Kind of Medaka

Japanese Medaka is called Japanese Rice Fish or Japanese Killifish, there are only two kinds of Japanese Medaka, but there are many improved varieties, which are increasing year by year. Originally, even wild species of black medaka had variations in color and shape depending on the region, but only one kind of black medaka, to be exact, only Kitanomedaka from Aomori on the Sea of Japan side of Kyoto and other southern medaka, was used as a cultivar. However, fixation of mutant species now produces various varieties. There are nearly 500 varieties in detail, and new varieties are steadily increasing every year. Here are some of them.

A list of medaka varieties can be found later in the page.

About medaka varieties

Medaka is a generic name for freshwater fish classified as the genus Medaka, and there are more than 20 medaka friends not only in Japan but also in various parts of Asia. However, medaka other than Japanese medaka are all tropical fish, and only Japanese medaka has cold resistance.

Often referred to as the "kind of medaka", this is not exactly a "kind" but a "breed". The varieties of medaka introduced here are all improved medaka with fixed mutant species except black medaka.

Medaka varieties are classified according to the visual differences shown in the following list.

• Body color
• Coloring
• Body shape
• Eyes
• Fin shape

Medaka body color

The color of an organism's body is determined by pigment cells. Fish have five pigments, black, red, yellow, white and rainbow. The color and pattern are determined by their combination and density.
Medaka has four pigment cells: black, yellow, white and rainbow. However, albino is an individual that has no pigment or has declined.

The main body colors of medaka are black, yellow, white, blue, brown and albino.
A variety of color variations have been created by crossing medaka with these body colors.

Coloring of medaka

By crossing various variations of medaka, medaka that has a different color from the original body color has been born.
In the so-called “Hikari”, due to the mutation, the iridescent pigment reflecting the light on the edge and abdomen of the eyes moved to the back, and the back became shiny.
The ones that lose their pigment cells and see the gills are called transparent scales.
In addition, the body light is transparent throughout the body and emits light from the body.

However, for Hikari, not only the back shines, but also the body shape changes, the dorsal fin and buttocks fin have the same shape, and the tail fin has a diamond shape. The body is symmetrical around the body.
Recently, those with the characteristics of this body shape have been called “Hikari”, and whether or not the back is shining has become less important.
In addition, like Miyuki, there are those whose body is normal but whose back is very shiny. These are not called “Hikari”.
Based on the above, it can be said that it is appropriate to consider Hikari as a feature of the body, not a feature of coloring.

Medaka body shape

There are three types of medaka body types. Normal, Dharma, and Semi-Dharma.
In addition, “Hikari” introduced in the section of coloring of medaka is recently called “Hikari figure”. Therefore, it may be said that there are four body shapes of medaka.

•  Normal figure
  The shape of the original medaka.
•  Dharma figure
  Due to the mutation, the number of stone pillars is small, and it has a rounded body shape.
•  Semi-Dharma (Half-Dharma) figure
  It has an intermediate shape that is shorter than normal and longer than Dharma.
•  Hikari figure
  The dorsal fin and buttocks fin have the same shape, and the tail fin has a diamond shape.

Eye variations

Medaka also has variations such as eye shape and color.
The main variations are listed below.

• Panda
  The eyes are black and look like panda eyes.
• Small eyes
  The eyes are dots and there is little eyesight.
• Big eyes
  The eyes themselves are big.
• Protruding eyes
  Both eyes protrude. In rare cases, one eye may protrude due to a disease such as cancer, but the Protruding eyes are due to heredity.
• Previous eyes
  The eyes are facing diagonally forward. Looking from the front is very cute.
• Water bubbles eyes
  There are blisters in the eyes that are filled with lymph.

Fin variations

The medaka has 5 types of 7 fins: chest, back, belly, buttocks and tail.
There are changes in the shape and length of all these fins. Below is a list of typical fin variations.

• Long-fin
  All or some fins will be longer. Unlike swallows, the entire fin extends.
• Swallow
  All or some fins will be longer. Unlike Long-fin, part of the fin grows like distorted hair.
• Samurai
  Hikari body medaka back fin is divided into two.
• No-back-fin
  As the name suggests, there is no back fin. Miyuki Medaka that has no back fins is very beautiful because the light on the back does not break up to the base of the tail.