Venus (Japanese Journal of Malacology)

Ephippodonta gigas n. sp. (Bivalvia : Galeommatoidea) from Okinawa Island, Southwestern Japan

Hirofumi KUBO

Article type: Article
1996 Volume 55 Issue 1 Pages 1-5
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_1

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A new species of the galeommatoidean bivalve is described from Okinawa Island, East China Sea. Ephippodonta gigas n. sp. belongs to the subgenus Ephippodonta Tate, 1889 with cardinal tooth and plain inner margin. This species has a large shell with the glossy surface and differs morphologically from all of its congeners.

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A New Pyramidellid Gastropod Ectoparasitic on Conus

Shigeo HORI, Takashi OKUTANI

Article type: Article
1996 Volume 55 Issue 1 Pages 7-14
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_7

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A pyramidellid species which is ectoparasitic on Conus (Rhizoconus) okamotoi (Kuroda & Ito, 1961), C. (Rhizoconus) sazanka yoshioi Azuma, 1973, and C. (Virroconus) flavidus Lamarck, 1810 in Kii Peninsula, Izu-shichito Islands, and Southwest Shikoku has been recognized for several times. Although this species has been treated as Coneodostomia okamurai Habe, MS., it has not been described in due form to date. This paper describes it as a new species Boonea okamurai. Main conchological characters of this new species are, small and ovate thin shell with almost no sculpture on its outer surface, extremely large body whorl, possessing an oblique and strong columellar fold.

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A New Eulimellid Gastropod Collected by the R/V Tansei-Maru from Bathyal Depth off Daio-Saki

Shigeo HORI, Eiji TSUCHIDA

Article type: Article
1996 Volume 55 Issue 1 Pages 15-23
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_15

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The Pyramidellidae have seldom been reported from bathyal depth reaching to 500 m to date in Japan. A pyramidellid species was collected from a depth of 424-425 m off Cape Daio-Saki by the R/V Tansei-Maru in 1986. The detailed morphological investigation on this species revealed that it is a new species described in this paper. Main conchological differences between this new taxon and many other similar-looking Indo-West Pacific species are regularly slender conic shell with low and wide whorl being swollen at its lower part.

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Genetic Divergence in Two Forms of Pen Shell Atrina pectinata

Koji YOKOGAWA

Article type: Article
1996 Volume 55 Issue 1 Pages 25-39
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_25

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Genetic divergence between non-scaly form and scaly form of pen shell Atrina pectinata (Linne) was examined. Isozyme analyses indicated replacement of major alleles at the AAT^*, CK-1^*, GPI-1^*, GPI-2^*, LAP^*, MDH^*, MPI^* and PGM^* loci, and difference of allele frequency at the GAPDH^* loci. Heterozygosity histogram of scaly form indicated a bimodal distribution, some individuals of the scaly form had many heterozygotes at the diagnostic loci. The obsevation that the shell morphology of the individuals showed intermediate state between non-scaly and scaly form suggested that they were hybrids between the two forms. The genetic distance (D value) between the two forms, calculated from isozymic allele frequencies, was 0.469, a figure significant at the inter-specific level. The considerable genetic difference and the presence of low frequency of hybrids in a sympatric population suggested that the two forms are distinct species. Morphologically, since the two forms could be completely distinguished by presence of the squamation, the two forms should be taxonomically distinguished.

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Distribution of Four Species of Acanthopleura (Polyplacophora : Chitonidae) in Sesoko Island, Okinawa

Eiji YOSHIOKA, Yasuhiro NAKASHIMA

Article type: Article
1996 Volume 55 Issue 1 Pages 41-49
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_41

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Horizontal and vertical distribution of chitons, Acanthopleura gemmata, A. loochooana, A. tenuispinosa and A. miles, have been investigated. In the horizontal aspect, they have specific distribution in the sheltered-exposed gradation. A. gemmata distributes all rock shores around the island. A. loochooana distributes almost all around the island except the most exposed area. A. tenuispinosa mainly distributes the most sheltered area. A. miles mainly distributes the most exposed area. In the vertical aspect, their habitats are mostly overlapping, but their mean height have significant difference except between A. tenuispinosa and A. miles. The mean height of A. gemmata is lower, that of A. loochooana is middle, those of A. tenuispinosa and A. miles are higher in their habitat zone. Putting the horizontal and vertical accounts together, those four species have specific 'space sharing' in the two dimensions although their habitat area and range overlap in the most cases.

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Genetic Variability and Population Structure of Phacosoma japonicum (Bivalvia : Veneridae)

Shinichi SATO

Article type: Article
1996 Volume 55 Issue 1 Pages 51-63
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_51

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In order to estimate genetic variability and population structure of Phacosoma japonicum, allozymes were studied by polyacrylamide gel electrophoresis. Eighteen enzymes were examined, and twenty loci were detected. Averaging the seven samples analyzed, the proportion of polymorphic loci was 0.386, and the average heterozygosity was 0.146. Latitudinal clines were present in the gene frequency of four allozyme loci (GPI^*, MEP^*, PGM-1^*, PCDH^*), with northern populations possessing higher average heterozygosity than southern ones. Also, latitudinal clines had been found in the life-history traits of this species, but the Ariake population does not fit with this general trend. Although life-history traits of the Ariake population are very similar to those of the Hakodate population, the genetic distance between the two populations was demonstrated to be much greater than those between the Ariake population and populations neighboring Ariake Bay. These facts suggest that the aberrant life-history traits in the Ariake population cannot be explained solely by phylogenetic restrictions.

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Chromosomes and Nuclear DNA Contents of Limnoperna in Japan (Bivalvia : Mytilidae)

Hiroshi IEYAMA

Article type: Article
1996 Volume 55 Issue 1 Pages 65-68
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_65

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Chromosome number and karyotype of Limnoperna fortunei were as follows : 2n=30, 20m+8sm+2st, NF=60. Nuclear DNA contents (pg/haploid) of L. fortunei were 1.48, and those of L. fortunei kikuchii was 1.18.

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On the pediveligers of Flabellina athadona and Flabellina amabilis (Nudibranchia : Aeolidacea)

Yoshiaki J. HIRANO

Article type: Article
1996 Volume 55 Issue 1 Pages 69-73
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_69

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Pediveligers of Flabellina athadona (Bergh, 1875) and Flabellina amabilis Hirano & Kuzirian, 1991 possessed transient but distinct black pigmentation on the soft part. The two species showed different patterns of the pigmentation, by which the discrimination of species became possible at that stage.

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[title in Japanese]

H. SAITO

Article type: Article
1996 Volume 55 Issue 1 Pages 75-77
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_75

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[title in Japanese]

K. HASEGAWA

Article type: Article
1996 Volume 55 Issue 1 Pages 77-78
Published: April 30, 1996
Released on J-STAGE: January 31, 2018

DOIhttps://doi.org/10.18941/venusjjm.55.1_77

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