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Toxic effects of MPs and Up Grade® herbicide on the Nile tilapia (Oreochromis niloticus): Oxidative stress, immune responses, and histopathological investigations

Original title: Toxic effects of MPs and Up Grade® herbicide on the Nile tilapia (Oreochromis niloticus): Oxidative stress, immune responses, and histopathological investigations

Veterinary Research Communications 2026
Rashad E.M. Said, Ahmed E. A. Badrey, Mohamed Hamed, Ibrahim Mohamed, Hamdy A. M. Soliman et al., Alaa El-Din H. Sayed

Summary

Scientists found that when tilapia fish were exposed to both microplastics and a common weed-killer chemical together, the damage to their gills, gut, and reproductive organs was worse than exposure to either pollutant alone—along with signs of inflammation and cellular stress. Since these two pollutants often show up together in rivers and lakes where fish are farmed or caught for food, this research suggests we may be underestimating the health risks these combined chemicals pose to the fish we eat and to aquatic ecosystems overall.

This study explored the combined toxicity of polyethylene microplastics (PE-MPs) and the herbicide Up Grade46% SL (UPGR) on Nile tilapia (Oreochromis niloticus), focusing on antioxidant, immunological, and histopathological responses. Nile tilapias were divided into four groups: control, UPGR exposure (2.916 mg/L), PE-MPs exposure (10 mg/L), and combined PE-MPs and UPGR exposure. Over 15 days, significant changes were observed in various biomarkers. Total antioxidant capacity (TAC) levels significantly decreased in the PE-MPs group compared to the control (p < 0.05), while superoxide dismutase (SOD) levels increased in both PE-MPs and UPGR groups (p < 0.05). The combination group showed significantly elevated levels of immune biomarkers IL-1β and IL-6 compared to individual exposures (p < 0.05). Histopathological examination revealed severe alterations: gills showed degenerated lamellae, malformed secondary lamellae, and congested blood capillaries; intestines had vacuolations, degenerated muscularis, hydropic degeneration, and numerous inflammatory cells; and testes exhibited degraded tubules, pigmentation, few primary spermatogonia, and necrosis of many cysts. The present study indicates that exposure to sub-lethal concentrations of UPGR and PE-MPs individually and in combination for 15 days induce oxidative stress, immunotoxic impairments and cause severe histological changes in the gills, intestines and testes of O. niloticus. The study underscores the urgent need to explore how microplastics interact with other pollutants in aquatic ecosystems, posing combined threats to aquatic life. The observed joint toxicity suggests potential long-term impacts on fish health and calls for comprehensive risk assessments and mitigation strategies to protect aquatic environments from such chemical pollutants.

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