From among gastropod specimens collected from the hydrothermal vent site at Kairei Field near the Rodriguez Triple Junction in the Central Indian Ocean, by the ROV Kaiko and the crewed submersible Shinkai 6500, three new species are described: Bruceiella wareni, Desbruyeresia marisindica, and Iphinopsis boucheti. The occurrence of an Alviniconcha species very similar to A. hessleri, is also reported.
Four fasciolariid species from Japan and the Western Pacific are examined and described. The shell consistently misidentified as Fusinus longicaudus (Lamarck, 1801) in Japanese literature is identified as F. perplexus (A. Adams, 1864). Fusinus longicaudus (Lamarck, 1801) is treated as a junior synonym of F. colus (Linnaeus, 1758). Fusinus perplexus nagasakii Grabau, 1904 is shown to be a junior synonym of F. perplexus, and the synonymy of F. inconstans Lischke, 1869 with F. perplexus is reaffirmed. Comparison is also made with F. forceps (Perry, 1811) and F. salisburyi Fulton, 1930. Lectotypes are selected for F. perplexus, F. p. nagasakii, F. inconstans, F. forceps, F. turriculus (Kiener, 1840) and F. ferrugineus Kuroda & Habe, 1960, which is provisionally retained as a valid species.
Calyptogena (Archivesica) edisonensis n. sp. is described from the hydrothermal vent field of the New Ireland Basin (Edison Seamount). This is the first taxonomic description of a vent-associated Calyptogena from the Southwest Pacific. This new species is closely allied to C. (A.) nankaiensis from the Nankai Trough off Honshu, Japan.
Based on fertilized eggs obtained from artificially induced spawning of the brackish water clam Corbicula japonica, the larvae and post-larvae were reared for 18 days in the laboratory. Planktonic larvae of C. japonica passed through the trochophore and D-shaped larval stages (the early stage of veliger larvae), but lacked umbo larvae (the latter stage of veliger larvae), with the result that the late-stage D-shaped larvae with a developed foot settled and metamorphosed on the bottom and walls of culture vessels. To aid in the identification of the larvae of C. japonica in plankton samples and their post-larvae in benthos samples, larval and post-larval shell morphology of the clam is described and compared with that of the other bivalves dominant in Japanese estuarine waters.
Drift and upstream movement of the freshwater snail Semisulcospira libertina were investigated at the Iwai River, Nara, Japan, from May 1999 to February 2000, in natural conditions. Water temperature, snail size and discharge were measured. Drift and upstream-movement were observed mainly from May to October, when water temperature was higher than 13.2℃. Most drifted snails were smaller than 6mm in shell width, whereas snails that moved upstream belonged to all size classes. The number of drifted snails per hour after rainfall (60≦discharge<130l/s) was smaller than during normal discharge (<60l/s), whereas the number of snails moving upstream per hour did not change between the normal discharge days and days after rainfall. From these results, it is concluded that small S. libertina disperse downstream by drift on days with normal discharge, and snails of all sizes move upstream irrespective of discharge rate.