Surrogate production of ricefield eel sperm by germ cell transplantation in adult zig-zag eel

The reproductive mode of ricefield eel ( Monopterus albus ) severely affects the sex ratio, and decreases the productivity of broodstock. Germ cell transplantation has been widely applied in fish reproduction and genetic resource conservation. Here, we describe the surrogate production of donor sperm by injecting female germline stem cells (fGSCs) from ricefield eel into adult male zig-zag eel ( Mastacembelus armatus ). Two-year-old male zig-zag eel are treated with busulfan to deplete its endogenous germ cells and used as recipients. The fGSCs purified from ovaries of the one-year-old ricefield eel are used as donors and transplanted into zig-zag eel testes through the genital pore. Histological and fluorescent observations demonstrate the colonization, proliferation, and differentiation of donor fGSCs in gonads of the recipient fish. During the breeding season, 5 recipients survive and can produce donor-derived sperm. When donor-derived sperm are used to fertilize the eggs of wild-caught ricefield eel, healthy offspring are obtained. Analyses of morphology and DNA confirm that the offspring are of donor origin. We report the first surrogate production of functional ricefield eel sperm, which can be applied to shorten the breeding cycle and enhance breeding efficiency in future. • Adult zig-zag eels are treated with busulfan to deplete their endogenous germ cells and subsequently used as recipients. • The surrogate production of functional sperm of ricefield eel is achieved in zig-zag eel testes. • Healthy offspring are obtained by fertilizing ricefield eel eggs with recipient-produced sperm.