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Cichlid fishes use their vision for recognition of other fishes, feeding, and in habitat selection. Neotropical cichlids can be found in a range of different habitats differing in their light regimes, and therefore it is interesting to determine if this is associated with molecular variation of genes responsible for expressing visual pigments. Here, we studied codon variation of the LWS gene in cichlids from South America, and compared it with the variation among species from the African Great Lakes. Partial fragments of this gene were sequenced, including spectral tuning sites. There were notable differences in codons under selection between Neotropical and African cichlids, with Neotropical species exhibiting an overall higher genetic variation than African species, but weaker positive selection. This study provides novel data that contributes to our understanding of the evolution of the visual system in Neotropical cichlids. [ABSTRACT FROM AUTHOR]

Abstract: Marsupials are largely confined to Australasia and to Central and South America. The visual pigments that underlie the photosensitivity of the retina have been examined in a number of species from the former group where evidence for trichromatic colour vision has been found, but none from the latter. In this paper, we report the cone opsin sequences from two nocturnal South American marsupial species, the gray short-tailed opossum, Monodelphis domestica, and the big-eared opossum, Didelphis aurita. Both are members of the Order Didelphimorphia (American opossums). For both species, only two classes of cone opsin were found, an SWS1 and an LWS sequence, and in vitro expression showed that the peak sensitivity of the SWS1 pigment is in the UV. Analysis of the Monodelphis genome confirms the absence of other classes of cone visual pigment genes. The SWS1 and LWS genes with 4 and 5 introns respectively, show the same exon–intron structure as found for these genes in all other vertebrates. The SWS1 gene shows a conserved synteny with flanking genes. The LWS gene is X-linked, as in all therian mammals so far examined, with a locus control region 1.54 kb upstream. [Copyright &y& Elsevier]