Investigation of the impacts of second-generation antihistamines on free-living marine nematodes and their interaction with ZnS nanoparticles: Mechanistic insights from community and population approaches and molecular interactions modeling.

The current research investigates the impact of loratadine and its active metabolite desloratadine, applied at environmentally relevant concentrations (40 and 80 ng/L), using community-level, population-based, and molecular modeling approaches, on meiofauna from the Dammam coast, Saudi Arabia. The results indicate a significant reduction in the abundance of meiobenthic organisms, accompanied by a marked decline in nematode diversity across treatments, especially under combined exposures at higher concentrations. Additionally, trophic groups 1B and 2B, characterized by clavate tail morphologies, were the main contributors to the observed dissimilarity patterns across treatments. The mixture of 40 ng/L of antihistamines with ZnS nanoparticles (4.1 nm) enhanced catalase and GST activities in Metoncholaimus pristiurus. An increase in growth rate was also observed, along with larger pharyngeal lumens, suggesting higher food pumping under stress. Locomotion issues and decreased fertility are also suggested, with signs of masculinization. This highlights the intensified toxic effects of antihistamines following the addition of ZnS NPs. Overall, the findings suggest synergistic or additive interaction between loratadine, desloratadine, and ZnS nanoparticles. Their toxicokinetic properties, along with strong binding affinities and stable molecular interactions with GLD-3 and SDP receptors, provide a mechanistic basis and support ecotoxicological impacts of these antihistamines and ZnS NPs on nematodes.