It is imperative that highly effective containment methods are available to prevent highly selectively bred aquaculture animals escaping from captivity and propagate and/or interbreed with wild stocks. The use of reproductively sterile farmed animals is the most effective strategy for genetic-containment in aquaculture. Sterility carries environmental significance, preventing the escapees from spreading and genetic mixing with natural populations . Sterilization also prevents sexual maturation and minimizes energy input toward gonadal growth while enhancing flesh development and promoting animal health . Furthermore, sterility is a means for producers to protect their valuable strains from unauthorized propagation.
We have developed a technology to efficiently produce infertile fish by disrupting primordial germ cell development in embryos without introducing any genetic modification. This technology administers Vivo -conjugated Morpholino oligomer (MO) through bath-immersion targeting at Deadend (Dnd), an essential protein for early germ cell development in fish , which led to the elimination of germ cells and consequently sterile fish.
We have applied this novel sterilization technology to several salmonids, including rainbow trout, Atlantic salmon, and coho salmon. In coho salmon, the treated fish and control fish were reared for 14 months before examining their gonadal development. Infertile coho salmon (Fig.1 C & c) with the absence of gonad were achieved through dnd knock-down by immersion. Histology also shows the devoid of any germ cells in treated sterile fish compared with control fish. Optimizations towards better survival and higher sterility rates are ongoing. These sterile animals also provide excellent opportunities to study the involvement of germ cells/gonads in the development and regulation of the reproductive neuroendocrine axis. The contrast of gene expression profiles between 3-year-old sterile and fertile rainbow trout in spawning season is discussed.