Oryzias latipes
Encyclopedia
Oryzias latipes, also known as Medaka and Japanese killifish, is a member of genus Oryzias (ricefish
), the only genus in the subfamily Oryziinae. This rather small (2-4 cm long)
native of Southeast Asia
is a common denizen of rice paddies
in coastal Asia. It became popular as an aquarium fish because of its hardiness and pleasant coloration: its coloration varies from brown or yellow-gold in the wild to white, creamy yellow, or orange in aquarium-bred individuals. The medaka has been a popular pet since the 17th century in Japan
. It is amphidromous
, meaning it moves between salt and freshwater at some point in its life. It is found in both ocean and river habitats. The female carries her eggs attached between her anal fins.
Oryzias latipes is a model organism
and is extensively used in many areas of biological research. Medaka have a short gestation period and are reproductively prolific — characteristics that make them easy to rear in the laboratory. They can withstand cold and can be shipped easily. Nearly all aspects of the life cycle of medaka have been analyzed by researchers including sexual behavior, genetic inheritance of coloration, spawning habits, feeding, pathology, embryological development, ecology, etc.
It has relatively small genome (~800 Mb, half the size of the genome of another popular model fish, the zebrafish) as well as a generation time of 7 weeks (rather than 9 weeks for zebrafish) also hardier growth in a broad temperature range (6-40 degrees C).
Transgenic
medaka are relatively easy to produce. They have been genetically modified to secrete various human hormone
s, express promoter sequences from other fish, and to make antimicrobial proteins and a protein that makes the medaka glow fluorescent
green. There are also many mutations that show up in medaka at random, for example, a mutant strain that lacks scales, and one with extra-long fins. Haploid embryonic stem cell lines have been established.
O. latipes has gone into space aboard the space shuttle
. It carries the distinction of having been the first vertebrate to mate in orbit. The result of the mating was a brood of healthy fry, hatched on the space shuttle Columbia
in 1994.
Ricefish
The ricefishes are a family 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...
), the only genus in the subfamily Oryziinae. This rather small (2-4 cm long)
native of Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
is a common denizen of rice paddies
Paddy field
A paddy field is a flooded parcel of arable land used for growing rice and other semiaquatic crops. Paddy fields are a typical feature of rice farming in east, south and southeast Asia. Paddies can be built into steep hillsides as terraces and adjacent to depressed or steeply sloped features such...
in coastal Asia. It became popular as an aquarium fish because of its hardiness and pleasant coloration: its coloration varies from brown or yellow-gold in the wild to white, creamy yellow, or orange in aquarium-bred individuals. The medaka has been a popular pet since the 17th century in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
. It is amphidromous
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
, meaning it moves between salt and freshwater at some point in its life. It is found in both ocean and river habitats. The female carries her eggs attached between her anal fins.
Oryzias latipes is a model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
and is extensively used in many areas of biological research. Medaka have a short gestation period and are reproductively prolific — characteristics that make them easy to rear in the laboratory. They can withstand cold and can be shipped easily. Nearly all aspects of the life cycle of medaka have been analyzed by researchers including sexual behavior, genetic inheritance of coloration, spawning habits, feeding, pathology, embryological development, ecology, etc.
It has relatively small genome (~800 Mb, half the size of the genome of another popular model fish, the zebrafish) as well as a generation time of 7 weeks (rather than 9 weeks for zebrafish) also hardier growth in a broad temperature range (6-40 degrees C).
Transgenic
Genetically modified organism
A genetically modified organism or genetically engineered organism is an organism whose genetic material has been altered using genetic engineering techniques. These techniques, generally known as recombinant DNA technology, use DNA molecules from different sources, which are combined into one...
medaka are relatively easy to produce. They have been genetically modified to secrete various human hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s, express promoter sequences from other fish, and to make antimicrobial proteins and a protein that makes the medaka glow fluorescent
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
green. There are also many mutations that show up in medaka at random, for example, a mutant strain that lacks scales, and one with extra-long fins. Haploid embryonic stem cell lines have been established.
O. latipes has gone into space aboard the space shuttle
Space Shuttle program
NASA's Space Shuttle program, officially called Space Transportation System , was the United States government's manned launch vehicle program from 1981 to 2011...
. It carries the distinction of having been the first vertebrate to mate in orbit. The result of the mating was a brood of healthy fry, hatched on the space shuttle Columbia
Space Shuttle Columbia
Space Shuttle Columbia was the first spaceworthy Space Shuttle in NASA's orbital fleet. First launched on the STS-1 mission, the first of the Space Shuttle program, it completed 27 missions before being destroyed during re-entry on February 1, 2003 near the end of its 28th, STS-107. All seven crew...
in 1994.