The ricefishes are a family (Adrianichthyidae) of small ray-finned fish that are found in fresh and brackish waters from India to Japan and out into the Indo-Australian Archipelago, most notably Sulawesi. The common name of the group derives from the fact that many species are found in Japanese rice paddies.^[1] About 27 species, some extremely rare and endangered, and some 2-4 may already be extinct.

Description

Most of these species are quite small, making them of interest for aquaria. The largest species, the Buntingi, is 20 centimetres (7.9 in) in length, but most are less than a fifth this length, with the smallest being only 1.7 centimetres (0.67 in) long. They have a number of distinctive features, including an unusual structure to the jaw, and the presence of an additional bone in the tail.^[1]

As with most fish, ricefish typically spawn their eggs, which are fertilised externally. However, some species, including the medaka, are known to fertilise the eggs internally, carrying them inside the body as the embryo develops. The female then lays the eggs just before they hatch. Several other species carry their eggs attached to the body between their pelvic fins.^[1]

The medaka, Oryzias latipes, is a popular model organism used in research in developmental biology.

Genetic study of the family suggests that it originally evolved on Sulawesi and spread from there to the Asian mainland; the supposed genus Xenopoecilus are apparently unrelated, morphologically divergent species of Oryzias.^[2]

Classification

As currently defined, the ricefishes include 28 species grouped into four genera^[3]:

Family Adrianichthyidae

• Genus Adrianichthys
  • Adrianichthys kruyti - Duckbilled buntingi
  • Adrianichthys roseni
• Genus Horaichthys
  • Horaichthys setnai - Malabar ricefish
• Genus Oryzias
  • Oryzias carnaticus
  • Oryzias celebensis - Celebes medaka
  • Oryzias curvinotus - Hynann ricefish
  • Oryzias dancena
  • Oryzias haugiangensis
  • Oryzias hubbsi
  • Oryzias javanicus - Javanese ricefish
  • Oryzias latipes - Japanese rice fish
  • Oryzias luzonensis
  • Oryzias marmoratus - Marmorated medaka
  • Oryzias matanensis - Matano medaka
  • Oryzias mekongensis
  • Oryzias melastigma
  • Oryzias minutillus - Dwarf medaka
  • Oryzias nebulosus
  • Oryzias nigrimas - Black buntingi
  • Oryzias orthognathus - Sharpjawed buntingi
  • Oryzias pectoralis
  • Oryzias profundicola - Yellow finned medaka
  • Oryzias sinensis
  • Oryzias songkhramensis
  • Oryzias timorensis
  • Oryzias uwai
• Genus Xenopoecilus
  • Xenopoecilus oophorus - Eggcarrying buntingi
  • Xenopoecilus poptae - Popta's buntingi
  • Xenopoecilus sarasinorum - Sarasins minnow

References

• Takehana, Yusuke; Naruse, Kiyoshi & Sakaizumi, Mitsuru (2005): Molecular phylogeny of the medaka fishes genus Oryzias (Beloniformes: Adrianichthyidae) based on nuclear and mitochondrial DNA sequences. Molecular Phylogenetics and Evolution 36(2): 417–428. doi:10.1016/j.ympev.2005.01.016