AI-generated image
Ryusei Medaka
IntermediateOryzias latipes
An improved medaka placing miyuki external luminescence on a maruko body type that has no dorsal fin, so the sheen runs unbroken from head to tail instead of stopping at the dorsal. Created in 2013 by Yoshinori Nakazato, it became the third variety certified by the Japan Medaka Association.
Difficulty
Intermediate
Temperature
18〜28℃
Lifespan
2-3 years
Size
Up to about 4cm SL
Diet
Prepared medaka food, green water
About
Ryusei is an improved medaka combining a blue body with external luminescence and the maruko trait of having no dorsal fin; its classification name is the blue external-luminescence maruko medaka. It was created in 2013 by Yoshinori Nakazato of Kanagawa Prefecture and is registered in the Medaka Web Encyclopedia as type No.0429, variety No.0410 and fixed variety No.0098, also known as the dorsal-less miyuki. Under the Japan Medaka Association's new-variety scheme it is certified variety No.3: it was shown at the 5th Autumn Japan Medaka Show in 2013, took first place in the new-variety division and received provisional recognition, and was certified at the 6th Spring Japan Medaka Show in 2014. The point of the variety is the absence of the dorsal fin. Miyuki external luminescence had always broken at the dorsal, and removing the fin lets the sheen on the back run unbroken to the tail. The nickname Ryusei, meaning shooting star, comes from that single unbroken line of light. The variety was bred by crossing dorsal-less medaka with miyuki, but because the dorsal-less fish used carried a yellow body colour, the work is said to have been extremely difficult.
Source: Wikipedia (CC BY-SA 4.0)
Lifespan of the Ryusei Medaka
The Ryusei Medaka lives 2-3 years.
Size of the Ryusei Medaka
The Ryusei Medaka grows to Up to about 4cm SL.
Temperature & humidity for the Ryusei Medaka
The ideal temperature for the Ryusei Medaka is 18〜28℃.
Basic Info
Origin
Japan (domestic variety created in 2013 by Yoshinori Nakazato of Kanagawa Prefecture)
Care Specifications
- pH
- 7–8
- Hardness (GH)
- 9–19 dGH
- Water Temp.
- 18–28℃
PeacefulGroupBreeding: Moderate
Sources: Medaka Web Encyclopedia: Complete Medaka Care Guide / FishBase Oryzias latipes / Medaka Web Encyclopedia No.0429
Morphs (Varieties)
The Japan Medaka Association's classification manual sorts varieties by traits that can be seen rather than by genotype, and does not set out how individual traits are inherited. Traits the manual explicitly says can be passed on and produced by selective, multi-generation breeding are listed as line-bred; the rest are grouped under Other.
Other
Blue body colourExternal luminescence (taigaikou)Maruko (no dorsal fin)
Sources: Japan Medaka Association: Variety Classification Manual, 5th ed. (Sep 2025) / Medaka Web Encyclopedia: Medaka Traits / Medaka Web Encyclopedia No.0429 / Medaka Web Encyclopedia: JMA Certified Variety Number List
A curated selection of notable morphs. Inheritance modes are a breeding-planning guide; actual appearance varies with combos.
References & Sources
Edited & verified by: BreederDirect editorial team
The taxonomic, regulatory, and husbandry data on this page are compiled and verified against the authoritative primary sources below.
Primary sources
- Wikipedia
- CITES Appendices (species not listed)
- FishBase (IUCN Red List: Least Concern, assessed 2018)
- Medaka Web Encyclopedia: Complete Medaka Care Guide
- Medaka Web Encyclopedia No.0429
- Japan Medaka Association: Variety Classification Manual, 5th ed. (Sep 2025)
- Medaka Web Encyclopedia: Medaka Traits
- Medaka Web Encyclopedia: JMA Certified Variety Number List
- FishBase
- GBIF
Taxonomy & Authority
Accepted name: Oryzias latipes (Temminck & Schlegel, 1846)
Breeder: 中里良則 (2013)
Parentage: 背ビレ無しメダカ × 幹之メダカ
Authority databases: FishBase · GBIF · Medaka Web Encyclopedia No.0429 · Medaka Web Encyclopedia: JMA Certified Variety Number List
Nomenclature follows global taxonomic authority databases.
Regulations & Conservation Status
Not CITES-listedIUCN LC · Least Concern
Sources: CITES Appendices (species not listed) / FishBase (IUCN Red List: Least Concern, assessed 2018)
Regulations may change. Always verify the latest information with the relevant authorities.
Ryusei Medaka Listings
Loading latest listingsFind listings for this species
