Effects of microplastics on larval ingestion, survival, and development of sea cucumber Holothuria leucospilota

The presence of microplastics in the marine environment poses a potential threat to juvenile and adult sea cucumbers; however, the effects of microplastics on the early developmental stages of sea cucumbers are poorly understood. In this study, the larvae of Holothuria leucospilota were exposed to polystyrene (PS) particles of varying sizes (1–60 μm) to investigate the influences of microplastics on food ingestion, digestion, and performance of larval H. leucospilota at different developmental stages. The fluorescence tracing experiment revealed that the early- and mid-auricularia were capable of ingesting particles up to 20 μm in size, whereas late-auricularia larvae could ingest particles up to 40 μm in size. It was observed that microplastic particles accumulated in the stomach of larvae over a certain period, making it difficult for them to eliminate. Microplastic particles of 10 μm could be observed aggregating in the stomach of larvae at all developmental stages. The 20 μm and 40 μm particles had limited effects on larval survival but caused developmental retardation. Larvae that were exposed to 10 μm and 60 μm particles had significantly lower survival rates compared to the control group. Moreover, microplastics had a negative effect on the growth of larvae, and larger particles (20 μm, 40 μm and 60 μm) had greater effects than smaller ones (1 μm, 5 μm and 10 μm). The presence of microplastics hindered the development and metamorphosis of larvae, in particular by inhibiting the maturation of their ciliary band and esophagus. In conclusion, microplastics have negative impacts on larval H. leucospilota , and therefore, effective measures should be taken to prevent the introduction of microplastics into hatcheries artificially breeding sea cucumbers. • Larval Holothuria leucospilota were subjected to microplastics of various sizes. • Particles of 10 μm microplastic were accumulated in the larvae's gut. • Microplastics had a negative effect on the performance of larvae.