Production of semah mahseer (Tor douronensis) donor-derived offspring through xenogeneic germ cell transplantation

Germ cell transplantation is a powerful technique for the production of gametes of commercially important or endangered fish species. Semah mahseer is a high-value freshwater fish distributed in Southeast Asia; however, they are currently facing extinction. Therefore, in this study, we performed cryopreservation and transplantation of germ cells into Nile tilapia as a host to produce gametes of semah mahseer. As a result, we found that germ cells could be preserved in liquid nitrogen with 10% dimethyl sulfoxide cryoprotectant for at least a year. Through the transplantation of previously frozen germ cells into the peritoneal cavity of tilapia larvae, the colonization of donor germ cells in recipient gonads was observed by the fluorescent signal of PKH26 dye and in situ hybridization using a vasa RNA probe specific to the donor. The recipients were reared to sexual maturity, and the resulting male and female recipients were mated naturally. Remarkably, we found donor-derived offspring from recipients at 14 months post-transplantation. Polymerase chain reaction-restriction fragment length polymorphism, using cytochrome b mitochondrial DNA gene and recombination activating 2 nuclear gene, revealed that they carried identical genotypes to the donor individuals. This is the first report of donor-derived semah mahseer offspring from inter-order germ cell transplantation.