Benthos research
Online ISSN : 1883-8898
ISSN-L : 0289-4548
Volume 1986, Issue 29
Displaying 1-8 of 8 articles from this issue
  • Tatsuo HAMANO, Takashi KOUYA, Shoichi SHIMOYAMA, Shuhei MATSUURA
    1986 Volume 1986 Issue 29 Pages 1-8
    Published: February 28, 1986
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    The dynamics of the molluscan community inhabiting the soft bottom of Hakata Bay, north Kyushu, was studied during May to October, 1984. Distribution of animal density depended mainly on two dominant species, Theora Zubriea and Museulista senhousia. The center of mollusc distribution moved out from the inner waters of the bay and stayed in the middle waters during the summer stratification period when the dissolved oxygen in the bottom water diminished. The center returned to the inner waters when dissolved oxygen returned to higher levels. The community structure in various parts of the bay was studied before, during and after the strati-fication period. The community structure changed in relation to the range of fluctuation and to th.e minimal values of dissolved oxygen concentration. The similarity indices among the communities from various waters also changed seasonally. Two molluscan communities sometimes had similar structure but the formative processes may not have been the same. Different oxy-gen levels affect the process of community formation.
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  • Tetsusi KAGAWA
    1986 Volume 1986 Issue 29 Pages 9-15
    Published: February 28, 1986
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    The spatial distribution patterns of macrobenthic fauna and their temporal fluctuation were investigated in the eastern part of Hiuchi-nada during the stratification period (July-September) in 1982. To analyse re-cruitment patterns of benthos in the hypoxic environment, weekly sampling was carried out at the station of the deeper area in the same season. The dominant macrofauna in the hypoxic stations consists of two categories with different types of life cycles and reproductive patterns. One is represented by Prionospio ehiersi and Paraprionospio sp. type B which have annual life cycle with single reproductive season. The other group which includes Theora fragilis, Prionospio cirrifera, Cossura coasta and Sigambra tentaculata are short-lived species, considerable number of juveniles recruited several times during the stratification period. However, most of the juveniles found at hypoxic stations died off immediately after settlement and never grown up to adult size.
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  • Isao HAYASHI
    1986 Volume 1986 Issue 29 Pages 16-24
    Published: February 28, 1986
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    Sampling efficiency of the Smith-McIntyre grab was evaluated by comparing the sampling data with those from the Scripps-type Box Corer (Spade Corer) at 3 sampling stations from two different depth zones (100m and 200m) around the shelf edge of the Wakasa Bay, the Sea of Japan. At two shallower sandy stations (100m) the efficiency appeared to be highly dependent on the sediment volume collected up to the volume of 7 liter or more, where the maximum level (almost 100%) was obtained. Sampling too much volume of sediment beyond 10 liter or more rather tends to lower the efficiency. Whithin the range of the moderate sediment volume the actual efficiency level was somewhat higher than that theoretically supposed to be. Brief discussion was focused on this point. At the deeper mud station (200m), the efficiency was extremely low in terms of the number of individuals: the level hardly exceeds 40%. The reason why such an inadequate sampling would be made at the deeper station is not clear at present since the sediment volume collected does not seem to affect the efficiency here, in sharp contrast to the cases at the shallower stations.
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  • Toshiyuki Yamaguchi
    1986 Volume 1986 Issue 29 Pages 25-36
    Published: February 28, 1986
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    Three “subspecies” of Tetraclita squamosa, “T, s. squamosa”, “T. s. formosana” and “T. s. japonica”, live in intertidal rocky shore of Japan. It is easy to distinguish them from color of shell and other morphologies. Their geographic distributions overlap with each other in areas of south of central Japan and west Kyushu. In open coast of those areas, it is found a microgeographic sympatric relationship among three “subspecies”. The segregation of ecological niche among them is not present in open coast. These evidences indicate that they are not different subspecies of same species, but they are either different species or different phena of same species. Their reproductive seasons coincide with each other and are from summer to autumn in Kii Peninsula. In electrophoretic analysis of an isozyme (Malate dehydrogeneses), it is found the different gene frequencies among three “subspecies”. Namely, it is distinct that gene flow among them is not present. They are not subspecies, but different species. Tetraclita squamosa widely distributes in Indo-Pacific region. The lther two species narrowly distribute in northeastern periphery of the distribution of T. squamosa. Characteristics of their distributions suggest that T. squamosa is a parental species of them, and that T. formosana and T. japonica had derived from ancester of T. squamosa. T. formosana and T. japonica had differentiated from the common ancester by peripheral speciation.
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  • Keiji WADA
    1986 Volume 1986 Issue 29 Pages 37-43
    Published: February 28, 1986
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    Two forms of Macrophthalmus japonicus De Haan, Forms V and L (Wada, 1978), have been studied on their geographical distributions and geographical variations in their morphological and behavioral characters. Form V occurred along the coast of Honshu, Shikoku, Kyushu and Tane Is., whereas Form L was recorded from southwestern Honshu, Shikoku and Kyushu, and the Nansei Shoto Group from the Ohsumi Group to the Yaeyama. Serial variation was recognized in some morphometrical characters in the following order: Form L in Amami-Ohshima Is, & Okinawa Is., Form L in Honshu, Shikoku, Kyushu and Iriomote Is., Form V in localities other than Aomori Pref., and Form V in Aomori Pref. (northern limit of its range). The mean duration of waving display also decreased in the order of Form L in Amami-Ohshima Is. & Okinawa Is., Form L in other localities, and Form V. These findings may be useful in determining evolutionary relationships between the two forms.
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  • Teruaki NISHIKAWA
    1986 Volume 1986 Issue 29 Pages 44-49
    Published: February 28, 1986
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    Three topics were referred to here. Firstly, the comparative studies were briefly reviewed between Ciona intestinalis (Linné) and C, savignyi Herdman, sometimes living together, inclusive of the observation that in Japan intestinalis spawns in the evening while savignyi at dawn. Secondly, the individuals of Halocynthia roretzi (Drasche) inhabiting Mutsu Bay are dividable into three types, sometimes found sympatrically, by the difference in the season and time of spawning. The season may shift, but the time seems stable, so the reproductive isolation may be suggested between these types. For several reasons, however, their occurrence was here regarded as the polymorphism or representing an early stage of sympatric speciation. Lastly, the intimate observations of the cultured colonies apparently of Botrylloides violaceus Oka revealed that they should be classified into 5 species, basing mainly on the differences in the sexual reproduction. Seemingly, further comparative studies will judge the validity of their present taxonomic rank.
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  • Keisuke MORI
    1986 Volume 1986 Issue 29 Pages 50-57
    Published: February 28, 1986
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    Intra-populational variation of life history traits in Chthamalus challengeri was studied in an intertidal bed rock which has a gentle slope with smooth surfaces. Although the occurrence of adults was restricted in the high tide-zone, the barnacle settled on rock surfaces from MHWS to MLWS with various density. Settlement, growth, reproduction (percentage of brooding, adult size versus total egg weight etc.) and survival pattern of the barnacle were investigated in detail at four different tidal zone including no-adult zone. Although it is considered that these four sub-populations of barnacles were from same gene-pool, it became clear that each sub-population had a highly differential life history pattern. Furthermore, timing of settlement affected the growth, reproduction and survival pattern of the barnacle. Intra-populational variation of life history traits in Chthamalus challengeri is very complicated. Factors affecting the population dynamics are discussed on the basis of the results of field and laboratory experiments. The comparison of life history traits of four sub-populations were carried out in full consideration of their environment conditions, and the importance of life history variation is discussed.
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  • 1986 Volume 1986 Issue 29 Pages 58-59
    Published: February 28, 1986
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
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