Abstract

Oysters are keystone species that use external fertilization as a sexual mode. The gametes are planktonic and face a wide range of stressors, including plastic litter. Nanoplastics are of increasing concern because their size allows pronounced interactions with biological membranes, making them a potential hazard to marine life. In the present study, oyster spermatozoa were exposed for 1 h to various doses (from 0.1 to 25 µg mL⁻¹) of 50-nm polystyrene beads with amine (50-NH₂ beads) or carboxyl (50-COOH beads) functions. Microscopy revealed adhesion of particles to the spermatozoa membranes, but no translocation of either particle type into cells. Nevertheless, the 50-NH₂ beads at 10 µg mL⁻¹ induced a high spermiotoxicity, characterized by a decrease in the percentage of motile spermatozoa (−79%) and in the velocity (−62%) compared to control spermatozoa, with an overall drop in embryogenesis success (−59%). This major reproduction failure could be linked to a homeostasis disruption in exposed spermatozoa. The 50-COOH beads hampered spermatozoa motility only when administered at 25 µg mL⁻¹ and caused a decrease in the percentage of motile spermatozoa (−66%) and in the velocity (−38%), but did not affect embryogenesis success. Microscopy analyses indicated these effects were probably due to physical blockages by microscale aggregates formed by the 50-COOH beads in seawater. This toxicological study emphasizes that oyster spermatozoa are a useful and sensitive model for (i) deciphering the fine interactions underpinning nanoplastic toxicity and (ii) evaluating adverse effects of plastic nanoparticles on marine biota while waiting for their concentration to be known in the environment.

摘要

牡蛎是利用外部施肥作为性模式的基石物种。配子是浮游生物，面对各种各样的压力源，包括塑料垃圾。纳米塑料越来越受到关注，因为其尺寸允许与生物膜发生明显的相互作用，从而使其对海洋生物具有潜在危害。在本研究中，牡蛎精子暴露于具有胺（50-NH ₂珠）或羧基（50-COOH珠）功能的 各种剂量（50纳米聚苯乙烯珠）（剂量范围从0.1到25  µg mL ^-1）1 h 。显微镜检查显示颗粒粘附在精子膜上，但两种颗粒类型均未转移到细胞中。尽管如此，50-NH ₂珠的浓度为10 µg mL ^-1 诱导的精子毒性很高，其特征是运动精子的百分比（-79％）和运动速度（-62％）与对照精子相比降低，胚胎发生成功率总体下降（-59％）。这种主要的繁殖失败可能与裸露的精子体内的稳态破坏有关。仅当以25  µg mL ^-1的剂量给药时，50-COOH珠子才能抑制精子的活力。并导致运动精子百分比（-66％）和速度（-38％）下降，但不影响胚胎发生成功。显微镜分析表明，这些影响可能是由于海水中50-COOH珠形成的微小聚集体造成的物理阻塞所致。这项毒理学研究强调，牡蛎精子是一种有用且敏感的模型，用于（i）破译支撑纳米塑料毒性的精细相互作用，以及（ii）在等待塑料纳米颗粒对环境的已知浓度之前评估塑料纳米颗粒对海洋生物的不利影响。