| Author |
Saad R, Sekiguchi T, Takai Y, Tsuruda Y, Kuroda S, Mizukami-Murata S, Lee S, Qiu X, Shimasaki Y, Oshima Y.
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| Abstract |
Microplastics (MPs) vary widely in size and shape, characteristics that critically influence their biological interactions and toxicity in marine organisms. We exposed juvenile Ciona intestinalis type A to three MP shapes: aged fragments (afrPE-MP), fibers (fiPET-MP), and spheres (sPS-MP) for 168 h, with a size range of 2-200 μm and concentrations of 0.1-1.0 mg L-1. Natural inorganic particles (IOPs) served as a reference. We quantified heart rates, squirting activity, and mucus secretion in relation to particle characteristics. Fibrous MPs exerted a highly significant depressive effect on cardiac activity. Heart rate declined significantly with increasing particle size. Squirting activity increased significantly with size and strongly with concentration, consistent with a clearance or rejection response. Mucus secretion was significantly elevated under fibrous MP exposure and strongly influenced by concentration, whereas IOPs produced minimal effects. Together, these results indicate that particle size and shape are key drivers of sublethal stress, with fibers imposing the greatest physiological burden. To the best of our knowledge, this study provides the first evidence in ascidians of concurrent MP-induced cardiac disruption heightened squirting, and increased mucus production, supporting C. intestinalis as a sensitive model for sublethal MP toxicity in marine filter feeders.
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