Impact of fullerene C₆₀ on behavioral and hematological changes in the freshwater fish, Anabas testudineus (Bloch, 1792)

The unique physico-chemical properties of fullerene C₆₀ have aided in its application in various fields along with several ecological impacts as an emerging pollutant. So, there is a significant need to demonstrate the ecological risk and toxic impact of fullerene C₆₀ in the freshwater ecosystem. The present study focused on the toxic impact of fullerene C₆₀ on behavioral and hematological changes in the freshwater fish, Anabas testudineus. The acute toxicity of fullerene C₆₀ in Anabas testudineus determined by Probit analysis was found to be 50 mg/L. For the analysis, the fish were exposed to two sublethal concentrations of 5 mg/L (one-tenth of LC₅₀-96 h) and 10 mg/L (one-fifth of LC₅₀-96 h) for short-term (24, 48, 72 and 96 h) and long-term (7, 15, 30 and 60 days) durations. Fullerene C₆₀ exposure showed prominent changes in behavior of the fish that comprises changes in swimming activity, disruption of schooling behavior, air engulping and surfacing along with morphological alterations such as descaling, slight hemorrhage and mucous secretion on the body surface, which was correlated to significant (P < 0.05) decrease in the activity of acetylcholinesterase enzyme in brain tissue. Hematological changes includes significant (P < 0.05) reduction in the erythrocyte and leukocyte counts, hemoglobin concentration, percentage of the packed cell volume (hematocrit) and the levels of serum albumin, globulin and total protein, whereas serum glucose concentration and the activities of the serum alanine and aspartate aminotransferases were significantly (P < 0.05) increased during the sublethal exposures. Severe degeneration in the columnar epithelial cells and lamina propria, along with increased number of mucous cells observed in the intestine of the fish indicates sublethal toxicity of fullerene C₆₀. The present findings led to the conclusion that the sublethal concentrations of fullerene C₆₀ have a toxic impact on the fish A. testudineus by affecting the normal physiology, and thus the presence of this nanomaterial in the environment may affect the health status of the ecosystem.