Germ cell manipulation in farmed fishes

In teleosts, when a testicular or ovarian cell suspension is injected into the peritoneal cavity of newly hatched larvae of a different species, a subset of donor-derived cells, presumably representing germline stem cells, migrates towards the recipient's genital ridge, becomes incorporated, and initiates donor-derived gametogenesis. Furthermore, when fish recipients are sterilized through triploidization or through the knockdown or knockout of the dead end (dnd) gene prior to transplantation, they produce only donor-derived gametes. Thus, in teleosts, the generation of surrogate broodstock that produce heterospecific gametes has become possible through a relatively simple transplantation procedure. This technology has already been applied successfully to species belonging to diverse fish taxa. This germ cell transplantation technology offers immense potential for aquaculture. Germline stem cells can be readily cryopreserved. Importantly, when cryopreserved germ cells are transplanted into suitable fish recipients, the recipients can produce functional eggs and sperm derived from these cells. This capability enables the regeneration of offspring from cryopreserved germ cells, making this technology an effective tool for the long-term preservation of genetic resources from elite fish strains. Moreover, the eggs and sperm of large-bodied fish species that are difficult to maintain as broodstock can now be produced in smaller, easily managed surrogate species. More recently, this technology has been investigated to accelerate selective breeding by enabling the production of eggs and sperm from target species in recipients with shorter generation times. This technology could be widely applied in the future.