Integrated assessment of Nitenpyram-induced physiological and microbial alterations in Chinese longsnout catfish.

Neonicotinoid insecticides such as nitenpyram pose potential risks to freshwater aquaculture species, yet their chronic effects on Chinese Longsnout Catfish remain unclear. Here, juvenile L. longirostris (12.5 ± 1.0 g; 8.2 ± 0.5 cm) were exposed to 0, 10, 100, and 1000 µg/L nitenpyram for 60 days under static-renewal conditions. Growth performance, oxidative stress, liver histopathology, and gut microbiota were assessed. Significant adverse effects occurred at ≥ 100 µg/L, including growth inhibition (weight gain 18.3–42.5%), oxidative stress (SOD and CAT 21.7–58.2%; MDA 35.6–89.1%), hepatic injury (vacuolation, nuclear pyknosis), and gut dysbiosis (alpha diversity 15.2–32.7%; beneficial bacteria; pathogens). No effects were detected at 10 µg/L, suggesting a no-observed-effect concentration near this level. Overall, chronic nitenpyram exposure at ≥ 100 µg/L impairs growth, redox balance, and microbial homeostasis in L. longirostris, posing ecological risks to aquaculture and freshwater ecosystems.