Introduction In spite of the past explorations of mycobiota in Yakushima Island (literature cited in Hosoya and Tanaka, 2007), there have been no records of aquatic hyphomycetes. Aquatic hyphomycetes were first found in Europe and are known for their characteristic morphology of the spores (In- gold, 1942). Later, the more highly diverse mor- phology of aquatic hyphomycetes in subtropical and tropical areas caught attention of many my- cologists (e. g., Goh, 1997; Marvanová, 1997). At present, more than 500 species are known from freshwater habitats (Tsui and Hyde, 2003). They are involved in the degradation of dead plant material and animal parts in freshwater ecosystems (Wong et al., 1998). Spores of aquatic hyphomycetes are caught in water foam in streams, and can be analyzed by fixed samples. Miura (1974) compared stream spora from three representative areas in Japan, and noted few overlap of mycobiota between a northern area (Rebun Island) and a southern area (Yaeyama Islands). Because of the diverse vege- tation, a diverse aquatic mycobiota is expected in Yakushima Island. During the exploratory visit to Yakushima in 2005 (Taxonomic research for plants and fungi in areas with remarkable biodi- versity in Japan), the authors collected water foam samples to contribute to elucidation of my- cobiota in aquatic habitats. In the present paper, a list is provided with taxonomic notes. Materials and Methods Five sites along major rivers and water falls in Yakushima Island were explored and 8 samples were obtained (Fig. 1, Table 1). Water foam was scooped up with an aluminum spoon, and imme- diately fixed on site by formalin with cotton blue stain. For examination, a drop of fixed sample was applied onto a slide glass, and water-soluble resin “Neo-shigaral” (Shiga konchu-fukyu-sha, Tokyo) was applied and mixed with the sample for solidification. The prepared slides were ex- amined by a compound microscope for identifi- cation. Results and Discussion In total, 32 taxa (including six unidentified and 10 not identified to specific rank) belonging to 22 Survey of Freshwater Hyphomycetes in Yakushima Island, Southern Japan Tsuyoshi Hosoya 1 and Kazuaki Tanaka 2 1 Department of Botany, National Museum of Nature and Science, Amakubo 4–1–1, Tsukuba, 305–0005 Japan E-mail: hosoya@kahaku.go.jp 2 Faculty of Agriculture and Life Science, Hirosaki University, Bunkyocho 3, Hirosaki, Aomori, 036–8561 Japan E-mail: k-tanaka@cc.hirosaki-u.ac.jp Abstract Fungal spores collected from streams in Yakushima Island are examined and reported with illustrations. Thirty two taxa of 22 genera were recognized, and their differences in occur- rence in relation to hitherto known Japanese stream spora were noted. Key words : aquatic hyphomycetes, freshwater hyphomycetes, fungal diversity, Ingoldian fungi, local mycobiota. Bull. Natl. Mus. Nat. Sci., Ser. B, 33(3 · 4), pp. 127–132, December 21, 2007