Amami Islands Research Articles

Notes on coastal driftages of Tokuhama beach, Kakeroma Island, Amami Islands, southwestern Japan

Notes on coastal driftages of Tokuhama beach, Kakeroma Island, Amami Islands, southwestern Japan

Understanding island residents’ anxiety about impacts caused by climate change using Best–Worst Scaling: a case study of Amami islands, Japan

Climate change poses significant risk to island communities; however, there has been limited quantitative investigation into local people’s perception toward the risk. This study applied Best–Worst Scaling (BWS) to understand residents’ anxieties about potential incidents caused by climate change in Amami islands, Japan. Through an interview with stakeholders, we selected five potential incidents for our BWS attributes: damage caused by typhoon and heavy rain (typhoon), damage caused by flood and a landslide (flood), damage from a drought (drought), damage from ciguatera fish poisoning (ciguatera), and incident caused by jellyfish (jellyfish). Changes in frequencies of the abovementioned incidents have already been observed in Japan. In 2016, we conducted a questionnaire survey of residents in Amami islands and received over 700 valid responses to BWS questions. Results showed that the average respondent was most anxious about the risk of typhoon, followed by flood, drought, ciguatera, and jellyfish. Furthermore, a comparative analysis did not find large variations among the islands in the residents’ anxiety ranking concerning the incidents, but the degrees of their anxieties were different. The Amami-Oshima residents, for example, had relatively higher anxieties about flood, whereas the Okinoerabujima residents showed higher anxiety about drought. These findings support that their risk perceptions are determined by their experience and surrounding environments. Understanding the sensitivity of residents to climate change risk will encourage stakeholders to communicate and enhance climate change adaptation in local communities.

Ritual Communication through Community Radio: A Case Study of FM Uken in the Amami Island

Ritual Communication through Community Radio: A Case Study of FM Uken in the Amami Island

A Study on Amami Islands Sugar Trading Monopoly Purchasing System Demolition Process: From the Viewpoint of Satsuma Rebellion

A Study on Amami Islands Sugar Trading Monopoly Purchasing System Demolition Process: From the Viewpoint of Satsuma Rebellion

Fossil and Archeological Records of the Ryukyu Long-Furred Rat Diplothrix legata (Rodentia, Muridae)

This study presents a compilation of fossil and archeological records of the Ryukyu long-furred rat Diplothrix legata, a murid rodent endemic to the central part of the Ryukyu Archipelago (Amami and Okinawa Islands) of Japan, in order to further understand the distributional history of this endangered species. Although the species is currently confined to restricted forest areas on three islands (Amamioshima, Tokunoshima, and Okinawajima), fossiles or archeological occurrences have been reported at several extralimital localities on these islands, as well as on three other islands (Okinoerabujima, Kumejima, and Miyagijima). The records from the small island of Miyagijima are most likely remains from animals artificially brought to the island. The southern part of Okinawajima is devoid of Holocene records of the species during and after the Gusuku Period (from the 11th to 15th centuries Current Era [CE]) except for a single case. The species' decline in this area has been attributed to human activity in the Gusuku Period.

P-293 - Analysis of oxidative stress marker, mitochondrial DNA copy numbers and mitochondrial DNA oxidation among 135 persons who live in Amami islands, a high centenarian population district in Kagoshima

In this study, the DNA array, quantitative PCR, 8-hydroxydeoxyguanosine (8OHdG detection), relative mtDNA copy number compared to the nuclear DNA, and mitochondrial mutation rate were analyzed using blood samples kindly donated by 135 persons, who live in Amami island district, highest centenarian rate (the number of centenarian in 100,000 people) in Japan. The results showed that three genes significantly decreased in over 90-aged population. The genes are, HSPD1, heat shock 60 kDa protein 1 (chaperonin), GADD45G, GADD45gamma, growth arrest and DNA-damage-inducible, and LTBP-3, latent transforming growth factor beta binding protein 3. The results of 8OHdG detection showed that gradually and significantly increase of 8OHdG as a function of the age. The detection copy number of mtDNA resulted in increase in the copy number dependent on the age. The mtDNA mutation resulted in no difference among the age. The results showed that the Amami population over 90 years old did not show substantial change in the copy number and the frequency of mutation in mtDNA, suggesting maintaining good health in Amami region.

Relationship between Dietary Habits and Plasma Homocysteine Concentrations in Elderly Japanese Women and Men

The plasma homocysteine concentration is a good indicator of various diseases such as cardiovascular disease, stroke, and dementia. This study examined the relationship between plasma homocysteine concentrations and dietary habits in a population of elderly Japanese people from the Amami Islands. Data from 1131 participants collected during a baseline survey for the Japan Multi-institutional Collaborative Cohort study, which is a prospective cohort study, were used. Information on dietary habits was collected using a food frequency questionnaire. The plasma homocysteine concentration was associated with age in women only. Smoking in men and menopause were significantly associated with homocysteine concentrations. Analysis of blood biochemical data showed that estimate of glomerular filtration rate negatively correlated with plasma homocysteine in women (R = ?0.91, p < 0.001) and men (R = ?0.49, p < 0.001). There was no common food associated with homocysteine concentrations among the groups, but in each group, some food types were associated with homocysteine concentrations. In men, Chinese tea was a common factor showing a negative correlation with homocysteine concentrations. Natto showed a negative correlation with homocysteine concentrations in non-smoking men (β = ?0.11, p < 0.05) and premenopausal women (β = ?0.20, p < 0.01). Eggs (β = ?0.21, p < 0.01) and food processed from fish eggs (β = ?0.21, p < 0.01) negatively correlated with homocysteine concentrations in smoking men. Miso soup (β = ?0.13, p < 0.01) and yoghurt (β = ?0.10, p < 0.05) negatively correlated with homocysteine concentrations in postmenopausal women. Consumption of folate-rich food did not necessarily correlate with a low plasma Hcy concentration.

Molluscs drifted on the coast of Amami-Oshima Island, Amami Islands, southwestern Japan

Molluscs drifted on the coast of Amami-Oshima Island, Amami Islands, southwestern Japan

Riding the Kuroshio Current: Stepping stone dispersal of the Okinawa tree lizard across the East Asian Island Arc

AbstractAimLocated hundreds of kilometres offshore of continental mainland Asia, the extremely high level of land vertebrate endemism in the East Asian Island Arc provides an excellent opportunity to test hypotheses regarding biogeographic processes and speciation. In this study, we aim to test alternative explanations for lineage diversification (vicariance versus dispersal models), and further develop a temporal framework for diversification in our focal taxon, which is consistent with the known age of these islands. We achieve these tests by investigating the historical biogeography of the Okinawa tree lizard (Japalura polygonata), one of the few widely‐distributed reptiles across this archipelago.LocationThe East Asian Island Arc: (1) Central Ryukyu (Amami and Okinawa groups); (2) Southern Ryukyu (Miyako and Yaeyama groups); (3) Taiwan and adjacent islands.MethodsA total of 246 tissues were sampled from 10 localities in the Ryukyu archipelago and 17 localities in Taiwan, covering the entire distributional range of this species, including all subspecies. DNA sequences of the mitochondrial cytochrome b, 16S ribosomal RNA, nuclear BACH‐1 and RAG‐1 genes (total: 4,684 bp) were obtained from these samples. We used maximum likelihood and Bayesian methods to infer phylogeny and divergence time, and used a model‐fitting method of biogeographical inference to estimate ancestral range evolution.ResultsMultiple lines of evidence combine to identify a general pattern of dispersal‐mediated diversification northward through the archipelago, following initial dispersal from Taiwan. These included (1) a phylogenetic estimate, revealing a sequential, south‐to‐north branching pattern; (2) ancestral range estimation, inferring multiple overseas dispersals and subsequent colonization of new landmasses; and (3) a reduction in genetic variation observed in successively‐diverging lineages, decreasing from Taiwan northward, towards more remote islands. These results provide strong statistical support for an interpretation of successive bouts of dispersal via the powerful, well‐documented, south‐to‐north Kuroshio Current. Estimation of divergence times suggests that most clades in southern Ryukyu and Taiwan diverged early, giving rise to lineages that have remained isolated, and that more recently‐diverged lineages then colonized northward to subsequently occupy the landmasses of the Central Ryukyu archipelago.Main conclusionsOur general inference of biogeographic history in Japalura polygonata suggested that this species originated on Taiwan and the Yaeyama group, and arrived at its current distribution in Miyako, Okinawa, Toku and Amami islands by a series of stepping‐stone dispersals, which we report for the first time for a terrestrial vertebrate endemic to this region.

A new large tellinid species of the genus Pharaonella from the Ryukyu Archipelago, Japan (Mollusca, Bivalvia).

A new tellinid species, Pharaonella amanyu sp. n., is described from sand banks around Amami Islands, the Ryukyu Archipelago, in southern Japan. A molecular phylogenetic analysis suggests that this new species is closely related to P. sieboldii. This species has long siphons and lives buried deep in well-sorted white sand syntopically with Tonganaella tongana. These rare, large tellinid species are indicators of unspoiled tidal/subtidal sand flats, which should receive the highest priority conservation in the Ryukyu Archipelago.

ポスト九学会連合の奄美調査の可能性(第十二部会, 第73回学術大会紀要)

ポスト九学会連合の奄美調査の可能性(第十二部会, 第73回学術大会紀要)

Interactions between inflammatory gene polymorphisms and HTLV-I infection for total death, incidence of cancer, and atherosclerosis-related diseases among the Japanese population.

BackgroundAn increased risk of total death owing to human T-lymphotropic virus type-I (HTLV-I) infection has been reported. However, its etiology and protective factors are unclear. Various studies reported fluctuations in immune-inflammatory status among HTLV-I carriers. We conducted a matched cohort study among the general population in an HTLV-I-endemic region of Japan to investigate the interaction between inflammatory gene polymorphisms and HTLV-I infection for total death, incidence of cancer, and atherosclerosis-related diseases.MethodWe selected 2180 sub-cohort subjects aged 35–69 years from the cohort population, after matching for age, sex, and region with HTLV-I seropositives. They were followed up for a maximum of 10 years. Inflammatory gene polymorphisms were selected from TNF-α, IL-10, and NF-κB1. A Cox proportional hazard model was used to estimate the hazard ratio (HR) and the interaction between gene polymorphisms and HTLV-I for risk of total death and incidence of cancer and atherosclerosis-related diseases.ResultsHTLV-I seropositivity rate was 6.4% in the cohort population. The interaction between TNF-α 1031T/C and HTLV-I for atherosclerosis-related disease incidence was statistically significant (p = 0.020). No significant interaction was observed between IL-10 819T/C or NF-κB1 94ATTG ins/del and HTLV-I. An increased HR for total death was observed in the Amami island region, after adjustment of various factors with gene polymorphisms (HR 3.03; 95% confidence interval, 1.18–7.77).ConclusionThe present study found the interaction between TNF-α 1031T/C and HTLV-I to be a risk factor for atherosclerosis-related disease. Further follow-up is warranted to investigate protective factors against developing diseases among susceptible HTLV-I carriers.

Duplex of metamorphic units including ultramafic rocks in the central region of Tokunoshima, Southwest Japan

AbstractGeological observations in the central part of Tokunoshima in the Amami Islands, Southwest Japan, reveal that discrete layers of serpentinite, dioritic gneiss, and amphibolite are intercalated into pelitic schist and these rock bodies form a northwest‐dipping tectonic stack. A subhorizontal psammitic schist layer overlies them. These rocks underwent ductile deformation that is denoted by penetrative foliation and mineral lineation. Microstructures of the sheared metamorphic rocks and serpentinite indicate top‐to‐the‐east, ‐southeast or ‐south (hanging‐wall up) displacements. The en echelon array of rock bodies is interpreted as a duplex with the psammitic schist layer on its top and the pelitic schist layer on its bottom. It is inferred that the serpentinite‐bearing duplex was formed due to the tectonic erosion and the subsequent accretionary growth operated in a Cretaceous or older subduction zone. Tokunoshima has been considered to belong to the Shimanto Belt. However, regional low‐pressure and high‐temperature type amphibolite‐facies metamorphism and related ductile deformation have not been recognized in the other areas of the Shimanto Belt. There is no metamorphic rock occurrence comparable to that of Tokunoshima in the neighboring islands. The metamorphic rocks in Tokunoshima can be correlated to any of low‐pressure/temperature type metamorphic regions in Kyushu.

Tight species cohesion among sympatric insular wild gingers (Asarum spp. Aristolochiaceae) on continental islands: Highly differentiated floral characteristics versus undifferentiated genotypes.

The Amami Island group of the Ryukyu Archipelago, Japan, harbors extensive species diversity of Asarum in a small landmass. The fine-scale population genetic structure and diversity of nine insular endemic Asarum species were examined using nuclear DNA microsatellite loci and ITS sequences. High population genetic diversity (HS = 0.45–0.79) was estimated based on the microsatellites, implying outcrossing of Asarum species within populations accompanied by inbreeding. Bayesian clustering analyses revealed that species were divided into three robust genetic clusters and that the species within each cluster had a homogeneous genetic structure, indicating incomplete lineage sorting. This conclusion was supported by an ITS phylogeny. The degree of genetic differentiation among species was very low both within and between clusters (FST = 0.096–0.193, and 0.096–0.266, respectively). Although species can be crossed artificially to produce fertile hybrids, our results indicate that there is very little evidence of hybridization or introgression occurring among species in the wild, even within stands composed of multiple sympatric species. The highly differentiated floral morphology of the studied species is likely to impose reproductive isolation between them and maintain their integrity in the wild. A lack of genetic differentiation between sympatric species suggests that speciation within this group occurred rapidly and recently.

Modulation of light localization in the iridophores of the deep-sea highlight hatchetfish Sternoptyx pseudobscura under magnetic field

Efficient light control by certain tissue in bioluminescent fish offers potential for new optical devices. In the world’s deep-seas, there are numerous fish species with such bioluminescence yet to be discovered. One such species, the deep-sea highlight hatchetfish Sternoptyx pseudobscura, which was found at depths of ca. 800–900 m in the neighboring waters off the Amami Islands, Japan, exhibits a new form of light-reflection produced in guanine crystal platelets present in the skin Strongly reflecting platelets in the dorsal and anterior-ventral region enhance its reflection in the presence of magnetic fields either in parallel or perpendicular to the incident light. A diamagnetic ordering of the platelet alignment is suggested in producing a small angular rotation of the platelets when placed in a magnetic field. The synchronized ordering of these platelets in parallel possibly modulates the localization of light in a multilayer structure inside the iridophore. The developed method should be useful for investigating the bio-ethological meaning of guanine crystal platelet arrangements in the deep sea fish reflecting light.

Fine‐scale demographic processes resulting from multiple overseas colonization events of the Japanese stream tree frog, Buergeria japonica

AbstractAimAmphibians are considered poor transoceanic dispersers because of their permeable skin. However, overseas dispersal of amphibian species has been revealed by recent phylogeographical studies and the role of overseas colonization of amphibians on their evolution and diversification has also been highlighted. However, no studies have investigated in detail the demographic processes related to these overseas colonization events. To clarify how amphibians achieve overseas colonization, we estimated the demographic history of the Japanese stream tree frog, Buergeria japonica, which is distributed on Amami Island and four northern neighbouring islands of the Tokara Archipelago, Japan.LocationSouth‐western islands of Japan and Taiwan.MethodsWe analysed the mitochondrial cytb gene and 20 microsatellite loci, and constructed phylogenetic trees based on these data. We also performed demographic analyses by applying approximate Bayesian computation (ABC) method and an isolation‐with‐migration model.ResultsPhylogenetic and demographic analyses based on cytb and 20 microsatellite genotype data revealed that divergence among island populations took place recently, mostly within the last few thousand years. Populations from the northern islands had reduced genetic diversity compared with southern islands, and ABC analyses supported the hypothesis that the species colonized islands from south to north.Main conclusionsGiven that the islands are separated from each other by deep sea, the recent divergences observed indicate overseas colonization events among the five islands. ABC analyses support the hypothesis that B. japonica underwent a stepping‐stone overseas colonization from southern to northern neighbouring islands during the past few thousand years accompanied by multiple founder effects. These results support the hypothesis that overseas colonization could have had a substantial impact on amphibian evolution and diversification.

Allopatric color forms of Scaphidium morimotoi Löbl, 1982 (Coleoptera, Staphylinidae, Scaphidiinae) endemic to the Amami Islands, the Ryukyus, Japan.

The shining fungus beetle, Scaphidium amamiense Hoshina & Morimoto, 1999 is synonymized with S. morimotoi Löbl, 1982, based on a review of morphological characters and molecular analysis. This species is endemic to the Amami Islands, the Ryukyus, Japan. An almost completely melanic form (morimotoi in strict) is known only on the island Yoro-shima, where the ordinary form with reddish fasciae on the elytra (previously called amamiense) is absent. The present study suggests that the melanic form on the small island has been fixed by random genetic drift.

Unexpectedly complex gradation of coral population structure in the Nansei Islands, Japan.

To establish effective locations and sizes of potential protected areas for reef ecosystems, detailed information about source and sink relationships between populations is critical, especially in archipelagic regions. Therefore, we assessed population structure and genetic diversity of Acropora tenuis, one of the dominant stony coral species in the Pacific, using 13 microsatellite markers to investigate 298 colonies from 15 locations across the Nansei Islands in southwestern Japan. Genetic diversity was not significant among sampling locations, even in possibly peripheral locations. In addition, our results showed that there are at least two populations of A. tenuis in the study area. The level of genetic differentiation between these populations was relatively low, but significant between many pairs of sampling locations. Directions of gene flow, which were estimated using a coalescence‐based approach, suggest that gene flow not only occurs from south to north, but also from north to south in various locations. Consequently, the Yaeyama Islands and the Amami Islands are potential northern and southern sources of corals. On the other hand, the Miyako Islands and west central Okinawa Island are potential sink populations. The Kerama Islands and the vicinity of Taketomi Island are potential contact points of genetic subdivision of coral populations in the Nansei Islands. We found that genetic population structure of A. tenuis in the Nansei Islands is more complex than previously thought. These cryptic populations are very important for preserving genetic diversity and should be maintained.

Ecotourism and World Natural Heritage: Its influence on islands in Japan

Abstract The article discusses the influence of World Natural Heritage registration on ecotourism by looking at the cases of Yakushima as the first World Natural Heritage site and Ogasawara as an advanced region of ecotourism in Japan, and also the Amami Islands and Iriomote Islands where various efforts have been taken toward the registration of World Natural Heritage.

The taxonomic position and the unexpected divergence of the Habu viper, Protobothrops among Japanese subtropical islands

There are four Habu species currently recognized in Japan: Protobothrops flavoviridis from the Amami Islands and the Okinawa Islands, P. tokarensis from the Tokara Islands, P. elegans from the Yaeyama Islands and Ovophis okinabvensis from the Amami Islands and the Okinawa Islands. To clarify their taxonomic positions, we determined the complete mitochondria genome sequence (approx. 17kb) from two specimens from two different islands each for P. flavoviridis, P. tokarensis and P. elegans as well as one specimen of O. okinavensis and reconstructed the molecular phylogeny of Protobothrops using the published sequences of related species. The maximum likelihood tree showed four major species groups within Protbothrops: Group I consisting of P. cornutus, P. dabieshanensis, P. jerdonii and P. xiangchengensis; Group II consisting of P. flavoviridis and P. tokarensis; Group III consisting of P. maolensis, P. mucrosquamatus and P. elegans; Group IV consisting of P. himalayanus and P. kaubacki. Since we observed an unexpected divergence and the paraphyly of the two samples of P. flavoviridis collected from different islands, Amami-Oshima and Okinawajima within the Group II, we expanded the analysis by increasing the number of P. flavoviridis and P. tokarensis collected from 10 islands: Amami-Oshima (5 specimens), Kakeromajima (4) and Tokunoshima (4) from the Amami Islands, Okinawajima (4), Iheyajima (4), Iejima (4), Tokashikijima (4) and Kumejima (4) from the Okinawa Islands, Kodakarajima (P. tokarensis) (4) and Takarajima (P. tokarensis) (4) from the Tokara Islands. The maximum likelihood tree of the 44 samples replicated the significant divergence of P. flavoviridis between the Amami Clade including Amami-Oshima, Kakeromajima and Tokunoshima and the Okinawa Clade including Okinawajima, Iheyajima, Iejima, Tokashikijima and Kumejima. The Amami Clade also include all specimens from the Tokara Islands currently known as an independent species, P. tokarensis, suggesting the paraphyly of the taxon, P. flavoviridis. In contrast, we observed a distinct lineage of the two specimens from the Yaeyama Islands, supporting the validity of the taxon, P. elegans as an independent species. By MCMC method, we estimated the divergence time between the Amami Clade and the Okinawa Clade to be 6.51MYA, suggesting that the vicariance of the two clades preceded the geological separation of the Amami Islands and the Okinawa Islands (∼1.5MYA). As expected from the limited mobility of terrestrial reptiles including snakes, we observed high genetic divergence in Habu mtDNA among Japanese subtropical island populations.