Effect of experimentally induced glyphosate exposure on haematological parameters and erythrocyte structure in Labeo rohita from the Khajikotnoor Reservoir, Kalaburagi, Karnataka

Glyphosate is one of the most widely used herbicides worldwide and poses significant ecotoxicological risks to aquatic ecosystems due to its persistence and potential toxicity. This study investigated the haematological and cytological effects of sub-lethal glyphosate exposure (1.0–2.5 mg/L) for 9 days in 90-day-old Labeo rohita under controlled laboratory conditions. Haematological analysis revealed dose-dependent decreases in red blood cell (RBC) counts (6.50–4.80 × 10⁶/mm³), haemoglobin concentration (9.20–6.60 g/dL), and body weight (3.98–18.03% reduction). White blood cell (WBC) counts initially increased, reaching a peak of 9.40 × 10³/mm³ at 1.5 mg/L, followed by a decline to 5.80 × 10³/mm³ at the highest exposure concentration (2.5 mg/L). Morphological examination of erythrocytes revealed several abnormalities, including dacrocytes, enucleated cells, eccentric nuclei, and spindle- and pear-shaped cells, indicating cytotoxic and genotoxic effects. Compared with findings reported for other fish species, including Piaractus mesopotamicus and Clarias gariepinus, L. rohita exhibited comparable reductions in haematological parameters but more pronounced erythrocyte abnormalities, suggesting a relatively high sensitivity to glyphosate exposure. These findings demonstrate the adverse effects of glyphosate on fish physiology and highlight the usefulness of haematological and cytological biomarkers for monitoring aquatic pollution.