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Oryzias javanicus

Oryzias javanicus
Javanese Ricefish
This species is infrequently seen in the hobby but is exported on occasion and sometimes referred to as the 'blue-eyed ricefish'. It has a truncate, rather than lunate or emarginate, caudal fin which distinguishes it from the congeners O. bonneorum, O. nebulosus, O. nigrimas, O. orthognathus, and O. sarasinorum , and in this respect appears to be a member of a large, unnamed clade or 'species group' containing all other members of the genus. 

It is further distinguishable from congeners by the following combination of characters: 10-13 pectoral fin rays; 18-25 (usually 23) anal fin rays; anal fin rays in males with bony contact organs; 6-8 (usually 7) dorsal fin rays; caudal fin with yellow submarginal bands in both lobes; premaxillary with enlarged teeth on posterior side; relatively deep body. 

Members of the family Adrianichthyidae are often referred to collectively as 'ricefishes' and were traditionally considered to be members of the family Cyprinodontiformes and thus closely-related to toothcarps. This misconception is sometimes still upheld despite the fact that Rosen and Parenti reclassified them within the cyprinodontiform sister group Beloniformes as long ago as 1981. The most well-known member of the family is the medaka or Japanese ricefish, Oryzias latipes which has been widely used as a model organism in genomic and experimental biology for well over a century and was in fact the first vertebrate animal to mate in space during the mid-1990s. 

There are currently just two genera included in the family, Oryzias and Adrianichthys, with the historically-recognised groupings Xenopoecilus and Horaichthys having been synonymised with Oryzias by Parenti (2008). Of the three species previously included in the paraphyletic Xenopoecilius, X. oophorus and X. poptae were moved into Adrianichthys with the third, X. sarasinorum currently recognised as Oryzias sarasinorum . The monotypic Indian species Horaichthyws setnai is now known as O. setnai.