Gut microbiome dysbiosis is a major off-target effect of many pharmaceuticals, personal care products (PPCP), and plant protection products (PPP). This study aims to characterize these effects for two compounds, glyphosate (a PPP) and triclosan (a PPCP), in Daphnia magna juveniles and to trace the downstream consequences for gut- and brain-associated metabolite levels, reproductive performance, and behavior. Both compounds altered levels of neurotransmitters and related metabolites in both head and gut at the ppb-ppt dose range, promoting anxiogenic behavior and inhibiting reproductive traits in a concentration-related manner. These effects occurred concomitantly with alterations in the gut microbiome, analyzed by 16S rDNA sequencing. Correlation analyses between the observed metabolic, reproductive, and behavioral effects and the changes in the metabolic pathway prediction for the treated gut microbiomes revealed an enrichment in pathways related to the biosynthesis of vitamins, of essential fatty acids, and production of short chain fatty acids, which are known to affect systemic serotonin levels. The results suggest a direct link between gut microbiome dysbiosis and cognitive and reproduction effects in D. magna, with implications for the environmental and human health hazard assessment of these and other substances with broad antimicrobial spectra.

Parkinson’s disease (PD) is associated with dopaminergic neurodegeneration, in which mitochondrial dysfunction and oxidative stress play central roles. However, environmentally relevant invertebrate models for studying dopaminergic neurotoxicity remain limited. Here, we developed a Parkinsonism-like model in Daphnia magna using sublethal exposures to the model and environmental relevant dopaminergic neurotoxicants MPTP and rotenone, respectively. Both compounds induced concentration‑dependent increases in reactive oxygen species, marked depletion of dopamine and related metabolites in the head, and a strong downregulation of key dopaminergic genes, indicating profound disruption of dopaminergic homeostasis and redox balance and supporting the construct validity of the model. These molecular alterations were accompanied by functional phenotypes supporting face validity, including reduced hopping distance, increased low‑locomotion states, impaired photomotor responses and habituation, altered phototaxis and colour preference, particularly after MPTP exposure, and reduced heart rate. Together, these construct- and face-valid alterations support D. magna as a sensitive, integrative, and ecologically relevant model for investigating dopaminergic neurotoxicity and Parkinson’s disease-related adverse outcome pathways triggered by environmental chemicals.

Bisphenol A (BPA) is one of the most extensively studied endocrine-disrupting chemicals, but its increasing replacement by alternative bisphenols has raised concerns about the safety of these substitutes. In the present study, we compared the effects of BPA, bisphenol F (BPF), bisphenol S (BPS), bisphenol Z (BPZ), bisphenol AP (BPAP) and bisphenol A diglycidyl ether (BADGE) in Daphnia magna, focusing on lipid storage, feeding activity, photomotor behaviour and molecular biomarkers related to lipid metabolism and endocrine regulation. The tested compounds produced distinct biological responses. BPA increased neutral lipid accumulation, whereas exposure to BPF, BPS, BPZ, BPAP and BADGE generally resulted in reduced lipid reserves. Several compounds also decreased feeding activity, suggesting that altered energy intake may contribute to the observed changes in lipid storage. Behavioural analyses revealed significant effects on photomotor responses, particularly after exposure to BPA, BPF, BPS and BADGE. At the molecular level, bisphenol exposure modified the expression of genes involved in lipid metabolism, lipid transport and endocrine-related pathways. BPA induced the expression of genes associated with lipid synthesis and storage, while compounds causing lipid depletion more frequently affected genes involved in lipid mobilization and fatty acid metabolism. Marked effects were also observed for endocrine biomarkers. BADGE increased the expression of neverland, a key gene in ecdysteroid biosynthesis, while reducing the expression of the juvenoid-responsive gene hb2 and vitellogenin. In contrast, BPF significantly increased hb2 transcription. Correlation analyses further supported links between metabolic, behavioural and endocrine responses. Overall, the results show that bisphenol analogues differ substantially in their mode of action and biological effects. While BPA displayed clear obesogenic properties, most replacement bisphenols reduced lipid stores and altered endocrine-regulated pathways. These findings indicate that BPA substitutes cannot be assumed to represent safer alternatives and highlight the need for a broader evaluation of their ecological impacts in aquatic organisms.