Ultra-fast generation of all-female grass carp via transplantation of female germline stem cells into zebrafish.

Surrogate reproduction offers a promising biotechnological approach for accelerating aquaculture breeding. Grass carp (Ctenopharyngodon idellus), a key freshwater species, faces significant constraints in breeding due to its prolonged sexual maturation of 5 years and huge body size. Here, we establish an ultra-fast breeding strategy to generate all-female grass carp within six months via surrogate production in tiny laboratory fish, zebrafish (Danio rerio). We identify and isolate female GSCs from juvenile ovaries of 3-month-old grass carp. Three months after transplantation into zebrafish larvae, the donor-derived female GSCs undergo ultra-fast spermatogenesis and differentiate into functional grass carp sperm carrying X chromosomes. Fertilization of wild-type grass carp eggs with this sperm yields all-female offspring. This work demonstrates that fish female GSCs with XX chromosomes can differentiate into functional sperm in a short time in zebrafish gonadal somatic niche, opening a new avenue for precision breeding and sex control in aquaculture species.