Cultivate YY supermale fish for the production of genetically all male zig-zag eel (Mastacembelus armatus) by MAS-GM technique

Mastacembelus armatus is an important economic fish in China. Since males grow faster and larger than females, breeding monosex M. armatus has great value in the aquaculture industry. Cultivating YY fish is the key to producing genetically all male M. armatus . However, there have been no reports on production of fertile YY supermale, and the production technique of all-male fish has not yet been established in M. armatus . In this study, YY M. armatus offspring were obtained by mating XY pseudofemales with XY males and it was proved that YY fish is sublethal. The offspring were cultured under LE and AS treatment, followed by sex-linked marker screening, to obtain YY pseudofemales and YY supermales, respectively. A portion of YY supermales proved to be viable and fertile, but the fertility of YY pseudofemale still needs further verification. Subsequently, by mating XX females with YY supermales and performing AS treatment on their offspring, mass production of genetically all male M. armatus could be achieved. For the first time, YY M. armatus was confirmed to be able to survive and has obtained fertile YY supermale fish. In addition, marker assisted selection (MAS) technique was established to produce genetically all male fish (GM) in M. armatus (MAS-GM technique). This is expected to significantly increase the yield and economic benefits of the M. armatus aquaculture industry. Beyond that, YY fish provides useful material for understanding the sex determination mechanism of M. armatus . In summary, MAS-GM technique can achieve the all-male breeding of M. armatus , laying the foundation for the development of standardized M. armatus farming. • YY Mastacembelus armatus was obtained by mating XY pseudofemale with XY male and it was proved that YY fish is sublethal. • YY pseudofemale was obtained by feeding fry with Limnodilus spp. and soaking in low-dose estrogen E2 water at 10-30 dpf. • Marker-assisted selection (MAS) of genetically all male fry (GM) technique (MAS-GM) was established in M. armatus .