Opsin gene expression and vision modification during ontogeny in European cyprinid fishes
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1
Department of Zoology, Division of Biology, Faculty of Science, Charles University, Czechia
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2
Institute for Environmental Studies, Faculty of Science, Charles University, Czechia
Vision plays a key role in life of many vertebrates. Fishes have colonized a wide range of both marine and freshwater habitats, which trigger numerous visual system adaptations. Photoreceptor cells in retina, i.e. cone and rod cells, are responsible for light detection, and multiple different cell types enable colour vision. Cone cells are used for photopic vision when light intensity is sufficient, while rod opsin is used for scotopic vision during low light level conditions. Teleost fishes possess more genes for photoreceptor proteins (opsins) in their genome than they usually actively use (express). Their opsin gene expression may further vary during ontogeny when different developmental stages express alternative opsin combinations and, hence, modify their visual abilities. Such alterations may serve for adaptation to various environmental conditions they encounter in different life stages, e.g. influencing their trophic ecology or habitat preference. This phenomenon has been so far investigated in few groups of teleost fishes (cichlids, salmons), however, general and/or specific patterns of such ontogenetic plasticity are yet to be identified.
We studied genetic basis of the visual system in Cyprinidae, a species-rich family of freshwater fishes with almost worldwide distribution. We focused on the cone and rod opsin genes in the genome of different species, and their expression in retina in larvae and adults. We found that cyprinids possess a complete set of opsin genes in their genomes consisting of four types of cone opsin genes sensitive to various parts of light spectrum (SWS1, SWS2, RH2 and LWS) and one type of rod opsin gene (RH1).
We found that rod opsin gene and some cone opsin genes (mostly RH2 sensitive to the middle – green wavelengths) are duplicated in cyprinids. In our study, we focused on larvae, juveniles and adults of common freshwater cyprinid fish species of Central Europe. We have investigated vision in adults of sixteen species and larvae of eleven species of cyprinid fishes from Czech Republic.
We applied transcriptome sequencing and we have identified the level of opsin gene expression in different species, and compared the expression patterns between their different ontogenetic stages. We found that vision in cyprinids is based on the most dominant red-sensitive photoreceptor (containing the LWS opsin sensitive to the long wavelengths) and contains three to five other cone opsins expressed in retina with variation between species. We further found changes in expression ratios for cone opsins in different stages of development. In larval stages, cyprinids express predominantly short wavelength-sensitive opsin genes (SWS1, SWS2 and some of RH2 opsins), switching to opsins sensitive to longer wavelengths with dominance of SWS2 and RH2 during juvenile period of development, while adult vision is dominated by long wavelength-sensitive opsin (LWS).
Cyprinids also express both copies of rod opsin gene present in their genome; however, in the contrast to cone opsins, it is always the same type of rod opsin that dominates in the transcriptome of both larval and adult stages.
Keywords:
Opsin,
Vision,
adaptation,
Cyprinid fish,
Transcriptomics
Conference:
XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019.
Presentation Type:
Poster
Topic:
EVOLUTIONARY GENOMICS OF FISHES
Citation:
Truhlářová
V,
Musilová
Z and
Horká
P
(2019). Opsin gene expression and vision modification during ontogeny in European cyprinid fishes.
Front. Mar. Sci.
Conference Abstract:
XVI European Congress of Ichthyology.
doi: 10.3389/conf.fmars.2019.07.00047
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Received:
17 May 2019;
Published Online:
14 Aug 2019.
*
Correspondence:
Mx. Veronika Truhlářová, Department of Zoology, Division of Biology, Faculty of Science, Charles University, Prague, Czechia, truhlave@natur.cuni.cz