[Trivia] A quiz to learn about the ecology and habits of medaka (Japanese rice fish)

Water temperature change

One thing medaka fish are not good with is changes in water temperature. Medaka are prone to stress when they encounter large, rapid fluctuations in water temperature, which can harm their health. Proper temperature control is very important when keeping medaka.

Shape of the dorsal fin and anal fin

The most reliable way to tell male and female medaka apart is by looking at the shapes of the dorsal and anal fins. Male medaka have long, slender dorsal and anal fins, and during the mating season the anal fin often extends even longer. In contrast, female medaka have relatively round, short dorsal and anal fins. Keeping this difference in mind will help you identify the sex of medaka.

1 to 2 years

The average lifespan of wild medaka is considered to be 1 to 2 years. This is because, in nature, they are easily preyed upon and are greatly affected by environmental conditions. In artificial environments, they may live a little longer with proper care, but remember that medaka are fundamentally very short-lived creatures.

Oryzias latipes

The scientific name of the medaka is Oryzias latipes. Medaka are widely distributed in freshwater habitats across Asia, including Japan, and due to research on their ecology and genetics, they have become a very popular model organism in the field of biology.

Indian subcontinent

The medaka’s place of origin is the Indian subcontinent. Over millions of years of evolution, medaka have come to inhabit a wide area across East Asia, including present-day Japan. It is thought that they spread from the Indian subcontinent through Southeast Asia and eventually reached Japan. The reason medaka have become a familiar and popular presence around Japan’s waters lies in this long history of migration and adaptation.

Himedaka (Japanese rice fish, orange variety)

Himedaka are a type of medaka (Japanese rice fish) with a beautiful orange body color. Thanks to their bright hue, they are popular ornamental fish kept by many enthusiasts. Especially among selectively bred varieties, some have deeper coloration and greater luster, offering additional appeal and a wide range of types to enjoy.

Driftwood and stones

Medaka eggs are often laid by the parent fish on underwater objects such as driftwood and stones. These locations provide protection for the eggs and serve as hiding places for the fry after they hatch, helping them avoid predators. Driftwood and stones rest stably on the bottom and offer an environment suitable for medaka to lay their eggs.