Efficient production of donor-derived gametes from triploid recipients following intra-peritoneal germ cell transplantation into a marine teleost, Nibe croaker (Nibea mitsukurii)

Abstract

Intra-peritoneal spermatogonial transplantation could become important in the production of allogenic or xenogenic donor-derived offspring from surrogate parent fish in commercial aquaculture. However, the rates at which surrogates with chimeric germ-lines are produced and contribute donor-derived gametes and offspring to subsequent generations must be improved for this technology to become practical, especially for marine fishes. Here, we performed intra-peritoneal spermatogonial transplantation into triploid Nibe croaker Nibea mitsukurii to evaluate the suitability of functionally sterile triploids as surrogates. Donor testicular cells were collected from hemizygous pHSC-GFP transgenic (gfp/−) individuals and then transplanted into the peritoneal cavities of 12-day-old larvae (diploid or triploid). By 6months after transplantation, 37% (male) and 29% (female) of triploid recipients had produced gfp-positive, donor-derived gametes; these rates were 7- and 4-fold higher, respectively, than the rates for diploid male and female recipients, respectively. Sperm and eggs from triploid recipients were artificially fertilized with eggs or sperm, respectively, from wild-type fish; approximately 50% of the resulting offspring were gfp-positive, suggesting that nearly all of offspring originated from donor-derived gametes that had descended from transplanted gfp/− germ cells. The fecundity and spawning frequency of surrogate triploid recipients were not significantly different to those of non-transplanted diploids, and the triploid recipients produced subsequent donor-derived offspring for at least two spawning seasons. Our results demonstrated that use of functionally sterile triploid recipients improved the percentage of recipients that produce donor-derived gametes. Further, the use of triploid recipients resulted in exclusive production of donor-derived gametes in this marine teleost. Statement of relevanceIntra-peritoneal spermatogonial transplantation using allogenic triploid recipients was first demonstrated in marine teleosts. In addition to efficient and exclusive donor-derived gametogenesis, we found that use of functionally sterile triploid recipients improved the percentage of recipients that produce donor-derived gametes. Consequently, triploid surrogates were more suitable than diploid surrogates and that use of triploid surrogates may accelerate the application of surrogate broodstock technology in aquaculture-targeted, genetically valuable, or endangered marine teleosts.