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Physiological responses of juvenile Ciona intestinalis type A (C. robusta) to microplastic shape and size: Pronounced effects of fibrous particles
Summary
Researchers exposed juvenile sea squirts to three different shapes of microplastics and found that fibrous particles had the most pronounced negative effects on heart rate, squirting activity, and mucus secretion. The shape of microplastics proved to be a more important factor than size or chemical composition in determining biological impact. The findings highlight that fiber-shaped microplastics, which are among the most common forms in the ocean, may pose greater risks to marine organisms than spherical particles.
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. 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.