Abstract: The transplant fish production method includes selecting a donor fish species, selecting first and second fish species which are a combination that could be sterile, producing a hybrid fish species of the selected first fish species and second fish species, and transplanting reproductive cells of the donor fish species into the produced hybrid fish species.

Abstract: The transplant fish production method includes selecting a donor fish species, selecting first and second fish species which are a combination that could be sterile, producing a hybrid fish species of the selected first fish species and second fish species, and transplanting reproductive cells of the donor fish species into the produced hybrid fish species.

Abstract: In order to examine whether or not a germ cell derived from a donor fish, which has been transplanted into a recipient fish of a different species by a surrogate fish technique, grows or matures in the gonad of the recipient fish, it is necessary to use, as an indicator, a trait that is specifically expressed in the germ cell and can be used to distinguish the recipient fish from the donor fish. Vasa gene, which is a germ cell-specific gene, is specific to a primordial germ cell and a spermatogonium/an oogonium, and it is not expressed in a somatic cell. In the present invention, the Vasa gene sequences of a tuna, a chub mackerel, a spotted mackerel, an eastern little tuna, and a drumfish are determined, and the expression of such gene is used as a marker for a germ cell. In addition, according to the present invention, it is possible to specifically detect only a tuna Vasa gene in Vasa gene sequences that are highly conserved in fishes, without sequencing.

Abstract: An object of the present invention is to provide a means for distinguishing between a germ cell derived from a donor (tuna) and a germ cell derived from a recipient in a method for inducing differentiation of a tuna germ cell, wherein a primordial germ cell derived from the tuna is transplanted into an early embryo of the heterologous recipient fish. The present inventors compared a Vasa amino acid sequence of bluefin tuna with those of other fish (black skipjack, skipjack, chub mackerel, blue mackerel, round frigate mackerel and frigate mackerel), identified amino acid sequence regions specific to bluefin tuna, and, by using the amino acid sequences specific to bluefin tuna as antigens, successfully produced monoclonal antibodies specifically recognizing primordial germ cells, spermatogonia, oogonia or oocytes derived from bluefin tuna, thus accomplishing the present invention.

Abstract: In order to examine whether or not a germ cell derived from a donor fish, which has been transplanted into a recipient fish of a different species by a surrogate fish technique, grows or matures in the gonad of the recipient fish, it is necessary to use, as an indicator, a trait that is specifically expressed in the germ cell and can be used to distinguish the recipient fish from the donor fish. Vasa gene, which is a germ cell-specific gene, is specific to a primordial germ cell and a spermatogonium/an oogonium, and it is not expressed in a somatic cell. In the present invention, the Vasa gene sequences of a tuna, a chub mackerel, a spotted mackerel, an eastern little tuna, and a drumfish are determined, and the expression of such gene is used as a marker for a germ cell. In addition, according to the present invention, it is possible to specifically detect only a tuna Vasa gene in Vasa gene sequences that are highly conserved in fishes, without sequencing.

Abstract: The present invention relates to fish with increased unsaturated fatty acid content by transfer of a fatty acid desaturase gene thereinto, and a production method of these fish with increased unsaturated fatty acid content. The fatty acid desaturase gene is one or more members selected from among ?4 fatty acid desaturase gene, ?5 fatty acid desaturase gene and ?6 fatty acid desaturase gene, and it is preferable that these genes originate in a freshwater fish. It is preferable that the expression of a fatty acid desaturase gene originating in a freshwater fish is promoted by a ?-actin promoter originating in medaka. By modifying the fatty acid metabolic pathway of fish, problems to be solved by the present invention may be to provide fish having a high vitality and a tolerance to handling and low temperature, which will enable the use of a vegetable fat or animal fat as a formula feed.