• Animal Systematics, Evolution and Diversity
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• v.17 no.2
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• pp.171-177
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• 2001

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$^{\circ}C$ and 8$^{\circ}C$ and at the temperature above 9$^{\circ}C$ the hydroids begin to degenerate. In August the surface water temperature is around $25^{\circ}C$ 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$0^{\circ}C$) for mature after releasing. Obelia bicuspidata turned out to be boreal species in this work.

• Animal Systematics, Evolution and Diversity
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• v.9 no.2
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• pp.261-280
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• 1993

The marine hydroids of Cheju Island in this work identified into 46 species and/or subspecies of 25 genera in 10 families. Of which four species: Rhizocaulus chinensis, Obelia bicuspidata, Sertularia desmoides and Plumularia spinulosa are new to the hydroid fauna of Cheju Island and four species: Hebella parastica, Campanularia groenlandica, Campanularia everta and Sertulareffa natalensis are new to the Korean fauna. Adding these eight species to the previous known species (83 species and/or subspecies) in Cheju Island, the hydroid fauna in Cheju Island identified up to date consists of 91 species and/or subspecies of 41 genera in 12 families. Macrorhynchia phoenicea is dominant species which occur in 10 points, Aglaophenia suensonii in eight points. 71 species (78%) occur in Songsanp'o, 43 species (47%) in Munsom, 26 species (29%) in Supsom, 13 species (14%) in Wimi-ri and 11 species (12%) in P - omsom in order. Thirty-three percent (30 species) of the hydroids of Cheju Island was only found in Cheju Island.