CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chengdu, 610041, China; College of Life Sciences, Nanjing Normal University, Nanjing, China.
CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chengdu, 610041, China.
Environ Pollut. 2023 Jul 1;328:121634. doi: 10.1016/j.envpol.2023.121634. Epub 2023 Apr 11.
Concerns about the implications of microplastics (MPs) on aqueous animals have gained widespread attention. It has been postulated that the magnitude of MPs can influence its toxicity. However, little is known about how MPs toxicity changes with particle size. Amphibians are reliable bioindicators of ecosystem health due to their complex life cycles. In this study, we compared the influences of two sizes nonfunctionalized polystyrene microspheres (1 and 10 μm) on the metamorphosis of Asiatic toad (Bufo gargarizans). Acute exposure to MPs at high concentrations led to bioaccumulation in the digestive track and internal organs (i.e., liver and heart) of tadpoles. Long-term exposure to either size, at environmentally-related concentrations (1 and 4550 p/mL), led to growth and development delay in pro-metamorphic tadpoles. Remarkably, developmental plasticity mitigated these deleterious effects prior to the onset of metamorphic climax without compromising survival rate in later stages. MPs with a diameter of 10 μm dramatically altered the gut microbiota (e.g., abundance of Catabacter and Desulfovibrio) of pro-metamorphic tadpoles, whereas MPs with a diameter of 1 μm induced much more intensive transcriptional responses in the host tissues (e.g., upregulation of protein synthesis and mitochondrial energy metabolism, and downregulation of neural functions and cellular responses). Given that the two MPs sizes induced similar toxic outcomes, this suggests that their principal toxicity mechanisms are distinct. Small-sized MPs can travel easily across the intestinal mucosa and cause direct toxicity, while large-sized MPs accumulate in gut and affect the host by changing the homeostasis of digestive track. In conclusion, our findings indicate that MPs can affect the growth and development of amphibian larvae, but their developmental plasticity determines the ultimate detrimental effects. Multiple pathways of toxicity may contribute to the size-dependent toxicity of MPs. We anticipate that these findings will increase our understanding of the ecological effects of MPs.
人们普遍关注微塑料 (MPs) 对水生动物的影响。据推测，MPs 的大小会影响其毒性。然而，关于 MPs 毒性随粒径变化而变化的情况知之甚少。由于其复杂的生命周期，两栖动物是生态系统健康的可靠生物指示剂。在这项研究中，我们比较了两种尺寸的非功能化聚苯乙烯微球（1 和 10μm）对亚洲蟾蜍（Bufo gargarizans）变态的影响。MPs 在高浓度下的急性暴露导致微球在蝌蚪的消化道和内脏（即肝脏和心脏）中积累。长期暴露于环境相关浓度（1 和 4550 p/mL）的任何一种尺寸的 MPs 都会导致处于前变态期的蝌蚪生长和发育迟缓。值得注意的是，在变态高峰期之前，发育可塑性减轻了这些有害影响，而不会影响后期的存活率。直径为 10μm 的 MPs 显著改变了处于前变态期的蝌蚪的肠道微生物群（例如，Catabacter 和 Desulfovibrio 的丰度），而直径为 1μm 的 MPs 在宿主组织中引起了更强烈的转录反应（例如，蛋白质合成和线粒体能量代谢的上调，以及神经功能和细胞反应的下调）。鉴于两种 MPs 尺寸诱导了相似的毒性结果，这表明它们的主要毒性机制不同。小尺寸的 MPs 可以很容易地穿过肠黏膜并引起直接毒性，而大尺寸的 MPs 则在肠道中积累并通过改变消化道的动态平衡来影响宿主。总之，我们的研究结果表明 MPs 会影响两栖动物幼虫的生长和发育，但它们的发育可塑性决定了最终的有害影响。多种毒性途径可能导致 MPs 尺寸依赖性毒性。我们预计这些发现将提高我们对 MPs 生态影响的理解。
