Original Articles
Elachisina ziczac Fukuda & Ekawa, 1997 (Caenogastropoda: Elachisinidae) from artificial canals on the coast of Tokyo Bay
Takeshi YUHARA, Yuki TATARA and Masanori TARU
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Summary Live individuals of Elachisina ziczac were found in the brackish waters of Kuranamigawa and Maekawa rivers which are artificial canals in the innermost parts of Tokyo Bay. In the Bay, the habitat of the species is recorded in detail for the first time. Although the present estuaries are artificial canals which have been ignored in the context of conservation, the protection of these sites is desirable because many other rare benthos species were found together with E. ziczac. |
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Key words: Rissooidea, conservation, rare species, habitat, reclaimed land, tidal flat, intertidal, brackish water, estuary, Chiba Prefecture |
Fauna of the Recent freshwater molluscs of Lake Kojima, Okayama Prefecture, western Japan
Hiroshi FUKUDA, Jun ISHIKAWA and Wataru MURAKAMI
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Summary Lake Kojima is an artificial lake on the southern part of Okayama Prefecture. Fauna of the Recent freshwater molluscs was investigated in the lake. Sixteen species of gastropods and eight bivalves were recognized. Dominant species were Sinotaia histrica, Pomacea canaliculata and Physella acuta, all of which are abundant in the eutrophic standing waters in Japan. Nine introduced species including unidentified ones of Radix and Corbicula were found. Some species with literature records before the completion of the lake in 1959 (e.g. Cipangopaludina laeta, Semisulcospira libertina, Stenothyra japonica) were not rediscovered and thus they might have become extinct due to water pollution. On the other hand, some species that are threatened in the other regions of Japan (e.g. Parafossarulus manchouricus japonicus, Cristaria plicata) are still commonly found. The vicinity of the Sasagase River estuary with slightly running waters showed the richest species diversity including some threatened unionid bivalves. Hippeutis cantori and Pettancylus japonicus were newly recorded in Okayama Prefecture, though the former species may be an introduced population from the other region of Japan. |
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Key words: artificial lake, water pollution, eutrophication, threatened species, introduced species, Tamano |