|Breeding country of origin|
|during the Edo period (1603–1863)|
The Tosakin or just Tosa is a Japanese cultivated form of goldfish that comes from the city of Kōchi (formerly Tosa) and was named after her. Today it is mainly bred there. Occasionally one can also find breeding sites in China.
Two versions are mentioned about the origin. The earliest mention shows that it is a cross (during the Edo period (1603–1868)) between the goldfish cultivated forms Osaka Ranchu and Ryukin . The second version assumes a direct mutation of the Ryukin. In both representations, however, one points to the potential archetype Ryukin. The shape of the body is also very reminiscent of the Ryukin. However, the tosakin has a peculiarly shaped caudal fin, which initially resembles a closed veil tail, but which arches forward towards the head at the lateral ends. Despite its special and unique tail fin shape, it is not very common, which is partly due to the fact that breeding success is only achieved to a limited extent. On the one hand, reproduction itself is very difficult and, on the other hand, only 30% of the offspring have the special caudal fin. The posture itself is not considered easy either. Due to the shape of the fin, it is only held in very shallow water. Allegedly this contributed to the development of such a caudal fin. It became more popular in the 1970s, when it was increasingly exported to the West. However, even today it is rarely found, even in the country of origin, Japan.
- Rudolf Piechocki: The goldfish . 6th edition. Neue Brehm Bücherei-Westarp, 1990, ISBN 3-7403-0244-5 .
- Bernhard Teichfischer: Goldfish all over the world . 1st edition. Tetra Verlag, Berlin, 1994, ISBN 3-89745-095-X .
- Joseph Smartt: Varieties and Genetics - Handbook for Breeders . 1st edition. Wiley-Blackwell, 2001, ISBN 0-85238-265-0 .