Long-wavelength sensitive opsin (LWS) gene variability in Neotropical cichlids (Teleostei: Cichlidae)

ABSTRACT Cichlid fishes are an important group in evolutionary biology due to their fast speciation. This group depends widely of vision for feeding and reproduction. During the evolutionary process it plays a significant role in interspecific and intraspecific recognition and in its ecology. The molecular basis of vision is formed by the interaction of the protein opsin and retinal chromophore. Long-wavelength sensitive opsin (LWS) gene is the most variable among the opsin genes and it has an ecological significance. Current assay identifies interspecific variation of Neotropical cichlids that would modify the spectral properties of the LWS opsin protein and codons selected. Neotropical species present more variable sites for LWS gene than those of the African lakes species. The LWS opsin gene in Crenicichla britskii has a higher amino acid similarity when compared to that in the African species, but the variable regions do not overlap. Neotropical cichlids accumulate larger amounts of variable sites for LWS opsin gene, probably because they are spread over a wider area and submitted to a wider range of selective pressures by inhabiting mainly lotic environments. Furthermore, the codons under selection are different when compared to those of the African cichlids

Molecular characterization of Moenkhausia (Pisces: Characiformes) populations with different lateral line developmental levels

ABSTRACT The genera Hemigrammus and Moenkhausia have been traditionally diagnosed mainly by the former having lateral line completely pored whereas the latter having a lateral line with a few pored scales. Those features have been used to diagnose species of both genera in the upper Paraná River floodplain. Specimens with the diagnostic features of Moenkhausia bonita, collected in the upper Paraná River floodplain, exhibited different developmental levels of the lateral line, making it difficult to distinguish them from specimens of Hemigrammus sp. We analyzed the gene encoding cytochrome C oxidase I (COI) and intron 1 of the nuclear gene S7 to investigate the genetic similarities between the called Hemigrammus marginatus and M. bonita and to confirm their identities. Molecular sequences of other Moenkhausia species were analyzed for genus delimitation tests. The results reveal genetic similarities of M. bonita specimens with different developmental levels of the lateral line, and also distinguish between M. bonita and Hemigrammus sp. Species delimitation tests revealed that specimens from the upper Paraná River floodplain were M. bonita and were distinct from other Moenkhausia species. The developmental level of the lateral line is not a consistent characteristic that distinguishes between Moenkhausia and Hemigrammus species