Can Betadine (10% povidone-iodine solution) act on the survival rate and gill tissue structure of Oranda goldfish (Carassius auratus)?

Industrial chemical solutions are widely used as a method to disinfection of aquaculture water and environments. The aim of the present study was to evaluate the toxicity effect of Betadine (10% solution of povidone-iodine) as a disinfectant solution on the survival and gill tissue of Oranda goldfish (Carassius auratus). For these purposes, 225 fingerling Oranda goldfish with an average weight 5 ± 0.67 g were divided into 15 groups with 3 replications. Fish were exposed to series of concentrations (0, 10, 20, 40, 60, 80, 90, 100, 120, 140, 160, 180, 200, 220 and 240 mg/L) of Betadine for 96 h. The mortality of fish and the samples of gill were observed at 6, 12, 18, 24, 48, 72 and 96 h after exposure. The results of the present study showed that the half-life of Betadine was less than 24 h and mortality were not record after 24 h. The highest mortality rate was at 240 mg/L, and LC50 24 h of Betadine was 158.800 mg/L. Histopathological results showed that lethal concentrations of Betadine lead to hyperemia, hypertrophy, hyperplasia and adhesion of secondary lamellar of the gill. Moreover, fish that were exposed to these concentrations displayed clinical signs such as anxiety, darkening of the skin. Overall results showed that Betadine have short half-life in the aquatic environment and are toxic to fish at very high concentrations, therefore it can be considered as practically non-toxic and useful for disinfection of the aquatic environment.