A novel non-invasive imaging technique for mapping microplastic accumulation and distribution in different organ systems of Indian major carp Labeo rohita (Ham. 1822)

Microplastic (MP) pollution poses an increasing threat to the aquatic ecosystems, yet most existing detection methods remain largely destructive and spatially limited. Here, we present a novel, non-invasive imaging framework integrated with micro-computed tomography (µ-CT) and fluorescence microscopy to investigate ingestion, accumulation and internal distribution of fluorescently labelled polystyrene microplastics (PS-MP) in the commercially important fish species Labeo rohita. Fluorescence microscopy confirmed presence of MPs in the gastrointestinal (GI) tract, gills, muscle tissues and excreta of exposed fish, whereas, micro-computed tomography (µ-CT) facilitated non-destructive, three-dimensional whole-body imaging, allowing precise localization and visualization of internalized particles within intact organisms. A clear, progressive and exposure-dependent increase in microplastic presence was observed over the 28-day experimental period, supported by non-parametric trend and effect-size analyses, with consistently higher relative burdens under waterborne exposure compared to the dietary exposure, as revealed by complementary µ-CT and fluorescence imaging. Detection of microplastics in muscle tissue indicates systemic translocation beyond primary uptake organs, whereas their presence in excreta confirms active elimination processes. Strong spatial concordance between µ-CT and fluorescence microscopy validates the robustness of the dual-imaging approach. Collectively, this study advances microplastic ecotoxicology by establishing a scalable, high-resolution, non-invasive imaging framework for mapping and tracking microplastic fate in freshwater systems as well as organ-specific microplastic distribution and burden in freshwater fish under environmentally realistic exposure conditions.