The Yuriyagai: J. Malacozool. Ass. Yamaguchi, 10 (1/2). October 2008

Original Articles

New records of rare species of two bivalves from the Tidalflat Park of Nanaura, Saga Prefecture, Ariake Inland Sea, Japan

Tsunenori KOGA, Hiroyoshi YAMASHITA, Kiyoshi SATAKE and Toru YABE

Summary On a soft mud tidalflat, Nanaura Tidalflat Park in Saga Prefecture, facing the Ariake Inland Sea, two bivalve species were collected alive: two specimens of Estellacar olivacea (Reeve, 1844) and 22 specimens of Glauconome chinensis Gray, 1828. These two species were cited in some Red Data Books as threatened. We surveyed the museum specimens and literature records and reviewed their appearance in the Ariake Inland Sea. E. olivacea was found or recorded in small number of localities, while G. chinensis was in relatively large number of localities in the Ariake Inland Sea. However, because the destruction of their habitats has still continued there, we should be care about the rapid decline of the both species in the near future.

Key words: Estellacar olivacea, Glauconome chinensis, soft mud substratum, endangered species, biodiversity, conservation, Ariake Inland Sea

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Molluscan fauna of the Awase Tidal Flat, Nakagusuku Bay, Okinawa Island


Summary Molluscan fauna was surveyed in the Awase Tidal Flat (at the northern edge of Nakagusuku Bay on southeastern Okinawa Island) where is one of the widest tidal flats in the Ryukyu Islands. 322 species were recorded during field collecting from 1999 to 2005. The species number is the largest amongst numbers from other tidal flats on the Ryukyus. The species can be classified into seven different ecological communities. Especially the community that is characteristic in seagrass bed is unique in having rich species diversity and biomass. Biogeographycally, most species belong to the tropical Indo-Pacific faunal components. A few species (e.g. Cyclina sinensis, Glauconome chinensis) have their origins in temperate waters around the Chinese Continental coast. 101 species were listed as threatened in the Red Data Books by Okinawa Prefectural Government and 51 by WWF Japan, and thus it was confirmed that many threatened species are still living at the present locality. Leucotina sp. appears to be undescribed. Monitilora simplex and Solen soleneae are new to Japan. Mactra pulchella is restricted to extremely narrow range in the Ryukyus. Conservation of the present tidal flat is thought to be an urgent issue because of the rich species diversity and the large number of threatened species.

Key words: conservation, endangered species, Nakagusuku Bay, Ryukyu Islands, seagrass bed, species diversity

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