Functional Sperm of the Yellowtail ( Seriola quinqueradiata ) Were Produced in the Small-Bodied Surrogate, Jack Mackerel ( Trachurus japonicus )

Production of xenogeneic gametes from large-bodied, commercially important marine species in closely related smaller surrogates with short generation times may enable rapid domestication of the targeted species. In this study, we aimed to produce gametes of Japanese yellowtail ( Seriola quinqueradiata ) using jack mackerel ( Trachurus japonicus ) as a surrogate with a smaller body size and shorter maturation period. Donor spermatogonia were collected from the testes of yellowtail males and transferred into the peritoneal cavity of 10- and 12-day-old jack mackerel larvae. Twenty days later, 59.5 % of the recipients survived of which 88.2 % had donor-derived germ cells in their gonads. One year later, genomic DNA templates were prepared from the semen of 96 male recipients and subjected to polymerase chain reaction (PCR) analyses using primers specific for the yellowtail vasa sequence, resulting in the detection of positive signals in semen from two recipients. The milt collected from the recipients was used for fertilization with yellowtail eggs. Of eight hatchlings obtained from the crosses, two were confirmed to be derived from donor yellowtail by DNA markers, although the others were gynogenetic diploids. These findings indicate that it is possible to produce donor-derived sperm in xenogeneic recipients with a smaller body size and shorter generation time by transplanting spermatogonia. Thus, the xenogeneic transplantation of spermatogonia might be a potential tool to produce gametes of large-bodied, commercially important fish, although the efficiency of the method requires further improvement. This is the first report demonstrating that donor-derived sperm could be produced in xenogeneic recipient via spermatogonial transplantation in carangid fishes.