Development and assays estradiol equivalent concentration from prawn (p-EEQ) in river prawn, Macrobrachium nipponense, in Taiwan

The present study established a fast and convenient bioassay method for aqueous ecosystems using the prawn estradiol equivalent concentration (p-EEQ) of male Macrobrachium nipponense, which produce vitellogenin (VTG) after exposure to xeno-estrogens. This method was then used to determine the concentrations of xeno-estrogen pollutants in the rivers of Taiwan. To establish the calibration curve for the concentrations based on the p-EEQ, the induced VTG content was determined using the alkali-labile phosphate method after male M. nipponense were exposed to 0, 10, 100, 1,000 and 10,000 ng/L of 17β-estradiol for 1, 3, 5, 7, 10 and 14 days, respectively. The results of the experiments showed that the induced VTG content in all of the experimental groups stabilized after 10 days, except for the 10,000 ng/L experimental group, in which the induced VTG content decreased after 10 days. A 17β-estradiol–VTG_10day response curve was then established based on the induced VTG content in the 0, 10, 100 and 1000 ng/L experimental groups at day 10. After establishing the curve, male M. nipponense were captured from the upper, middle and lower reaches of the Chuo-shui River, the Beigang River, the Jishui River, the Agongdian River and the Sichong River in Taiwan, and the VTG content in these prawns was determined. In addition, the p-EEQ in the waters was determined based on the VTG content, and the estradiol equivalent concentration (EEQ) in the waters was also measured immediately after sampling using the solid-phase extraction-enzyme-linked immunosorbent assay (SPE-ELISA) method. The results showed that the p-EEQ in the middle and lower reaches of the rivers in certain parts of Taiwan ranged from 38 to 400 ng/L, and the detection rate was 100%. Moreover, the EEQ ranged from 7.9 to 92.9 ng/L, and the detection rate was 42.9%, indicating that most of the middle and lower reaches of the rivers in Taiwan were polluted by xeno-estrogens. The 17β-estradiol concentrations determined based on the p-EEQ were all higher than those based on the EEQ (SPE-ELISA method). The results of the present study showed that the use of M. nipponense to determine the p-EEQ in environmental waters provided advantages that included a high detection rate, high sensitivity and convenience. However, the p-EEQ cannot be used in waters that do not contain M. nipponense.