Mechanisms of embryonic drift in the amphidromous goby,Rhinogobius brunneus |
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Authors: | Kei'ichiroh Iguchil Nobuhiko Mizuno |
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Institution: | (1) National Research Institute of Fisheries Science, 1088 Komaki, Ueda, Nagano Prefecture, 386, Japan;(2) Department of Biology, Faculty of Science, Ehime University, Bunkyocho, Matsuyama, Ehime Prefecture, 790, Japan |
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Abstract: | Synopsis We tested the reactions of free embryos of the amphidromous goby, Rhinogobius brunneus, to light under both artificial and ambient conditions along streams in which their downstream migration occurs. The embryos showed a positive phototaxis to 500 1ux light but a negative response to light of more than 5000 lux. They were able to swim at 1.54 cm sec–1 t in still water and showed positive rheotaxis, but their swimming ability was not sufficient to allow active movement in rapids. Ambient natural light conditions varied among locations in relation to local topographical features. The variation in the diel periodicity of their migration could be explained by the interaction between behavioral reactions of embryos and environmental factors along river courses. |
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Keywords: | Phototactic reaction Swimming ability Reach type Downstream migration Diel drift pattern Perciformes Gobioid fishes |
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