Generation of donor-derived spermatozoa by cross-subfamily transplantation of purple loach (Leptobotia taeniops) spermatogonia into triploid loach (Misgurnus anguillicaudatus).

Germ cell transplantation plays an important role in the conservation of endangered fish species. As one of the most promising and valuable techniques, there are only few successful cases of cross-subfamily germ cell transplantation in fish. The purple loach Leptobotia taeniops, belonging to the subfamily Botiinae, genus Leptobotia, has been classified as "vulnerable" on the "China Biodiversity Red List." Due to the difficulty of artificial breeding of Botiinae fish, we chose hybrid triploid loach belonging to the subfamily Cobitinae as recipient fish for spermatogonia transplantation to obtain donor-derived spermatozoa. Upon their sexual maturity, with gonadosomatic index analysis and histological observation, we found significant differences between the recipient and the control hybrid triploid loach. The number of sperm produced by recipient fish was about 200 times higher than that of hybrid triploids. Combined with the results of sperm motility analysis and sperm DNA gel electrophoresis, recipient fish were able to produce motile donor-derived spermatozoa. Through further scanning electron microscopy observation, we speculated that structurally intact donor-derived spermatozoa had the potential to inseminate. Taken together, to our knowledge, this is the first successful attempt to conduct cross-subfamily germ cell transplantation in fish of the family Cobitidae. This study provides a way for the conservation of Leptobotia fish species, in which there are many endangered fish species.