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Absence of short-wavelength sensitive cones in the retinae of seals (Carnivora) and African giant rats (Rodentia)

Authors

  • Leo Peichl,

    1. 1 Max-Planck-Institut für Hirnforschung, Deutschordenstrasse 46, D-60528 Frankfurt a. M., Germany, 2 1Department of Biochemistry and Cellular Biology, FAST, National University of Benin, BP 526, Cotonou, Republic of Benin
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  • and 1 Kabirou Moutairou 2

    1. 1 Max-Planck-Institut für Hirnforschung, Deutschordenstrasse 46, D-60528 Frankfurt a. M., Germany, 2 1Department of Biochemistry and Cellular Biology, FAST, National University of Benin, BP 526, Cotonou, Republic of Benin
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Dr Leo Peichl. E-mail: peichl@mpih-frankfurt.mpg.de

Abstract

Most non-primate mammals have two types of cone: short-wavelength sensitive (S) and middle-to-long-wavelength sensitive (M/L) cones. In two species of African giant rats, Cricetomys gambianus and C. emini, and in two species of earless seals, Phoca hispida and P. vitulina, the retinal cone types and cone distributions were assessed with antibodies specific for the M/L-cone opsin and the S-cone opsin, respectively. All four species were found to completely lack S-cones, while M/L-cones were present in low densities. M/L-cone densities, rod densities and cone/rod ratios were determined across the retina. Cone proportions are about 0.3–0.5% in C. gambianus, 0.5–0.8% in C. emini, and 1.5–1.8% in P. hispida. An absence of S-cones has previously been reported in a few nocturnal mammals. As earless seals are visually active during night and day, we conclude that an absence of S-cones is not exclusively associated with nocturnality. The functional and comparative aspects are discussed.

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