Exposure to environmentally relevant oxytetracycline induced gut histopathological damages and microbiota alterations of Pelophylax nigromaculatus larvae

Antibiotics such as Oxytetracycline (OTC) is widely used around the world and it caused serious environmental issues in China, especially in Yangtze delta area. However, its effects on amphibian gut morphology and intestinal microbiota are still unclear. In this study, tadpoles of Pelophylax nigromaculatus was exposed to 0, 5, 90 and 450 mu g/L OTC of environmentally relevant concentrations from Gosner (Gs) 26 to Gs 38. The results showed that severe histopathological injuries including cytoplasmic damage, cell arrangement disorganisation and structure deformation were observed in the gut of larvae in 90 and 450 mu g/L OTC exposure groups. Moreover, Tunel assay also revealed higher apoptotic ratio in the intestine of tadpoles in 90 and 450 mu g/L OTC treatment groups. Furthermore, the relative abundance of dominant phyla and genera of gut microbial community in OTC exposure groups was significantly different from that of control though the richness and species diversity did not show remarkable changes. We concluded that OTC may pose potential health risks to amphibian larvae through inducing gut histopathological injury and intestinal microbiota dysbiosis.