Venus (Journal of the Malacological Society of Japan)
Search
OR
Browse
Search
Volume 70 , Issue 1-4
Showing 1-8 articles out of 8 articles from the selected issue
    • |<
    • <
    • 1
    • >
    • >|
Original Articles
  • Tomoyasu Yamazaki, Seiji Goshima
    Type: Original Article
    Volume 70 (2012) Issue 1-4 Pages 1-10
    Released: May 31, 2016
    JOURNALS OPEN ACCESS
    Morphological and ecological differences of the periwinkle Littorina sitkana (Philippi, 1845) were investigated between two adjacent habitats (inner and outer habitats) of a small harbor in southern Hokkaido, Japan. The inner side of the harbor was well sheltered, and many shore crabs Hemigrapsus sanguineus, a potential predator for gastropods, were present, whereas the outer side of the harbor was very exposed, with few shore crabs. In the inner habitat, most periwinkles possess a uniformly dark-colored, large and solid shell, which is sculptured only at the base of the last whorl, and a comparatively small foot. In the outer habitat, periwinkles possess a small, thin, and light-colored shell with a dark apex and spiral sculpture throughout the surface, and a comparatively large foot. Predation and flume experiments were conducted in the laboratory using snails from both habitats. Only snails from the outer habitat were predated by the shore crabs during the 120-h experiments, and snails from the outer habitat showed significantly stronger resistance to water flow. These morphological and ecological differences of L. sitkana exhibited in the present study may suggest a local adaptation of the same species to different habitats, created by an artificial structure.
    View full abstract
    Download PDF (1684K)
  • Taeko Kimura, Hideo Sekiguchi
    Type: Original Article
    Volume 70 (2012) Issue 1-4 Pages 11-24
    Released: May 31, 2016
    JOURNALS OPEN ACCESS
    During the period 1991–1992, we examined temporal fluctuations in densities of the native and exotic mytilids Musculista senhousia and Xenostrobus securis in the brackish Lake Hamana on the Pacific coast of central Japan, using cohort separation of planktonic stages and benthic stages (i.e., new settlers and small individuals). Temporal fluctuations in densities of both planktonic and benthic stages were similar between the two species. However, the densities of benthic stages were much higher for M. senhousia than for X. securis. There was a similar trend of variation in densities of benthic stages among sampling sites for each mytilid. This suggests that microhabitat separation of large individuals (≥ 1.0 mm in shell length) between these two species may be determined at the post-recruitment stage, when X. securis individuals with shell lengths of ≥ 2.0 mm probably immigrate into the study area from other areas.
    View full abstract
    Download PDF (1068K)
  • Kazuyuki Mashino, Kenji Torigoe
    Type: Original Article
    Volume 70 (2012) Issue 1-4 Pages 25-40
    Released: May 31, 2016
    JOURNALS OPEN ACCESS
    Traditional taxonomy of shell-bearing mollusks has generally been dependent on the shell morphology including surface sculpture and color pattern. Nowadays, most researchers also use anatomical information and molecular analysis as the basis of the classification in addition to the shell morphology. In this study, we examined anatomical features in two presumed subspecies of Trishoplita eumenes, land snails distributed in Yamaguchi Prefecture. We then did a statistical comparison of the measured data. The results showed no significant differences between the two in the coloration of the dorsal soft-body, radular morphology, radula formula, jaw-plate morphology or general morphology of the genital system, including the form and microstructure of the penial verge. However, we did find distinct differences in the distribution pattern of black pigments in the dorsal mantle, the ratio of the length of the genitalia to shell diameter, the number of mucus glands, love dart morphology, and the ratio of the length of the love dart to the dart sac. These findings strongly suggest that the two forms represent two distinct species rather than subspecies.
    View full abstract
    Download PDF (3090K)
Short Notes
    • |<
    • <
    • 1
    • >
    • >|
feedback
Top