Conservation of freshwater and blackish water benthic invertebrates endemic to the Bonin Islands

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The quantitative and qualitative sampling on the freshwater and brackish water macro-invertebrates were conducted at more than 50 sites covering five islands belonging to the Ogasawara (Bonin) Islands, Japan during 2005-2007. As a result, four endemic species belonging to three arthropod orders and an alien thiarid species were newly found in the streams of these islands. At first, a new atyid shrimp of the genus Paratya is described based on the specimens collected from the head-water regions of Chichi-jima and Haha-jima. Secondary, a new caddisfy of the genus Goera is described from the streams of Chichi-jima. Third, a new flabelliferan isopod of the genus Gnorimosphaeroma is described from the streams of Haha-jima. And last, another new isopod of the genus Spherillo is also described from a reservoir of Haha-jima. During the course of this survey, an introduced thiarid snail of the genus Malanoides recorded from the streams of Chichi-jima for the first time.The surveys on the endemic chironomids were also conducted in the islands to assess their vulnerability. The habitats of Chironomus claggi, Cricoropus ogasaseptimus, Macropelopia ogasaseztdecima ant Tanytarsus ogasaquartus were confirmed based on larval collection from varous habitats. The larvae of Glyptotendipes tokunagai were collected at the shore of a reservoir in Hana-jima Island. This is the first record of Glyptotendipes from the oceanic islands.As for the caddisflies, even though an immature Rhyacophila larva was collected from Haha-jima, its taxonomic status and origin is still uncertain. On the other hand, the endemic species Goera ogasawaraensis showed a decline in its larval densities, compared with previous study. In relation to the two crustacean endemic species, declinations in population's size are observed, compared with study. Based on red list criteria, these three species were listed as endangered and threatened species by the Ministry of Environment, Japan.