Crossing test among floating Viva thalli forming 'green tide' in Japan

Crossing tests were made to determine the relationship between the identified Viva pertusa, which commonly grows in Japan as an attached form on exposed rocks, and the floating Viva forming "green tide" inside calm bays. The floating Viva thalli were collected from five major green tide sites in Japan (Yokohama, Mikawa, Miyajima, Kochi and Hakata). Reproductive maturation was induced in U. pertusa and the floating thalli from each site. Mating between induced gametes was observed. It is therefore believed that the floating thalli from Yokohama, Mikawa and Miyajima were mainly U. pertusa, while those from Kochi and Hakata were of a different species (Viva sp.l). Furthermore, the Viva species found in Mikawa is also a species (Viva sp.2) different from both U. pertusa and Viva sp. 1.