Effects of perchlorate and exogenous T4 on growth, development and tail resorption of Rana chensinensis.

Endocrine disruptors have been demonstrated to exert adverse effects on growth and development of amphibians by disrupting hormone levels. Tail resorption, which is one of the most remarkable events during amphibian metamorphosis, is closely associated with thyroid hormones levels. However, limited research has been conducted on the effects of endocrine disruptors on tail resorption in amphibians. This study explored the effects of NaClO and T4 on the growth, development and tail resorption during the metamorphosis of Rana Chensinensis. The results demonstrated that exposure to NaClO led to an increase in body size and a delay in metamorphosis of R. Chensinensis tadpoles. Histological analysis revealed that both NaClO and exogenous T4 exposure resulted in thyroid gland injury, and NaClO treatment delayed the degradation of notochord and muscles, thereby delaying tail resorption. Moreover, transcriptome sequencing results showed that apoptosis-related genes (APAF1, BAX and CASP6) and cell component degradation-related genes (MMP9 and MMP13) were highly expressed in the T4 exposure group, and the expression of oxidative stress-related genes (SOD and CAT) was higher in the NaClO exposure group. Taken together, both NaClO and exogenous T4 affect tail resorption in R. Chensinensis, thereby affecting their adaptation to terrestrial life. The present study will not only provide a reference for future experimental research on the effects of other endocrine disruptors on the growth, development and tail resorption of amphibians but will also provide insights into environmental protection and ecological risk assessment.