Publications
A first case of Hepatozoon infection in a wild Amami rabbit (Pentalagus furnessi) in Tokunoshima Island, Japan
Researchers have documented the first confirmed Hepatozoon infection in an endangered Amami rabbit (Pentalagus furnessi) from Tokunoshima Island, Japan. The discovery, made through necropsy and histopathological examination, revealed meronts—asexual reproductive stages—in the rabbit's lung, heart, and skeletal muscle tissues, with no associated inflammatory response. Transmission electron microscopy confirmed these intracellular structures at various developmental stages. Molecular and phylogenetic analyses identified the protozoan as Hepatozoon sp., closely related to Hepatozoon felis. The presence of asexual stages suggests that Amami rabbits may serve as intermediate hosts rather than paratenic hosts in the parasite's life cycle. This finding underscores the need for further study into the ecology, transmission dynamics, and conservation implications of protozoan infections in endangered wildlife.
Case Report: Neurological and pulmonary angiostrongylosis in a Ryukyu long-furred rat (Diplothrix legata) on Amami-Oshima Island, Japan
A Ryukyu long-furred rat (Diplothrix legata) on Amami-Oshima Island, Japan, exhibited neurological and pulmonary symptoms of angiostrongylosis caused by Angiostrongylus cantonensis. The case highlights the potential for this endangered rodent to manifest both neurological and respiratory disease manifestations due to infection with the ac1 lineage of A. cantonensis, distinct from lineages found on nearby islands. Gross and histopathological examinations revealed nematodes in the brain, lungs, and heart, accompanied by severe inflammation, hemorrhage, edema, thrombosis, necrosis, and concurrent Aspergillus infection. This finding underscores the need for further epidemiological studies to clarify transmission dynamics involving invasive rodents, terrestrial gastropods, and potential paratenic hosts within the Amami Islands.
eDNA reveals extraordinary fish diversity in the Urauchi River, Iriomote Island, Japan, a UNESCO World Heritage Site
A groundbreaking study using environmental DNA (eDNA) metabarcoding has uncovered extraordinary fish diversity in the Urauchi River, Iriomote Island, Japan—a UNESCO World Heritage Site. The research identified 254 fish species across 10–11 sampling sites along an 18.8 km stretch, with species richness peaking in mangrove zones of the mid-to-lower estuary. Notably, eDNA detected 16 conservation-priority taxa listed on Japan's Red List and six IUCN Red List species, including critically endangered Anguilla japonica and Cheilinus undulatus. The study also revealed unexpected detections of deep-sea taxa, likely due to tidal transport or diel migrations. Using high-throughput sequencing and advanced biodiversity analyses, the research demonstrated that fish biodiversity in this system remains incompletely characterized, underscoring the importance of integrating eDNA with conventional surveys for comprehensive assessments. This first molecular baseline provides a practical early warning system for detecting ecological shifts and guiding targeted conservation efforts in this globally significant watershed.
Foraging of Endangered and Endemic Plant Species by a Non-Native Sika Deer Found in the Northern Part of Okinawa-Jima Island, Japan: Evidence from Fecal DNA Metabarcoding Analysis
A non-native sika deer (Cervus nippon) was discovered in the northern part of Okinawa-Jima Island raising concerns about its potential impact on endangered and endemic plant species. Fecal DNA metabarcoding analysis of one fecal sample from the deer revealed 24 plant species, including two endemic to the Ryukyu Islands, with one listed as critically endangered (CR) by Japan's Environment Ministry. The study suggests that if sika deer establish a population in this region, they could pose significant threats to local biodiversity and ecosystems. Immediate measures are recommended to prevent further invasions and mitigate potential ecological damage.
Predation on an Okinawa Tree Lizard by an Amami Thrush Endemic to Amami-Oshima Island
Researchers documented the first recorded instance of vertebrate predation by the Amami Thrush (Zoothera dauma major), a bird endemic to Amami-Oshima Island, which preyed on an Okinawa tree lizard (Diploderma polygonatum polygonatum). This observation, made at the Amami Nature Observation Forest in February 2025, provides critical insight into the feeding habits of this scarce-foraging species. The study highlights the significance of such records for understanding predator-prey dynamics and the ecological role of endemic birds in the UNESCO World Heritage Sites of the Ryukyu Archipelago.
A new species of Rimboda Heller (Coleoptera, Curculionidae, Conoderinae, Othippiini) reared from Distylium racemosum Siebold & Zucc. in the Ryukyu Islands, Japan
Researchers have identified a new species of weevil, Rimboda saekii, from the subtropical forests of Amami-Oshima Island, Tokunoshima Island, Northern part of Okinawa Island, and Iriomote Island in Japan. This discovery marks a significant northward expansion of the genus Rimboda's known geographic range, which was previously limited to Indonesia, Malaysia, and the Philippines. The species was reared from Distylium racemosum (Hamamelidaceae), providing new insights into its ecological associations. The study includes detailed habitus photographs, 3D models, and illustrations of male and female genitalia, along with a comprehensive checklist of all known Rimboda species worldwide.
An Attempt at Age Estimation of the Ryukyu Long-Furred Rat (Diplothrix legata) Using Tooth Wear Analysis: First Report on the Difference in Molar Wear Patterns between Rats in Okinawajima and Amami-Oshima Islands
Researchers found that molar wear patterns differ significantly between Ryukyu Long-Furred Rats (Diplothrix legata) on Okinawa Island and Amami-Oshima Island, complicating age estimation methods. By analyzing 106 skulls—87 from Okinawa and 19 from Amami—the study identified seven distinct stages of molar wear, with Stage I (minimal wear) only observed in Okinawa rats, suggesting these were recently weaned individuals under 50 mm in skull length. However, Amami rats showed inconsistent relationships between fur growth, skull size, and tooth wear, indicating that age estimation based on molar wear may not apply uniformly across islands. The findings highlight the need for island-specific approaches to studying this endangered species' lifespan and ecology.
Biological invasion by the cycad‐specific scale pest Aulacaspis yasumatsui ( Diaspididae ) into Cycas revoluta ( Cycadaceae ) populations on Amami‐Oshima and Okinawa ‐jima, Japan
A recent biological invasion by the cycad-specific scale pest Aulacaspis yasumatsui threatens wild populations of Cycas revoluta, Japan's only native cycad, on Amami-Oshima and Okinawa-jima islands. This invasive species, originally from southeastern Asia, causes significant mortality in non-adapted cycad populations, with potential ecological impacts still understudied. The research highlights the urgent need for monitoring the pest's spread and evaluating biological control methods using native predators. Given C. revoluta's known genetic diversity, establishing in situ and ex situ conservation colonies is recommended to preserve its genetic composition if populations decline.
Bone Histology Reveals the Slow Life History and Skeletal Adaptations of the Amami Rabbit Pentalagus furnessi (Lagomorpha: Mammalia)
Bone histology of the Amami rabbit (Pentalagus furnessi) reveals its slow life history and unique skeletal adaptations, contrasting sharply with mainland lagomorphs. The study found that Amami rabbits exhibit rapid growth until about two years old, followed by gradual growth until five years, when bone growth ceases due to epiphyseal closure. This delayed maturation aligns with K-strategy reproductive traits, suggesting a response to island ecological conditions characterized by limited predation and resources. Additionally, the Amami rabbit's dense limb bones with thick cortices and small medullary cavities indicate robustness suited for its steep, rugged habitat, differing from other lagomorphs adapted for leaping locomotion. The research used histological analysis of limb bones to uncover these growth patterns and ecological adaptations, providing insights into insular mammal evolution.
Faecal Pellets of the Endangered Amami Rabbit ( Pentalagus furnessi ) as an Allochthonous Resource for Benthic Macroinvertebrates in a Forest Stream in Amami‐Oshima Island, Japan
Faecal pellets of the endangered Amami rabbit (Pentalagus furnessi) serve as a significant allochthonous resource for benthic macroinvertebrates in forest streams on Amami-Oshima Island, Japan. Stable isotopic analysis revealed that rabbit faeces contribute 12% to 66% to the diets of these aquatic animals, highlighting their ecological importance. The study employed underwater behavioural observations using time-lapse photography and experimental faecal introductions to demonstrate that decapod crustaceans actively forage on rabbit faeces in streams. This finding underscores the unique role of insular stream ecosystems in supporting biodiversity through allochthonous inputs.
First record of Angiostrongylus cantonensis infection in Diplothrix legata (Rodentia: Muridae) in Tokunoshima Island, Japan
Researchers have documented the first occurrence of Angiostrongylus cantonensis infection in the endangered Ryukyu long-furred rat (Diplothrix legata) on Tokunoshima Island, Japan. This discovery extends the known range of the zoonotic parasite, which typically infects invasive rats and relies on mollusks as intermediate hosts. The finding was made during a pathological examination of a deceased wild D. legata individual, revealing co-infections with two additional non-native parasites: Trichosomoides crassicauda and Hydatigera taeniaeformis. Notably, A. cantonensis has now been confirmed in wild populations of D. legata across all three islands where the species is endemic—Tokunoshima, Amami-Oshima, and Okinawa—highlighting a potential conservation concern due to its impact on this critically endangered rodent.
First report of systemic round cell tumor, suspected lymphoma, in a wild Amami rabbit (Pentalagus furnessi) from Tokunoshima Island
Scientists report the first documented case of systemic round cell tumor, suspected to be lymphoma, in a wild Amami rabbit (Pentalagus furnessi), an endangered species endemic to Japan’s Amami-Oshima and Tokunoshima Islands. The discovery was made during a necropsy of a deceased rabbit found on Tokunoshima Island in January 2018, which revealed severe pathological changes including lymphadenopathy, splenomegaly, and a mediastinal mass encasing the heart. Histopathological examination confirmed significant proliferation of tumor cells resembling lymphocytes, while PCR analysis ruled out retroviral or herpesviral involvement. The study underscores the critical need for enhanced pathological surveillance and conservation efforts to protect this vulnerable species from emerging threats like neoplasia.
Role of an Eco-tour Guide Certification System in SustainableEcotourism on Amami-Oshima Island, Japan
A certification system for eco-tour guides on Amami-Oshima Island, Japan, shows potential to promote sustainable ecotourism but requires stronger enforcement and broader stakeholder involvement. The study found that while certified guides contribute significantly to tourism quality and frequency, the current voluntary approach lacks penalties for misconduct and fails to address unqualified operators effectively. Introducing legal frameworks and engaging both guides and local residents in regulatory discussions, alongside third-party accreditation, could enhance the system's effectiveness. This research highlights the need for a balanced approach that aligns with regional autonomy while ensuring environmental protection.
Simulation of island ecotourism development based on SD and DPSIRM models: a case study of Amami-Oshima Island
A study on Amami-Oshima Island, part of the UNESCO World Heritage Sites, reveals that a balanced approach to ecotourism development—enhancing tourism benefits while conserving natural resources—yields the most effective outcomes. Using an optimized Driver-Pressure-State-Impact-Response-Management (DPSIRM) framework and System Dynamics (SD) modeling, researchers simulated various scenarios from 2010 to 2035. The Coordinated Development Model emerged as the optimal strategy, achieving a win-win balance between economic growth and ecological preservation. In contrast, models prioritizing either socioeconomic growth or strict ecological protection showed limitations, with the former lacking in service provision and the latter stifling tourism and economic activity. This research provides critical insights for policymakers, offering data-driven support for sustainable ecotourism planning.
Trend Analysis of Roadkill Risk of the Amami Rabbit Using Maxent on Amamioshima Island
A trend analysis reveals that roadkill risk for the critically endangered Amami rabbit (Pentalagus furnessi) on Amami Oshima Island increases significantly from mountainous regions to coastal areas, with particularly high risk in coastal zones featuring major roads. This finding underscores the vulnerability of the species to human infrastructure, especially along key transportation routes. The study employed MaxEnt (Maximum Entropy Modeling) to identify high-risk areas and environmental factors contributing to roadkill events, addressing a critical gap in previous research that had not analyzed the island's entire territory. By mapping these risks, the research provides actionable insights for developing targeted conservation strategies to mitigate roadkill threats, which are rapidly escalating and pose a significant threat to the species' survival.
A New Feather Mite Species of the Genus Metanalges (Acariformes: Analgidae) from the Okinawa Rail, Hypotaenidia okinawae (Gruiformes: Rallidae), in Okinawa Island, Japan
Researchers have identified a new feather mite species, Metanalges (M.) agachi, associated with the endangered Okinawa Rail on Okinawa Island. This discovery marks the first report of feather mites linked to this avian host and the first record of the genus Metanalges in Japan. The new species is distinguished by unique morphological traits, such as male legs III extending slightly beyond setae h2 bases and female ventral setae 4a nearly reaching the opisthosoma's posterior margin. Given the Okinawa Rail's high risk of population decline, this finding underscores potential conservation concerns for both the host bird and its associated mite species.
Coordinated development of island ecotourism: A comprehensive evaluation of Amami-Oshima Island
Amami-Oshima Island has shown significant progress in the coordinated development of ecotourism from 2010 to 2021, with a shift from minimal coordination to an intermediate level. The study, using advanced models like the Coupling Coordination Degree Model and Grey Verhulst model, reveals that while environmental tourism remains robust, social tourism exhibits fluctuating growth, and economic and other-sector tourism progress in tandem. Predictions suggest a slight increase in ecotourism coupling coordination through 2030. These findings underscore the potential for enhancing high-quality coordination and offer policy recommendations for sustainable ecotourism development on Amami-Oshima Island and similar destinations.
Fertilizer Management, Soil Chemical Properties, Leaf Mineral Contents, and Fruit Quality in Passion Fruit Orchards on Amami-Oshima Island
Excessive phosphorus and potassium fertilization in passion fruit orchards on Amami-Oshima Island, Japan, is linked to reduced fruit quality. The study found that eight out of 12 commercial orchards had excess available phosphorus (P₂O₅) and exchangeable potassium (K), with high P levels decreasing Brix—a measure of fruit sweetness. Cattle manure compost application was identified as a primary contributor to P accumulation, while nitrogen (N) deficiency was noted in leaves, suggesting that increasing N while reducing P and K could improve fruit quality. Soil pH was also found to be elevated in some orchards, potentially due to chemical fertilizers or shell-containing topsoil, which may have suppressed vegetative growth. Additionally, fruit yield and diameter declined with longer cultivation years.
Genetic and Morphological Studies on Goniurosaurus kuroiwae (Squamata: Eublepharidae), with a Description of a New Species from the Northern Part of Okinawajima Island, Ryukyu Archipelago, Japan
A new species of eublepharid lizard, Goniurosaurus nebulozonatus, has been identified from the northern part of Okinawajima Island and Kourijima in the Ryukyu Archipelago. Genetic analysis using single nucleotide polymorphism data revealed significant differentiation between this northern lineage and the southern lineage of Goniurosaurus kuroiwae, which are separated by a narrow hybrid zone on Okinawajima. Morphological comparisons further supported their distinction, leading to the proposal that all five currently recognized subspecies of G. kuroiwae should be elevated to full species status. This includes G. orientalis, G. sengokui, G. toyamai, G. yamashinae, and G. yunnu, bringing the total number of extant Goniurosaurus species in the Ryukyus to seven, with one extinct species. The new species is characterized by unique features such as a reddish-brown iris, specific scale patterns, and distinct dorsal banding.
New host crab Macrophthalmus (Macrophthalmus) convexus Stimpson, 1858 of the endangered pedunculate barnacle Octolasmis unguisiformis Kobayashi & Kato, 2003 (Lepadomorpha: Poecilasmatidae) in Amami Oshima Island, Japan
Researchers have identified the crab species Macrophthalmus (Macrophthalmus) convexus as a new host for the endangered pedunculate barnacle Octolasmis unguisiformis, expanding the known range of this symbiotic relationship in the Ryukyu Archipelago. The discovery was made during a survey at Kise Bay, Amami Oshima Island, where two hermaphrodites and one dwarf male of O. unguisiformis were found attached to a female M. (M.) convexus. This finding adds to the understanding of the barnacle's unique sexual system, known as androdioecy, which involves both hermaphrodites and males within the same population. The study highlights the importance of this symbiotic relationship in tidal flat ecosystems and contributes to the conservation efforts for O. unguisiformis, which is listed as endangered.
Seasonal diet partition among top predators of a small island, Iriomote Island in the Ryukyu Archipelago, Japan
A study on Iriomote Island, part of the Ryukyu Archipelago, reveals that two top predators—the endangered Iriomote cat and the Crested Serpent Eagle—coexist by partitioning their diets seasonally. Using DNA metabarcoding analysis of fecal samples, researchers identified significant differences in diet composition between the species during summer and winter, despite some overlap at the species-to-order level. The findings suggest that dietary niche differentiation is a key factor enabling these predators to thrive on a small island with limited resources. This research sheds light on the ecological dynamics of predator coexistence in constrained environments.
Shear‐Dominant Continental Rifting in Northern Ryukyu Revealed by Ambient Noise Tomography
Researchers have uncovered evidence of shear-dominant continental rifting in the northern Ryukyu Arc, challenging traditional models of backarc extension. Using ambient noise tomography with ocean-bottom seismometer data, they revealed distinct crustal deformation structures, including arc-parallel and arc-perpendicular seismic anisotropy in the upper to mid-crust and lower crust to uppermost mantle, respectively. The findings suggest that vertical shearing from right-lateral arc retreat and horizontal shearing from mantle wedge corner flow drive the rifting process. Additionally, arc-perpendicular anisotropy in the forearc upper crust may indicate crack alignment due to the Amami Plateau collision. This study highlights the transtensional nature of the northern Ryukyu rift system, offering new insights into continental rifting mechanisms.
The commodification of romance in relation to fertility rate in Japan: a case study in Tokunoshima
Inhabitants of Tokunoshima Island exhibit notably higher fertility rates compared to other developed countries, attributed to unique dating practices that deviate from commodified romantic norms. Unlike mainstream dating trends, which often involve costly gestures and material expectations, Tokunoshima's approach prioritizes genuine connections over commercialized romance. This cultural distinction facilitates matchmaking, reducing instances of late and lifelong singlehood (bankonka and mikonka) and contributing to higher family formation rates. The study suggests that the absence of commodification in romantic relationships allows for more straightforward pathways to marriage, offering insights into potential solutions for Japan's persistently low fertility rate.
The Tokunoshima Belt: A New Geotectonic Unit in Central Ryukyus, Japan
Researchers have identified the Tokunoshima belt, a new geotectonic unit in central Ryukyus, Japan, characterized by its high-grade metamorphic rocks and distinct geological features. This discovery challenges existing models of the region's tectonic evolution. The study reveals that the Inokawadake metamorphic complex (IMC), part of this new belt, underwent amphibolite-facies metamorphism, a rarity in the Shimanto belt. Paleoproterozoic zircons suggest a complex history, while detrital zircon ages indicate metamorphism occurred in the Paleocene or later. The IMC structurally overlies Cretaceous accretionary complexes as a klippe, hinting at subhorizontal faulting and potential heat sources from either the San-in batholith belt to the north or an unknown collided island arc system to the south.
Characterization of cell wall polysaccharide from Cladosiphon okamuranus cultivated in different locations
Cladosiphon okamuranus, a prime source of fucoidan among brown algae, exhibits consistent structural characteristics for its cell wall polysaccharide across different geographical locations within Okinawa Prefecture during peak harvesting times. A study analyzing samples from eight sites in the Ryukyu archipelago revealed that while the hot water fraction (HW) and hemicellulose-I fraction (HC-I) remained predominant, with HW accounting for 60–70% and HC-I for 15–20%, the chemical composition of fucoidan within HW showed minimal variation. Fucoidan consistently maintained a molar ratio of fucose (Fuc), glucuronic acid (GlcA), and sulfate (SO3−) at approximately 1.0:0.5:0.7–1.0, indicating structural uniformity across locations. However, HC-I displayed significant variability in sugar composition, particularly in samples from Bise, the northern part of Okinawa Island, which contained notably higher amounts of glucose (Glc), galactose (Gal), mannose (Man), and xylose (Xyl), along with thicker lateral branches compared to other regions.
Coral distribution and diversity in Sakiyamawan–Amitoriwan nature conservation area of Iriomote Island in Japan
A comparative analysis of coral distribution and diversity between Sakiyama Bay and Amitori Bay on Iriomote Island, Japan, reveals significant differences influenced by soil inflow and geographical characteristics. While Amitori Bay exhibits maximum coral diversity in its intermediate part, aligning with the Intermediate Disturbance Hypothesis (IDH), Sakiyama Bay shows peak diversity at its reef edge, deviating from IDH predictions. Tabular and branching corals dominate Amitori Bay's mouth and inner parts, respectively, whereas branching and massive corals prevail in Sakiyama Bay's reef edge and coastal sides. These findings underscore the critical role of environmental factors in shaping coral community structure.
Estimation of the Origin of suspended fine particulate organic matter in the subtropical Amami-Oshima Island streams
A new study reveals that the Amami rabbit (Amami-no-Kurousagi) significantly contributes to the production of suspended fine particulate organic matter (SFPOM) in subtropical Amami-Oshima Island streams, accounting for 39% of its origin. This suggests that the species plays a crucial role in converting terrestrial organic matter into SFPOM within riverine ecosystems. The research used carbon and nitrogen stable isotope ratios to trace the origins and pathways of SFPOM production. While Ryukyu sweetfish (Ryukyua yu) showed higher population densities in areas with abundant attached algae, their contribution to algal-derived SFPOM was found to be minimal, with no significant correlation between fish density and algal biomass in SFPOM.
Geographic Variation in Skull Morphology of the Japanese Crocodile Newt, Echinotriton andersoni (Amphibia: Urodela: Salamandridae), Inferred from Geometric Morphometrics
A study on the Anderson's crocodile newt, Echinotriton andersoni, reveals significant geographic variation in skull morphology across its range in the Central Ryukyus, Japan. Using geometric morphometrics, researchers identified distinct differences between populations from Okinawa Island and those from Amami-Oshima and Tokunoshima Islands, with Taiwanese specimens showing a closer resemblance to females from Amami-Oshima. This finding highlights previously unexplored morphological diversity within this endangered species, which is known for its high genetic variation among islands.
Habu snakes (Protobothrops flavoviridis) show variation in thoracic aortic vasoreactivity between adjacent Japanese islands
Habu snakes (Protobothrops flavoviridis) from adjacent Japanese islands exhibit significant variation in thoracic aortic vasoreactivity. Researchers found that Tokunoshima Habu display stronger contractile responses to angiotensin II, acetylcholine, and noradrenaline compared to Amami-Oshima Habu, with higher affinities for the first two substances—a previously unreported response to acetylcholine in snakes. This suggests intraspecific physiological divergence potentially driven by ecological differences between the islands. The study employed isolated aorta experiments to assess vasoreactivity, providing insights into how local environmental factors may influence snake physiology.
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
Amami-Oshima and Tokunoshima Islands, part of Japan's newest natural World Heritage Site, exhibit exceptionally high plant diversity in their broad-leaved evergreen forests. This study reveals that the islands' flora is characterized by unique species richness anomalies, particularly among shared plant families, setting them apart from regions at higher and lower latitudes. Environmental factors such as temperature and altitude positively influence this diversity, while regional weather variations also play a significant role. Notably, both tree and herbaceous plants contribute substantially to biodiversity metrics, including rarity. The research employed 5 × 100 m plots across seven sites on the Amami Islands, alongside data from the Monitoring Sites 1000 Project, to analyze α and β diversity patterns using environmental variables and species frequency. These findings underscore the islands as critical biodiversity hotspots, emphasizing the importance of evaluating herbaceous species in comprehensive biodiversity assessments.
Infestation Survey of Lynxacarus radovskyi on Feral Cats in the Northern Part of Okinawa Island, Japan
A survey of feral cats on the northern part of Okinawa Island, Japan, revealed that 12.6% were infested with the mite Lynxacarus radovskyi (cat fur mite), confirming its presence year-round across multiple regions. While this infestation rate was lower than that of fleas (93.7%), all cats with L. radovskyi also harbored fleas, suggesting potential co-infection dynamics. The study, conducted on 127 feral cats in Koun village, used visual inspection and microscopic examination to identify external parasites under general anesthesia. No significant differences were found based on sex or age, indicating widespread infestation regardless of these factors. The findings highlight the need for vigilance regarding this mite, which can cause skin conditions in cats, alongside other external parasites in Okinawa.
Middle Miocene forearc alkaline magmatism in Amami-Oshima Island, central Ryukyu Arc: implications for paleoreconstruction of Shikoku Basin
A significant discovery of middle Miocene forearc alkaline magmatism on Amami-Oshima Island, central Ryukyu Arc, challenges previous assumptions about the southwestern margin of such magmatic activity. The study identifies basaltic dikes with ocean island basalt (OIB)-like chemical signatures, indicating low-degree partial melting from a deep mantle source. 40Ar/39Ar dating and paleomagnetic analyses reveal that these dikes intruded simultaneously around 16.5–16.4 Ma during reversed polarity chron C5Cn.2r. This finding suggests the northern end of the Kyushu-Palau Ridge was south of Amami-Oshima Island at this time, later moving eastward to its current location. The research employs a combination of chemical analysis, radiometric dating, and paleomagnetic studies to reconstruct the paleogeography of the Shikoku Basin.
Relationship between herbivory and leaf traits in mangroves on Iriomote Island, southern Japan
Mangrove ecosystems on Iriomote Island, Japan, exhibit a distinct pattern where leaf herbivory rates decline from seaward to landward species, driven primarily by the concentration of condensed tannins and the tannins:nitrogen ratio. This study reveals that these chemical traits are key determinants of grazing pathways in mangroves, contrasting with other leaf traits like physical or physiological properties. Seasonal variations, leaf phenotype (sun or shade), and leaf age had minimal impact on herbivory rates overall, though exceptions were noted in seaward and rhizophoraceous species where summer herbivory was higher. The research highlights the critical role of condensed tannins in shaping nutrient cycling dynamics in mangrove forests, offering insights into their high productivity.
Relationship between Regional Distribution of Centenarians and Drinking Water Hardness in the Amami Islands, Kagoshima Prefecture, Japan
A strong correlation exists between drinking water hardness and the rate of centenarians in Japan's Amami Islands, suggesting that hard water—particularly from coralline limestone bedrock—may enhance longevity. The study analyzed four islands (Amami-Oshima, Tokunoshima, Okinoerabu, and Yoron), finding that water hardness, primarily determined by calcium and magnesium content, closely mirrored the distribution of centenarians. Yoron Island, with predominantly coralline limestone bedrock, reported the highest centenarian rate (29.7 per 10,000) alongside the hardest water, while Amami-Oshima, lacking such bedrock, had the lowest rates (0.0 to 12.2). The findings propose a potential cardiovascular benefit from hard water, contributing to ongoing discussions on global drinking water quality and its impact on health.
The effect of temperature and irradiance on the photosynthesis of a seagrass, Halodule uninervis, from Amami-Oshima Island, Kagoshima
Research on the seagrass Halodule uninervis from Amami-Oshima Island reveals that its photosynthesis is significantly inhibited at low temperatures (15°C) and under strong irradiance, suggesting temperature-dependent light inhibition. The study found optimal photosynthetic performance at 30.5°C for total rates and 23.9°C for maximum quantum yield, with notable declines in quantum efficiency under low-temperature and high-light conditions that persisted even after dark acclimation. This indicates potential vulnerability to environmental changes near the northern limit of its distribution.
A dataset for vascular plant diversity monitoring for the natural World Heritage site on Amami‐Oshima Island, Tokunoshima Island, and the northern Okinawa Island
A comprehensive dataset of vascular plant biodiversity from four UNESCO World Heritage Sites—Amami-Oshima Island, Tokunoshima Island, and the northern part of Okinawa Island—reveals a rich diversity of 381 species across 99 families. This dataset, collected using standardized belt-transect surveys between July 2012 and October 2020, provides critical baseline data for monitoring plant diversity in these ecologically significant regions. It includes detailed records of species occurrence, tree girth, and height measurements, serving as a foundational resource for future biodiversity assessments. The dataset is openly accessible via the Global Biodiversity Information Facility (GBIF) under a Creative Commons license, ensuring broad utility for researchers and conservationists.
A New Record of Hypsugo pulveratus on Amami-Oshima Island, Japan and Comparison with H. alaschanicus
Researchers document the first recorded presence of Hypsugo pulveratus bats on Amami-Oshima Island, Japan, distinguishing them from the morphologically similar H. alaschanicus. The discovery was confirmed through morphological analysis—including skull and baculum shape—and mitochondrial COI gene sequencing, which placed the bats in a distinct clade with H. pulveratus. Key differences between the two species, such as skull ridge curvature and premolar size, were highlighted. This study advances understanding of bat biodiversity in Japan's UNESCO-listed Ryukyu Islands by providing genetic and morphological evidence for species identification.
A new species of the genus Sergentomyia França and Parrot (Diptera: Psychodidae) from Iriomote Island, Ryukyu Archipelago, Japan
Researchers have identified and described a new species of sand fly, Sergentomyia iriomotensis, from Iriomote Island in the Ryukyu Archipelago, Japan. This discovery contributes to the understanding of biodiversity in the region, particularly within the genus Sergentomyia. The study provides detailed morphological descriptions and illustrations, focusing on key anatomical features such as genitalia (coxite, style, aedeagus, surstyle, paramera, and genital pump), head structures (pharynx, cibarium, antennal segments), and wing morphology. These findings are significant for taxonomic studies and may have implications for vector-borne disease research in the area.
A psychological model to understand background reasons for different attitudes and behaviors of youth residents in relation to free-roaming cat problems on a human-inhabited World Heritage Island in Japan
A psychological model reveals that cat owners and those who believe cats control rodents are more likely to feed outdoor cats, exacerbating ecological harm. While perceptions of negative impacts on people—such as zoonoses—strongly influence support for outdoor cat management, attitudes toward ecological damage have a weaker effect. The study highlights the need for targeted education, particularly among youth, to shift behaviors and reduce free-roaming cat populations, which threaten native species on UNESCO-listed islands like Tokunoshima in Japan.
Aspects of distribution, growth, and reproduction of the fluvial prawn, Macrobrachium shokitai, in a subtropical river on Iriomote Island, Japan
A female-biased sex ratio and bimodal carapace length distribution suggest that the fluvial prawn Macrobrachium shokitai on Iriomote Island, Japan, exhibits prolonged lifespan (>1 year) with distinct juvenile and adult cohorts. Recruitment occurs from August to December, while ovigerous females peak in abundance between June and August, aligning with breeding patterns typical of subtropical East Asian Macrobrachium species. Monthly sampling at seven stations along a 4.0-km river revealed stable populations above waterfalls (>270 m elevation), highlighting critical habitat preferences for this regional and vulnerable species.
Building IoT Systems - Challenges and Insights from a Pilot Case Study
A pilot case study on Okinawa Island, Japan, reveals that despite advancements in IoT technologies and internet accessibility, building and deploying efficient IoT systems for specific environments presents significant challenges. These include power supply, power consumption, operation costs, connectivity coverage, range, and ease of deployment. The study examined an automated bicycle-monitoring and navigation system to explore these practical hurdles, highlighting the need for tailored solutions that balance technical feasibility with user requirements.
Coastal ecological impacts from pumice rafts
A volcanic eruption in the Ogasawara Islands in August 2021 led to unprecedented pumice rafting, with significant ecological impacts observed along the coasts of Amami-Oshima Island, Tokunoshima Island, northern Okinawa Island, and Iriomote Island. The study documents early evidence of ecosystem changes, including disruptions to coral reefs, mangrove forests, and estuaries, as well as obstacles to fishing and maritime activities. Pumice stranding caused short- and long-term alterations in coastal ecosystems, with potential implications for similar regions like Kyushu, Shikoku, and Honshu Islands where pumice later washed ashore. The research highlights the need for further investigation into the broader ecological consequences of such events.
First Records of an Estuarine Goby Acentrogobius ocyurus (Gobiiformes: Gobiidae) from Japan and the Sulu Sea in the Philippines
Researchers document the first records of the estuarine goby Acentrogobius ocyurus in Japan and the Sulu Sea, Philippines. Previously known from the South China Sea, Andaman Sea, and northern Australian waters, this species was found on muddy substrata at low-tide zones, often inhabiting burrows of mangrove pistol shrimp (Alpheus richardsoni). Morphological analysis reveals close relationships with Acentrogobius globiceps, A. kranjiensis, and an unnamed Japanese species, characterized by distinctive features such as a transverse sensory papillae pattern on the cheek, bright blue body spots, and an oblique yellow stripe on the caudal fin. The study, based on 20 specimens collected from Okinawa-jima Island (Japan) and Palawan Island (Philippines), expands the known distribution of this species and contributes to regional ichthyological knowledge.
First records of the arboreal wolf spider species Hogna trunca Yin, Bao & Zhang 1996 (Araneae: Lycosidae) from Japan
A new record of the arboreal wolf spider species, Hogna trunca, has been documented in Japan, marking its first occurrence outside China. Originally described from Zhejiang Province, this lycosid spider was found in Nara Prefecture and northern Okinawa Island, with observations in forest habitats along streams. Notably, Hogna trunca exhibits a rare arboreal behavior within the Lycosidae family, which typically comprises ground-dwelling species. The discovery suggests that its unique ecology may have previously hindered detection. This finding also represents the first record of the genus Hogna in Japan.
Noteworthy foliicolous lichens collected from Iriomote Island, southern Japan
A notable discovery of foliicolous lichens on Iriomote Island, part of Japan's UNESCO-listed Okinawa Islands, reveals three species—Byssoloma chlorinum, B. vanderystii, and Gallaicolichen pacificus—previously unrecorded in Japan, alongside two others new to the island (B. minutissimum and Fellhanera rhapidophylli). The study also describes key morphological features of Tricharia kashiwadanii for the first time, using both original material and specimens from Iriomote Island. Genetic analysis of mitochondrial small subunit (mtSSU) sequences confirmed the identity of these species, providing new baseline data for lichen diversity in this biodiversity hotspot.
Procedure and challenges of World Heritage nomination of Amami-oshima Island, Tokuno-shima Island, northern part of Okinawa Island and Iriomote Island
Amami-Oshima Island, Tokunoshima Island, the northern part of Okinawa Island, and Iriomote Island were successfully inscribed as UNESCO World Heritage Sites after an 18-year nomination process, beginning in 2003. The study highlights the challenges and procedural hurdles encountered during this lengthy journey, particularly focusing on the 2018 IUCN evaluation report's assessment of Outstanding Universal Value (OUV) for natural heritage criteria (ix). While the exact scientific insights or discoveries are not detailed, the research underscores the complexities of meeting international conservation standards and the rigorous evaluation processes required for World Heritage designation. The study serves as a case example for understanding the intricacies of global heritage nomination procedures.
Records and distribution of the coral-killing sponge Chalinula nematifera in the Ryukyu Islands, Japan
A coral-killing sponge, Chalinula nematifera, has been documented across the Ryukyu Islands in Japan, including Amami-Oshima, Tokunoshima, northern Okinawa Island, and Iriomote Island. This species exhibits a broad substrate preference, thriving on scleractinian corals and occasionally octocorals, while also adapting to varying depths (0–24 m). Analysis of photographic records and specimens spanning over 20 years suggests its presence predates recent observations in Indonesia, indicating it is not a novel arrival. Researchers emphasize the need for comprehensive field surveys to establish baseline data on distribution and abundance, crucial for monitoring potential impacts on coral reef ecosystems.
Reproductive Isolation and a Change in the Development Mode of the Tideland Snail Batillaria flectosiphonata (Gastropoda: Batillariidae)
A new study confirms reproductive isolation between two tideland snail species, Batillaria flectosiphonata and Batillaria multiformis, endemic to the Nansei Islands, Japan. Using microsatellite analysis, researchers demonstrated that B. flectosiphonata maintains distinct genetic boundaries despite sympatric distribution with its sister species on Amami-Oshima Island. The study also reveals a significant evolutionary shift in B. flectosiphonata: it is a direct developer, meaning its offspring hatch as miniature adults rather than passing through a larval stage—a trait that has independently evolved twice within the Batillariidae family in Japanese waters. Additionally, the lower genetic diversity observed in B. flectosiphonata compared to B. multiformis suggests long-term isolation within the Amami insular group may have constrained its genetic variation.
Role of landscape context in Toxoplasma gondii infection of invasive definitive and intermediate hosts on a World Heritage Island
A study on Tokunoshima Island, a UNESCO Natural World Heritage site, reveals that high cattle barn density correlates with increased Toxoplasma gondii infection rates in both free-ranging cats and black rats. Seroprevalence exceeded 70% in these landscapes, aligning with higher rat densities observed during trapping surveys. The spatial scale of landscape influence differed between species: cats showed broader effects (1 km buffer radius) compared to black rats (100 m buffer radius). Both hosts exhibited rising antibody concentrations with increasing body weight and cattle barn density, indicating heightened exposure risk. The findings underscore the need for targeted management strategies—such as prohibiting cat feeding and rat control without feline involvement—to mitigate zoonotic risks while preserving endangered species on the island.
Seismicity and Stress State in the Ryukyu Islands Subduction Zone
Research reveals distinct stress field variations in the Ryukyu Islands subduction zone, with extensional stress observed north of the Tokara Strait and compressional stress south of it. The study utilized a comprehensive earthquake catalogue and damped regional stress tensor inversion to analyze shallow and intermediate earthquakes. Findings indicate that the Okinawa Trough's stress field transitions from strike-slip to normal fault type, suggesting the southern segment is entering an expansion stage. Additionally, the northeastern region exhibits biaxial tension–uniaxial compression, with principal compressive stress oriented SEE. This study enhances understanding of seismicity characteristics and subduction zone dynamics, providing critical insights for earthquake hazard analysis in this area.
The First Record of the Fairy Pitta Pitta nympha from Iriomote Island, Japan
A groundbreaking record of the Fairy Pitta (Pitta nympha) on Iriomote Island, part of Japan's UNESCO World Heritage-listed Ryukyu Archipelago, marks the species' first documented presence there. Captured via infrared camera on September 1, 2016, this observation expands the known distribution of a rare bird species in Japan. The study, published in the Journal of the Yamashina Institute for Ornithology, relied on sensor technology to document the pitta's presence, offering critical insights into its habitat use and range within the island's unique biodiversity hotspot.
Three new species of Eimeria (Apicomplexa: Eimeriidae) from the Amami rabbit, Pentalagus furnessi (Mammalia: Leporidae)
Researchers have identified three new species of Eimeria parasites, Eimeria furnessi n. sp., Eimeria hilleri n. sp., and Eimeria sagentae n. sp., in fecal samples from wild Amami rabbits (Pentalagus furnessi) on Amami-Oshima and Tokunoshima Islands, Japan. These species are distinguished by oocyst size, shape, and color, with prevalence rates of 58.3%, 25.0%, and 36.1% respectively. The discovery contributes to understanding the parasitic load in this endangered lagomorph, potentially informing conservation efforts and breeding programs. Further studies on pathogenicity could enhance captive propagation strategies for the Amami rabbit.
Three-dimensional Flow Simulation of Amitori Bay in Iriomote Island during Typhoon 1513
Amitori Bay in Iriomote Island, designated as Japan's sole marine natural conservation area, experiences complex 3D flow dynamics during extreme typhoons like Typhoon 1513, which recorded wind speeds exceeding 20 m/s. This study reveals that conventional models overestimate flow speeds when using monotonically increasing drag coefficients, suggesting a need for constraints on these coefficients under certain wind conditions. The unique reef topography of the bay significantly influences fluid dynamics, with implications for coral habitats. Researchers employed typhoon modeling to assess the impact of sea surface drag and Smagorinsky coefficients on flow patterns, comparing simulated data with field observations.
Tokunoshima (Kagoshima, Northern Ryukyuan)
Tokunoshima dialect, spoken on Tokunoshima Island in the Northern Ryukyus, exhibits unique linguistic features that distinguish it from other Amami languages. Despite lacking comparative studies on its genetic relationships, Uemura's (1972) typological classification places Tokunoshima within the Oshima-Tokunoshima group, alongside nearby islands like Amami Oshima and Kakeromajima. The study focuses on three villages in Isen Town—Higashihama, Kenbuku, and Uemonawa—revealing distinct dialectal variations across dozens of villages on the island. While Nakamoto (1990) proposed a broader 'Amami dialect' classification, Tokunoshima's linguistic diversity remains understudied, highlighting gaps in regional comparative linguistics.
Visual Preferences for Slope Greening and Stabilization Techniques: the Case Study of Northern Part of Okinawa Island, Japan
A preference for natural, unstructured roadside vegetation emerges as the top choice for slope greening and stabilization techniques on forest roads in Okinawa, Japan. This finding underscores the importance of balancing aesthetic appeal with functional safety, particularly as recreational use of these routes increases. The study, involving 143 survey responses, reveals that public visual preferences vary significantly based on socio-demographic factors such as age, gender, and residential location. While scenic quality is highly valued, respondents prioritize safety even more, highlighting a critical consideration for roadside management in UNESCO World Heritage Sites like the Amami-Oshima, Tokunoshima, and Iriomote Islands. The research employs non-parametric analyses to explore these preferences, offering actionable insights for sustainable tourism and infrastructure planning.
A new species of Expanathura (Crustacea: Isopoda: Anthuroidea) from Iriomote Island, Japan, with a note on male polymorphism
Researchers have identified a new species of isopod, Expanathura monile, from Iriomote Island, part of the Ryukyu Archipelago in Japan. This discovery was made through detailed morphological analysis, distinguishing it from similar species such as E. collaris and E. macronesia by unique traits like a V-shaped pigment band on the female's head, specific antennular flagellum structure, and distinct uropodal features. The study also notes male polymorphism in this species, contributing to the understanding of biodiversity in the region. A revised key for identifying Expanathura species is provided, enhancing taxonomic resources.
Choice of tree holes as oviposition sites by Kurixalus eiffingeri on Iriomote Island
Research on Kurixalus eiffingeri frogs on Iriomote Island, part of the UNESCO World Heritage Sites in Japan, reveals that these frogs prefer tree holes for oviposition based on their height and opening angle. The study found that higher tree holes with larger opening angles were more frequently used, likely due to reduced predation risk. This preference contrasts with findings from Taiwan, where height was the primary factor, suggesting that environmental differences may influence oviposition site selection in this species. The study analyzed eight tree hole variables, identifying height above ground and opening angle as key factors in the best predictive model.
Development of a Camera-Installed Nest Box for Small Mammals and Its Application in Reproductive Schedule Estimation for the Okinawa Spiny Rat
Reproduction in the endangered Okinawa spiny rat is primarily limited to autumn and winter, with subadults emerging predominantly between December and March. This finding was derived from a novel camera-installed nest box system deployed on Okinawa Island, which captured 850 images of rats over six months. By analyzing the distribution of body size (measured as eye distance) using a Gaussian mixture model, researchers identified two distinct clusters: subadults (11% of individuals) and adults (89%). The seasonal emergence pattern suggests that weaning occurs mainly during winter, providing critical insights into the species' reproductive ecology. This non-invasive method offers a scalable approach for studying small mammals in their natural habitats.
Development of a male specific genetic marker for Garcinia subelliptica Merr. tree
Researchers have developed the first male-specific genetic marker for Garcinia subelliptica, a dioecious tree species known as "fukugi" in Japan. This breakthrough, achieved through restriction site-associated DNA sequencing (RAD-seq), enables early sex diagnosis and selection at the seedling stage, addressing long-standing challenges in afforestation and landscape maintenance. The marker, named FSDM, is a 660 bp fragment that consistently appears in male but not female G. subelliptica genomes, with a confirmed 1:1 segregation ratio in tested populations. Notably, the DNA sequence of FSDM shares significant similarity to the antifungal protein ginkbilobin-2 gene. This innovation holds promise for conserving traditional landscapes and supporting future village designs around the northern part of Okinawa Island, a potential World Natural Heritage site.
Distribution and habitat selection of species of the genus Tadarida Rafinesque, 1814 (Chiroptera: Molossidae) in the Amami-Oshima Island, Japan
Research on Amami-Oshima Island reveals that the genus Tadarida (Molossidae) bats predominantly inhabit southern and western coastal regions, favoring open areas with fewer obstacles. This preference is linked to higher land use in these zones, suggesting that mosaics of forests and open spaces are crucial for their foraging behavior. The study, conducted via acoustic surveys from May 2018 to February 2020, also highlights the need for improved forest quality in northern regions to support bat populations by providing essential food resources and open areas for flight.
Diuron concentrations along shorelines of Ishigaki and Iriomote islands, Japan
A study analyzing diuron concentrations along the shorelines of Ishigaki and Iriomote Islands, part of Japan's UNESCO World Heritage Sites, found generally low levels (≤32 ng l⁻¹) of this herbicide, with no evidence of toxicity to organisms. The highest concentrations were detected at a fishing port in Iriomote Island (32 ng l⁻¹) and a mooring point in Ishigaki Island (19 ng l⁻¹), suggesting contamination likely from antifouling paints used on boats. A notable concentration (14 ng l⁻¹) was also found in the estuary of Arakawa River, hinting at potential land-based sources. The study, conducted in September 2019, indicates localized contamination but reassures low environmental impact during the sampling period.
Ecological notes on the filter-feeding water scavenger beetle, Spercheus stangli Schwarz and Barber, 1917 (Coleoptera: Spercheidae), on the Iriomote Island, Japan
Research on the filter-feeding water scavenger beetle, Spercheus stangli, reveals that it is likely bivoltine or multivoltine, meaning it can produce multiple generations per year. This finding sheds light on the species' reproductive strategy and underscores the importance of ponds with floating substrates like wood fragments as critical habitats for its conservation. The study, conducted on Iriomote Island in Japan, combined field surveys with rearing experiments to gather ecological data. Given that S. stangli is a rare species in Japan, known only from one pond, this research provides valuable insights for developing targeted conservation strategies to protect this unique and endangered beetle.
Effects of topography and anthropogenic alterations in forest environments on the breeding use by two endangered frog species in Amami-Oshima Island
Two endangered frog species, Babina subaspera and Odorrana splendida, exhibit distinct breeding site preferences shaped more by topographic factors than anthropogenic alterations in Amami-Oshima Island's subtropical forests. The study found that upstream contributing area (UCA), topographic wetness index (TWI), and altitude were critical determinants for B. subaspera, while O. splendida prioritized altitude, followed by UCA and TWI. Anthropogenic factors—forest age, road density, and mongoose presence—had a lesser but still notable impact, with younger forests (<40 years old) and higher road or mongoose densities reducing breeding site suitability. These findings suggest that the species' specific topographical requirements may mitigate some anthropogenic pressures, offering insights for targeted conservation strategies.
Eradication of the mongoose is crucial for the conservation of three endemic bird species in Yambaru, Okinawa Island, Japan
Eradication of the small Indian mongoose (Urva auropunctata) is critical for the conservation of three endemic bird species—Okinawa rail, Okinawa woodpecker, and Okinawa robin—in Yambaru, northern Okinawa Island. A study using playback surveys conducted every three years from 2007 to 2016 revealed that these birds' distribution areas expanded within mongoose-controlled zones. Analysis with a generalized additive mixed model (GAMM) demonstrated that their abundance correlated positively with hardwood forest area and negatively with mongoose density, indicating the invasive species' detrimental impact on all three species. While logging has ceased in Yambaru due to protected forest designations, mongoose eradication remains essential for their survival.
Facts and Regional Differences of the Priests in the Northern Part of Okinawa Island: Connection between the Priests and the Priestess
A comprehensive investigation of village-level ritual prayers in the northern part of Okinawa Island reveals distinct regional differences and roles among priests, challenging the periphery propagation theory. The study identifies seven categories of priests—including public female priestesses (Noro) and male priests—and finds that male priests are predominantly paired with female priestesses, with significant variation in their role names. Unlike the southern part of Okinawa or Sakishima islands, where male priests are rare, northern Okinawa shows a higher prevalence, suggesting historical continuity rather than peripheral influence. This research provides new clues to understanding the historical transition and placement criteria of priests under royal governance.
First Record of the Soil-feeding Higher Termites (Isoptera: Termitidae) from Okinawa Island, the Central Ryukyus, Japan
Scientists document the first occurrence of the soil-feeding termite Pericapritermes nitobei on Okinawa Island, part of Japan's UNESCO-listed Ryukyu Archipelago. This discovery challenges prior assumptions about termite dispersal, as P. nitobei, which thrives in soil rather than wood, was absent from previous exhaustive surveys across the region. The team suggests human activity—likely via transportation or trade—recently introduced this species to the Motobu Peninsula, mirroring patterns seen with other invasive termites like Odontotermes formosanus. Their findings imply that non-wood-dependent termites can establish in new environments, expanding our understanding of how these insects colonize and adapt beyond their native ranges. The study highlights the role of human-mediated dispersal in shaping termite distributions, with broader implications for biodiversity and ecosystem dynamics.
Gilpinia hakonensis and similar species in Japan and ovipositors of five European Gilpinia species (Hymenoptera, Diprionidae)
A new species of conifer sawfly, Gilpinia okinawa sp. nov., has been identified from Okinawa Island, Japan, along with the redescription of two similar Japanese species, G. hakonensis and G. amamiana. The study also designates a lectotype for Lophyrus hakonensis and reveals that G. fukudai is a synonym of G. hakonensis. For the first time, male descriptions are provided for G. hakonensis and G. amamiana, with G. amamiana newly recorded from Tokunoshima Island. Additionally, the study compares ovipositors of five European Gilpinia species, including new illustrations for G. frutetorum, G. laricis, and G. variegata, while also recording G. laricis in Bulgaria. This research contributes to the taxonomy and distribution of the G. socia group within Japan and Europe.
Molecular epidemiology of Leptospira spp. among wild mammals and a dog in Amami Oshima Island, Japan
A study on Amami Oshima Island, Japan, reveals diverse Leptospira genotypes and serotypes maintained among wild mammals, with black rats identified as a source of canine leptospirosis infection. Researchers isolated seven Leptospira strains from black rats, wild boars, a rabbit, and a dog using flaB sequencing and microscopic agglutination tests. Multilocus sequence typing (MLST) and multiple-locus variable-tandem repeat analysis (MLVA) showed identical genetic profiles in rat and canine isolates, while two distinct types were found in wild boar isolates. Wild boars exhibited a high infection rate (58.3%), suggesting they are significant maintenance hosts for Leptospira interrogans serogroup Hebdomadis, which has been linked to human and canine leptospirosis cases on the island.
One Health approach in the control of zoonosis with special attention on Toxoplasmosis
A One Health approach is critical for controlling toxoplasmosis, a zoonotic disease caused by Toxoplasma gondii. The study found that 47.2% of free-ranging cats on Tokunoshima Island were seropositive for T. gondii between 2017 and 2018, highlighting the importance of managing felid behavior to mitigate transmission. Toxoplasmosis poses a significant food-borne health risk due to its transmission through undercooked meat and environmental contamination with oocysts. The research underscores the need for integrated strategies that address human, animal, and environmental health to effectively control this parasitic disease.
Seasonal occurrence of ixodid ticks on the vegetation in the northern part of Okinawajima Island, Japan
A study on Amami-Oshima Island, Tokunoshima Island, the northern part of Okinawa Island, and Iriomote Island revealed distinct seasonal patterns in the occurrence of ixodid ticks. Researchers collected 3,326 ticks over a year-long period (June 2017 to June 2018) using flagging on vegetation, identifying five species: Amblyomma geoemydae, Amblyomma testudinarium, Haemaphysalis hystricis, Haemaphysalis formosensis, and Haemaphysalis flava. The predominant species exhibited unique seasonal distributions—A. geoemydae was absent in January and February, while A. testudinarium was present nearly year-round with a dominance of nymphs. H. hystricis larvae were collected throughout the year, but adults and nymphs only appeared from January to August. This research highlights the seasonal dynamics of tick populations, which could inform disease surveillance strategies in these regions.
Species composition and mitochondrial molecular phylogeny of Acropora corals in Funakoshi, Amami-Oshima Island, Japan: A proposal for its new taxonomic grouping
Researchers propose a new taxonomic grouping for Acropora corals in Japan, based on morphological, molecular phylogenetic, and ecological data. The study, the first to report species diversity and phylogeny of Acropora in Amami-Oshima Island, identified 26 species, including three new records for Japan or the Amami Islands. Using mitochondrial DNA analysis, the team found that most Acropora species formed distinct clades, with notable exceptions like A. hyacinthus and A. cytherea, which were highly polyphyletic. The proposed grouping of eight species groups aims to improve identification and understanding of Acropora diversity until a formal taxonomic revision is conducted.
The Relationship between the Transition of Tourism Image and Activity, and Accommodations in Amamioshima
Amami Oshima Island, a potential natural UNESCO World Heritage site, is poised for significant growth in tourism due to increased international recognition and the introduction of low-cost carrier (LCC) flights. This study reveals that the island's tourism landscape is undergoing transformation, with expectations of rising tourist numbers and an expanded customer base. By analyzing the transition of tourism images, activities, and accommodations, researchers aim to provide a foundation for sustainable tourism development. The findings suggest that proactive planning can balance growth with environmental and cultural preservation, ensuring long-term viability. This research combines quantitative analysis with qualitative insights to offer actionable recommendations for stakeholders.
Within host acoustic signal preference of frog‐biting mosquitoes (Diptera: Culicidae) and midges (Diptera: Corethrellidae) on Iriomote Island, Japan
Frog-biting mosquitoes and midges on Iriomote Island, Japan, show a strong preference for the acoustic signals of male Ryukyu Kajika frogs, particularly those containing a lower frequency peak (1.8 kHz) in addition to a high-frequency peak (3 kHz). Field phonotaxis experiments revealed that Type I calls, which include this lower frequency component, are significantly more attractive to these insects compared to Type II calls lacking it. This suggests that frog-biting Nematoceran flies in this ecosystem have evolved acoustic preferences tailored to specific host call characteristics, providing insights into the evolution of antennal hearing and host-seeking behaviors in these haematophagous insects.
Anguillid eels as a surrogate species for conservation of freshwater biodiversity in Japan
Anguillid eels, including the Japanese eel (Anguilla japonica) and giant mottled eel (A. marmorata), serve as effective surrogate species for conserving freshwater biodiversity in Japan. These eels, being widespread across river systems and high-order predators, exhibit a significant positive correlation with the density of other diadromous species. However, this relationship is indirectly linked to river-ocean connectivity, as both eel density and diadromous species abundance decrease with distance from the river mouth and cumulative height of trans-river structures. The study, conducted across 78 sites in six rivers in mainland Japan and Amami-Oshima Island, used stable isotopic analyses and optimal modeling to assess these relationships, highlighting the potential of anguillid eels as indicators, umbrella, and flagship species for freshwater biodiversity conservation.
Characteristics of Sea Current under Typhoons due to Long-term Fixed Observations in Amitori Bay, Iriomote Island
A study conducted in Amitori Bay, Iriomote Island, reveals that the traditional bulk formula for estimating sea surface resistance coefficients, derived from past typhoon wind speeds, may not accurately predict coastal flooding under the intensified typhoons expected with climate change scenario A1B. This finding underscores the urgent need for more observational data on future typhoons to improve the accuracy of storm surge prediction models. The research utilized long-term fixed observations to analyze sea current characteristics during typhoons, highlighting a critical gap in current predictive modeling that could significantly impact coastal management strategies.
Clinical characteristics of stonefish “Oni‐daruma‐okoze” envenomation in Japan
A comprehensive analysis of stonefish envenomation, specifically the 'Oni-daruma-okoze' species, in Japan reveals that 15 cases were recorded over five years (2013–2017), with most incidents occurring in the northern part of Okinawa Main Island. Despite severe envenomations, all patients recovered without antivenom treatment, though two required hospitalization for over a week (8–9 days). The study, conducted through retrospective questionnaires across four hospitals, found no significant differences between tourists and non-tourists in terms of baseline characteristics or outcomes. This research highlights the increasing risk of stonefish envenomation in Japan due to global warming and tourism, while also underscoring the effectiveness of supportive care without antivenom in severe cases.
Comparison of Symbiodiniaceae diversities in different members of a Palythoa species complex (Cnidaria: Anthozoa: Zoantharia)—implications for ecological adaptations to different microhabitats
A study comparing Symbiodiniaceae diversities among closely related Palythoa species in the Ryukyu Archipelago, Japan, revealed distinct genotypic compositions of Cladocopium symbionts associated with different Palythoa species and microhabitats. The research, focusing on P. tuberculosa, P. sp. yoron, and P. mutuki, used nuclear ITS and plastid psbA ncr markers to analyze genetic variations. Findings suggest that ecological divergence among these species may be linked to differences in Symbiodiniaceae diversity, which could contribute to their adaptation to varying microhabitats on coral reefs.
Does HLB Disease Prefer Citrus Growing in Alkaline Soil?
HLB disease, or citrus greening, shows a significant preference for citrus trees grown in alkaline soil, where nutrient deficiencies—particularly manganese, copper, zinc, and iron—are more pronounced. This was revealed through an epidemiological study across 57 private gardens on Amami-Oshima and Tokunoshima Islands, where 47.8% of trees in alkaline soils tested positive for HLB, compared to none in acidic soils. The research employed PCR testing to detect infection and soil component mapping to correlate disease distribution with pH levels. Leaf microelement analysis further confirmed that alkaline conditions reduce essential nutrient availability, suggesting a link between soil chemistry and HLB susceptibility.
Exchange between the Ryukyu Islands and the Korean Peninsula from the Production of the Ceramic Industry in Tokunoshima
Archaeological evidence from Tokunoshima Island reveals that the production of 'Kamui-yaki' ceramics, previously thought to be sourced from various regions, was primarily manufactured locally. This discovery, supported by the excavation of kiln sites in Isenchō, indicates a significant ceramic industry centered on Tokunoshima during the 11th century, predating earlier estimates by about 50 years. The study also suggests that Kamui-yaki ceramics share stylistic similarities with Korean pottery from the Goryeo Dynasty (918–1392), implying cultural and trade exchanges between the Ryukyu Islands and the Korean Peninsula. Researchers propose that these exchanges were facilitated by international trade activities, such as the Japanese-Song (Jp.-Song) and Japanese-Liaoning (Jp.-Liao) trades, which thrived in ports like Hakata, Japan's sole international trade hub at the time.
Habitat preference, movements and growth of giant mottled eels, Anguilla marmorata , in a small subtropical Amami-Oshima Island river
A two-year study on Amami-Oshima Island, Japan, revealed that giant mottled eels (Anguilla marmorata) exhibit distinct habitat preferences and movement patterns in subtropical rivers. Eel density was highest near the river mouth, particularly in vegetated areas, while they avoided concrete and sand banks. Small eels preferred riffle or run habitats characterized by specific depth and velocity, whereas larger individuals were found in varied conditions. The study also documented that eels disperse both upstream and downstream from the tidal limit, with growth rates varying significantly among individuals. Notably, small eels exhibited greater mobility than larger ones, traveling distances up to 380 meters compared to a maximum of 120 meters for larger eels. This research provides critical insights into the ecological behavior of tropical eels, offering a foundation for targeted conservation strategies.
Identification of the population source of free-ranging cats threatening endemic species on Tokunoshima Island, Japan
Free-ranging cats on Tokunoshima Island, Japan, are primarily sustained by feeding practices in cattle barns and thrive in landscapes dominated by woodlots. This study reveals that cat density is positively correlated with the presence of cattle barns and woodlot areas but negatively associated with residential zones. Nearly half of the cattle barns surveyed contribute to cat sustenance, suggesting a significant bottom-up population growth process. The research analyzed live-capture data and conducted interviews to identify these patterns, emphasizing that halting cat feeding in barns could mitigate their impact on endemic species. Further stakeholder engagement is recommended based on ecological risk assessments.
Movement of Sterile Melon Flies in Okinawa, Japan
A study on the movement of sterile melon flies (Bactrocera cucurbitae) in Okinawa, Japan, reveals that these insects could rapidly expand their distribution northward through natural flight, potentially aided by wind. The research, conducted between 1972 and 1993, aimed to evaluate the possibility of re-invasion after a successful eradication program. Flies were captured in coastal regions across multiple islands, including Amami-Oshima, Tokunoshima, northern Okinawa Island, and Iriomote Island, during summer, fall, and winter. The findings suggest that once established on an island, melon flies can quickly spread to adjacent areas, posing a risk of re-establishment in previously eradicated regions.
Notes on Forefoot Characteristics of the Ryukyu Long-Furred Rat, Diplothrix legata, for Its Arboreal Lifestyle
A unique adaptation for arboreal life is identified in the Ryukyu long-furred rat (Diplothrix legata), native to Amami-Oshima, Tokunoshima, and Okinawa Island. The study reveals that the species possesses a nail on its pollex—a rare feature among murids—and a linear palmar groove between interdigital pads, which enables it to grip thin branches effectively. This groove allows the rat's fingers (excluding the pollex) to securely grasp twigs, suggesting an evolutionary specialization for tree-dwelling behavior. Additionally, geographical variation in unguis size was observed, with larger claws noted on Okinawa Island compared to Amami-Oshima Island. The research combines morphological analysis with functional testing to elucidate these adaptations.
Paleoproterozoic to Cenozoic zircon U–Pb ages with Hf signatures from metamorphic rocks and granodiorite of Tokunoshima: constraints on the geotectonic subdivision of the Ryukyu island arc, Southwest Japan
A groundbreaking study reveals that the Omo Formation on Tokunoshima Island, part of the Ryukyu island arc in Southwest Japan, shares geological origins with Cathaysia in the South China block. Using LA-ICP-MS U–Pb and Hf isotope analysis on zircons from metamorphic rocks and granodiorite, researchers identified Paleoproterozoic to Cenozoic age ranges, indicating Early Jurassic reworking of older continental crust. The positive εHf(t) values in Paleoproterozoic zircons (+12.7 to +0.8) contrasted with negative values in Jurassic zircons (−19.6 and −22.8), suggesting significant tectonic activity. Additionally, granodiorite zircon ages (61.3 ± 1.0 Ma) with positive εHf(t) values (+12.0 to +12.6) correlate with juvenile magmatic activity in the San-in batholith belt, hinting at a shared geological history across Southwest Japan.
Present status and countermeasure of the Domestic Cat predation on endemic birds in Yambaru area of the northern part of Okinawa Island
Domestic cats (Felis catus) pose a significant threat to endemic bird species in the Yambaru region of northern Okinawa Island, including the flightless Yambaru rail (Gallirallus okinawae). A local ordinance requiring microchip registration for pet cats has proven effective in distinguishing between domestic and feral cats, facilitating targeted feral cat management. This study highlights the critical role of regional collaboration in mitigating predation risks to vulnerable endemic species, emphasizing the need for island-wide efforts to sustain conservation outcomes.
Prevalence of serum antibodies to Toxoplasma gondii in free-ranging cats on Tokunoshima Island, Japan
A study on Tokunoshima Island, Japan, reveals a high prevalence of Toxoplasma gondii infection among free-ranging cats, with 47.2% testing positive for antibodies against the parasite. The research, conducted using serum samples from 125 cats, found significantly higher seropositivity rates (57.4%) in cats weighing over 2.0 kg compared to smaller cats (12.5%). Additionally, infected cats were detected across 17 of 23 settlements on the island, indicating widespread distribution. This is the first study to document T. gondii prevalence in free-ranging cats on Tokunoshima Island, providing critical data for preventing transmission among animals and humans.
Records of the giant spoon worm Ikeda taenioides (Annelida: Echiura: Ikedidae) from the Kii Peninsula, the Sea of Japan, and Amami-Oshima Island
New records of the giant spoon worm Ikeda taenioides, one of the largest echiuran species, extend its known distribution along Japanese coasts. Researchers documented proboscises from Tanabe Bay (Kii Peninsula) and Maizuru Bay (Sea of Japan), updating historical records by 70 and 51 years, respectively. A potential sighting off Amami-Oshima Island may further push the species' southern range limit. Genetic confirmation using the COI marker validated these findings, suggesting I. taenioides persists broadly from Mutsu to Ryukyu Islands. This study highlights the species' resilience but underscores urgent conservation needs due to habitat loss and human pressures.
Survivorship after flowering and flowering synchronicity of three cultivated Strobilanthes flexicaulis individuals from Iriomote Island, Japan
A study on Strobilanthes flexicaulis, a monocarpic perennial plant from Iriomote Island, Japan, reveals that cultivation may alter its reproductive traits, shifting it toward polycarpy. The research observed three cultivated individuals, finding synchronized flowering initiation but variable termination among them and between treatments involving disbudding (flower bud removal). While disbudding did not affect survivorship, individual variation in reproductive traits suggests an intermediate evolutionary state between polycarpic perennials and periodical mass-flowering plants. This study sheds light on how cultivation influences the reproductive strategies of this species.
Temporal Changes in Number of Breeding Individuals of the Amami Tip-Nosed Frog
A rapid decline in breeding activity was observed among the endangered Amami tip-nosed frog (Odorrana amamiensis) on Amami-Oshima Island, Japan. The study, conducted over eight days in late 2015, documented a high density of breeding individuals—over 200—with active mating calls around a small stream at night for three consecutive days, followed by a sharp decrease. This is the first quantification of such temporal changes in this species. Notably, while primarily nocturnal, some frogs were observed during daylight, suggesting daytime field research could be safer and more efficient than nighttime surveys, given the presence of venomous snakes like the Habu (Protobothrops flavoviridis). These findings provide critical insights for conservation efforts, highlighting the need to understand breeding ecology to protect this threatened amphibian.
Unique Evolution of Hyla hallowellii Among Amphibians of the Central Ryukyus, Japan (Anura: Hylidae)
Hyla hallowellii, a tree frog endemic to the Central Ryukyus, exhibits a unique evolutionary pattern distinct from other amphibians in the region. Genetic analyses of eight island populations revealed low overall differentiation but notable divergence between northern and intermediate populations, contrasting with known patterns in other species. Morphological and karyotype studies showed no clear interpopulation differences, suggesting a complex evolutionary history influenced by geographic isolation and genetic exchange.
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