Resumo

NARANJO-GOMEZ, Juan S.; VARGAS-ROJAS, Luisa F.  e  RONDON-BARRAGAN, Iang S.. ACUTE TOXICITY OF MERCURY CHLORIDE (HGCL₂) TO CACHAMA BLANCA, Piaractus brachypomus (CUVIER, 1818). Actu Biol [online]. 2013, vol.35, n.98, pp.85-93. ISSN 0304-3584.

The improper disposal of mercury-containing substances may cause toxicity and accumulate in fish tissues. In this study, the median lethal concentration (LC₅₀) of mercury exposure at 96 hours in cachama blanca [Piaractus brachypomus (Cuvier, 1818)] was estimated through a semi-static acute toxicity test by using mercury chloride (HgCl₂) as a metal source. The experiment was carried out in the toxicology laboratory of the University of Tolima (Colombia), under controlled conditions (28.09 ± 1.86 °C) and a 12:12 (light:darkness) photoperiod. The cachama blanca fingerlings (6.55 ± 1.3 g) were housed in glass aquaria with constant aeration without filter and feeding was suppressed 24 hours before beginning the experiment. Four cencnetrations of mercury (Hg) were used with replicas including controls. The concentrations were: 0.45, 0.55, 0.65, and 0.75 mg Hg/l. Histopathological analyses were conducted on 2 fish per treatment group on samples of liver, brain and gills tissues. Fish exposed to the lowest concentrations (0.45-0.55 mg Hg/l) of HgCl₂ showed hyperactivity, whereas fish exposed to high concentrations (0.65-0.75 mg Hg/l) showed decreased activity. Histopathological analysis showed gills and liver lesions, like a lamellar hyperplasia and lipid vacuolization, respectively, in response to detoxification processes. The value of LC₅₀-96 h was estimated by using the TSK software (Trimmed-Spearman-Karber) and produced a value of 0.56 mg Hg/l. This value is close to those reported for other fish species and represents the first report of acute toxicity to the mercury in cachama blanca.

Palavras-chave : aquatic toxicology; mercury; mercury chloride; Piaractus brachypomus.

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