JapaneseJapaneseSociety Society ofSystematicof Systematic Zoology Species Diversity, 2005, 10, 27-36 Hygrobates (Hygrobates) capillus sp. nov. (Araehnida: Acari: Hydrachnidia: Hygrobatidae) from South-central Honshu, Japan, with Records of Two Allied Species Noriko Matsumoto, Hiroshi Kajihara and Shunsuke F. Mawatari Division ofBiological Sciences, Graduate School of Science, Hbkkaido University. Sapporo, 0600810 .lapan E-mail: noriho-m@./sci.hokudat.ac.J'p aVAD; kazia[t;sct,hohudai.ac,jp (HK);
[email protected] (SFIVO (Received 13 July 2004; Accepted 12 January 2005) Three sjmilar species of water mite in the subgenus Hygrobates (genus Hy- grobates) are reported firom middle Henshu, Japan. These include two re- cently described lacustrine species, H)lgrobates (ltvgrobates) biu)aensis Tu- zovskij, 2003 and H. (H.) rarus Tuzovskij, 2oo3, which are known only from Lake Biwa, and one new fluvial species, Il (HL) copiltus sp. nov. The new species is distinguished from the other two by the truncate P-2 ventral pro- jection; the female genital plates being longer than the genital opening and extending to the post-genital sclerite; the anterior border of the flat male genital plate; and the ]arger body size (408-603um). Two or three setae are confirmed to be present on the fernale pre-genital sclerites in the three species reported herein; this character state has never so far been recorded in any member of this subgenus, Key Words: Hydrachnidia, water mites, new species, central Japan, ft'esh- water, fine structure, taxonomy, scanning electron microscopy, Introduction Most species of H),grobates Koch, 1837, one ef the largest genera of the water- mite family Hygrobatidae, occur in still or slowly fiowing waters, such as lakes, ponds, and the middle and lower reaches of rivers.