Bioaccumulation of heavy metals and their toxicity assessment in Mystus species

This study was conducted on two native fish species namely Mystus vittatus and Mystus tengara inhabiting challenging environment of Yamuna River. The heavy metals concentrations in the river water were found to be as follows: Fe > Mn > Zn > Cu > Ni > Cr > Cd, all above the Bureau of Indian Standards (BIS) and World Health Organization (WHO) guidelines. The high metal pollution index in gill, liver, and kidney of M. vittatus was recorded compared to M. tengara. The pathology caused by the accumulation of heavy metals resulted significantly (p < 0.05) higher enzyme activities of alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatinine kinase (CK) in M. tengara as compared to M. vittatus. However, albumin: globulin ratio was found to be below 0.8 in both fishes. Higher total leukocyte (TLC) (48.5 × 10³/mm³), lymphocytes (40%), respiratory burst activity (1.9), and nitric oxide synthase (NOS) activity (13.11 U/L) in M. vittatus reflect high immune response. In addition, chromosomal breakage study showed significantly (p < 0.05) low micronuclei frequency, lobed nuclei, and kidney-shaped nuclei (KSN) in M. vittatus. These results indicate that under the same challenging conditions M. vittatus have more capability of resistance and its continuous survival points towards its suitability to serve as a bioindicator than M. tengara.