Involvement of sex steroids,luteinizing hormone and thyroid hormones in upstream and downstream swimming behavior of land-locked sockeye salmon <Emphasis Type="Italic">Oncorhynchus nerka</Emphasis> |
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Authors: | Arimune Munakata Masafumi Amano Kazumasa Ikuta Shoji Kitamura Katsumi Aida |
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Institution: | (1) Department of Biology, Miyagi University of Education, Sendai Miyagi, 980-0845, Japan;(2) School of Marine Biosciences, Kitasato University, Ofunato Iwate, 022-0101, Japan;(3) Research Management Department, Headquarters, Fisheries Research Agency, Yokohama Kanagawa, 220-6115, Japan;(4) Freshwater Fisheries Research Division, National Research Institute of Fisheries Science, Tochigi 321-1661, Japan;(5) Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan |
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Abstract: | The involvement of testosterone (T), estradiol-17β (E2), 11-ketotestosterone (11-KT), 17,20β-dihydroxy-4-pregnene-3-one (DHP), luteinizing hormone (LH), thyroxine (T4), and triiodothyronine (T3) in the regulation of downstream and upstream movement (swimming behavior) was investigated in land-locked sockeye salmon
Oncorhynchus nerka, using an artificial raceway. During the downstream migratory period, T implant resulted in high plasma T levels and inhibited
the occurrence of downstream swimming behavior (negative rheotaxis) in yearling (1+) immature smolts. In terms of upstream
behavior, 2-year-old (2+) males exhibited high plasma T and 11-KT levels, while 2+ females had elevated T and DHP levels.
In 1+ immature fish, a T implant induced upstream swimming behavior (positive rheotaxis). In experiments 1 and 3, the plasma
T4 and T3 levels of non-migrants tended to be higher than those of migrants. In contrast, no marked changes in plasma and pituitary
LH were found in both downstream and upstream migrants. These results suggest that sex steroids, such as T, play significant
roles in the regulation of downstream and upstream swimming behaviors in land-locked sockeye salmon. |
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