ウミニナ科 1 種とフトヘナタリ科 3 種の分布と底質選好性 : 特にカワアイを中心にして

抄録

The oviparous snail Cerithideopsilla djadjariensis (K. Martin, 1889) is distributed on tidal flats in south-west Japan. Seasonal changes in the distribution of C. djadjariensis were studied in the world's northernmost mangrove forest at the mouth of the Atago River in southern Kyushu Island. Four gastropod species : Batillaria multiformis (Lischke, 1869), Cerithideopsilla djadjariensis (K. Martin, 1899), Cerithideopsilla cingulata (Gmelin, 1791) and Cerithidea rhizophorarum A. Adams, 1855, show sympatric distribution in this area. Newly recruited juveniles (3-6 mm shell length) of C. djadjariensis appeared from August to November. To established the main habitat of the four species, the substrate on the tidal flats was classified into six types ; gravel, sandy gravel, sand, muddy sand, sandy mud and mud. From the patterns of distribution of the four species on the tidal flat, C. djadjariensis prefers sandy mud and muddy sand ; B. multiformis prefers sandy gravel and sand, and C. cingulata prefers the muddy sand and mud. Stomach contents were observed under a fluorescent microscope with a rhodamine filter in order to determine the food preference among the four species. It is suggested that Cerithidea rhizophorarum has a stronger preference for algae than the other three species.