| Summary: | 碩士 === 國立中山大學 === 海洋資源學系 === 82 === The fauna of the choanoflagellates from the coastal waters of Taiwan and the effects of temperature on the species composition of choanoflatellates were investigated. Observations from transmission electron microscope revealed 42 species representing 23 genera of choanoflagellates all belonging to the familly Acanthoecidae. Three new genera, 9 new species and 1 new subspecies were identified. These new species and subspecies belong to six genera: Stephanoeca (S. elegans supracostata), genus nov. 1 (sp. nov.1, sp.nov.2, sp.nov.3), genus nov.2 (Parvicorbicula superpositus aff., sp.nov.4), genus nov.3 (sp.nov.5), Diaphanoeca (D. spiralis, sp.nov.6) and Acanthocorbis (A.. camarensis).
Studies in southern Taiwan (Nan-wan) registered 25 species. More species were observed in summer (21 species ) than in other seasons (7 in water, 6 in autumn and 5 in spring ). The abundance of choanoflagellates ranged from 0 to 5.7x10 3 cells/1 in Nan-wan samples. Cell densities in the discharge cannal of a power plant was one order of magnitude lower ( 0-1.6x10 2 cells/1) than other waters in Nan-wan.
In a laboratory experiment, choanoflagellates were acclimatized in 25℃ for 2 days and then tested at 4 temperatures ( 15℃ , 25℃, 30℃, 35℃), Choanoflagellates had the hightest survival rate at 25℃ than the other groups after 2 hrs exposure. The survival rate at 25℃ (54.1%) was still higer than the other groups (15℃: 41.4%, 30℃ 0w 20.6%, 35℃:2.0%) after 7 days of exposure, Stephanoeca diplocostata paucicostata was the most domonant species at 15℃, while Acanthocorbis camarensis dominated at temperatures higher the 25℃.
Effects of temperature on the length of lorica and the length of costal strips on lorcia varied among choanoflagellate species. The length of lorica and costal stips of A. camarensis decreased with increasing temperature. The length of lorical and costal strips of A. apoda and S. diplocostata paucicostata, in contrast, showed varied responses to incremental changes in temperature. No such significant temperature dependences was found in S. diplocostata and Diplotheca costata. Samples collected from Nan-wan showed that the length of the anterior transverse costa of Crinolina aperta increased with increasing water temperature. No such correlation was found in parvicorbicula superpositus aff. and Platypleura acuta. No intra-specific difference was found in the lorcia dimension and longitudinal costae number of most choanoflagellates from Taiwan and those from higher latitudes. Few exceptional species exhibited morphological differences due to geographical variation. Among these species, the probability that those occurring in cold waters would have larger lorica dimensions and longer longitudinal costa than Taiwanese counterparts was higer than that the case vice verse.
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