Complete feminization of catfish by feeding Limnodilus, an annelid worm collected in contaminated streams

Abstract Background Feminization of animals derived from areas polluted by endocrine disrupting chemicals (EDCs) has been observed in all classes of vertebrates. However, feminization of artificially reared offspring by feeding of specific living organisms has never been reported. Methods Different food (including Limnodilus spp collected from the wild) and time treatment were applied to southern catfish. In addition, EDCs in Limnodilus spp., an annelid worm collected from wild contaminated small streams, was detected by LC–MS (Liquid chromatography-mass spectrometry). Serum estradiol-17 β and vitellogenin (VTG) levels and gonadal Sf 1, Dmrt 1, Foxl 2, Cyp 19 a 1 a expression levels in the catfish were measured through Estradiol/VTG EIA Kit and real-time PCR. Results Here we report that feeding of Limnodilus spp. resulted in complete feminization of southern catfish, which has a 1:1 sex ratio in wild conditions. Furthermore, HPLC analysis showed that the extraction of Limnodilus spp. contained EDCs, including bisphenol A (BPA), diethylstilbestrol (DES), 4-tert-octylphenol (4-t-OP) and 4-nonylphenol (4-NP), which were further confirmed by LC–MS. Feeding southern catfish using commercial diets sprayed with EDCs cocktail also resulted in 100% female, whereas the control fish displayed approximate 1:1 sex ratio. Limnodilus spp. fed fish displayed similar serum estradiol-17 β and VTG levels and gonadal Sf 1, Dmrt 1, Foxl 2, Cyp 19 a 1 a expression levels to those of female control. Conclusion These results demonstrated that EDCs in Limnodilus spp. cause southern catfish feminization by affecting aromatase expression and endogenous estrogen level. This is the first report showing that feeding of any living organism resulted in complete feminization of a vertebrate.