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Volume 57 (1998)
- Issue 4 Pages 241-
- Issue 3 Pages 155-
- Issue 2 Pages 75-
- Issue 1 Pages 1-
Volume 57, Issue 2
Displaying 1-7 of 7 articles from this issue
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Yuri KANTOR, M. G. HARASEWYCHArticle type: Article
1998 Volume 57 Issue 2 Pages 75-84
Published: July 31, 1998
Released on J-STAGE: January 31, 2018
JOURNAL FREE ACCESSBathybuccinum (Ovulatibuccinum) clarki new species, is described from bathyal depths off the central Aleutian Islands. This new species is provisionally assigned to the genus Bathybuccinum primarily on the basis of its distinctive triangular operculum with terminal nucleus, and large osphradium, which are rare features in Buccininae. Conchologically, the new species most closely resembles Buccinum (Epistobuccinum) epistomium Dall, 1907, which, however, has a typical buccinid operculum that is large, oval, with a subcentral nucleus.View full abstractDownload PDF (1206K) -
Takaki KONDOArticle type: Article
1998 Volume 57 Issue 2 Pages 85-93
Published: July 31, 1998
Released on J-STAGE: January 31, 2018
JOURNAL FREE ACCESSThree species belonging to the genus Inversiunio were briefly redescribed. Shell is elongated and its beak is situated anterior in I. reinianus. It is roundly elliptical with slightly incurved posterior margin in I. yanagawensis. Shell of I. yokohamensis is oblong and resembles to that of I. reinianus. Although it is difficult to distinguish some large shells of I. yokohamensis from those of I. reinianus, their distributions do not overlap. I. yokohamensis is distributed in the eastern part of Japan, whereas I. reinianus is endemic in Lake Biwa. I. yanagawensis is distributed in the western part of Japan.View full abstractDownload PDF (559K) -
Akiko IIJIMAArticle type: Article
1998 Volume 57 Issue 2 Pages 95-104
Published: July 31, 1998
Released on J-STAGE: January 31, 2018
JOURNAL FREE ACCESSDistribution pattern of intertidal molluscs was studied on a rocky shore on the Pacific coast of Boso Peninsula, Central Japan. Quantitative surveys were carried out on November 23, 1991 and June 2, 1992 in the following six habitats which were characterized by substratum structures, tidal level and vegetation ; upper rock (Ur), middle rock (Mr), Hizikia bed (Hbd), lower rock (Lr), middle boulder (Mb) and lower boulder (Lb). Herbivorous molluscs were abundant in the upper rock and the middle boulder areas where substratum surfaces were not covered with foliose macroalgae. Lack of macroalgae cover may allow the growth of much epilithic microalgae, a food resource for many herbivorous molluscs. Carnivorous gastropods were distributed mainly in the area where herbivores were abundant. There were many chitons and limpets (including pulmonate limpets) were observed on the bed-rock area but small on the boulder area. The results suggested that the moving of boulder area by wave action prevent them from homing.View full abstractDownload PDF (616K) -
Keiji IWASAKI, Yumiko URYUArticle type: Article
1998 Volume 57 Issue 2 Pages 105-113
Published: July 31, 1998
Released on J-STAGE: January 31, 2018
JOURNAL FREE ACCESSLife cycle of a freshwater mytilid, Limnoperna fortunei (Dunker), was studied in the Uji River, Kyoto Prefecture, from September, 1994, to October, 1995. Gonads of both sexes of this species began to develop in May and matured in June. Percentage of wet gonad weight to whole wet tissue weight attained a maximum in June for males and in July for females. The gonad degenerated in October for both sexes. Thus this species reproduced from June to September in 1995. Water temperature during this period ranged from 21 to 26℃. No newly settled juveniles smaller than 2 mm in shell length were found in this study, but small mussels of 2-8 mm in length appeared from July to September. They attained 20 mm in average shell length and reproduced in the next summer. Size histogram showed a bimodal distribution which consisted of 0+ and 1+ cohorts from August to April. Mean shell lengths of both cohorts increased in autumn and spring. Maximum shell length of the large-sized cohort attained 35 mm in spring and summer, but most mussels larger than 26 mm disappeared by September. Therefore longevity of this species is suggested to be two years.View full abstractDownload PDF (612K) -
Naoko ADACHI, Keiji WADAArticle type: Article
1998 Volume 57 Issue 2 Pages 115-120
Published: July 31, 1998
Released on J-STAGE: January 31, 2018
JOURNAL FREE ACCESSDistributions of two intertidal gastropods, Batillaria multiformis (Lischke) and B. cumingi (Crosse), were studied in relation to intertidal height and vegetation on a tidal flat where they co-occurred. B. multiformis occurred abundantly in the intertidal higher level, while B. cumingi did in the lower level around low tide shore line. In areas with halophilous plants, the two species tended to segregate to each other with regard to plant species. Laboratory experiment indicated that B. cumingi preferred to stay in water to more extent than B. multiformis, corresponding with the distributional difference in intertidal height between the two species.View full abstractDownload PDF (417K) -
Koji YOKOGAWAArticle type: Article
1998 Volume 57 Issue 2 Pages 121-132
Published: July 31, 1998
Released on J-STAGE: January 31, 2018
JOURNAL FREE ACCESSA Japanese common clam Ruditapes philippinarum population (Awazu population) which shows specialized appearance was morphologically and genetically compared with a normal type (Yashima population). Morphologically, proportions of shell height with shell width and the shell weight index in the Awazu population showed considerably larger than those of the Yashima population, that is, the Awazu population had significantly more globular shell shape. Since fitness for Hardy-Weinberg equilibrium by chi-square tests indicated no significance at any polymorphic loci detected by isozyme analysis in both the populations, they were both regarded as simple Mendelian populations. Values to indicate genetic features in both the populations were all close each other. Although significant differences were recognized in allelic frequencies between the two populations at the GPI^*, LAP^* and PGDH^* loci, the genetic distance (D value) between the two populations resulted in 0.0054, being a figure within inter-local populations reported for this species. The results suggested that the Awazu population is not genetically diverged in particular, the morphological peculiarity of the population might have been caused by environmental factors.View full abstractDownload PDF (1478K) -
Hiroshi IEYAMA, Hiroshi OGAITOArticle type: Article
1998 Volume 57 Issue 2 Pages 133-136
Published: July 31, 1998
Released on J-STAGE: January 31, 2018
JOURNAL FREE ACCESSChromosomes of diplommatinid snails have been studied for 14 species, and all species studied have a diploid chromosome number of 2n=26 (Ieyama & Tada, 1991, Ieyama, et al., 1993, Ogaito & Ieyama, 1997). Nuclear DNA contents reported for 18 species in Diplommatinidae range from 3.87 pg to 16.08 pg in diploid cells (Ieyama & Tada, 1991, Ieyama, et al., 1993, Ogaito & Ieyama, 1997). Ogaito and Ieyama (1997) used the DNA amount as circumstantial evidence in description of a new species. We studied the chromosomes and nuclear DNA contents of two subspecies, Diplommatina (Sinica) kiiensis kiiensis and D. (S.) kiiensis ssp. This paper reports the karyotypes and nuclear DNA contents of these two subspecies.View full abstractDownload PDF (307K)
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