掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

Abstract

Symbiotic relationships between dinoflagellates of the family Symbiodiniaceae and other marine organisms support coral reef ecosystems. Reef-dwelling, large, benthic foraminifers contribute to reef substrate formation. Although foraminifera in the subfamily Soritinae host dinoflagellates of the family Symbiodiniaceae to form unique relationships, the diversity of these dinoflagellates and their spatial and population-level variation are not yet understood. Here, we investigated the diversity of the mutualistic dinoflagellate community in the foraminifer Amphisorus kudakajimensis collected from different depth at nine sites at three reef locations on Akajima Island, and from a single depth at one location on Okinawa Island, Okinawa, Japan. Next-generation sequencing technology and the SymPortal pipeline specific to analyses of the internal transcribed spacer 2 region of the ribosomal RNA gene of Symbiodiniaceae yielded 39 lineages in 154 specimens. Dominant lineages were the genera Cladocopium, Freudenthalidium, and Halluxium; the dinoflagellate community in one foraminifera comprised  multiple lineages. Halluxium was dominant in deep communities (> 9 m water depth) at Akajima, whereas it was not detected in shallow populations (< 2 m). Dinoflagellate genus richness was greater in the eight deep populations than in the two shallow populations. Specific combinations of Cladocopium and Freudenthalidium in A. kudakajimensis of the shallow reef suggest that symbiont communities converge in low-diversity combinations to accommodate large environmental fluctuations in shallow water with high UV light intensity. Our results provide insights into possible host–symbiont patterns for accommodating future climate change.

添付ファイル： Maeda25CoralReefs.pdf

DOI： 10.1007/s00338-025-02671-4

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その他リンク： https://link.springer.com/article/10.1007/s00338-025-02671-4/fulltext.html

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

Abstract

Background

Marine benthic prokaryotic communities play crucial roles in material recycling within coastal environments, including coral reefs. Coastal sedimentary microbiomes are particularly important as potential reservoirs of symbiotic, beneficial, and pathogenic bacteria in coral reef environments, and therefore presumably play a core role in local ecosystem functioning. However, there is a lack of studies comparing different environments with multiple sites on the island scale, particularly studies focusing on prokaryotic communities, as previous investigations have focused mainly on a single site or on specific environmental conditions. In our study, we collected coastal sediments from seven sites around Okinawa Island, Japan, including three different benthic types; sandy bottoms, seagrass meadows, and hard substratum with living scleractinian corals. We then used metabarcoding to identify prokaryotic compositions and estimate enzymes encoded by genes to infer their functions.

Results

The results showed that the three substrata had significantly different prokaryotic compositions. Seagrass meadow sites exhibited significantly higher prokaryotic alpha-diversity compared to sandy bottom sites. ANCOM analysis revealed that multiple bacterial orders were differentially abundant within each substratum. At coral reef sites, putative disease- and thermal stress-related opportunistic bacteria such as Rhodobacterales, Verrucomicrobiales, and Cytophagales were comparatively abundant, while seagrass meadow sites abundantly harbored Desulfobacterales, Steroidobacterales and Chromatiales, which are common bacterial orders in seagrass meadows. According to our gene-coded enzyme analyses the numbers of differentially abundant enzymes were highest in coral reef sites. Notably, superoxide dismutase, an important enzyme for anti-oxidative stress in coral tissue, was abundant at coral sites. Our results provide a list of prokaryotes to look into in each substrate, and further emphasize the importance of considering the microbiome, especially when focusing on environmental conservation.

Conclusion

Our findings prove that prokaryotic metabarcoding is capable of capturing compositional differences and the diversity of microbial communities in three different environments. Furthermore, several taxa were suggested to be differentially more abundant in specific environments, and gene-coded enzymic compositions also showed possible differences in ecological functions. Further study, in combination with field observations and temporal sampling, is key to achieving a better understanding of the interactions between the local microbiome and the surrounding benthic community.

添付ファイル： (Hamamoto et al. 2024) Diversity, composition and potential roles of sedimentary microbial communities in different coastal substrates around subtropical Okinawa Island, Japan.pdf

DOI： 10.1186/s40793-024-00594-1

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その他リンク： https://link.springer.com/article/10.1186/s40793-024-00594-1/fulltext.html

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.scitotenv.2024.173248

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担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Plankton Society of Japan/The Japanese Association of Benthology  

添付ファイル： (Hamamoto et al. 2024) A discovery of the northernmost population of the giant mangrove whelk Terebralia palustris (Mollusca: Gastropoda: Potamididae) on Zamami Island and its genetic variability.pdf

DOI： 10.3800/pbr.19.60

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Plankton Society of Japan/The Japanese Association of Benthology  

DOI： 10.3800/pbr.17.338

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：{PeerJ}  

Sea cucumbers are important ecological engineers in marine ecosystems. However, the fishery demand of some species, especially large-epifaunal and commercially used (LEC) sea cucumbers, has risen drastically, resulting in serious depletion of local populations for many species. Despite this problem, basic ecological data on sea cucumbers, such as population densities and preferred habitats, are often still insufficient. Here, we report on the population densities of multiple LEC sea cucumber species, and their ambient benthic communities at eight sites around Okinawa Islands. Further, we discuss the correspondence between sea cucumber densities and the surrounding coral communities. Our results show two sites within national or quasi-national parks, Aka and Manza, where stricter rules have been placed on fisheries and land reclamation compared to other areas, had the highest and third highest sea cucumber population densities among sites, respectively. Holothuria atra was observed at all survey sites and made up the majority of sea cucumber populations at all sites except for Chatan and Sesoko, where Holothuria leucospilota and Stichopus chloronotus were most abundant, respectively. Regarding the relationships between benthic composition and LEC sea cucumber species, S. chloronotus was significantly correlated with dead corals, scleractinian corals, and coralline algae. As well, H. leucospilota had significant correlations with rubble. Although there were no significant correlations between any specific scleractinian coral genus and sea cucumber densities, S. chloronotus was marginally insignificant with Platygyra and Psammocora. Notably, medium- to highly valued species were sparse in our surveys, and most of them appeared at only one site. Additionally, at one site (Odo), only three LEC sea cucumber individuals were observed. Combining these facts with relatively low population densities around the Okinawa Islands compared to densities reported in previous research from the Indo-West Pacific Ocean region, we conclude that Okinawan LEC sea cucumber populations have been and are being impacted by high levels of direct (e.g., overexploitation, as well as coastal development) and indirect anthropogenic pressure (e.g., decreasing water quality). To address the current situation, repeated monitoring and more detailed investigations to reveal the drivers that determine LEC sea cucumber species aggregations and population densities are urgently needed, along with more robust management of remaining LEC sea cucumber populations.

DOI： 10.7717/peerj.14181

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その他リンク： https://peerj.com/articles/14181.xml

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Magnolia Press  

<jats:p>A new porcellanid species of the genus Enosteoides Johnson, 1970 is described on the basis of a single specimen collected from the burrow of an unidentified snapping shrimp of the genus Alpheus Fabricius, 1798, on the subtidal coarse sediment in Okinawa Island, Ryukyu Islands, southwestern Japan. Enosteoides lapis n. sp. is similar to E. melissa (Miyake, 1942) and E. philippinensis Dolorosa &amp; Werding, 2014 in the general morphology of the frontal region of the carapace, third thoracic sternite, and ambulatory legs, but is distinguished from both by the dorsal surface of the carapace being more strongly uneven, as well as by the absence of dense plumose setae on the lateral margins of the carapace, anterodorsal surfaces of the chelae, and anterior and posterior margins of the ambulatory meri.&#x0D;
 </jats:p>

DOI： 10.11646/zootaxa.5182.6.6

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media {SA}  

Recently, sea cucumbers (Echinodermata: Holothuroidea) have been over-exploited in many areas of the world, including in the Ryukyu Islands, southern Japan, due to increases in their economic importance. Nevertheless, management and protection of sea cucumbers are insufficient worldwide. The black sea cucumber Holothuria (Halodeima) atra Jaeger, 1833, inhabits a large range across the Indo-West Pacific Ocean and is a widely harvested species. Here we conducted population genetic analyses on H. atra using partial mitochondrial DNA sequences of cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S) to examine 11 different populations around three island groups in the middle Ryukyus; Okinawajima Island, the Kerama Islands, and the Sakishima Islands, all within Okinawa Prefecture. We found 27 haplotypes for COI and 16 haplotypes for 16S. Locations within national and quasi-national parks (Zamami Island, Keramas, and Manza, Okinawajima; managed by the national Ministry of Environment and Okinawa Prefecture, respectively) had the highest number of haplotypes, whereas locations with less management and more anthropogenic pressure had lower numbers The mean of all samples' genetic diversity indices was moderate with regards to both haplotype and nucleotide diversity. According to our results, Zamami Ama was the most genetically diverse location based on both markers used, likely because it is located within Kerama-Shoto National Park with comparatively stricter regulations than most other locations. Based on our COI sequences, three-quarters of the locations with the highest haplotype diversity were found to be distant from Okinawajima Island, indicating that the genetic diversity of H. atra was reduced around Okinawajima Island. Our results possibly reflect negative impacts from anthropogenic pressures such as over-harvesting and coastal development, although future comprehensive research including sequences of nuclear loci is needed to confirm this hypothesis.

DOI： 10.3389/fcosc.2021.736633

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開催年月日： 2021年5月

記述言語：英語   会議種別：口頭発表（一般）  

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開催年月日： 2018年5月 - 2018年6月

記述言語：英語   会議種別：ポスター発表  

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記述言語：日本語   会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

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種別：講演会

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種別：講演会

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