Amami Islands Research Articles

Threats to cycad biocultural heritage in the Amami Islands, Japan

AbstractThis article details the significance of Cycas revoluta in the cultural ecology of the Amami Islands, Japan. Although this plant was never domesticated, multiple lines of evidence elucidate a long history of its alimentary, ethnoecological, and symbolic saliency within Amami culture. Despite this fact, Amami cycad culture remains understudied and virtually unknown outside of Japan. This article summarizes previous and current research on the social roles and environmental significance of C. revoluta in the Amami Islands, with a specific focus on current threats to these plants and the cultural ecologies that surround them, including the ongoing biological invasion by the cycad aulacaspis scale. In doing so, the article seeks to highlight a unique form of biocultural heritage and ancestral cultural traditions that are in danger of being lost. It concludes with brief observations on potential avenues for future research that can both foment interest in and promote the holistic conservation of Amami cycad culture.

New species Pythium amaminum sp. nov. isolated from river water on Amami Island in Japan.

Pythium amaminum sp. nov. was isolated from river and reservoir water on Amami island, Kagoshima Prefecture, Japan. The species can grow at temperatures between 10 °C and 35 °C. At the optimum temperature of 25 °C, the radial growth rate is 22.5 mm per day. Pythium amaminum produces filamentous sporangia consisting of branched, lobulate or digitate elements forming large complexes. Zoospores form inside the vesicle, which is discharged through a long tube at least 320 μm. Globose oogonia are ornamented with conical blunt spines. Oospores are aplerotic and globose. Antheridia twine around the oogonia or stick to them. These features having a both of the long discharge tube from sporangium and oogonia with spines are not observed in any other species of the genus Pythium, and thus we conclude that P. amaminum is a new Pythium species.

Infection Control Improvement and Regional Cooperation in Amami Islands

Infection Control Improvement and Regional Cooperation in Amami Islands

Universal Method for Determination of Ciguatoxins by LC-MS/MS

Ciguatera poisoning (CP) is one of the most frequent seafood poisonings across the globe. CP results from the consumption of fish flesh that has accumulated principal toxins known as ciguatoxins (CTXs), and it mainly occurs in tropical and subtropical regions. In Japan, incidents of CP have been reported primarily from Okinawa and Amami Islands in the subtropical area. Meanwhile, there have also been reports from Mainland sporadically. Since the amount of CTXs contained in fish flesh is extremely low, a highly sensitive detection method by LC-MS/MS is required. But the currently reported detection method is applicable only to specific equipment, and many laboratories have difficulty to respond CP. In this study, to prepare for the risk of nationwide CP, we researched a universal analytical method for CTXs based on LC-MS/MS. Using a water/acetonitrile mobile phase supplemented with lithium hydroxide and formic acid gave rise to prominent peaks of the stable [M+Li]+ions. As the [M+Li]+ions did not produce valid product ions even with high collision energy, the [M+Li]+ions of each analog were set for both precursor and product ions ([M+Li]+>[M+Li]+) and monitored under the multiple reaction monitoring (MRM) mode. With the method described above, analyses of nine CTX congeners were carried out. The limit of detection (LOD, S/N>5) and quantitation (LOQ, S/N>10) were estimated as 0.005-0.030 ng/mL and 0.010-0.061 ng/mL, respectively. When the 1 mL of extract solution is prepared from 5 g of the fish tissue, the LOD and LOQ will be at 0.001-0.006 μg/kg and 0.002-0.012 μg/kg, respectively. This result indicates that we could detect the required level of 0.175 μg/kg CTX1B equivalent in fish flesh which is recommended for safe consumption in Japan. This method is considered to be a universal analytical method without depending on the specific equipment. Thus it could contribute to improving the CP investigations in nationwide laboratories.

Retrospective Study to Reduce Blood Transfusion Waste in Remote Island Healthcare Settings.

Tokunoshima is a remote island in the Amami Islands, 470 km southwest of the Kagoshima mainland. It has a population of 23,000 and consists of three towns: Tokunoshima, Isen, and Amagi. Three medical institutions on the island are responsible for blood transfusion medicine, but there is no blood stockpiling station on the island, and blood is stockpiled in each of the hospitals. Although Tokunoshima Tokushukai Hospital is responsible for 70% of transfusion medicine on Tokunoshima, it is difficult to maintain a sufficient amount of blood in stock considering disposal. To determine whether changing the distribution of blood types in a hospital's stockpile would reduce the transfusion disposal rate. This was a retrospective survey. By changing the in-house stock of blood products for transfusions delivered to our hospital over 10 years from January 2013 to December 2017 (preintervention) and from January 2018 to December 2022 (postintervention), we compared the cost-saving effects of these two intervention strategies on disposal rates and blood inventories, as well as the survival rates of case profiles requiring transfusion interventions in hospital-donated transfusion and ABO-incompatible transfusion between two periods. The hospital's stock of RBC had changes that storage of type (A, B, O, AB) RBC from (4, 4, 4, 2) units in the pre-interventon to (2, 2, 6, 0) units in the postintervention. The annual blood product waste rate decreased from 23.4% in the preintervention period to 17.9% in the post-intervention period. By changing the blood products stockpiled for transfusion medicine in Tokunoshima, the transfusion disposal rate can be reduced.

Association between brown sugar intake and decreased risk of cancer in the Amami islands region, Japan.

Although excess white sugar intake imposes various health burdens, brown sugar is high in minerals, polyphenols, and polycosanol. However, few epidemiological studies have assessed brown sugar intake for health benefit. People in the Amami islands region, with a relatively high proportion of individuals with longevity, consume brown sugar as a type of refreshment. This cohort study was conducted in Amami to clarify the association of brown sugar intake with mortality risk and cancer incidence. Participants were recruited from the general population of Amami as part of the Japan Multi-Institutional Collaborative Cohort Study. The number of eligible participants was 5004 (2057 men and 2947 women). During the median follow-up period of 13.4 years, 274 deaths and 338 cases of cancer were observed. HRs and 95% CIs were estimated using the Cox proportional hazard model, after adjusting for sugar-related and other variables. After adjusting for their related confounding factors, brown sugar intake was associated with decreased HRs and a decreasing trend for all-site and stomach cancer incidence (p = 0.001 and 0.017, respectively) in women and men, and for breast cancer incidence (p = 0.034) in women. Additionally, a decreasing trend in the HRs for lung cancer incidence was observed among never and ex-smokers (p = 0.039). Decreased HRs for overall death, cancer, and cardiovascular disease were not apparent. Brown sugar intake was associated with decreased risk of all-site, stomach, and breast cancer incidences in the Amami population.

Extraction of acoustic features of calls of five Platypleura species using the field recordings

Five Platypleura species are distributed in the south of Amami Island in Japan. At particular, P. albivannata, and P. yayeyamana are distributed at the same area in Ishigaki island. The survey of P. albivannata, which is endangered species, is important problems for conservation. Although it is necessary to discriminate between these species, it is difficult to discriminate between them from the morphology, that is, visual information. It is necessary to discriminate with these species by using another cue. In this presentation, we proposed the analysis methods to extract acoustic features dependent on Platypleura species to the south of Amami Island in Japan. We primarily aimed to examine whether these classifications correspond to the resemblance in the time and frequency domain of calling songs. Furthermore, we tried to extract characteristics that can be used for species identification in monitoring endangered species, P. albivannata. We found that maximum peak frequencies are feasible for species identification, especially for the detection of P. albivannata in the wild.

A new species of Arthromelodes Jeannel from Okinawa-jima, Japan (Coleoptera, Staphylinidae, Pselaphinae).

To date, twenty species and subspecies of Arthromelodes Jeannel were known to occur in Japan, distributed in Honsh, Kysh, Shikoku, Yakushima, and Amami Islands. No species have been recorded from central or southwestern Ryky. Arthromelodes tokushigei sp. n., the first species known to inhabit Okinawa Island of the central Ryky is described. This wingless species seems to be restricted to the northern Yambaru forest of Okinawa. In order to facilitate future studies on Arthromelodes and related, poorly-defined genera of Batrisini, detailed morphological documentation of the new species is provided.

Survival of young planted mangroves in a calm bay environment during a tropical cyclone

The efforts of mangrove plantations are not always successful, and the reasons for their failure remain unclear. In this study, the growth of planted mangroves (Kandelia sp.) was monitored in a mangrove forest on Amami Island, Japan, to investigate their survival over the first three years. A strong typhoon passed near the island 16 months after planting. Although the mangroves were planted at the frontal edge of the intertidal zone, most of young mangroves survived without visible damage. The external forces acting on the plants, such as wave forces, storm surge forces, wind drag forces, and oscillatory acceleration, were estimated by applying an integrated analysis model for tropical cyclones, storm surges, wind waves, and plant kinematics. These analyses yielded three main results. First, although large waves over 10 m in height were generated offshore, the mangrove forest was located in the innermost part of the bay, resulting in considerable wave attenuation. Second, the wave period in the bay was much shorter than that in the open ocean, which may have promoted resonance between waves and mangrove plants. The oscillatory acceleration of the young mangroves was estimated to have approximately the same magnitude as that of the gravitational force. Third, the young mangroves could withstand a fairly strong typhoon, but this may have been fortuitous because the timing of the adverse wind wave conditions coincided with low tide. It is estimated that if the tides had been higher, the oscillatory acceleration would have been five times that of the gravitational acceleration. Although this study only presents examples of specific mangrove species in a particular location, the findings can be used to improve the attempts to restore mangrove forests and thereby protect coastal settlements from the adverse effects of tropical cyclones.

First Japanese Records of the Indo-Pacific Scorpionfish (Scorpaenidae) <i>Scorpaenodes corallinus</i>, with a Re-evaluation of Coronal Spines as a Diagnostic Character

Fifteen specimens (70.9–95.5 mm standard length) of the Indo-Pacific species Scorpaenodes corallinus Smith, 1957, previously recorded from Mozambique, Tanzania, Kenya, the Seychelles, Indonesia, Australia, the Hawaiian Islands, New Caledonia and French Polynesia, and recently collected from Okinawa Island (Okinawa Islands) and Yoron Island (Amami Islands), represent the first Japanese records of the species. Examination of a wide range of specimens indicated that the presence of coronal spines (formerly considered diagnostic of the species) was inconsistent. The new standard Japanese name “Ichigo-isokasago” is proposed for the species.

Relationship between Regional Distribution of Centenarians and Drinking Water Hardness in the Amami Islands, Kagoshima Prefecture, Japan.

People who drink naturally hardened water may experience longevity-enhancing effects. In this study, we investigated water hardness and longevity from both geological and epidemiological perspectives in Japan's Amami islands, where drinking water is drawn from coralline or non-coralline bedrock. We investigated drinking water hardness, limestone bedrock occupancy, and the centenarian rate (number per 10,000 population) by municipality across four adjacent islands (Amami-Oshima (non-coralline), Tokunoshima, Okinoerabu, and Yoron (predominantly coralline)). Limestone was strongly correlated with water hardness (r = 0.99; p < 0.01), occupying more than 80% of the bedrock where the water was the hardest (Tokunoshima's Isen municipality: 86.5%; Yoron: 82.9%) and being scarcely detectable in Amami-Oshima (0.0 to 0.2%), where the water was the least hard. The centenarian rate was also strongly correlated with water hardness (r = 0.84, p < 0.01), with the highest figures in Yoron (29.7) and Isen (29.2), and the lowest in Amami-Oshima (0.0 to 12.2). Therefore, we hypothesize a potentially beneficial effect of hard water on longevity when that water is drawn from coralline limestone. Water hardness is determined by the water content of calcium and magnesium and may plausibly influence life expectancy through a preventative effect against cardiovascular disease. Our findings are of interest to current debates about future global access to drinking water and its quality.

Analytical Studies on Ciguateric Fish in Okinawa, Japan (II): The Grouper Variola albimarginata

Ciguatera fish poisoning (CFP) refers to an illness caused by ingesting fish that have accumulated ciguatoxins (CTXs). CFP frequently occurs in the tropical and subtropical Indo-Pacific Ocean and the Caribbean Sea. In Japan, CFP occurs sporadically but constantly in Okinawa and the Amami Islands. The grouper Variola albimarginata is regarded to be safe for consumption. To assess the real risk of V. albimarginata, we analyzed 133 specimens of the fish in Okinawa using liquid chromatography–tandem mass spectrometry (LC–MS/MS). Ciguatoxin-1B, 54-deoxyciguatoxin-1B, and 52-epi-54-deoxyciguatoxin-1B were detected in 28 specimens (21%). In 11 of these specimens (8%), the CTX levels exceeded the US FDA guidance level (0.01 µg/kg CTX1B equivalent). However, only one fish (&lt;1%) was found to have levels above the recommended level in Japan (0.175 μg/kg CTX1B equivalent). The amount of CTXs in the flesh (280 g) of the most toxic specimen (0.225 μg/kg) did not reach the level needed to cause illness. The CFP risk due to the consumption of this species was thus considered to be low in Okinawa, supporting local belief. The CTX levels in the flesh were positively correlated with standard length, body weight, and age. The total CTX levels significantly fluctuated between the male and the female of the species. The estimated annual catch of V. albimarginata in Okinawa and Yaeyama Islands was 4909 kg or 13,636 fish. As many as 1227 fish had levels over the US FDA guidance level, but only 136 fish had levels above the Japanese recommendation. Risk management based on the Japanese recommendation level seems to be effective in protecting public health and enabling appropriate exploitation of fishery resources.

High plant diversity and characteristic plant community structure in broad‐leaved evergreen forests on Amami‐Oshima and Tokunoshima Islands, Japan's newest natural World Heritage Site

AbstractAmami‐Oshima and Tokunoshima Islands (the Amami Islands) are part of an important area for biogeography in Japan. Although the uniqueness of the islands' flora is well recognized, their plant diversity, including non‐tree life forms, has yet to be compared with that of other regions. Here, we characterize the plant community structure of the Amami Islands, and analyze the α and β diversity patterns with respect to environmental factors as well as the frequency of threatened and endemic species compared with that in regions at higher and lower latitudes. We used 5 × 100 m plots at seven sites on the Amami Islands, three sites further north, and one site further south to record the abundance of all vascular plant species and tree sizes. We also used tree census data from five plots from the Monitoring Sites 1000 Project. Three principal components from five environmental variables were used as factors affecting diversity. We found that the broad‐leaved evergreen forests on the Amami Islands have higher α diversity resulting from species richness anomalies in shared families among regions. Additionally, generalized linear mixed models indicated that temperature and altitude affect α diversity positively. Furthermore, multiple regression models on distance matrices showed that temperature and regional differences in weather conditions affect β diversity. Tree species were found to affect species diversity and rareness, but herbaceous plants also affect these parameters substantially. These results indicate that the two studied islands are biodiversity hotspots and that evaluating herbaceous species is important for determining forest biodiversity.

日本沿岸産イシガキダイのシガトキシン分析

Ciguatera fish poisoning (CFP) is recognized as the most frequent seafood poisoning due to the consumption of fish containing the principal toxins, ciguatoxins (CTXs). In Japan, CFP events have been reported annually from Okinawa and Amami Islands, locating subtropical regions. In addition, there have been reported several outbreaks due to consumption of the fish caught from the Pacific coast of the Mainland and they were often caused by the matured spotted knifejaw, Oplegnathus punctatus. As part of our research on CFP in Japan, we investigated CTXs analysis by LC-MS/MS on 176 individuals of O. punctatus (weight: 100-6,350 g, standard length: 13-60 cm) from the coast of the Mainland (Honshu, Shikoku, and Kyushu), Amami, Okinawa, and Ogasawara (Bonin) Islands. CTXs were detected from only two specimens collected from Okinawa. Total CTXs levels of the two specimens were at 0.014 and 0.040 μg/kg, respectively, exceeding FDA guidance level at 0.01 μg CTX1B equivalent/kg. However, they might be little risk of CFP because consuming over 1.5 kg of flesh is needed to develop intoxication. The toxins consisted of CTX1B analogs including CTX1B, 52-epi-54-deoxyCTX1B, CTX4A, and CTX4B, and no CTX3C analogs, supporting the finding that ciguatoxic fishes in Okinawan Waters containing only CTX1B analogs.

Morphological and taxonomic reexamination on a crocodile newt recently described from Japan (Urodela, Salamandridae, Echinotriton)

A crocodile newt, Echinotriton raffaellii, recently described from the Amami islands in the Ryukyu archipelago, western Japan has been regarded as Amami lineage of E. andersoni from the Okinawa islands, to which it is morphologically very similar, but genetically divergent. In the original description of E. raffaellii, only two specimens, including one born in captivity, were examined and only limited morphological comparisons with E. andersoni were made. Here we examined the morphological characteristics of E. raffaellii with an ample set of specimens, compared them with those of E. andersoni, and clarified their independent specific statuses.

Priority coral conservation areas under global warming in the Amami Islands, Southern Japan

Priority coral conservation areas under global warming in the Amami Islands, Southern Japan

Amami / Okinawa World Natural Heritage as seen from the promotion of tourism in the Amami Islands

Amami / Okinawa World Natural Heritage as seen from the promotion of tourism in the Amami Islands

Floral and pollination biology of the critically endangered insular orchid Calanthe amamiana: Implications for in situ conservation

AbstractCalanthe amamiana is a terrestrial orchid that thrives on the shady forest floors of broad‐leaved forests on Amami Island, central Ryukyus, Japan. Here, I report on the floral and pollination biology of this critically endangered orchid based on a 7‐year study conducted in the species' natural habitats. As the nectarless flowers are probably self‐compatible but are unable to autonomously self‐pollinate, they need to attract pollen vectors by deceit for pollination. To advertise themselves, the flowering inflorescences, which comprise a few to dozens of flowers, use whitish floral colors that are comparatively conspicuous against the shaded background. The exclusive pollinator was the long‐horned bee Eucera okinawae, which nests in soils of the forest floor, although bee abundance varied considerably among study years. Natural fruit‐set ratios were generally low but showed interannual variation. The annual fruit‐set ratios were positively correlated with annual bee abundance, thereby suggesting that under natural conditions, the orchid is pollinator‐limited. Given that C. amamiana is dependent exclusively on E. okinawae for pollination and is also probably pollinator‐limited, conservation plans for this orchid should take into consideration the welfare of long‐horned bees. In particular, as nectariferous flowers were unavailable within broad‐leaved forests, to satisfy the foraging requirements of long‐horned bees, conservation managers should be cognizant of conservation values of flowering plants distributed in sun‐lit sites near orchid habitats, and manage those in an appropriate manner.

Two hidden taxa in the Japanese encephalitis vector mosquito, Culex tritaeniorhynchus, and the potential for long-distance migration from overseas to Japan.

The Culex vishnui subgroups, particularly Culex tritaeniorhynchus, are considered the primary vectors of the Japanese encephalitis virus (JEV) in Asia. Recent molecular phylogenetic analyses of JEV isolates from Asian countries have shown that JEVs with diverse genetic variants are present in Asia. Furthermore, some JEV strains have been found to have crossed the East China Sea and been introduced into Japan. In this study, the possibility of overseas migration of the JE vector mosquito, Cx. tritaeniorhynchus was examined from the genetic, physical, and meteorological perspectives. Molecular phylogenetic analysis was performed based on both whole coding sequences and on the barcoding region of the mitochondrial cytochrome c oxidase subunit I (COI) gene of Cx. vishnui subgroups collected from Asian countries. Culex tritaeniorhymchus was classified into two genetically independent taxa by COI sequences: the Japanese type (Ct-J), which inhabits Japan except for the Amami Islands of southern Japan, and the continental type (Ct-C), which inhabits the Asian region except for Japan. It was confirmed that approximately 10% of Cx. tritaeniorhynchus trapped during the summer in western Kyushu were Ct-C, and that they could fly for up to 38 h continuously. The meteorological analysis also confirmed that the atmospheric flow occurring over the continent coincided with the date of Ct-C capture. This is the first report showing the existence of two taxa in Cx. tritaeniorhynchus. Their physical and physiological characteristics suggest the possibility of long-distance migration from overseas regions to Japan across the East China Sea. Future efforts are expected to provide evidence to support the occurrence of long-distance migration of Cx. tritaeniorhynchus with JEV.

Comparative mitogenomics elucidates the population genetic structure of Amblyomma testudinarium in Japan and a closely related Amblyomma species in Myanmar.

Ticks are the second most important vector capable of transmitting diseases affecting the health of both humans and animals. Amblyomma testudinarium Koch 1844 (Acari: Ixodidae), is a hard tick species having a wide geographic distribution in Asia. In this study, we analyzed the composition of A. testudinarium whole mitogenomes from various geographical regions in Japan and investigated the population structure, demographic patterns, and phylogeographic relationship with other ixodid species. In addition, we characterized a potentially novel tick species closely related to A. testudinarium from Myanmar. Phylogeographic inference and evolutionary dynamics based on the 15 mitochondrial coding genes supported that A. testudinarium population in Japan is resolved into a star‐like haplogroup and suggested a distinct population structure of A. testudinarium from Amami island in Kyushu region. Correlation analysis using Mantel test statistics showed that no significant correlation was observed between the genetic and geographic distances calculated between the A. testudinarium population from different localities in Japan. Finally, demographic analyses, including mismatch analysis and Tajima’s D test, suggested a possibility of recent population expansion occurred within Japanese haplogroup after a bottleneck event. Although A. testudinarium has been considered widespread and common in East and Southeast Asia, the current study suggested that potentially several cryptic Amblyomma spp. closely related to A. testudinarium are present in Asia.