Meeting Abstract

75.7  Monday, Jan. 6 09:30  Development of larval salinity tolerance in two populations of alligator gar Atractosteus spatula GREEN, C*; LUNDBERG, N; FERRARA, A; FONTENOT, Q; Louisiana State University Agricultural Center; Nicholls State University cgreen@agcenter.lsu.edu

Adult alligator gar Atractosteus spatula are euryhaline, but it is unclear when larvae or juveniles develop salinity tolerance. Larval gar cannot tolerate salinities >8 psu, however adults thrive in full strength seawater (~35 psu). The goal of this study was to determine the effects of salinity on ion regulation and overall survival of larval alligator gar using acute salinity transfers. Two geographically distinct populations of gar larvae were used, one inland population and one coastal population. Larval gar were subjected to a salinity challenge with increasing salinity in later trials to determine salinity tolerance and dose-response curves for acute salinity exposures. After each 24-h acute salinity exposure, dry mass, whole body ion composition, gill and intestinal Na⁺/K⁺-ATPase (NKA) activity, and ion transport protein levels (NKA, Na⁺/K⁺/2Cl^– cotransporter (NKCC); using qPCR) were measured. Larvae were dried at 60˚C for 24 hours, weighed in grams then dissolved in 50% nitric acid and analyzed using flame spectroscopy to quantify Na⁺, K⁺, and Ca⁺ whole body ion concentration. Older larvae of A. spatula survived salinities up to 18 psu. Based on LC50 dose response curves salinity tolerance of larval alligator gar increased in stages with the first increase occurring at 10 d post hatch and another increase at 25-30 d post hatch. Based on preliminary analysis dry mass was consistent across salinities for each population.