03773naa a2200193 a 450000100080000000500110000800800410001910000170006024501270007726000090020452029480021370000160316170000150317770000150319270000180320770000180322570000150324377303210325813150272008-10-03       2008    bl uuuu     u00u1 u    #d1 aHASEGAWA, M.  aCommunity structures of soil animals on Chichijima island in Ogasawara islands in relation to the survival of land snails.  c2008  aChichijima in Ogasawara (Bonin) Islands is located in the northwestern Pacific Ocean, about 100km south of the mainland of Japan. 95 species of land snails have been recorded from these islands, and of which more than 90 percent are endemic to the islands (Chiba eta al. 2007). Most of the endemic species, however, have already become extinct or endangered in Chichijima (Chiba eta al. 2007). Predation pressure by an invasive flatworm (Platyrdemus manokwari) on the land snails was suggested as one of the cause of the decline of snails (Ohbayashi et al. 2005, 2007, Sugiura et al. 2006). Soil fauna on Chichijima were investigated several times (Aoki and Harada 1978 and Ishizawa and Takehara 2001), but the related studies with decline of snails have not been conducted. The aim of this study was to investigate the relation of soil fauna with survival of land snails from the comparison of soil fauna on snail surviving and extinct areas of Chichijima Island. The research was conducted in June and November of 2005. Ten sites (3 snail surviving sites and 7 extinct sites) for soil macrofauna and six sites (3 snail surviving sites and 3 extinct sites) for soil mesofauna were set. Sampling of soil macrofauna was conducted at six quadrates (each 25 × 25 cm) set at 5 m intervals along a line (25 m) in each site. Litter layer and topsoil (15 cm deep) were collected at each quadrate. Soil macrofauna was immediately picked up from the soil and litter by hands. Soil mesofauna was extracted from the soil core samples. A 100 ml soil sample (20 cm2 × 5 cm in depth) including litter layer was taken by a cylindrical core sampler at each of the ten points set at 5 m intervals along another line (45 m) in each site. Soil mesofauna was extracted from the samples for three days at 35?? by Tullgren funnels. Most of soil fauna did not show the decline. However, one undescribed but endemic carabid species (Badister sp.), which have selective feeding habits on land snails, was not recorded on snail extinct area. Earthworm was recorded at all study sites, and dominant in soil macrofauna. All species of the earthworms seemed to be introduced species. The invasive flatworm P. manokwari has been reported to feed also on the carcasses of earthworms as well as live snails, therefore P. manokwari is expected to survive on most of the area of Chichijima Island. Comaparison of this examination with Aoki and Harada (1978) showed that the density of Isopods decreased. The density and species richness of ants, Collembola and oribatid mites were not so different between snail survived and exterminated area. In conclusion, the close relation between soil fauna and land snails has been rarely recognized except one carabid species, but the present (current) structure of soil animals as reflected in introduced earthworm, decline of endemic isopods and tramp species of ants indicated the various impacts on the fauna on Chichijima island.1 aSUGIURA, S.1 aITO, M. T.1 aYAMAKI, A.1 aHAMAGUCHI, K.1 aKISHIMOTO, T.1 aOKOCHI, I.  tIn: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.