RESUMO
The objective of this study was to evaluate the acute toxicity of formalin and its level of therapeutic safety in early stages of Lophiosilurus alexandri. Experiment 1, larvae 7 days after hatching (DAH) were exposed to 43.2, 86.4, 172.8, 345.6, 691.2, 1404.0â¯mg/L of formalin. Experiment 2, juveniles with 22 DAH exposed to 54, 108, 216, 432, 648â¯mg/L. Experiment 3, 45 DAH exposed to 86.4, 172.8, 345.6, 691.2, 1036.8â¯mg/L. The experiments had a control without addition of formalin and all were carried out in duplicate. The LC50-12â¯h were: Experiment 1â¯=â¯108.86â¯mg/L; 2: 152.74â¯mg/L; 3: 244.38â¯mg/L of formalin. The respective safety levels were: Experiment 1â¯=â¯66.22â¯mg/L (1â¯h), 10.89â¯mg/L (12â¯h); 2â¯=â¯49.17â¯mg/L (2â¯h), 15.27â¯mg/L (12â¯h); 3â¯=â¯68.89â¯mg/L (2â¯h), 24.44â¯mg/L (12â¯h). The results showed that the developmental stage influenced the sensitivity of animals to formalin.