title: Prolactin and upstream migration of the amphidromous teleost, ayu Plecoglossus altivelis.
abstract: Changes in mRNA levels of prolactin (PRL) during the upstream migration were examined in fry of the amphidromous fish, ayu Plecoglossus altivelis. Quantification of mRNA has been done with real-time PCR and expressed as whole body or pituitary contents depending the body size of fry. PRL mRNA levels of ayu caught in seawater of the coastal area remained low during early spring. Prior to the start of the upstream migration, the fish caught in the coastal area in mid spring showed increased levels of PRL mRNA. There were further increases in PRL levels in the fish caught in the river. Analysis of proportions revealed that there were significant differences among PRL mRNA in the fish caught in different environmental salinities. Body weight showed a positive relation with PRL mRNA in ayu caught in seawater. A landlocked population of ayu, which migrates from lake to river, showed no significant change in PRL mRNA levels before and after upstream migration. Results in this study indicate the importance of up-regulation of PRL gene expression of ayu during the upstream migration from seawater to fresh water. There is a possible relationship between body size and PRL in the early developmental stage of ayu in seawater, but not in the fish in fresh water.
authors.affiliation: 1 Nikko Station, National Research Institute of Aquaculture, Tochigi 321-1661, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yada
authors.forename: Kei'ichiro
authors.initials: K
authors.lastname: Iguchi
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sakano
authors.forename: Toshihide
authors.initials: T
authors.lastname: Takasawa
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Katsura
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Abe
authors.forename: Satoshi
authors.initials: S
authors.lastname: Aawata
authors.forename: Kazuo
authors.initials: K
authors.lastname: Uchida
mesh_terms: D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D005786:Gene Expression Regulation / Q000502:physiology; D036441:Osmeriformes / Q000502:physiology*; D011388:Prolactin / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D045483:Rivers
chemical_list: D012333:RNA, Messenger; D011388:Prolactin
keywords: ayu Plecoglossus altivelis; fish; migration; osmoregulation; prolactin