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(41-01) Ameliorating effect of sodium chloride on the tolerance of Hydropsyche tibialis to fluoride toxicity. Camargo, J.*,1, 1 Universidad de Alcala, Alcala de Henares (Madrid), Spain ABSTRACT- Static toxicity bioassays were conducted in duplicate to examine the effect of sodium chloride (NaCl) on the tolerance of caddisfly larvae (0.7 ± 0.1 mm in head capsule width) of Hydropsyche tibialis McLachlan, 1884 (Hydropsychidae; Trichoptera; Insecta) to fluoride toxicity in soft water. Test larvae were hand-collected from the unpolluted headwaters of Riaza river (Segovia, Central Spain). In the laboratory, larvae were acclimatised to water quality conditions for five days prior to fluoride toxicity bioassays. Glass aquaria, each containing 0.5 L of unpolluted Riaza-river water, were utilised. A control and five nominal fluoride concentrations were used per replicate (5, 10, 20, 40 and 80 mg F/L for the first replicate, and 7.5, 15, 30, 60 and 120 mg F/L for the second replicate), with 10 larvae per concentration/aquarium. Nominal fluoride concentrations were obtained using sodium fluoride (NaF). 50 mg of NaCl were added to each aquarium at the initiation of the second toxicity bioassay. In the first bioassay (with traces of NaCl), the 96 hours LC50 was 29.53 (25.22-34.67) mg F/L and the safe concentration (as infinite hours LC0.01s) was 1.00 (0.45-1.74) mg F/L. In the second bioassay (with a high concentration of NaCl), the 96 hours LC50 was 76.01 (64.82-92.97) mg F/L and the sage concentration (as infinite hours LC0.01s) was 3.13 (1.16-5.74) mg F/L. It is concluded that sodium chloride (esp chloride ions) increases the tolerance of H. tibialis larvae to fluoride toxicity.This ameliorating effect could be due to an improvement in the elimination process of fluoride ions. Key words: sodium chloride, ameliorating effect, fluoride toxicity |
