Effect of temperature on triclosan toxicity in Pangasianodon hypophthalmus (Sauvage, 1878): Hematology, biochemistry and genotoxicity evaluation.

The rising level of triclosan (TCS) in aquatic environment is raising concerns and in this context, evaluation of toxicity towards aquatic organisms under varying environmental conditions, especially temperature, is a pre-requisite for a better understanding of the toxic effects on specific metabolic processes. In this report, the mechanistic physiological responses of fish towards varying concentration of TCS at graded temperature were evaluated. The static renewal acute test was performed, and 96 h median lethal concentration (LC) of TCS for Pangasianodon hypophthalmus was estimated and the values were 848.33, 1181.94 and 1356.96 μg L at 25, 30 and 35 °C respectively. The chronic study was performed for 30 days at 1/5th and 1/10th concentration of the estimated LC of TCS at 25, 30 and 35 °C respectively. The chronic effects resulted in significant decrease in total erythrocyte count (TEC), hemoglobin (Hb), packed cell volume (PCV), mean corpuscular hemoglobin (MCH) and mean cell volume (MCV), while a significant increase in total leukocyte count (TLC), mean corpuscular hemoglobin concentration (MCHC) and red cell distribution width (RDW) was observed in TCS exposed groups at 25-35 °C. Further, a significant increase in activity of transaminase enzymes, lactate dehydrogenase (LDH) and antioxidant enzymes (superoxide dismutase) (SOD) and catalase (CAT) except glutathione-S-transferase (GST) in liver and acetylcholinesterase (AChE) in brain of the TCS exposed fish was recorded in all the above temperature range. Severe damage of DNA in nucleus of blood and liver cells, and high micronuclei frequency (MNi) was noticed in TCS exposed groups at 25 °C. The report provides convincing evidence for the effect of temperature on TCS toxicity. The findings will help in gaining a better insight into the change in toxicity of TCS in a natural environment where diurnal variations in temperature may be crucial in determining the overall extent of toxicity.