Study of Hematological Alterations and Oxidative Stress in Labeo rohita Exposed to Sub-lethal Methylene Blue

Pramod Kumar Chak; Devendra Pal Singh

doi:10.55544/jrasb.3.1.58

Authors

Pramod Kumar Chak Department of Zoology, Janta Vedic College, Baraut, Baghpat - 250611(U.P.), INDIA
Devendra Pal Singh Department of Zoology, Janta Vedic College, Baraut, Baghpat - 250611(U.P.), INDIA

DOI:

https://doi.org/10.55544/jrasb.3.1.58

Keywords:

Methylene Blue Toxicity, Hematological Biomarkers, Oxidative Stress, Aquatic Toxicology

Abstract

Methylene Blue (MB), a synthetic dye widely used in aquaculture for its antifungal properties, poses significant ecological risks due to its sub-lethal toxicity in aquatic organisms. This study investigates the hematological and oxidative stress responses in Labeo rohita (rohu) exposed to sub-lethal concentrations of MB (1/5th and 1/20th of the 96-hour LC50 of 8.5 mg/L) over 7, 14, and 28 days. Hematological parameters, including red blood cell (RBC) morphology, hemoglobin (Hb%) levels, total leukocyte count (TLC), and differential leukocyte profiles, were analyzed alongside lipid peroxidation (LPO) to assess oxidative damage. Results revealed significant dose- and time-dependent disruptions: RBCs exhibited crenation and membrane shrinkage, Hb% declined by 51% (4.8 ± 0.3%) in the 1/5th LC50 group by day 28, and TLC increased by 116% (15.8 ± 0.7 ×10⁴ cells/mm³), accompanied by neutrophilia (37.5 ± 1.8%) and lymphocytopenia (58.0 ± 1.8%). Oxidative stress markers, quantified as malondialdehyde (MDA), surged to 7.8 ± 0.6 nmol/g in high-dose groups, correlating strongly with Hb% reduction (r = -0.89, p < 0.01), underscoring ROS-mediated erythrocyte damage. Statistical analysis (ANOVA, p < 0.001) confirmed the significance of these alterations. The study identifies MB-induced anemia, immunosuppression, and oxidative stress as critical threats to fish health, validating hematological biomarkers as reliable indicators of sub-lethal toxicity. These findings emphasize the need for regulatory limits on MB discharge and advocate for eco-friendly alternatives in aquaculture. Future research should explore molecular mechanisms of MB toxicity and long- term ecological impacts to inform sustainable practices and mitigate risks to aquatic biodiversity.

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