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• Molecular ecology of the fiddler crab Austruca perplexa (H. Milne Edward 1852): genetic divergence along a major biogeographical barrier, Wallace’s Line

  Eko Hardianto, Diah Permata Wijayanti, Jhy-Yun Shy, Peter Mather, Jane Hughes, Hideyuki Imai

  Biological Journal of the Linnean Society ( The Linnean Society of London )  135   2022 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Patterns of genetic diversity and population structure in then fiddler crab, Austruca perplexa were assessed to develop a better understanding of this species’ evolutionary history. Nucleotide sequence analysis was performed from a PCR amplified fragment of mtDNA control region. A 691 bp nucleotide sequence was obtained from 618 specimens collected from thirteen sites across Japan, Taiwan, the Philippines, Indonesia, and Australia. Haplotype diversity ranged from 0.8 to 0.99, while nucleotide diversity values were lower (range: 0.30–1.9%) than those reported previously for other crustacean taxa. Gene flow was evident between populations in Japan and western Indonesia, while gene flow was absent between all other populations including eastern Indonesia. This pattern conforms to that in observed in many other marine taxa across the major biogeographical region referred to as, Wallacea. FST and FST P-values were high and significant among many sites inferring that gene flow is restricted among most of the geographical regions sampled here. We hypothesis that physical oceanic barriers coupled with a short pelagic larval stage duration is responsible for creating the patterns we report. Strong evidence for population structure in a species that has relatively high dispersal potential, that results in among population differentiation is a potential driver of evolutionary novelty. Results here provide a foundation for developing better conservation strategies for this widespread intertidal species in the future.

• Identification of fish species involved with ciguatera fish poisoning in Okinawan waters by using phylogenetic analysis

  OSHIRO AKIKO, SUMI TAKUTO, IMAI HIDEYUKI

  NIPPON SUISAN GAKKAISHI ( The Japanese Society of Fisheries Science )  88 ( 4 ) 271 - 283   2022.07 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  <p> Ciguatera fish poisoning (CFP), known as a seafood-borne illness, is caused by consumption of fish contaminated with ciguatoxins in tropical and subtropical seas. The ciguatera fishes <i>Variola louti</i>, <i>Lutjanus monostigma</i> and <i>Lutjanus bohar</i> have an absolute majority in the Ryukyu Archipelago, southwestern Japan. We obtained <i>V. louti</i>, <i>L. monostigma</i> and <i>L. bohar</i> and differentiated them from morphologically similar species (<i>Lutjanus fulviflamma</i>, <i>Lutjanus russellii</i>, <i>Lutjanus argentimaculatus</i>, <i>Plectropomus leopardus</i> and <i>Variola albimarginata</i>) from around Okinawajima Island and Okinawan Islands. We developed a cluster analysis of the molecular phylogenetic tree by using mitochondrial DNA 16S rDNA sequences of them and the bone and muscle of the fish that ciguatera patients had left on the plate. Molecular phylogenetic analysis showed that the method is useful for successfully identifying species without exception.</p>

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• Molecular ecology of a shallow water shrimp, <i>Acetes sibogae sibogae</i> Hansen 1919: evidence for strongly limited gene flow across the western Pacific

  Hardianto E, Fukuchi J, Hanamura Y, Wijayanti PD, Sabdono A, Imai H

  Marine Ecology   43   e12695   2022.04 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

• Analysis of human clinical and environmental Leptospira to elucidate the eco-epidemiology of leptospirosis in Yaeyama, subtropical Japan.

  Sato Y, Hermawan I, Kakita T, Okano S, Imai H, Nagai H, Kimura R, Yamashiro T, Kajita T, Toma C

  PLoS neglected tropical diseases ( PLoS Neglected Tropical Diseases )  16 ( 3 ) e0010234 - e0010234   2022.03 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Background Leptospirosis, a zoonosis caused by species in the spirochete genus Leptospira, is endemic to the Yaeyama region 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.

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• First record of the invasive alien species Neocardina spp from Okinawajima Island,central Ryukyus,Japan

  Hiroto Nagai, Hideyuki Imai

    76   51 - 57   2021.12 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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Grant-in-Aid for Scientific Research 【 display / non-display 】

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• Grant-in-Aid for Scientific Research(C)

  Project Year: 2017  -  2019 

  Direct: 0 (YEN)  Overheads: 3,600,000 (YEN)  Total: 0 (YEN)

• Grant-in-Aid for Scientific Research(B)

  Project Year: 2014  -  2017 

  Total: 650,000 (YEN)

• Grant-in-Aid for Young Scientists(B)

  Project Year: 2003  -  2004 

  Total: 3,900,000 (YEN)

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• 2018.08

  　

  　

• 2018.07

  　

  　

• 2018.04

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  2019.03

• 2016.07

  　

  　

• 2012.08

  　

  　

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