1.

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論文(リポジトリ)
Sato, Yukuto ; Hermawan, Idam ; Kakita, Tetsuya ; Okano, Sho ; Imai, Hideyuki ; Nagai, Hiroto ; Kimura, Ryosuke ; Yamashiro, Tetsu ; Kajita, Tadashi ; Toma, Claudia
出版情報: PLoS Neglected Tropical Diseases.  16  2022-03.  Public Library of Science
URL: http://hdl.handle.net/20.500.12000/0002019663
概要: Background Leptospirosis, a zoonosis caused by species in the spirochete genus Leptospira, is endemic to the Yaeyama reg ion in Okinawa, subtropical Japan. Species of the P1 subclade “virulent” group, within the genus Leptospira, are the main etiological agents of leptospirosis in Okinawa. However, their environmental persistence is poorly understood. This study used a combination of bacterial isolation and environmental DNA (eDNA) metabarcoding methods to understand the eco-epidemiology of leptospirosis in this endemic region. Findings Polymerase chain reaction (PCR) characterized twelve human clinical L. interrogans isolates belonging to the P1 subclade “virulent” subgroup and 11 environmental soil isolates of the P1subclade “low virulent” subgroup (genetically related to L. kmetyi, n = 1; L. alstonii, n = 4; L. barantonii, n = 6) from the Yaeyama region targeting four virulence-related genes (lipL32, ligA, ligB and lpxD1). Clinical isolates were PCR positive for at least three targeted genes, while all environmental isolates were positive only for lipL32. Analysis of infected renal epithelial cells with selected clinical and environmental strains, revealed the disassembly of cell-cell junctions for the Hebdomadis clinical strain serogroup. Comparison of leptospiral eDNA during winter and summer identified operational taxonomic units corresponding to the species isolated from soil samples (L. kmetyi and L. barantonii) and additional P2 subclade species (L. licerasiae, L. wolffii-related, among others) that were not detected by soil cultivation. Total Leptospira read counts were higher in summer than in winter and the analysis of leptospiral/animal eDNA relationship suggested Rattus spp. as a potential reservoir animal. Conclusion Our study demonstrated high environmental Leptospira diversity in the Yaeyama region, particularly during summer, when most of the leptospirosis cases are reported. In addition, several Leptospira species with pathogenic potential were identified that have not yet been reported in Yaeyama; however, the environmental persistence of P1 subclade species previously isolated from human clinical cases in this region was absent, suggesting the need of further methodology development and surveillance. 続きを見る
2.

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永井, 大翔 ; 今井, 秀行 ; Nagai, Hiroto ; Imai, Hideyuki
出版情報: 日本生物地理学会会報.  2021-12-20.  日本生物地理学会
URL: http://hdl.handle.net/20.500.12000/0002017805
概要: In September 2021, Neocardina sp. as a serious invasive alien freshwater shrimp were collected in Kakinohana spring, Oki nawajima Island, central Ryukyus, Japan. These shrimp were first recorded on Okinawajima Island and Ryukyu Archipelago. The phylogenetic tree based on the Bayesian inference of nucleotide sequences in the COI region of mitochondrial DNA was used to identify this shrimp as N. devidi type II (N. devidi koreana?). This species are highly reproductive and are likely to have a negative impact on the ecosystem as well as on native shrimp. Also, same genus shrimp are distributed in Ishigakijima and Iriomotejima Islands, hybridization and extinction are feared by the invasion of this species.
2021 年9 月〜10 月に沖縄島南部の垣花樋川において国外由来の外来淡水エビのカワリヌマエビ類の一種Neocardina sp. を138 個体採集した.この採集記録は,沖縄島で初めてだけでなく,琉球列島でも初記録である.ミトコンドリアDNA のCOI 領域における塩基配列のベイズ推定を用いた系統樹によって,シナヌマエビN. devidi のⅡ型系統(コウライヌマエビ?)とした.餌資源を共有する在来のコエビ類や生態系に負の影響を与える可能性がある.さらに石垣島と西表島には同属のイシガキヌマエビとイリオモテヌマエビが分布することから,シナヌマエビをはじめとするカワリヌマエビ類の侵入によって雑種化や絶滅が危惧されるため,行政によるモニタリングを喫急に開始するべきである.
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3.

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論文(リポジトリ)
下瀬, 環 ; 今井, 秀行 ; Shimose, Tamaki ; Imai, Hideyuki
出版情報: Fauna Ryukyuana.  60  pp.9-15,  2021-06-09.  Ryukyu University Museum, Fujukan — 琉球大学資料館 (風樹館)
URL: http://hdl.handle.net/20.500.12000/48547
概要: 八重山諸島の石垣島で, 2018年12月16日にゴマサバScomber australasicusの成魚が水揚げされた. ゴマサバは沖縄島から記録があるものの, 八重山諸島からは初記録であるため, ここに報告する. また, サバ属Scomb erとグルクマ属RastrelligerからなるScombriniの臀鰭棘数を観察したところ, 近年普及している図鑑での数値と異なる結果が得られたので, これについても考察した.
A single adult specimen of Scomber australasicus was collected from Ishigaki-jima Island, Okinawa, Japan, on 16 December 2018, which represents the first specimen-based record from the Yaeyama Islands. In this paper, the number of anal-fin spines in the tribe Scombrini is also discussed.
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4.

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Iwamoto, Kensuke ; Chang, Chin-Wei ; Imai, Hideyuki
出版情報: Biogeography : international journal of biogeography, phylogeny, taxonomy, ecology, biodiversity, evolution, and conservation biology.  22  pp.26-34,  2020-09-20.  Biogeographical Society of Japan — 日本生物地理学会
URL: http://hdl.handle.net/20.500.12000/46909
概要: Studies have suggested that fishes with broad distribution ranges, long pelagic duration, and great mobility in their ea rly life histories may have an advantage in their ability to return to their natal reef habitats. Siganus spinus is a siganid fish with a broad dispersal strategy, which may also exploit its great mobility to enhance self-recruitment. Variations in mitochondrial DNA sequences were analysed to estimate the genetic structure and demographic history of Siganus spinus in the West Pacific. In total, 446 nucleotide sequences, including the tRNAThr gene, the tRNAPro gene, and the first half of the control region, were analysed from 240 individuals sampled at five sites spanning the West Pacific Ocean; 37 haplotypes were identified. Our results showed significant geographic genetic structure as well as isolation by distance. Both neutrality tests and mismatch distribution indicated that the population expansion of S. spinus through the study area may have occurred in the late Quaternary. A dispersal strategy characterised by large juveniles and open-sea distribution may have contributed to a sudden population expansion after the last glacial period, along with an expansion of distribution.
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5.

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Tokuyama, Takenobu ; Shy, Jhy-Yun ; Lin, Hui-Chen ; Henmi, Yasuhisa ; Mather, Peter ; Hughes, Jane ; Tsuchiya, Makoto ; Imai, Hideyuki
出版情報: Crustacean Research.  49  pp.141-153,  2020-09-03.  Carcinological Society of Japan — 日本甲殻類学会
URL: http://hdl.handle.net/20.500.12000/46908
概要: The fiddler crab, Austruca lactea inhabits tidal flat areas and is widely distributed across Japan, the Korean Peninsula , China, Taiwan and northern Vietnam. Fiddler crab habitat is being lost rapidly due to human impacts and this species is currently listed as endangered in Japan. We studied the population genetic structure of A. lactea using mitochondrial DNA control region markers to define management units. A. lactea individuals were sampled from Osaka, Hiroshima and Kumamoto in Japan, and from Taichung and the Penghu Islands in Taiwan. All local samples exhibited high levels of genetic diversity, and no sampled populations showed evidence for a significant decline in effective population size that can result from population bottleneck effects. Pairwise FST estimates distinguished three discrete A. lactea populations corresponding with, the Seto Inland Sea (Osaka and Hiroshima), Kyushu (Kumamoto) and Taiwan. The three populations showed clear differences in historical population expansion times and their population dynamics after expansion. Results of the study indicate that A. lactea dispersal is limited geographically and that high levels of genetic diversity are maintained both within and among populations.
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6.

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畑中, ひらり ; 今井, 秀行 ; Hatanaka, Hirari ; Imai, Hideyuki
出版情報: 日本生物地理学会会報 — Bulletin of the Bio-geographical Society of Japan.  pp.60-69,  2018-12-20.  日本生物地理学会 — The Biogeographical Society of Japan
URL: http://hdl.handle.net/20.500.12000/43516
概要: This study included 508 individuals of Oryzias latipes from 15 sites in mainland Japan and 10 sites in the Ryukyu Archip elago and Taiwan used in Imai et al. (2017), and new samples from four sites in the Ryukyu Archipelago, four sites in China and South Korea, and one from hi-medaka. We developed four new PCR-RFLP nuclear DNA markers (Orla16- 185-MboI, Orla1-29-BstUI, Orla1-51-AluI, and P0Ex-HinfI) based on three universal microsatellite primer sets and an exon-primed intron-crossing (EPIC) primer set for fish. STRUCTURE analysis indicated that Amami-oshima, Iheya, Izena, Ginama, Ogimi, and Bios no Oka formed a cluster, while specimens from Fukuchi, the former Kadena Ammunition Storage area, Zamani, and other Okinawa Islands formed a different cluster. The genetic diversity of subpopulations from Fukuchi, the former Kadena Ammunition Storage area, and Zamani was higher than those from other Okinawa Islands. The individual exclusion test (>90% condition) was applied to the Okinawa Islands subpopulation using GeneClass2. It will be important to apply these genetic markers for periodical genetic monitoring of this subpopulation.
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7.

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Fuke, Yusuke ; Imai, Hideyuki ; 福家, 悠介 ; 今井, 秀行
出版情報: Fauna Ryukyuana.  44  pp.7-15,  2018-07-31.  Ryukyu University Museum, Fujukan — 琉球大学資料館 (風樹館)
URL: http://hdl.handle.net/20.500.12000/42406
概要: This paper reports the finding of one of the Palaemonidae freshwater prawns, Macrobrachium ustulatum, on Okinawa-jima Is land, Ryukyu Archipelago, Japan. This represents the first record of this species in this country and also the northernmost distributional record of the species. Macrobrachium ustulatum redescribed by Castelin et al. (2017) is a cryptic species of M. australe. However, there was uncertainty in the assignation of two nomina to Castelin’s et al. (2017) molecularly identified two species. Moreover, among females, it is difficult to recognize clear morphological differences between M. ustulatum and M. australe. Therefore, we examine their validity of the taxonomic identification based on DNA sequences using the mitochondrial 16S rRNA gene and the nuclear 28S rDNA gene as well as morphological analyses. Consequently, these results supported the identification of the previous study.
琉球列島沖縄島北部の河川から得られたテナガエビ科のMacrobrachium ustulatumの標本を記録した. これは本種の日本初記録であると同時に, 分布の北限記録となる. 本種は長らくザラテテナガエビM. australeの新参異名とされてきたが, Castelin et al. (2017) により独立種として再記載された. しかし, 分子系統解析によって認識された2種への名義の割り当ての妥当性には不明確な部分があった. そこで本報告では, 両種について形態形質とミトコンドリアDNAの16S rRNAと核DNAの28S rDNA領域を用いた相同性検索を併用することで, 先行研究で行われた分類の妥当性を検証した. その結果, 先行研究の結果を支持する証拠が得られ, それに従って両種の同定を行った. 併せて, Macrobrachium ustulatumの標準和名としてナンヨウテナガエビを提唱し, その基準標本にRUMF-ZC-4626を指定した. Macrobrachium australeの標準和名は従来通りザラテテナガエビとし, 和名の基準標本にRUMF-ZC-4645を指定した.
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8.

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論文(リポジトリ)
Abdullah, Muhamad Fadry ; Cheng, Jin-Hua ; Chen, Tzyy-Ing ; Imai, Hideyuki
出版情報: Biogeography : international journal of biogeography, phylogeny, taxonomy, ecology, biodiversity, evolution, and conservation biology.  pp.61-68,  2017-09-20.  Biogeographical Society of Japan — 日本生物地理学会
URL: http://hdl.handle.net/20.500.12000/37545
概要: Ten novel di- and tri-nucleotide polymorphic microsatellite loci were identified to aid in genetic\nstructure analysis o f the widely distributed pronghorn spiny lobster, Panulirus penicillatus. Genetic variation among populations was explored, and we compared our results to those of a previous mitochondrial DNA (mtDNA) analysis (Abdullah et al. 2014) conducted in the northwestern Pacific Ocean. A total of 129 P. penicillatus individuals were collected from three localities in Japan (Hachijojima Island, Okinawajima Island and Ishigakijima Island) and one in Taiwan (Taitung). F-statistical analysis revealed no significant genetic differences\namong animals collected at the different localities, in agreement with data from the previous mtDNA study. The combined data suggest that high-level gene flow exists among the explored localities, probably caused by the extended planktonic larval stage and the prevailing Kuroshio Current. On the scale of the northwestern Pacific, the results obtained in both studies suggest that P. penicillatus forms a single unique panmictic population, or at least that the several breeding grounds exchange significant amounts of genetic material.
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9.

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論文(リポジトリ)
Fukuchi, Jun ; Hanamura, Yukio ; Imai, Hideyuki
出版情報: Biogeography : international journal of biogeography, phylogeny, taxonomy, ecology, biodiversity, evolution, and conservation biology.  19  pp.31-34,  2017-09-20.  Biogeographical Society of Japan — 日本生物地理学会
URL: http://hdl.handle.net/20.500.12000/37548
概要: The occurrence of the shallow-water sergestid shrimp Acetes sibogae sibogae Hansen, 1919\n(Crustacea, Decapoda, Sergesti dae) in Japan has been confirmed. This is the first record of this species and\nreflects a notable northward range expansion to Okinawa-jima Island, Ryukyu Archipelago, Japan.
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10.

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今井, 秀行 ; 米沢, 俊彦 ; 立原, 一憲 ; Imai, Hideyuki ; Yonezawa, Toshihiko ; Tachihara, Katsunori
出版情報: 日本生物地理学会会報 — Bulletin of the Bio-geographical Society of Japan.  71  pp.121-129,  2017-01-20.  日本生物地理学会 — The Biogeographical Society of Japan
URL: http://hdl.handle.net/20.500.12000/37568
概要: The current study examined the distribution of minami-medaka (Oryzias latipes) across the Ryukyu Archipelago in Japan to assess if the Ryukyu subpopulation as described by Sakaizumi et al. (1983) may be significantly divergent. Between 2003 and 2010, O. latipes were sampled from across Japan and populations compared using two genetic markers, an allozyme locus (aspartate aminotransferase; Aat) originally screened by Sakaizumi et al. (1983) and a new PCR-RFLP mtDNA marker based on the ND1 region. Laboratory trials showed that the Ryukyu subpopulation of O. latipes crossed with the Eastern subpopulation produced viable hybrids possessing both alleles Aatb and Aatc confirming that this marker will be effective for distinguishing natural hybrids between the Ryukyu subpopulation and other subpopulations. Populations distributed from the Amamioshima Islands to the Okinawa Islands all conformed to Ryukyu subpopulation genotypes and were fixed for allele Aatc. In addition, Okinawa islands populations were discriminated for the first time successfully from other subpopulations based on haplotype 5 (PCR-RFLP marker). A population at Chinen on Okinawajima Island possessed different genotypes to other Ryukyu subpopulations suggesting that it may have resulted from an introduction from a non-native source. Genetic introgression from other non-native subpopulations of O. latipes is the first case found in the Ryukyu Archipelago. It will be important in the future therefore, to apply the genetic markers used here to periodically monitor the Ryukyu subpopulation to conserve unique regional genetic diversity.
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