title: Effects of salinity on growth and ion regulation of juvenile alligator gar Atractosteus spatula.
abstract: The alligator gar (Atractosteus spatula) is a primitive euryhaline fish, found primarily in estuaries and freshwater drainages associated with the northern Gulf of Mexico. The extent of its hypo-osmotic regulatory abilities is not well understood. In order to determine how salinity affects growth rates and ionic and osmoregulation, juvenile alligator gar (330 days after hatch; 185 g) were exposed to 4 different salinities (0, 8, 16, and 24 ppt) for a 30-day period. Specific growth rate, plasma osmolality and ion concentrations, gill and gastrointestinal tract Na(+), K(+)-ATPase activities, and drinking rate were compared. Juvenile alligator gar were able to tolerate hyperosmotic salinities up to 24 ppt for a 30 day period, albeit with decreased growth resulting largely from decreased food consumption. Plasma osmolality and ionic concentrations were elevated in hyperosmotic salinities, and drinking rates and gastrointestinal tract Na(+), K(+)-ATPase activities increased, particularly in the pyloric caeca, presumably the primary location of water absorption. Therefore, juvenile alligator gar<1 year of age are capable of prolonged exposure to hyperosmotic salinities, but, based on the inference of these data, require access to lower salinities for long-term survival.
authors.affiliation: Department of Wildlife, Fisheries and Aquaculture, Mississippi State University, Starkville, MS 39762, USA.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Schwarz
authors.affiliation: Department of Wildlife, Fisheries and Aquaculture, Mississippi State University, Starkville, MS 39762, USA. Electronic address: pallen@cfr.msstate.edu.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Allen
mesh_terms: D000818:Animals; D004326:Drinking; D029941:Fish Proteins / Q000378:metabolism; D005399:Fishes / Q000254:growth & development* / Q000378:metabolism; D005880:Gills / Q000201:enzymology; D009994:Osmolar Concentration; D010710:Phosphates / Q000097:blood; D011188:Potassium / Q000097:blood; D054712:Salinity; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013312:Stress, Physiological; D014882:Water-Electrolyte Balance
chemical_list: D029941:Fish Proteins; D010710:Phosphates; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium
keywords: Alligator gar; Drinking; Growth; Ion regulation; K(+)-ATPase; Na(+); Osmoregulation; Salinity