Life History of Obelia bicuspidata Clarke, 1875(Hydrozoa, Campanulariidae)in Korea

Abstract

The life history of Obelia bicuspidata Clarke, 1975 (Hydrozoa, Campanulariidae) was studied in its habitats, Jak-yk Island, Korea and in the laboratory It grows mainly attaching to the under sides of small rocks immersed in muddy shores, or the shade surfaces of oyster shells. The hydoids liberate medusae. The medusa buds develope twice per year, during from March to June and from September to October The optimum water temperature for the hydroids is between 4 ∘C and 8 ∘C and at the temperature above 9 ∘C the hydroids begin to degenerate. In August the surface water temperature is around 25∘C and the hydrothecae are all disappeared. The hydroids grow best during from February to May. The medusae are small, 0.3 mm high, 0.45 mm wide and require about 9 days at room temperature (about 2 0∘C ) for mature after releasing. Obelia bicuspidata turned out to be boreal species in this work.