Oryzias latipes

Basic information
Scientific name	Oryzias latipes	Click to magnify
Common names	Medaka, Japanese rice fish
Higher taxon	Adrianichthyidae, Beloniformes, Actinopterygii
Natural range	Honshu (except for Aomori Pref., Sea of Japan side of Tohoku District, Hokuriku District, and around Wakasa Bay), Shikoku, Kyushu, and nothern and central Ryukyus.
Habitat	Lowland lakes and ponds, rice field, canals, and slow streams.

Invasion information
Range in Japan	Established in Hokkaido. DNA analyses suggested that artificial introduction also occur in Tonegawa, Arakawa, and Sakawagawa River Systems in Kanto to southern Tohoku District.
Origin	According to DNA variation, Hokkaido population should be from Pacific side of Tohoku, Kanto, or Chubu District, and Kanto non-native population should be from around Seto Inland Sea,
Date	This species is often released across Japan
Route	Release of Medaka from different location for “conservation” and “environmental education”, and release and/or escape of pet animals
Impact	Hybridization with native population in except Hokkaido. Native organism(s) affected: Native Medaka populations.
Regulation in Japan	Vulnerable (VU), Red Data Book of Japan
Introduced range in other countries	Russia, Turkmenistan, Kazakhstan, Iran, Afghanistan, Hawaii, Cuba, etc. (O. latipes sensu lato).

Reference

Notes

Asai et al. (2011) Oryzias sakaizumii, a new ricefish from northern Japan (Teleostei: Adrianichthyidae). Ichthyol Explor Freshwaters. 22(4), 289-299.
Froese & Pauly (eds) (2009) FishBase (Accessed on 2010-12-07) http://www.fishbase.org/search.cfm
Kawanabe et al. (eds) (2002) Freshwater Fishes of Japan, 3rd ed.. Yama-kei Publishers, Tokyo (in Jpn)
Matsuzawa & Senou (2008) Alien fishes of Japan. Bun-ichi Sogo Shuppan, Tokyo (in Jpn)
Takehana (2010) Medaka (Oryzias latipes): Genetic introgression resulting from artificial transplantation. Jpn J Ichthyol. 57(1), 76-79 (in Jpn)
Takehana et al. (2003) Geographic variation and diversity of the cytochrome b gene in Japanese wild populations of Medaka, Oryzias latipes. Zool Sci. 20, 1279-1291
etc.

The populations on the entire Japan, Korean Peninsula, continental China, and Taiwan were formerly placed in Oryzias latipes sensu lato. However, the strain of Aomori Pref., Sea of Japan side of Tohoku District, Hokuriku District, around Wakasa Bay, and northern Hyogo Pref. (“Northern Japan Populations”) were described as a new species O. sakaizumii in 2011. Accordingly, the remaining populations of O. latipes sensu lato were devided as follows: the populations on the remaining part of Japan was O. latipes sensu stricto; the populations of western Korea, continental China, and Taiwan was O. sinensis; and the populations of eastern and southern Korea may be an undescribed species or subspecies of O. sakaizumii.
The non-native populations within Japan may belong to O. latipes sensu stricto. Those in Turkmenistan, Iran, Afghanistan, and Kazakhstan were from China, but the origins of those in the other countries were unknown.