Efficient Breeding of Fish by Self-Fertilization

Female fish with suppressed foxl3 expression are made to produce fertilizable eggs and sperms, and then self-fertilized by administering a virilizing agent to produce self-fertilized eggs.


  • It is easy to fix useful traits of farmed fish and ornamental fish, and the efficiency of breeding can be improved.
  • Productivity can be improved especially for transsexual fish, which are often found in edible farmed fish.
  • The world’s first artificial self-fertilization technology for vertebrates.


Breeding of edible farmed fish such as red sea bream, yellowtail, and tuna and ornamental fish such as medaka have been made to improve growth rate, disease resistance, deliciousness, aesthetics, and the like. Since normal breeding is by crossbreeding, even if useful traits are found, it takes time and effort to produce varieties in which they are fixed. In particular, most of the edible farmed fish are transsexual fish, and especially red sea bream is a female when it is a juvenile and changes to a male after 3 years. Therefore, it takes more than 3 years and a large breeding facility to collect sperm from adult fish. Therefore, a technique for collecting sperm from young fish and a technique for self-fertilization are required.

The Forkhead-box Protein L3 (foxl3) gene is a DNA-binding transcription factor known as the gene that determines whether germline stem cells become eggs or sperms. So far, we have discovered and reported that sperm are formed on the reproductive epithelium in addition to eggs in the ovaries of foxl3-deficient female medaka (Science (2015) 349, 328-331).

Here, we succeeded in releasing the above sperm into the ovarian cavity, self-fertilizing with an egg, and hatching by administering a virilizing agent to a female medaka whose expression of foxl3 was suppressed.

Data and Patent

Data:    From the self-fertilized medaka produced by this technique, 8 out of 33 ovulated eggs were fertilized eggs and 2 hatched normally. Reproducibility was confirmed in multiple medaka fish.

Patent:   PCT Patent Application (Publication No. WO2021/132205)

Principal Investigator

Minoru TANAKA (Tokai National Higher Education and Research System Nagoya University)

Development Stage

  • Currently, the concept of this technology has been demonstrated by confirming the production and hatching of self-fertilized eggs by medaka.
  • Next, we would like to collaborate with external partners (companies, fisheries experimental stations, etc.) to improve the efficiency of this technology and to promote the demonstration and development of self-fertilization with farmed fish such as red sea bream and tiger puffer, and put it into practical use in aquaculture and breeding.

Product No. BK-03685

Other than Medicine


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