Psychoactive contaminants alter fish sperm function via neurotransmitter signaling

The widespread occurrence of psychoactive pollutants in surface waters raises concerns for aquatic ecosystems, yet impacts beyond behavioral disruption remain poorly understood. Designed to target neurotransmitter (NT) systems in humans, these contaminants may also interfere with conserved NT pathways in fish. Here we provide the first evidence that fish sperm contain NTs and their receptors, indicating an active NT-mediated signaling system essential for sperm function. Using European perch (Perca fluviatilis) exposed to environmentally relevant concentrations of methamphetamine, we quantified NTs in brain, gonads, and sperm, assessed tissue-specific bioaccumulation, and evaluated sperm performance. Methamphetamine accumulated across tissues, modified NT profiles, and altered sperm motility and velocity. These findings reveal a previously unrecognized pathway of reproductive vulnerability, identifying NT signaling in sperm as a novel target of psychoactive pollutants with potential implications for fertilization success and population resilience in aquatic ecosystems.