MEDIAN LETHAL CONCENTRATION (LC50) OF MERCURY CHLORIDE (HgCl2) TO “GAMITANA” FINGERLINGS Colossoma macropomum (CUVIER, 1818) IN CONTROLLED ENVIRONMENTS

Abstract

In this study, the median lethal concentration (LC₅₀) of mercury exposure at 96 hours in [Colossoma macropomum (Cuvier, 1818)] was estimated through static acute toxicity test by using mercury chloride (HgCl₂) as a letal source. The experiment was carried out in a residence located in the district from San Juan Bautista, Province Maynas, Region Loreto (Peru), under controlled conditions (28.85 ± 0,15 °C) and a 12:12 (light: darkness) photoperiod. The gamitana fingerlings (4 ± 1 g) were housed in glass aquaria with constant aeration without filter and feeding was supressed 24 hours before beginning the experiment. Three concentrations of mercury (Hg) were used with replicas incluiding controls. The concentrations were: 0.01, 0.1 y 1 mg Hg/L. Histopathological analyses were conducted on 3 fish per treatment group on samples of gills tissues. Fish exposed to the lowest concentrations (0.01, 0.1 mg Hg/L) of HgCl₂ showed hyperactivity, whereas fish exposed to high concentration (1 mg Hg/L) showed decreased activity. Histopathological analysis showed gills lesions, like a lamellar hiperplasia and lipid vacuolization, respectively, in response to detoxification processes. The value of LC_50-96 h was estimated by using the TSK software (Trimmed-Spearman-Karber) and produced a value of 0.23 mg HgCl₂/L ± 0.15.