Marshes dominanted by reeds (Phragmites australis (Cav.)) are typical of the high intertidal zones of estuaries and seashores in inlets and bays in temperature Japan. However, recent coastal development has resulted in the reclamation of the coastline before thorough studies of these ecosystems could be undertaken in Japan. We conducted a faunal study of molluscan gastropods inhabiting the reed marshes at 20 locations along coast of Mikawa and Ise Bays in central Japan for 16 years (1982 to 1998). The marshes are categorized in terms of their locations and size, i.e., A: river marsh, which is small and occurs along a river (lower reaches to river mouth); B: seashore marsh, which is relatively large and occurs along the seashore; A+B: which occurs along the river and seashore without a break. Further we determine the degree of human disturbance of the marsh ecosystem, i.e., 1. highly disturbed: reeds remain only in the high intertidal zone, but does higher up the shore due to the installation of coastal protective barriers; 2. intermediately disturbed: reeds remain in the high intertidal zone on a small scale, but the marsh subsystems such as tidal creeks and backshore marshes have disappeared; 3. well conserved: human disturbance has scarcely affected the marsh vegetation. In this last case, reeds are broadly distributed from the high intertidal to higher shores, where growth of Erigeron canadernsis L., Solidago altissima L., Miscanthus sinensis Andress., Rosa wichuraiana Crep., and Vitex ratundifolia L. flu. are found; the marsh subsystems are well developed, which provide highly heterogeneous habitats for various biota. Types of marshes of reed are described. using combination of each three types as related with their locations, size (A, B, A+B) and the degree of human disturbance of the marsh ecosystem (1, 2, 3). In the type Al (St. 1, 4, 5, 6, 10, 11), 5 to 12 (average 7.5) species of gastropods were found. In the type A2 (St. 3, 7, 8, 14), 9 to 15 (average 13.0) species were found. In the type A3 (St. 9, 12, 13, 16, 17, 18, 20), 8 to 19 (average 13.9) species were found. In the type A3+B3 (St.2, 15, 19), 18 to 23 (average 21.0) species were found. The spatial distribution patterns of the mollusc species are categorized by micro-habitat as follows, i.e., S1, on stones; S2, under stones on soft sediment; S3, under the stones half buried in soft sediment; W 1, on decayed wood; W2, under decayed wood on soft sediment; W3, under decayed wood half buried in soft sediment; MU, on soft sediment. A total 26 species were collected during the 16 years (2 spp. of Neritidae, 1 sp. of Phenacolepadidae, 2 spp. of Batillariidae, 3 spp. of Cerithideidae, 2 spp. of Iravadiidae, 1 sp. of Stenothyridae, 1 sp. of Truncatellidae, 8 spp. of Assimineidae, 6 spp. of Ellobiidae). Among these were 18 species determined as “endangered” by the Fish-ery Agency and the Japan Fishery Resouce Conservation Association (1994), the Japan Fishery Resource Conservation Association (1995, 1996, 1997), and Wada et al. (1996): Clithon (Clithon) retropictus (Martens, 1879), Neritina (Dostia) violacea (Gmelin, 1791), Phenacolepas sp., Batillaria multiformis (Lischke, 1869), Cerithidea (Cerithidea) rhizophorarum A. Adams, 1855, Cerithidea (Cerithideopsilla) cingulata (Gmelin, 1791), Cerithidea (Cerithideopsilla) djadjariensis (K. Martin, 1899), Iravadia (Fairbankia) sakaguchii (Kuroda et Habe, 1954), Iravadia (Fluviocingula) elegantula (A. Adams, 1863), Stenothyra edogawaensis (Yokoyama, 1927), Angustassiminea yoshidayukioi Kuroda, 1959, Assiminea parasitologica Kuroda, 1958, Assimineidae gen. et sp., Ellobium chinensis (Pfeiffer, 1855), Auriculastra duplicata (Pfeiffer, 1855), Laemodonta siamensis (Morelet, 1875), Laemodonta exaratoides Kawabe, 1992, Melampus (Melampus) sincarporensis Pfeiffer, 1855. Brief diagnoses of Phenacolepadidae, Iravadiidae, Assimineidae, and Ellobiidae are provided.
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