Species- and sex-specific bioaccumulation, tissue-specific distribution, and maternal transfer of per- and polyfluoroalkyl substances in tiger frogs (Hoplobatrachus chinensis) and forest frogs (Rana chensinensis).

Amphibians are sensitive biomonitors of environmental pollutants. However, existing research on per- and polyfluoroalkyl substances (PFASs) between different species of amphibians is limited. In the present study, water, soil, tiger frog (Hoplobatrachus chinensis) and forest frog (Rana chensinensis) samples were collected from Qingyuan County, South China. The bioaccumulation, tissue distribution, and maternal transfer of 13 PFASs, including 9 perfluoroalkyl carboxylic acids (PFCAs) and 4 perfluoroalkyl sulfonic acids (PFSAs), in frogs were investigated. The ΣPFSA and ΣPFCA concentrations in frog tissues ranged from 0.25- 36.5 and 0.75-226 ng/g wet weight (ww), respectively. The testis in the male frogs had the highest ΣPFCA and ΣPFSA concentrations of all tissues, while the eggs and liver exhibited the highest ΣPFSA and ΣPFCA concentrations in female frogs, respectively. The ΣPFSA and ΣPFCA concentrations were significantly higher in the tiger frogs than in the forest frogs, which could be due to the different exposure scenarios. Male frogs exhibited significantly higher ΣPFCA concentrations than female frogs, which could be due to sex-specific elimination rates for PFASs. Certain tissues exhibited a special affinity for certain PFASs, such as C14 PFCA for the testis; C8 PFSA for the skin, carcass, and eggs; and C10 PFCA for the liver and digestive tracts. Therefore, more in-depth studies are needed on the mechanism of the affinity of a certain tissue for PFASs with specific carbon chain lengths. Approximately 7.4-40.4 % of PFASs were transferred from the maternal body to eggs, which could underestimate the maternal transfer efficiency of PFASs in frogs because the samples were collected in the early stage of frog breeding.