How can “my shoes” affect the amphibian health? A study of the toxicity of microplastics from shoe sole (Polyvinyl chloride acetate) on Physalaemus cuvieri tadpoles (Anura, Leptodactylidae)

Abstract

More recently, many studies have reported the impacts of microplastics (MPs) on the health of organisms. However, our knowledge of its effects on some vertebrate groups, such as amphibians remains incipient. Thus, we evaluated whether the exposure of Physalaemus cuvieri tadpoles to MPs from shoe soles can induce harmful effects on their health. After 30 days of exposure to different MP concentrations (2 ×105 MP particles/m3 and 4 ×106 MP particles/m3), we noticed that the tadpoles ingested particles with a mean diameter of 148.8 µm and irregular shapes, which accumulated in the intestinal tube. Such accumulation was associated with a lower-body condition index, non-uniformity in the keratinized structures of the jaw sheath, alterations in the intestine position in the abdominal cavity, bowel tube winding condition, and the emergence of dark regions in the intestine like pseudomelanosis. The reduction of superoxide dismutase and catalase activities suggests that MPs have affected the antioxidant system. The minor nitrite production provides evidence that the production of nitric oxide by cells of the intestinal immune system has been affected. In addition, we observed a significant reduction in the size (area, perimeter, and diameter) of MPs after ingestion, which suggests that tadpoles can act as vectors for their dispersal of MPs from shoe soles in the environment. The principal component analysis and integrated biomarker response assessment also confirm that higher MPs concentration induces a more stressful response. Therefore, our study demonstrates that “my sneakers,” while seemingly harmless, can pose a health risk to amphibians.