[Water environment adaptability and ecological groups of hydroidomedusae in East China Sea]

Based on the data of four seasonal oceanographic censuses in East China Sea (23 degrees 30' - 33 degrees 00' N, 118 degrees 30' - 128 degrees 00' E) in 1997-2000, the optimal water temperature and salinity and the ecological groups of Hydroidomedusae were studied by curve fitting, mathematical model forming, and geographic distribution analyzing. The results showed that Hydroidomedusae could live in the waters with different temperature and salinity. 15 species of Hydroidomedusae had an optimal water temperature of <20 degrees C, 8 species at 20 degrees C - 25 degrees C, 12 species at 22.5 degrees C - 25 degrees C, and 17 species at > or =25 degrees C. 32 species of Hydroidomedusae had an optimal salinity of 32-34, 13 species at 34, 6 species at 30-32, and only 2 species at <30. The weak adaptability of most Hydroidomedusae species to the variation of water salinity made them have low density and limited distribution in East China Sea. Sugiura chengshanense and Clytia hemisphaerica were of nearshore warm temperate water species, Cunina octonaria and other 12 species were of offshore warm temperate water species, 8 species represented by Ectopleura latitaeniata were of nearshore subtropical water species, 5 species represented by Aglaura hemistoma showed some oceanic tropical features, while 25 species represented by Liriope tetraphylla were of offshore subtropical species. Some Hydroidomedusae species could be used as an important bio-indicator of water mass in East China Sea.