Selective feeding behavior determines species specific sensitivity to microplastics: A comparative physiological and...

Microplastic (MPs) pollution poses an emerging threat to global food security and aquatic health. Comparative studies on the feeding behavior and physiological responses on aquaculture species remain limited. Therefore, the present study investigates the behavioral and physiological responses of two economically important cyprinids fishes, Catla, Common Carp, surface and bottom feeder respectively, under the exposure of polystyrene (PS-MPs, 0.6-0.8 mm) resembling natural prey zooplankton. Juveniles of both the species were subjected to three experimental conditions, Control (natural prey), T₁ (MPs only) and T₂ (Mixed Prey: MPs + Daphnia). The results of the behavioral assay in the current study revealed a distinct species-specific divergence where Catla exhibit complete avoidance of MPs in T₁ while Common Carp indiscriminately ingested MPs resulting in significantly reduced predatory performance and efficiency due to false satiety. Physiologically MPs ingestion in Common Carp triggered severe oxidative stress evidenced by significantly elevated Superoxide Dismutase, Catalase and Glutathione Peroxidase activities alongside neurotoxicity indicated by the inhibition of Acetylcholinesterase activity whereas Catla showed no such physiological alterations. The principal component analysis explained >92% of the total variances identifying oxidative stress and neuro-inhibition as the primary drivers distinguishing the sensitive Carp clusters from the resilient Catla groups. Integrated Biomarker Response analysis quantified a 13.5-fold higher sensitivity in Common carp to that of Catla in MP-only treatments. The present findings conclude that feeding strategy is a critical determinant of microplastic toxicity. It put a light on how indiscriminate bottom/column feeders face significantly higher bioaccumulation and health risks in contaminated aquaculture systems.