Molecular and behavioral responses in the marine rotifer Brachionus plicatilis in response to di(2-ethylhexyl)...

Di(2-ethylhexyl) phthalate (DEHP) is a widespread endocrine disruptor known to affect invertebrate physiology, yet its neuro-metabolic effects remain poorly understood. Here, we investigate the impact of DEHP exposure on the life history, locomotor behavior, and expression of acyltransferase genes in the marine rotifer Brachionus plicatilis. Exposure to DEHP altered reproductive timing. While initial offspring were suppressed, the reproductive period was extended (at 50 and 500 μg/L), which maintained total offspring counts. DEHP also induced distinct, non-monotonic behavioral changes. At 5 μg/L, hyperactivity resulted in an increased path length, while reduced turning angles were observed at 50-500 μg/L. Phylogenetic analysis identified two ChAT paralogs (ChAT1 and ChAT2), representing a lineage-specific divergence. Notably, 24 h DEHP exposure induced opposing responses in these paralogs, with an upregulation of ChAT1 and a downregulation of ChAT2. Specifically, the upregulation of ChAT1 coincided with behavioral hyperactivity, suggesting a high neurological demand. We propose that this DEHP-induced perturbation of the neuro-metabolic axis redirects Acetyl-CoA resources toward immediate neural survival, thereby forcing an energetic trade-off that results in the observed reproductive delays. By elucidating this link between molecular stress and ecological fitness, our study reinforces the utility of B. plicatilis as a sentinel model for integrative ecotoxicological assessment.