Plankton and Benthos Research
Online ISSN : 1882-627X
Print ISSN : 1880-8247
ISSN-L : 1880-8247
Volume 18, Issue 1
Displaying 1-8 of 8 articles from this issue
Original Papers
  • Yoshino Ishizaki, Masaya Ogura, Chihiro Takahashi, Maya Kaneko, Akari ...
    2023 Volume 18 Issue 1 Pages 1-12
    Published: February 28, 2023
    Released on J-STAGE: March 02, 2023
    JOURNAL FREE ACCESS
    Supplementary material

    Lack of evidence prevents an understanding of how ghost crabs create burrows underground. For the reconstruction of ichnogenetic stages in the burrows of ghost crabs, we report on how the burrows of the ghost crab Ocypode stimpsoni from the foreshore and backshore on Ikarashi beach, Niigata, Japan are created. Plaster casting of the burrows reveals detailed morphology with bioglyphs on the burrow wall. The casts of burrows show a variety of morphologies, such as J- and Y-shapes. Based on the burrow ichnogeny, J-shaped burrows were well constructed at a shallower level of the waterline underneath the beach, occasionally creating a second opening of the burrow. In turn, Y-shaped burrows were constructed at a deeper waterline, thereby recycling and reburrowing the deepest part of the J-shaped burrow. As a result, the total depth of Y-shaped burrows tends to be larger than that of J-shaped burrows. The depth and mean diameter of the burrows range from 3.3–37.6 cm and 9.28–31.54 mm, respectively, and the depths are apparently shorter than those on a Pacific beach. The lines of evidence suggest that the morphological features of burrows in Ikarashi beach are attributed to a smaller difference in tidal level in the Sea of Japan, where the available space for burrows ought to be limited by the waterline under the ground.

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  • Genki Kobayashi, Hajime Itoh, Gen Kanaya, Hirokazu Abe, Shigeaki Kojim ...
    2023 Volume 18 Issue 1 Pages 13-20
    Published: February 28, 2023
    Released on J-STAGE: March 02, 2023
    JOURNAL FREE ACCESS
    Supplementary material

    Genetic homogeneity among populations of marine organisms with high dispersal potential is maintained by high gene flow whereas genetic differentiation is often formed under the presence of dispersal barriers. One of the possible dispersal barriers for intertidal species in Japan is the Sea of Japan because several tidal-flat species are absent in the region due to the small tidal range. In this study, we aimed to validate this possibility by examining the population genetic structure of the intertidal crab Macrophthalmus japonicus, which possesses a long planktonic larval period indicating high dispersal potential but is absent on the Sea of Japan side in Honshu Island. In total, 83 haplotypes of the mitochondrial cytochrome c oxidase subunit I were recovered from 154 specimens collected from 10 Japanese sampling sites and three GenBank sequences from China and Korea. All populations showed high genetic diversity except for the northernmost population at Asadokoro site in Mutsu Bay. The ΦST values among populations were low, even between populations with great distances such as the Pacific side of northeastern Honshu and Kyushu Islands (ca. 1500 km). On the other hand, the ΦST values between Asadokoro site and the other Japan sites were high. The isolation of the northernmost population despite the high dispersal potential of M. japonicus is probably because of the absence of neighboring populations that can supply larvae to the northernmost population and the invasion of larvae from the Pacific side is blocked by ocean currents.

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  • Gen Kanaya
    2023 Volume 18 Issue 1 Pages 21-33
    Published: February 28, 2023
    Released on J-STAGE: March 02, 2023
    JOURNAL FREE ACCESS
    Supplementary material

    To assess the effects of seasonal irrigation subsidies from paddy fields, spatiotemporal changes in diets of detritus feeders including nereidid polychaetes Hediste diadroma and H. atoka (facultative suspension feeders) and Tylorrhynchus osawai (surface-deposit feeder) were examined in Idoura Lagoon, Sendai Bay, Japan, using carbon and nitrogen stable isotope ratios (δ13C and δ15N). δ13C ratios of Hediste species were much lower near a freshwater input (St. IB; −25.6 to −18.2‰) than in a seaward area (St. IA; −17.9 to −14.3‰), highlighting the assimilation of river subsidies in river-affected habitats. A δ13C-based isotopic mixing model showed that riverine phytoplankton and detrital matters became the major diet of Hediste species in August and December at St. IB (60 to 72%), which corresponded to the supply of irrigation drainage to the area. Contrastingly the contribution of microphytobenthos increased sharply in March at both stations (55 to 83%) because of benthic diatom blooms. These emphasize that the Hediste species can change their feeding modes (i.e., suspension- and deposit-feeding) depending on food availability in the habitat. In winter and/or spring, δ13C of H. diadroma negatively correlated with their body size, suggesting size-dependent variation in food utilization. δ13C ratios of the sympatric deposit-feeders and suspension-feeding bivalves were seasonally more stable, depending mainly on microphytobenthos and river derived materials, respectively. These suggest that a certain group of estuarine consumers including Hediste species act as significant links between terrestrial and estuarine food webs by incorporating riverine terrestrial subsidies to benthic secondary production in estuaries.

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  • Takashi Kamiyama
    2023 Volume 18 Issue 1 Pages 34-46
    Published: February 28, 2023
    Released on J-STAGE: March 02, 2023
    JOURNAL FREE ACCESS

    To evaluate the growth and feeding responses of the polyp stage of the moon jellyfish Aurelia coerulea to natural microzooplankton assemblages, bud production among A. coerulea polyps was monitored in field bottle incubation experiments using fractionated field seawater (<200-µm fraction) in summer. During this incubation period, feeding rates were measured twice by examining changes in the abundance of various microzooplankton taxa over two days. The number of buds increased with incubation period, reaching a mean of 5.8–9.3 buds per polyp after 16 days, at which point the carbon content of the new buds and the mother polyp was estimated to be 1.3–2.5 times higher than the carbon content of the initial polyp. Using these carbon content estimates, I calculated specific growth rates of 0.1–0.2 d−1 during the first 10 days. The results of the present feeding experiments suggest that polyps utilize diverse groups of microzooplankton and achieve relatively high carbon ingestion rates from ciliates, dinoflagellates, molluscs, and copepod nauplii. Total microzooplankton ingestion rates were estimated to be 4.05 and 3.27 µgC polyp−1 d−1 in the two experiments, respectively. These findings show that natural microzooplankton assemblages play a role as prey of polyps and can promote asexual reproduction of polyps under natural summer conditions.

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Notes
  • Shizuko Nakai, Shiro Itoi, Gen Kanaya, Hajime Itoh, Osamu Miura
    2023 Volume 18 Issue 1 Pages 47-51
    Published: February 28, 2023
    Released on J-STAGE: March 02, 2023
    JOURNAL FREE ACCESS

    The habitats of Batillaria multiformis (Near Threatened species) and Batillaria attramentaria are often overlapping on a mudflat, and young individuals of two Batillaria snails were difficult to identify by shell morphology. This is one of the causes that the study, such as population dynamics of two Batillaria species, did not advance. Recently, species identification by DNA analysis for B. multiformis and B. attramentaria was developed using a PCR-RFLP method. However, using only one restriction enzyme and universal primer may lead to misidentification. Therefore, this study examined a more precise method using two restriction enzymes for the PCR-RFLP technique. The mitochondrial DNA gene encoding cytochrome c oxidase subunit I (COI) was amplified, and two restriction enzymes, PstI and HinfI, were selected for this method. The number and position of bands after the agarose gel electrophoresis enable us to identify the two Batillaria species. After the effectiveness of this method was confirmed by adult B. multiformis and B. attramentaria that had each typical shell shape, young Batillaria snail samples that were difficult for morphological identification were identified by this PCR-RFLP method. We proved that the proposed PCR-RFLP identification method is simple and reliable in identifying the morphologically similar B. multiformis and B. attramentaria.

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  • Yuka Kushida, Shiori Kunihiro, James Davis Reimer
    2023 Volume 18 Issue 1 Pages 52-54
    Published: February 28, 2023
    Released on J-STAGE: March 02, 2023
    JOURNAL FREE ACCESS

    Associations between different taxa constitute critical data to recognize ecological symbioses. Acoela flatworms of the genus Waminoa are an overlooked but often present group in coral reef ecosystems. More than 97% of the reports on Waminoa individuals until now have found them on scleractinian coral species, and the relationships between Waminoa species and other potential hosts such as octocorals, which are often large and ecologically important components in coral reefs, are not known well. Here we report the first observation of Waminoa sp. from a species of Dendronephthya, at Zanpa, Okinawa, Japan. We observed three morphotypes on a colony of D. aff. rigida (Studer, 1888), with almost all Waminoa individuals in shaded locations.

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  • Masumi Kamata, Naohisa Wada, Nina Yasuda, Daniel Varela, Jorge I. Mard ...
    2023 Volume 18 Issue 1 Pages 55-59
    Published: February 28, 2023
    Released on J-STAGE: March 02, 2023
    JOURNAL FREE ACCESS
    Supplementary material

    Outbreaks of paralytic shellfish poisoning caused by the toxic dinoflagellate Alexandrium catenella (Dinophyceae) are currently a serious global problem both from economic and food hygiene perspectives. In Chile, A. catenella was first recorded in 1972 and is currently the main harmful algae species in the country, in terms of seafood security. As no relevant microsatellite markers for Chilean A. catenella populations were available, we isolated 23 new polymorphic microsatellite loci of A. catenella from Chile, of which 15 are applicable to both Chilean and Japanese populations. We found a strong genetic break between Chilean and Japanese A. catenella populations (FST=0.298, P<0.001), consistent with the morphological differences between them. In contrast to the Japanese population, for which genetic diversity ranged from 0.268 to 0.937, the Chilean population had a lower genetic diversity, ranging between 0.065 and 0.512. This study successfully developed A. catenella microsatellite markers that can be used to investigate its genetic spatial and temporal bloom diversity and assess further genetic connectivity between the population from southern and northern Chilean areas.

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  • Mariko Kawamura, Rina Ishihara, Kohei Oshiro, Masaki Ishida
    2023 Volume 18 Issue 1 Pages 60-62
    Published: February 28, 2023
    Released on J-STAGE: March 02, 2023
    JOURNAL FREE ACCESS

    We collected 43 medusae of Aurelia coerulea from Tanabe Bay, Wakayama, Japan, and measured the tubule lengths of 1,613 nematocysts at different growth stages: ephyra, juvenile, subadult, and adult. The median tubule lengths for ephyrae, juveniles, subadults, and adults were 72, 51, 79, and 58 µm, respectively. No nematocysts in ephyrae, juveniles, or subadults exceeded 200 µm in tubule length. In the tentacles of 15 adults, we detected nematocysts with tubule lengths exceeding 200 µm. The average proportion of nematocysts with long tubules was 9.1% in medusae with bell diameters of 110 mm or more, in contrast to only 1.0% in medusae with bell diameters of less than 110 mm. Among the 1,613 nematocysts examined, there were two different tubule groups with modes at 54 µm and 230 µm in length. Nematocysts in the short-tubule group were composed of microbasic euryteles and small isorhizas, whereas the long-tubule group was composed of only microbasic euryteles. These long tubules of microbasic euryteles can potentially penetrate not only large planktonic crustaceans but also human skin. The growth-related and intra-species variation in tubule length could also modify the degree of envenomation in humans.

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