Effects of extremely high concentrations of polystyrene microplastics on asexual reproduction and nematocyst discharge in the jellyfish Sanderia malayensis

Numerous studies have assessed the detrimental effects of microplastics (MPs) on aquatic invertebrates due to their ubiquitous and persistent nature. In this study, the toxic effects of MPs were examined on the polyp and ephyrae of the marine hydrozoan Sanderia malayensis. The jellyfish were exposed to different sizes (1-6 μm) of non-functionalized polystyrene microbeads at a concentration of 1 × 10 particles mL. The MPs randomly attached to the external and internal parts of the jellyfish body, and the longest MP attachment was 52 days during the depuration after initial exposure (for 24 h). Consistent seventeen-day exposure to MPs significantly reduced the asexual reproduction of the S. malayensis polyps. To assess if the MPs can stimulate nematocyst discharge in polyp and ephyrae stages via direct contact, they were exposed to particle sizes up to 430 μm. None of the MPs or their aggregates, including the 430 μm particles, induced nematocyst discharge. These results suggest that prolonged exposure to relatively high MP concentrations affects the early stages of jellies and provides evidence for the no effect on nematocyst discharge.