Abstract
Vision is very important to fish as it is required for foraging food, fighting competitors, fleeing from predators, and finding potential mates. Vertebrates express opsin genes in photoreceptor cells to receive visual signals, and the variety of light levels in aquatic habits has driven fish to evolve multiple opsin genes with expression profiles that are highly plastic. In this study, red shiners (Cyprinella lutrensis) were exposed to four water turbidity treatments and their opsin genes were cloned to elucidate how opsin gene expression could be modulated by ambient light conditions. Opsin gene cloning revealed that these fish have single RH1, SWS1, SWS2 and LWS genes and two RH2 genes. Phylogenetic analysis also indicated that these two RH2 opsin genes–RH2A and RH2B –are in-paralogous. Using quantitative PCR, we found evidence that opsin expression is plastic in adults. Elevated proportional expression of LWS in the cone under ambient light and turbid treatment indicated that the red shiner’s visual spectrum displays a red shift in response to increased turbidity.
Highlights
Fish make up the largest and most diverse group of vertebrates; some species have successfully adapted to a variety of physiologically challenging habitats that range from freshwater to seawater, cold polar regions to hot desert climates, and the Mariana Trench to high mountain lakes
Within the group of four genes, SWS1 split earlier, SWS2 was derived later, and RH1 was a sister to RH2
Our study sequenced all four cone opsin families; surprisingly, single RH1, SWS1, SWS2 and LWS genes and two RH2 genes were amplified from the red shiner
Summary
Fish make up the largest and most diverse group of vertebrates; some species have successfully adapted to a variety of physiologically challenging habitats that range from freshwater to seawater, cold polar regions to hot desert climates, and the Mariana Trench to high mountain lakes. With rare exceptions, such as eyeless cave-dwelling species, vision is necessary for fish to forage for food, fight competitors, flee from predators, and find potential mates [1].
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