Fish
Medaka
Oryzias latipes · also called japanese rice fish
Orbiting the Earth aboard a space shuttle, a pair of medaka became the first fish ever to successfully breed in space, a small, hardy species traditionally found in Japanese rice paddies that has since become one of the most important model organisms in modern genetics.
Overview
The medaka, Oryzias latipes, is a Near Threatened fish native to still and slow-moving fresh water, including rice paddies, across Japan and parts of East Asia. Its landmark role as the first fish to breed in space, importance as a scientific model organism, and traditional ties to Japanese agricultural landscapes make it one of the most scientifically significant small fish in the world.
From rice paddies to orbit
A species once defined by its presence in traditional Japanese rice paddies has become equally defined by its role in cutting-edge science, carrying the distinction of being the first fish to complete a full breeding cycle in the microgravity of space.
Status
Near Threatened, with a declining population in parts of Japan linked to agricultural changes and the loss of traditional rice paddy habitat.
Medaka: common questions
Why is the medaka significant in space history?
It became the first fish to successfully breed in orbit during a Japanese space shuttle experiment, with offspring completing their life cycle in microgravity, a landmark moment in studying how vertebrate reproduction functions in space.
Why is the medaka important to scientific research?
It is widely used as a model organism in genetics, developmental biology, and environmental toxicology research, thanks to its transparent eggs that make observing development easy and its well-mapped genome.
Why is the medaka declining in parts of Japan?
Changes to traditional agricultural practices and the loss of the rice paddy and irrigation channel habitat it has historically relied on have contributed to population declines in parts of its native range.
Is the medaka a hardy fish?
Yes, it tolerates a wide range of water temperatures and salinities, a hardiness that has helped make it both a resilient wild species and a convenient subject for scientific study.