Dopaminergic system disruption induced by envrionmentally-realistic glyphosate leads to behavioral alteration in crayfish, Procambarus clarkii.

Glyphosate, a widely used herbicide, is frequently detected in freshwater systems, posing potential risks to non-target aquatic species. This study investigates the effects of environmentally realistic glyphosate concentrations (0.1, 1, and 10 µg/L) on the behavior, dopamine regulation, and oxidative stress in the red swamp crayfish (Procambarus clarkii), a key species in freshwater ecosystems and also an important commercial species in China. Crayfish were exposed to glyphosate-based herbicide (Roundup®, 41 % glyphosate) for two weeks, after which behavioral changes, dopamine levels, dopaminergic gene expression, and oxidative stress markers were analyzed. Behavioral tests showed dose-dependent increases in anxiety-like behaviors and reduced exploratory activity, indicated by decreased movement in the light zone and increased retreat behavior. Correspondingly, dopamine levels in the eyestalk increased significantly in Roundup-treated crayfish, with associated downregulation of key dopaminergic genes, including tyrosine hydroxylase (TH), dopamine receptor (DDR), and dopa decarboxylase (DDC). Additionally, Roundup exposure induced oxidative stress, as evidenced by elevated levels of reactive oxygen species (ROS), lipid peroxidation (LPO), and superoxide dismutase (SOD) activity, suggesting that oxidative damage may further exacerbate dopaminergic disruption. These findings highlight the neurotoxic and oxidative impacts of glyphosate at concentrations found in aquatic environments, underscoring the ecological risks of glyphosate contamination and supporting the use of crayfish as bioindicators of aquatic neurotoxicity and oxidative stress.