Acute and Chronic Toxicity of Waterborne Arsenite to Rainbow Trout (Oncorhynchus mykiss)

Abstract

The 144-h LC50 (95% fiducial limits) of arsenite for 4.5-g rainbow trout (Oncorhynchus mykiss) was 18.5 (17.9–19.1) mg∙L−1. In a pair-fed growth study which exposed trout to 0.0, 0.76, 2.48, or 9.64 mg arsenite∙L−1 over 17 wk, growth was significantly reduced (by 55%) only at 9.64 mg∙L−1. The reduction was attributable to both reduced appetite (primarily) and direct metabolic impact (marginally). Fish at 9.64 mg∙L−1 suffered 10% mortality, usually associated with necrotic erosion of the mandibular and olfactory regions of the head. All fish exposed to 9.64 mg∙L−1 showed inflammation of the gallbladder wall, a lesion absent at lower exposure concentrations. There were no arsenite impacts on hepato- and splenosomatic index, hematocrit, hemoglobin, total plasma lipid, cholesterol, and protein or brain concentrations of norepinephrine, dopamine, and serotonin. Exposure to 0.0, 0.76, 2.48, and 9.64 mg arsenite∙L−1 for 26 wk resulted in mean (SE) equilibrium whole-body As concentrations of 0.3 (0.02), 0.2 (0.02), 0.4 (0.10), and 1.7 (0.40) μg As∙g wet weight−1, respectively, No depuration below these concentrations occurred during a 12-d period in arsenite-free water. The threshold of chronic toxicity was estimated to be 4.9 mg∙L−1.