title: The osmoregulatory effects of rearing Mozambique tilapia in a tidally changing salinity.
abstract: The native distribution of Mozambique tilapia, Oreochromis mossambicus, is characterized by estuarine areas subject to salinity variations between fresh water (FW) and seawater (SW) with tidal frequency. Osmoregulation in the face of changing environmental salinity is largely mediated through the neuroendocrine system and involves the activation of ion uptake and extrusion mechanisms in osmoregulatory tissues. We compared plasma osmolality, plasma prolactin (PRL), pituitary PRL mRNA, and mRNA of branchial ion pumps, transporters, channels, and PRL receptors in tilapia reared in FW, SW, brackish water (BW) and in tidally-changing salinity, which varied between FW (TF) and SW (TS) every 6h. Plasma PRL was higher in FW tilapia than in SW, BW, TF, and TS tilapia. Unlike tilapia reared in FW or SW, fish in salinities that varied tidally showed no correlation between plasma osmolality and PRL. In FW fish, gene expression of PRL receptor 1 (PRLR1), Na(+)/Cl(-) cotransporter (NCC), aquaporin 3 (AQP3) and two isoforms of Na(+)/K(+)-ATPase (NKA α1a and NKA α1b) was higher than that of SW, BW or tidally-changing salinity fish. Gene expression of the Na(+)/K(+)/2Cl(-) cotransporter (NKCC1a), and the cystic fibrosis transmembrane conductance regulator (CFTR) were higher in fish in SW, BW or a tidally-changing salinity than in FW fish. Immunocytochemistry revealed that ionocytes of fish in tidally-changing salinities resemble ionocytes of SW fish. This study indicated that tilapia reared in a tidally-changing salinity can compensate for large changes in external osmolality while maintaining osmoregulatory parameters within a narrow range closer to that observed in SW-acclimated fish.
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA; Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Moorman
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
authors.forename: Mayu
authors.initials: M
authors.lastname: Inokuchi
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yamaguchi
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA; University of Hawaii Sea Grant College Program, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
authors.forename: Darren T
authors.initials: DT
authors.lastname: Lerner
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
authors.forename: E Gordon
authors.initials: EG
authors.lastname: Grau
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA. Electronic address: seale@hawaii.edu.
authors.forename: Andre P
authors.initials: AP
authors.lastname: Seale
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D051400:Aquaporin 3 / Q000235:genetics / Q000378:metabolism; D005618:Fresh Water; D007124:Immunoenzyme Techniques; D017136:Ion Transport; D010902:Pituitary Gland / Q000378:metabolism*; D011388:Prolactin / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011981:Receptors, Prolactin / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054712:Salinity; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D017210:Tilapia / Q000254:growth & development* / Q000378:metabolism; D014872:Water Movements; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D012333:RNA, Messenger; D011981:Receptors, Prolactin; D051400:Aquaporin 3; D011388:Prolactin; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Ion transporter; Osmoregulation; Prolactin; Rearing salinity; Tidal cycle; Tilapia