Developmental biotechnology for aquaculture, with special reference to surrogate production in teleost fishes

This review introduces surrogate production as a new technique for fish-seed production in aquaculture. Surrogate production in fish is a technique used to obtain the gametes of a certain genotype through the gonad of another genotype. It is achieved by inducing germ-line chimerism between different species during early development. Primordial germ cells (PGCs) are the key material of this technique to induce germ-line chimera. In several species, it has been reported that PGCs differentiated from the blastomeres inherited some maternally supplied mRNA located in the terminal regions of the early cleavage furrows. PGCs from donor species (or strains) are isolated and transplanted into host species to induce the germ-line chimera. Four methods for inducing germ-line chimera are described: blastomere transplantation, blastoderm-graft transplantation, transplantation of PGC from the genital ridge, and transplantation visualised PGC with GFP fluorescence. Several problems preventing the successful induction of germ-line chimera in various fish species are discussed. Surrogate production, however, opens the possibility of efficient fish-seed production and effective breeding and transfer of biodiversity to an aquaculture strain. Conservation and efficient utilisation of genetic resources will be achieved through surrogate production combined with the cryopreservation of PGCs.