Venus (Japanese Journal of Malacology)

Description of New Genus Japanonoba and New Species Japanonoba itoi

Tadashige HABE, Yasuji ANDO

Article type: Article
1987 Volume 46 Issue 4 Pages 179-181
Published: December 31, 1987
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.46.4_179

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The new genus Japanonoba is proposed for Onoba patula A. Adams, 1863 as type characterized in having distinctly reticulated sculpture on the surface and the marginated carina on the shoulder of whorls. New species Japanonoba itoi is also here described. This differs from the type species in having the much slenderer shell.

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Studies on the Biology and Ecology of the Intertidal Animals of Chichijima Island in the Ogasawara (Bonin) Islands II : Description, Distribution, Size Structure in the Population, and Allometric Growth of the Limpet, Notoacmea schrenckii boninensis n. subsp

Akira ASAKURA, Shiro NISHIHAMA

Article type: Article
1987 Volume 46 Issue 4 Pages 182-193
Published: December 31, 1987
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.46.4_182

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A new subspecies of Acmaeidae, Notoacmea schrenckii boninensis, is described, and general biology of this limpet is observed. At Chichijima Island of the Ogasawara Islands, this limpet was collected from underside of boulders in the intertidal zone of the wave-exposed beaches. The shell size is smaller than that of N. schrenckii schrenckii (Lischke) from Japanese temperate region. The shell is green color with radially scattered lines and V-shape pattern, and is wider and the apex situated more anteriorly than that of N. schrenckii schrenckii. They mainly inhabit the middle intertidal zone and were also distributed in lower number in the lower intertidal zone. No individual was found in a sheltered boulder beach, rock platforms, or tide pools.

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Studies on the Biology and Ecology of the Intertidal Animals of Chichijima Island in the Ogasawara (Bonin) Islands III : Description, Form and Habitat of the Trochid Snail, Monodonta perplexa boninensis n. subsp. in Comparison with those in Monodonta perplexa perplexa (Pilsbry)

Akira ASAKURA, Shiro NISHIHAMA

Article type: Article
1987 Volume 46 Issue 4 Pages 194-201
Published: December 31, 1987
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.46.4_194

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Monodonta perplexa boninensis n. subsp. is described and its form and habitat are observed. This new subspecies is endemic to the Ogasawara Island and has a flatter shell with less constricted sutures and lighter greencolor surface than M. perplexa perplexa from Japanese temperate region. Its habitat is a lower intertidal zone in boulder beaches, although M. perplexa perplexa inhabits a middle intertidal zone.

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Description of Four New Species of Muricidae (Mollusca : Gastropoda) from New Caledonia

Roland HOUART

Article type: Article
1987 Volume 46 Issue 4 Pages 202-210
Published: December 31, 1987
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.46.4_202

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Four new muricid species are described from the coral-reef lagoon (25-80 m) of southern New Caledonia : Aspella media n. sp. is characterized by its reticulated intritacalx and is most similar to A. platylaevis Radwin and D'Attilio, 1976 : Maculotriton ingens n. sp., is the second known Maculotriton ; it differs from the type species by having a strong intritacalx, a different protoconch, and stronger axial ridges ; Typhis carolinae n.sp. belongs to a small group of Indo-Pacific species only doubtfully referred to T. (Typhina) and Typhis neocaledonicus n. sp. is the third Indo-Pacific species of the predominantly Atlantic subgenus T. (Talityphis).

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Description of a New Subspecies of the Genus Euhadra Pilsbry, 1890 (Pulmonata : Bradybaenidae) from Shimane Prefecture, Japan

Masao AZUMA, Reiko TATEWAKI, Ichiro OKAMURA

Article type: Article
1987 Volume 46 Issue 4 Pages 211-218
Published: December 31, 1987
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.46.4_211

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Pleurobranchella nicobarica Thiele, 1925, New to the Japanese Notaspidea Fauna

Ryoko INOUE, Takashi OKUTANI

Article type: Article
1987 Volume 46 Issue 4 Pages 219-225
Published: December 31, 1987
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.46.4_219

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Seven notaspidean specimens collected from a deepwater in Suruga Bay were identified to be Pleurobranchella nicobarica Thiele, 1925. External morphology, radula and reproductive system are described. Taking some synonymies into account, this species is apparently distributed through the whole Indo-West Pacific region. This is the first record of this species from Japan.

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Breeding Seasons of Seven Species of Unionid Mussels (Bivalvia : Unionidae) in a Small Creek

Takaki KONDO

Article type: Article
1987 Volume 46 Issue 4 Pages 227-236
Published: December 31, 1987
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.46.4_227

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Breeding seasons of 7 species of unionid mussels were studied in a small creek by examining both mussels and host fish. There are two groups about the period of glochidial release ; "winter" and "summer" breeders. Here, winter and summer breeders are defined as the species that can release its glochidia even when water temperature is lower than 10℃ and only when water temperature is higher than 10℃, respectively. Glochidia of a species (Pseudodon omiensis) grew during the parasitic period, but those of the other species did not. Based on the results of this study and literature, 14 Japanese unionid mussels were classified into the following four categories ; winter breeder with glochidial growth (one species), summer breeder with glochidial growth (one species), winter breeders without glochidial growth (5 species) and summer breeders without glochidial growth (7 species).

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Light and Scanning Electron Microscopic Observations on Shell Chamber Formation in the Japanese Oyster Crassostrea gigas

Kenji OKOSHI, Yoshio SUGAWARA, Tadashi NOMURA

Article type: Article
1987 Volume 46 Issue 4 Pages 237-249
Published: December 31, 1987
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.46.4_237

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The growth front of paper shell obtained from a chambered oyster, Crassostrea gigas, was observed with light and scanning electron microscopes. In the very early stage of paper shell growth, many small, granular shell materials are randomly distributed in the membrane-like materials on the jelly-like material which is observed to be present on the interior surface of the shell. These small, granular shell materials are covered with a layer of larger circular disc shell materials. These circular disc shell materials which keep separate, gradually bind together, and make a thin brittle paper shell. Then, as it is covered with some structures such as comb, cracker, foliated and chalky deposits, the thin paper shell becomes thicker and harder, and makes a wall of the shell chamber. It is remarkable that the process of paper shell formation occurs on soft jelly-like material. It seems to be a new type of shell formation. Use of this early stage of paper shell as a material for the study of shell formation may be promising.

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