Okichimozuku Habitat

The Spring Where a Freshwater Red Alga Was First Found

The Okichimozuku Habitat (オキチモズク発生地, Okichimozuku Hasseichi) is a site in Yoshihisa, Toon City, Ehime Prefecture, where the freshwater red alga okichimozuku grows, which in 1944 was designated a Natural Monument.

The Agency for Cultural Affairs lists it under the criterion for areas producing rare water plants, algae and similar organisms in springs, rivers and lakes; its photographs name the spring as Okichi Spring. Toon City's cultural properties database gives the city as its manager.

The designation text calls okichimozuku a rare freshwater red alga, and notes that this is the place where it was first discovered in Japan and the northern limit of its range.

The Okichimozuku Alga

The Toon City board of education describes okichimozuku as a rare species of freshwater red alga growing in the stream that flows from Okichi Spring in Yoshihisa. Its soft, purplish-red, cylindrical body branches repeatedly and grows 5 to 30 centimetres long, occasionally 40 centimetres.

It sprouts each year in late autumn, releases spores around March and then disappears. It once clung to pebbles in the current for about 400 metres downstream of the spring.

The Legend Behind the Name

The board of education records a legend. Okichi, the good-natured and hardworking wife of Onishi Yaemon, could not get along with her mother-in-law and, while pregnant, threw herself into this spring, which has been called Okichi Spring ever since.

The alga's discoverer, Yagi Shigeichi, named it okichimozuku after Okichi. The Okichimozuku Habitat is a case of a local legend passing into the Japanese name of a living species.

The Site Today and Visiting

The board of education says okichimozuku is now close to extinction here. The cause is unclear, but may be linked to changes such as reduced spring flow; shading has been placed over the water in a continuing effort to bring it back.

The Okichimozuku Habitat, Okichi Spring and the stream below it in Yoshihisa, can be seen from outside. As a Natural Monument, visitors must not enter the spring or channel or remove algae or stones. Enquiries go to the Toon City board of education at the Toon City Museum of History and Folklore, 089-964-0701.