Introduction to Medaka Breeding: Genetics Fundamentals and Breeding Methods for Creating Your Own Original Variety
A beginner's guide for those who want to challenge medaka selective breeding. We explain the fundamentals of genetics, how inherited traits such as body color and fin shape work, and selection methods for stabilizing lineages.
Key Takeaways
A beginner's guide for those who want to challenge medaka selective breeding. We explain the fundamentals of genetics, how inherited traits such as body color and fin shape work, and selection methods for stabilizing lineages.
Related Species
Welcome to the World of Medaka Breeding
"I want to create my own original variety"—an increasing number of medaka breeders hold this dream. Medaka have rapid generation times (capable of breeding in 3-4 months) and significant genetic diversity, allowing even amateurs to see results from selective breeding in a relatively short period.
In this article, we explain the fundamentals of genetics that underpin selective breeding and practical methods for breeding and selection.
Genetics Fundamentals: Mendel's Laws
The foundation of selective breeding is genetics. Characteristics of medaka such as body color and fin shape (traits) are determined by genes.
Dominant and Recessive Traits
When different alleles exist at the same gene locus, traits that are readily expressed are called "dominant," while traits that are rarely expressed are called "recessive."
Example: Black body color (dominant) × white body color (recessive) → F1 generation is almost entirely black body color → When F1 individuals are crossed, white body color appears in approximately 1/4 of the F2 generation
Fixation (Homozygosity)
By repeatedly crossing from the same parents (self-fertilization or sibling crosses), specific traits can be stabilized (fixed).
Major Heritable Traits in Medaka
Body Color - Basic body colors such as white, black, yellow (Himedaka), blue, and brown - "Body-light" (dorsal shimmer) as seen in Mikino medaka - Composite colors such as tricolor and red-and-white
Fin Shape - Matsui long-fin, Swallow, and Hikari body types - Daruma (shortened body type)
Other Traits - Light-body type (dorsal-light body type) - Special medaka varieties such as Milky and Aurora
Practical Breeding Plan Development
- Clarify your target phenotype: Be specific, such as "tricolor with vivid red and white contrast"
