著者

Tatsuya Ishikawa Akira Kurashima

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.15, no.2, pp.112-120, 2020-05-27 (Released:2020-05-30)

参考文献数

50

被引用文献数

3

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This study aimed to estimate the feeding pressure of a Diadema setosum population on a barren ground in Kata Bay, Mie Prefecture, Japan, which is a temperate region. We combined data of the feeding rate of D. setosum from tank experiments and of the D. setosum population dynamics obtained from monthly surveys. We conducted tank experiments to clarify the relationships between the feeding rate of D. setosum and the water temperature and test diameter of the sea urchins. The feeding rate and water temperature were positively correlated over the range of 15°C to 30°C. The test diameter composition of the D. setosum population in Kata Bay was stable throughout the study period (June 2014 to May 2015). The results revealed distinct seasonal changes in the feeding pressure of the D. setosum population owing to temperature variations.

著者

Yusuke Yamana Hayato Tanaka

出版者

日本プランクトン学会、日本ベントス学会

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.12, no.2, pp.83-94, 2017-05-30 (Released:2017-06-06)

参考文献数

32

被引用文献数

3

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Two new taeniogyrinid sea cucumbers collected in the intertidal zone of southern Japan, Taeniogyrus verruculosus sp. nov. and Scoliorhapis sesokoensis sp. nov. are described. Both species possess a small body size (approximately 30–40 mm), light body color (translucent white in preserved specimens), ten tentacles, and numerous verrucous surfaces on the body, within which small (mostly less than 70 µm in length) sigmoid-hook ossicles are present. The two new species have a very similar external appearance to each other, however they do differ in the number of tentacle digits: T. verruculosus possesses up to eight digits, whereas S. sesokoensis possesses up to six. In both species, wheel papillae are not present. T. verruculosus possesses only a few small (mostly less than 30 µm in diameter) wheel ossicles in the anterior dorsal skin, which are not present in S. sesokoensis. Additionally, the DNA barcode sequences of two new species were determined and are available in the DDBJ/NCBI/GenBank databases under the accession numbers.

著者

Tatsuya Ishikawa Miyuki Maegawa Akira Kurashima

出版者

日本プランクトン学会、日本ベントス学会

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.11, no.4, pp.112-119, 2016-11-25 (Released:2016-11-23)

参考文献数

30

被引用文献数

13

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This study examines the effects of the sea urchin Diadema setosum on algal composition, coverage and biomass on barren ground. In cage experiments, the effects of D. setosum density were examined at 5 levels over the range of 0–8 ind. m−2. Algal coverage and number of species, densities and lengths of Sargassum spp. on experimental blocks in each cage were measured monthly. In the cage without D. setosum, algal coverage and biomass were higher than in cages with D. setosum. For D. setosum density of 1 ind. m−2 and higher, decreased algal coverage and decreased biomass and density of Sargassum spp. were observed. D. setosum at a density higher than 2 ind. m−2 had a negative effect on algal species numbers. Consequently, algae could grow when the D. setosum density was fewer than 2 ind. m−2. This study revealed that grazing by D. setosum has a great effect on the seaweed bed ecosystems along the coast of central Japan.

著者

Takashi Kamiyama

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.18, no.1, pp.34-46, 2023-02-28 (Released:2023-03-02)

参考文献数

45

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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.

著者

KATSUHIKO TANAKA

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.2, no.1, pp.1-11, 2007 (Released:2008-05-09)

参考文献数

71

被引用文献数

45 53

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Gnathiidae is a family of Isopoda, showing a distinct morphology and ecology. Species in the family have ten walking legs compared to 14 for isopods in general. The life cycle of the Gnathiidae is biphasic including a fish-parasitic larval phase and a non-feeding adult phase, whereas most other isopods have a monophasic life cycle with direct-developing young similar to adults in morphology and ecology. Although the ecological information on gnathiids has been described fragmentally, studies on the life cycles and population biology have increased dramatically since the 1980's. Larval biology including the host species, emergence pattern and predation risks during parasitism have also been studied from the view of fish disease and symbiotic interactions among fishes. Some authors reported the utilization patterns of benthic substrata and harem formation of adults therein. However, the ecological knowledge of gnathiids is based on a limited number of species of which the benthic habitats are known. Studies rarely identify larvae because of the lack, or insufficiency, of the taxonomic description of larvae of most species. The difficulty in identifying larvae has prevented detailed examination of ectoparasitic behaviour. Furthermore, gnathiid larvae emerging from the benthos or attaching to hosts have been investigated separately from benthic individuals. More efforts on taxonomy and the classification of larvae are necessary to elucidate the larval ecology and the integration of larval and adult biology.

著者

Gaku Yamamoto Sho Toshino

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.16, no.2, pp.129-138, 2021-05-27 (Released:2021-06-11)

参考文献数

32

被引用文献数

1

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A new hydromedusa belonging to the order Anthoathecata is reported from Sagami Bay, eastern Japan. Tiaricodon orientalis sp. nov. can be distinguished from other Tiaricodon species by the umbrella size of the medusa, manubrium length, interradial peaks in the subumbrella, and a red band on the upper part of the manubrium. A comparative table of the primary diagnostic characters of the genus is provided. Our morphological and molecular phylogenetic analyses suggest that Tiaricodon from China is not Tiaricodon coeruleus but Tiaricodon orientalis.

著者

James Davis Reimer Takuma Fujii Hiroki Kise Kensuke Yanagi Katie Cook James Cant Keita Koeda Tatsuki Koido Takaya Kitamura Takuma Mezaki

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.15, no.2, pp.185-187, 2020-05-27 (Released:2020-05-30)

参考文献数

13

被引用文献数

1

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The zooxanthellate scleractinian species Goniopora stokesi is widely distributed across the Indo-Pacific Ocean, and in Japan the northernmost records of this species are from Tatsukushi, Kochi on Shikoku, although these records are not associated with specimens deposited in museums. The species is unique among Goniopora in that it lives on soft bottom sediment, forming free-living colonies, and produces asexual daughter colonies, or ‘polyp balls,’ via budding from parent colonies. Here we report on a large G. stokesi community from Otsuki, Kochi, Japan, representing the northernmost specimen-based record of the species. Specimen-based records are important as verifiable baseline data in light of global warming and climate change, which is expected to drastically effect the marine flora and fauna of Kochi and surrounding areas.

著者

Koji Seike Ryutaro Goto

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.15, no.3, pp.220-227, 2020-08-14 (Released:2020-08-04)

参考文献数

35

被引用文献数

6

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Burrows produced by marine invertebrates often harbor other small commensal invertebrates. The mud shrimp Upogebia is known to coexist with the myid bivalve Cryptomya in a burrow produced by the shrimp. Both species are filter-feeders, and thus interspecific competition or trophic niche segregation may occur in the burrow. Samples for carbon and nitrogen stable isotope analysis were collected from a tidal flat near the tidal inlet of Akkeshi Lake, Hokkaido, northern Japan in April 2013. In addition, stratified benthos sampling was conducted on the tidal flat in August 2018, to clarify the interspecific relationship between U. major and C. busoensis in the burrow. The stratified benthos sampling showed the vertical distribution of these species, and indicated that both species filter water from the same part of the burrow for feeding. The stable carbon and nitrogen isotope analysis showed that important food sources for both U. major and C. busoensis are marine phytoplankton and microphytobenthos. In addition, C. busoensis is likely to consume terrestrial organic matter whereas U. major is unable to utilize it. The partial trophic segregation between the species increases the potential benthic filtering because it allows the Upogebia burrow complex to consume a wide variety of organic matter, and it might reduce interspecific competition between the filter-feeding host and its commensal species. These results demonstrate how ecologically similar macrobenthos can coexist in a burrow.

著者

Yasuhide Nakamura Akihiro Tuji Wataru Makino Shin-ichiro S. Matsuzaki Nobuaki Nagata Megumi Nakagawa Noriko Takamura

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.15, no.1, pp.44-54, 2020-02-28 (Released:2020-03-25)

参考文献数

40

被引用文献数

9

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Neomysis awatschensis is an important prey item for various fishes in Lake Kasumigaura, Japan. There is, however, a contradiction concerning the major food sources of this mysid species: whether “bottom mud”, “particulate organic matter (POM) including phytoplankton”, or “mesozooplankton” is the main diet, and this uncertainty may be due to differences in the methodology used to determine the prey items in previous studies. This study examined the main food sources of N. awatschensis by combining three methods to eliminate methodological biases: DNA metabarcoding, microscopy and stable isotope analysis. Planktonic diatoms and green algae sequences were the main taxa detected by DNA metabarcoding and microscopy on the fecal pellets. The δ15N values of the mysids were similar to those of phytoplankton feeders rather than carnivorous planktonic crustaceans. These results suggest that diatoms and green algae were the major food sources for N. awatschensis in Lake Kasumigaura during the investigation period, and that its trophic level is as low as that of herbivores. However, the partial contribution of other “POM” (e.g., benthic diatoms) is also implied, considering the dispersion in δ13C values. Mesozooplankton prey, such as copepods, were detected both using DNA metabarcoding and microscopy, but they could not be a major food source due to the low nitrogen stable isotopic signature of the mysids. The opportunistic feeding habits of N. awatschensis possibly explain the consistent dominance of this species in the lake, where the ecosystem structure was substantially changed because of successive desalination.

著者

Kotaro Kan Yoshifumi Kuroki Masanori Sato Hiroaki Tosuji

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.15, no.1, pp.30-43, 2020-02-28 (Released:2020-03-25)

参考文献数

46

被引用文献数

7

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The recruitment process of planktic larvae of the nereidid polychaete Hediste diadroma, which has a catadromous life cycle, was examined in an estuary in Kagoshima Bay, Southern Japan. Our laboratory experiments showed that the phototaxis of the planktic larvae changed drastically from positive to negative during the 3-chaetiger nectochaeta, 3.5–4.0 days after fertilization. During this stage, the prostomial antennae, first peristomial cirri, and anal cirri appeared and the ciliary bands used for swimming were reduced; these results suggest that larvae shifted from pelagic to demersal stage at approximately 4.0 days after fertilization. Field sampling took place in the estuary, where reproductive swarming of mature adults was observed in late February to April; planktic larvae of, mainly, 5- to 8-chaetiger stages were collected in evening high tides during the spring tides of April and May 1989, 2013, and 2015. During the same period, 5- or higher chaetiger benthic juveniles were collected at low tide from intertidal flats from a wide area of the estuary where adults inhabited. The morphology of benthic juveniles of 5- and 6-chaetiger stages differed from that of planktic larvae of the same stages in the following characteristics: (1) the long larva-specific spinigers were lost; (2) the second peristomial cirri, originating from the parapodial lobes of chaetiger 1 of the planktic larvae, appeared; and (3) the anal cirri were elongated. Our results indicate that 5- to 8-chaetiger nectochaeta are critical phases for the successful settlement of planktic larvae, which come back into an estuary with rising tides.

著者

Kazutaka Miyahara Katsuya Fukui Tatsuaki Nagahama Tetsuya Ohatani

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.1, no.1, pp.59-63, 2006-02-25 (Released:2009-04-20)

参考文献数

27

被引用文献数

8 9

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This paper provides the first evidence that Thysanoteuthis rhombus spawns in the Sea of Japan. Five planktonic egg masses were collected in the southern Sea of Japan during 29 October to 24 November 2004 and transported to onshore laboratories for observation. Part of each egg mass was reared in indoor, aerated tanks supplied with filtered running seawater. The egg masses (ca. 60–120 cm in total length and 13–15 cm in diameter) were cylindrical with rounded ends and consisted of a resilient, transparent gelatinous core with a pair of egg rows forming spiral loops around the core. The embryos had dome-shaped mantles covered with many chromatophores and slowly rotated inside the spherical egg capsules. Hatching was observed in all the egg masses 3–10 days after collection. Morphological characteristics of the egg masses, eggs and embryos, especially the large number of chromatophores present in the early embryonic stages, agreed with the descriptions in previous studies. Near the collections sites, surface water temperature and salinity ranged 18–22 °C and 33.3–33.7, respectively, both of which were lower than the optimum conditions for T. rhombus spawning. The early embryonic stages of the egg masses at collection such as cleavage and slow currents at the sea surface suggest the egg masses were spawned near the collection sites. Increased abundance of T. rhombus in the Sea of Japan and increased sampling efforts were proposed as two possible causes for the egg-mass discoveries.

著者

Hiroaki Tosuji Taeseo Park Yuya Goryo Kotaro Kan Hirokazu Abe Masanori Sato

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.18, no.3, pp.124-130, 2023-08-31 (Released:2023-08-31)

参考文献数

28

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The present study was carried out to design a simple, new and accurate method for identification of the morphologically similar four species (forms A and B of P. shikueii, P. mictodonta, and P. wilsoni) of the Perinereis nuntia species complex by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) patterns of the internal transcribed spacer (ITS). Restriction digestion analysis in the following two steps generated a specific restriction pattern for each species: (1) by the first digestion of amplified ITS fragments with AluI, we can distinguish the two forms of P. shikueii from P. mictodonta and P. wilsoni; (2) by the subsequent digestion of ITS fragments with Cfr10I, we can distinguish between the forms A and B of P. shikueii, and by that with HinfI, we can distinguish P. mictodonta from P. wilsoni. Our result indicates that this method enable easy and accurate identification of these taxa. We additionally examined the distributions of the two forms of P. shikueii in Japan, Korea and Taiwan using this new method. The form B was distributed in a wide range in western Japan and Korea, whereas the form A was distributed in few limited sites in the inner parts of the Seto Inland Sea and the Ariake Sea in Japan, the western and southern coasts of Korea, and the western coast of Taiwan.

著者

Justus O. Omweri Keita W. Suzuki Shouji Houki Edouard Lavergne Hiroshi Inoue Hisashi Yokoyama Yoh Yamashita

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.16, no.4, pp.278-291, 2021-11-17 (Released:2021-11-18)

参考文献数

64

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The euryhaline mysid Neomysis awatschensis occurs widely in estuaries and brackish lakes in Japan. Although N. awatschensis may serve as an essential energy channel to higher trophic levels, its feeding ecology has been studied only in sheltered and desalinated Lake Kasumigaura. To determine major food sources for N. awatschensis, monthly sampling was conducted during the day along the microtidal Yura River estuary from March 2014 to July 2015. Additional sampling was conducted in May 2019 to assess diel vertical migration in relation to feeding. Microscopic examinations revealed that benthic diatoms (e.g. Bacillaria paxillifer and Navicula spp.) dominated in the stomach irrespective of developmental stage, diel cycle, or season. Stable carbon and nitrogen isotope ratios in N. awatschensis and its potential food sources indicated great contributions to the diet of N. awatschensis from benthic microalgae (mainly benthic diatoms) in 2014 and from particulate organic matter (mainly phytoplankton) in 2015. Although N. awatschensis always concentrated close to the bottom in 2019, diel vertical migration might have happened in 2015, when fresh water occupied the whole estuary possibly due to river mouth clogging. Under the stagnant and oligohaline conditions, N. awatschensis could have swum up into the water column and fed on phytoplankton at night in 2015. This hypothesis may resolve the apparent contradiction between the microscopy and stable isotope analysis in 2015. In the Yura River estuary, N. awatschensis feeds primarily on benthic diatoms, although it can utilize phytoplankton flexibly in response to prevailing environmental conditions.

著者

Tetsuya Nishikawa Kazuhiro Harada Tsuyoshi Watanabe

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.17, no.1, pp.83-90, 2022-02-22 (Released:2022-02-23)

参考文献数

40

被引用文献数

1

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In the Sea of Japan, changes in the oceanographic conditions affect fisheries, and new phenomena such as blooms of the harmful dinoflagellate Margalefidinium polykrikoides and mass occurrences of the giant jellyfish Nemopilema nomurai have been observed since the 2000s. In order to elucidate and formulate countermeasures to such new issues, it is essential to enhance the oceanographic/biological data. However, data especially on the phytoplankton assemblage are limited. In the present study, we investigated the population dynamics of the phytoplankton community together with environmental factors at two stations off Tajima, southwestern Sea of Japan for seven fiscal years from September 2009 to March 2016. The oceanographic observations revealed the general pattern in the seasonal and annual abundance of phytoplankton off Tajima. The major component of size-fractionated chlorophyll a concentrations were micro-size (filtered pore size: >10 µm). The results indicated that there was usually a low abundance of phytoplankton in this area. Relatively high abundances (cell densities over 100 cells mL−1) of micro-sized phytoplankton were observed only in spring, but total cell densities were less than 10 cells mL−1 in most months of the other three seasons. The major phytoplankton component was diatoms. Based on the abundance and frequency, the dominant seven diatom taxa were classified into three groups: Skeletonema spp., Thalassiosira spp. and Eucampia zodiacus were dominant in spring, Chaetoceros spp. and Pseudo-nitzschia spp. were dominant in spring and autumn, and Rhizosolenia spp. and Leptocylindrus danicus were dominant in autumn.

著者

Akihiro Yoshikawa Akikazu Yasuda Takato Izumi Kensuke Yanagi

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.17, no.2, pp.208-213, 2022-05-30 (Released:2022-05-31)

参考文献数

32

被引用文献数

1

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This is the first record of an epibiotic association between an acontiate sea anemone and a fish. We collected unidentified epibiotic sea anemones living on the necto-benthic fish Inimicus japonicus (Cuvier 1829) from the Seto Inland Sea, Japan. Molecular analyses revealed that the anemones were most closely related to Verrillactis paguri (Stimpson in Verrill 1869) sensu England (1971), which has a mutualistic relationship with hermit crabs. Therefore, we tentatively assigned the collected species as Verrillactis sp. (Actiniaria: Sagartiidae). This finding of sea anemones using fish as substrate is unprecedented. Future research into this relationship to determine if this is an incidental occurrence or facultative symbiosis is warranted. Our findings contribute to a wider understanding of symbiosis in sea anemones.

著者

Giovanni D Masucci Piera Biondi James D Reimer

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.16, no.4, pp.237-248, 2021-11-17 (Released:2021-11-18)

参考文献数

72

被引用文献数

7

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Shoreline armouring has progressively affected the coastal landscapes of countries all over the world, and armouring construction will increase in coming years as a consequence of climate change. Armouring has the potential to affect coastal environments and induce changes in the abundance and diversity of marine communities, and its effects might by increased by wide adoption. Moreover, compared with temperate locations, the effects of armouring have been less studied in tropical and subtropical areas. Okinawa Island, the largest and most populated island of the Ryukyu Archipelago in southern Japan, has been affected by numerous civil and military engineering works. After decades of development, less than 40% of its coastline remains natural, and yet impacts from armouring on local marine communities have been overlooked until recent years. The aim of this research was to evaluate effects of near-shore armouring on the surrounding environment by comparing diversity and abundance of coral rubble mobile cryptofauna benthic communities between armoured and control sites. Across six different geographic locations, coral rubble was sampled in front of subtidal breakwaters and at nearby control sites. Armoured sites were associated with lower cryptofauna abundances and reduced richness and diversity at higher taxonomic levels (phylum and class). Reduction in spatial complexity could be a plausible reason for the observed patterns. Impacts could be mitigated by combining technical innovations, habitat restoration, and use of natural spaces as buffers for coastal protection. Since less than half of Okinawa Island’s coastline remains in a natural state, environmental conservation should be prioritized.

著者

Yasuhide Nakamura Rei Somiya Noritoshi Suzuki Mitsuko Hidaka-Umetsu Atsushi Yamaguchi Dhugal J. Lindsay

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.12, no.2, pp.95-103, 2017-05-30 (Released:2017-06-06)

参考文献数

46

被引用文献数

3 15

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Optics-based surveys for large unicellular zooplankton were carried out in five different oceanic areas. New identification criteria, in which “radiolarian-like plankton” are categorized into nine different groups, are proposed for future optics-based surveys. The autonomous visual plankton recorder (A-VPR) captured 65 images of radiolarians (three orders: Acantharia, Spumellaria and Collodaria) and 117 phaeodarians (four taxa: Aulacanthidae, Phaeosphaerida, Tuscaroridae and Coelodendridae). Colonies were observed for one radiolarian order (Collodaria) and three phaeodarian taxa (Phaeosphaerida, Tuscaroridae and Coelodendridae). The rest of the radiolarian orders (Taxopodia and Nassellaria) and the other phaeodarian taxa were not detected because of their small cell size (< ca. 400 µm).

著者

Sakiko Orui Sakaguchi Hiroshi Ueda

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.13, no.4, pp.173-179, 2018-11-21 (Released:2018-11-14)

参考文献数

22

被引用文献数

6

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Pseudodiaptomus inopinus, a common estuarine calanoid copepod in the Northwest Pacific, has been suggested to be a species complex. The population of the mainland of Japan consists of two allopatric forms that are distinguishable by the length of the posterior processes of the genital operculum; the forms with short and long processes are tentatively called SP- and LP-forms, respectively. We analyzed the mitochondrial cytochrome c oxidase subunit I (COI) gene and the nuclear ribosomal internal transcribed spacer 1 (ITS1) gene of 34 individuals (12 SP- and 22 LP-forms) collected from various localities. The genetic differences between the two forms were 12–15% for COI and 7–10% for ITS1. They were clearly separated into different clades in both COI and ITS1 trees. These results confirmed that the two forms belong to different species. The SP-form is a distinct species because the shape of the genital operculum of P. inopinus s. str. has long posterior processes as in the LP-form. Pseudodiaptomus japonicus Kikuchi, 1928, which is the SP-form and was once synonymized with P. inopinus, is revived. The genetic comparison using available sequence data indicates that Pseudodiaptomus koreanus Soh et al., 2012 is the same species as P. japonicus.

著者

Kringpaka Wangkulangkul Ruaengrit Promdam

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.13, no.4, pp.154-162, 2018-11-21 (Released:2018-11-14)

参考文献数

47

被引用文献数

1

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Scale-dependent spatial patterns of coastal benthic assemblages have been analyzed in many studies, especially in temperate regions, but such analyses are scarce in tropical waters. Hierarchical analysis of variance was performed using data from a nested sampling design to test whether variability in assemblages of midshore macrofauna from rocky intertidal ecosystems on the southern Thailand coastline differs over different spatial scales and whether assemblages on natural and artificial rocky reefs are similar. Analyses revealed that the composition of macrofaunal groups on the coastline facing the Andaman Sea did not differ from that of the assemblage on the Gulf of Thailand coastline; however, significant variation was detected on the scale of region (within coast) and shore (within region). The abundance of some macrofaunal groups differed among coasts and regions, but all groups exhibited high variation between shores. High variation between shores may mask larger-scale patterns in the composition of macrofaunal groups. Interestingly, the composition of macrofaunal groups and abundance of each group were not influenced by the type of habitat, suggesting that artificial structures may provide a habitat for hard-bottom species where the natural hard substrate is lacking.

著者

Tomohiro Nishimura Wittaya Tawong Hiroshi Sakanari Takuji Ikegami Keita Uehara Daiki Inokuchi Masatoshi Nakamura Takuya Yoshioka Shota Abe Haruo Yamaguchi Masao Adachi

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.13, no.2, pp.46-58, 2018-05-30 (Released:2018-05-24)

参考文献数

68

被引用文献数

13

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Ciguatera fish poisoning (CFP) is caused by toxins originating from an epiphytic/benthic dinoflagellate of the genus Gambierdiscus. In Japan, CFP cases have been increasingly reported not only in subtropical areas but also in temperate areas. It is therefore important to study Gambierdiscus cell occurrences, cell densities, and population dynamics to address CFP outbreaks in Japan. This study assessed the densities in Japanese shallow waters (0.1–3 m depths) and revealed that the densities were lower than those in tropical and subtropical areas worldwide. In the shallow waters of Tosa Bay, a Japanese temperate area, population dynamics of Gambierdiscus cells were assessed monthly between 2007 and 2013. Gambierdiscus did not show substrate preferences for macroalgal species. The cell densities in the area ranged from 0 to 232.2 cells g−1 wet weight algae. The average cell densities in spring, summer, autumn, and winter were 0.1±0.4, 0.9±2.6, 4.0±20.6, and 0.4±1.4 cells g−1 wet weight algae, respectively. The cell densities in summer and autumn were not significantly different (p>0.05), whereas those in summer and autumn were significantly higher than those in spring and winter (p<0.01). A significant positive correlation between cell densities and sea surface temperatures (SSTs) was observed (rs=0.21, p<0.001), while a significant negative correlation between cell densities and salinity was recognized (rs=−0.18, p<0.001). These results suggest that cell densities of Gambierdiscus in Japanese temperate shallow waters increase in summer and autumn when the SST is high and salinity is moderately low.