title: Effect of short-term decrease in water temperature on body temperature and involvement of testosterone in steelhead and rainbow trout, Oncorhynchus mykiss.
abstract: The Pacific salmonid species Oncorhynchus mykiss is separated into a migratory form (steelhead trout) and a non-migratory form (rainbow trout). A decrease in water temperature is likely a cue triggering downstream behavior in the migratory form, and testosterone inhibits onset of this behavior. To elucidate differences in sensitivity to water temperature decreases between the migratory and non-migratory forms and effect of testosterone on the sensitivity, we examined two experiments. In experiment 1, we compared changes in body temperature during a short-term decrease in water temperature between both live and dead steelhead and rainbow trout. In experiment 2, we investigated effects of testosterone on body temperature decrease in steelhead trout. Water temperature was decreased by 3°C in 30min. The body temperature of the steelhead decreased faster than that of the rainbow trout. In contrast, there was no significant difference in the decrease in body temperature between dead steelhead and rainbow trout specimens. The body temperature of the testosterone-treated steelhead trout decreased more slowly than that of control fish. Our results suggest that the migratory form is more sensitive to decreases in water temperature than the non-migratory form. Moreover, testosterone might play an inhibitory role in sensitivity to such decreases.
authors.affiliation: Graduate School of Environment and Information Sciences, Yokohama National University, Yokohama, Kanagawa 240-8501, Japan. yhfnx644@yahoo.co.jp
authors.forename: Go
authors.initials: G
authors.lastname: Miura
authors.forename: Arimune
authors.initials: A
authors.lastname: Munakata
authors.forename: Takashi
authors.initials: T
authors.lastname: Yada
authors.forename: Carl B
authors.initials: CB
authors.lastname: Schreck
authors.forename: David L G
authors.initials: DL
authors.lastname: Noakes
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Matsuda
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D001835:Body Weight / Q000187:drug effects; D017686:Oncorhynchus mykiss / Q000033:anatomy & histology / Q000502:physiology*; D013696:Temperature; D013739:Testosterone / Q000097:blood / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D013739:Testosterone
keywords: Body temperature; Downstream migration; Rainbow trout; Steelhead trout; Testosterone