Three cone opsin genes and cone cell arrangement in retina of juvenile Pacific bluefin tuna Thunnus orientalis |
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Authors: | Taeko Miyazaki Jun Kohbara Kenji Takii Yasunori Ishibashi Hidemi Kumai |
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Affiliation: | Laboratory of Fish Physiology, Major in Life Sciences, Graduate School of Bioresources, Mie University, Tsu, Mie 514-8507,;Uragami Experimental Station, Fisheries Laboratory, Kinki University, Wakayama 649-5145, and;Department of Fisheries, Graduate School of Agriculture, Kinki University, Nara 631-8505, Japan |
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Abstract: | ABSTRACT: In bluefin tuna aquaculture, collision of juveniles with the tank or net walls is a major cause of high mortality. This problem may be related to color sensibility of the visual mechanisms of this species. As a first step in understanding of color vision of Pacific bluefin tuna Thunnus orientalis , we applied a molecular technique and histology to study cone cell distribution in the retina of juvenile fish. We isolated three cone opsin genes encoding one blue-sensitive ( SWS2 ) and two green-sensitive ( RH2 ) visual pigments. In situ hybridization revealed that SWS2 mRNA is localized in the single-cone photoreceptors. The localization of the two RH2 signals in distinct cone cells was not determined, probably because of the high homology between the two RH2 genes. Single-cone photoreceptors appeared frequently in the ventral–temporal retina in approximately 80-mm fish and in the temporal retina in approximately 230-mm fish. These cone distributions may define a visual field with best color contrast vision in front and above the fish with a short wavelength (blue) reflecting target (sensed by single cones), and may be enhanced against the longer wavelength (green) background when fish see a target below them (sensed by double cones). |
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Keywords: | adaptation to optical property Pacific bluefin tuna in situ hybridization juvenile opsin gene spectral sensitivity Thunnus orientalis |
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