation in any mammal of an S-opsin dominance and low levels of L-opsin across the entire retina. It contrasts starkly with the situation in the muroid blind mole-rat Spalax ehrenbergi, which has been reported to possess L-opsin but no S-opsin. Evidently, within rodents an adaptation to subterranean life is compatible with very different spectral cone properties.
Peichl
Leo
L
Max Planck Institute for Brain Research, Deutschordenstr. 46, D-60528 Frankfurt a. M., Germany. peichl@mpih-frankfurt.mpg.de
Nemec
Pavel
P
Burda
Hynek
H
D000818:Animals; D002452:Cell Count; D005123:Eye / Q000033:anatomy & histology; D007150:Immunohistochemistry / Q000379:methods; D019577:Mole Rats; D010786:Photoreceptor Cells / Q000378:metabolism; D012160:Retina / Q000166:cytology* / Q000378:metabolism; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000378:metabolism*; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000378:metabolism*; D017299:Rod Opsins / Q000378:metabolism; D013045:Species Specificity; D015293:Transducin / Q000378:metabolism
D017299:Rod Opsins; D015293:Transducin