title: Osmoregulatory strategies in natural populations of the black-chinned tilapia Sarotherodon melanotheron exposed to extreme salinities in West African estuaries.
abstract: The effect of salinity was studied in natural populations of the black-chinned tilapia (Sarotherodon melanotheron) from West Africa. This euryhaline species colonizes nearly all coastal environments from bays to lagoons characterized by salinities ranging from fresh water to hypersaline water over 100 ‰. Individuals were sampled during the dry season at several locations characterized by different levels of salinity (3-102 ‰). Their osmotic status and their gills were analyzed. The branchial mitochondria-rich cells (MRC), localized at the basis of the filaments and along the lamellae in fish taken from the saline stations, showed a wide plasticity with significant differences in their number and size. The most striking results were a significant larger area (≈3x) and a higher number (≈55x) of MRC at high salinity (102 ‰) compared to low salinity (3 ‰). The major ion transporters and channels were localized by immunocytochemistry and different expression patterns have been recorded between stations. Despite an increased Na⁺/K⁺-ATPase (NKA) α-subunit expression and NKA activity, pointing to an increased monovalent ion excretion, a severe osmotic imbalance was recorded in animals living in hypersaline environments.
authors.affiliation: AEO Team "Adaptation Ecophysiologique et Ontogenèse", UMR 5119, ECOSYM-UM2, IRD, IFREMER, CNRS, CC 092, 34095 Montpellier Cedex 05, France. catherine.lorin@univ-montp2.fr
authors.forename: Catherine
authors.initials: C
authors.lastname: Lorin-Nebel
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Avarre
authors.forename: Nicolas
authors.initials: N
authors.lastname: Faivre
authors.forename: Sophie
authors.initials: S
authors.lastname: Wallon
authors.forename: Guy
authors.initials: G
authors.lastname: Charmantier
authors.forename: Jean-Dominique
authors.initials: JD
authors.lastname: Durand
mesh_terms: D000818:Animals; D063366:Estuaries; D005880:Gills / Q000648:ultrastructure; D008928:Mitochondria; D009994:Osmolar Concentration; D054712:Salinity; D012675:Senegal; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D017210:Tilapia / Q000502:physiology*; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase