Miyako Island Research Articles

Isopods on isopods: integrative taxonomy of Cabiropidae (Isopoda: Epicaridea: Cryptoniscoidea) parasitic on anthuroid isopods, with descriptions of a new genus and three new species from Japan.

Species in the parasitic isopod family Cabiropidae are known to utilise various isopods as hosts but there are currently no records of members parasitising anthuroid hosts. We describe Anthuroniscus gen. nov. for three new cabiropid species, Anthuroniscus shimomurai sp. nov. , Anthuroniscus dentatus sp. nov. and Anthuroniscus latus sp. nov. , all of which are parasitic on anthuroid isopods. Anthuroniscus gen. nov. differs from the other 14 cabiropid genera and 10 genera treated as family incertae sedis in females having an elongate, dorsally compressed, posteriorly tapering body with six pairs of lateral bulges; and cryptoniscus larvae in the following combination of characters: (1) eyes lacking, (2) antennular article 1 with eight teeth on the posterior margin, (3) uropodal exopod and endopod rectangular rather than tapering, and endopod longer than exopod, and (4) pleotelson trapezoidal, 2× as wide as long. Anthuroniscus shimomurai sp. nov. was parasitic on Mesanthura sp. from Kaichu Doro, Uruma, Okinawa, south-western Japan; A. dentatus sp. nov. on Accalathura sp. from Irabu Island, Miyako Islands, Okinawa; and A. latus sp. nov. on Colanthura nigra from Kanagawa, central Japan. In pairwise comparisons, the three new species showed p -distances of 0.6-1.3% for the 18S rRNA gene (1440 positions); and A. shimomurai sp. nov. and A. latus sp. nov. showed a p -distance of 36.2% for the 16S rRNA gene (412 positions). In an 18S -based maximum-likelihood tree, an Anthuroniscus gen. nov. clade was the sister group to Cryptoniscoidea sp., parasitic on an ostracod species. This is the first study reporting Cabiropidae from Japan and anthuroids as hosts for Cryptoniscoidea. ZooBank: urn:lsid:zoobank.org:pub:2EE042E2-AE48-4B87-B495-8436462146B9.

Precocious maturation and semi-multivoltine lifecycle in a subtropical grass lizard, Takydromus toyamai

Abstract There are many short-lived animals, but those displaying a lifecycle with more than one generation per year (multivoltine lifecycle) are rare among terrestrial vertebrates. The multivoltine lifecycle requires rapid growth and maturation and a long active season. Thus, small lizards in humid tropical or subtropical areas are candidates for multivoltine lifecycles. To test this prediction, we conducted a capture-mark-recapture study of a subtropical grass lizard, Takydromus toyamai, endemic to Miyako Islands, Japan. Juveniles grew very quickly, averaging 0.3 mm/day in the warm season, and attained sexual maturity at 2.5 months post-hatching. The breeding season was very long, and hatchlings emerged from May to November. The prolonged breeding season and rapid growth to maturity allowed some individuals to produce a second generation in their first year. Estimates of hatching date from growth rates indicated that many females that hatched in May–June became gravid 76–120 days after hatching and 122–165 days after oviposition of the eggs from which they hatched. Analyses of juvenile survivorship and month of hatching suggest that nearly half of breeding adults were members of multivoltine generations, although the 2 generations were not discrete. The species is short-lived, with only 16% of individuals surviving beyond 12 months, and few individuals reproduced in a second year. We refer to this condition as a “semi-multivoltine lifecycle.” Individuals that hatch late in the season defer reproduction until the following year and become founders of the next season’s cohort. This putative advantage of late-hatching individuals may have driven the evolution of this lifecycle.

Numerical Verification of Groundwater Suitability for Irrigation Around the Subsurface Dam Area of Miyako Island, Japan

The sustainable management of water resources is essential for agricultural productivity, especially in areas with scarce water availability. This study focused on assessing groundwater quality for irrigation near the subsurface dam area of Miyako Island, Japan. Water samples from three observation points were tested for various parameters, including electrical conductivity (EC), sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium bicarbonate (RSBC), permeability index (PI), Kelley's ratio (KR), and magnesium adsorption ratio (MAR). EC values ranged from 270 to 800 µS/cm, suggesting water quality ranging from doubtful to good. SAR values between 0.23 and 1.49 suggested excellent quality. SSP ranged from 7.90% to 31.71%, mostly indicating good to excellent quality. RSBC values fluctuated between -1.57 to 1.45 epm, largely within safe limits. PI values varied from 40.34 to 75.83, indicating good permeability. Total hardness (TH) ranged from 105.50 to 326.45 ppm, classifying the water as hard to very hard. MAR values were below 50, suggesting potential soil issues. A numerical model confirmed observed Ca²⁺ concentrations, showing an increasing trend due to enhanced CO₂ emissions and lower pH. The data analysis revealed strong positive relationships between SSP and KR (r = 0.984), SAR and SSP (r = 0.951), and SAR and KR (r = 0.960). Despite generally acceptable values, continuous monitoring is recommended, especially for hardness, to ensure sustainable crop production. This study underscores the need for regular assessment and management of groundwater quality in subsurface dam areas to mitigate potential adverse effects on soil and agricultural productivity.

Analysis of the interaction between the ORF42 and ORF55 proteins encoded by Kaposi's sarcoma-associated herpesvirus.

Kaposi's sarcoma-associated herpesvirus (KSHV) causes Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman disease. The tegument is a structure that is unique to herpesviruses that includes host and viral proteins, including the viral ORF42 and ORF55 proteins. Alphaherpesvirus tegument proteins have been well studied, but much is unknown regarding KSHV. Here, we report an interaction between the ORF42 and ORF55 proteins. ORF55 interacted with and recruited ORF42 from the nucleus to the cytoplasm. When ORF42 and ORF55 were expressed simultaneously in cultured cells, the expression level of these two viral proteins was higher than when either was expressed independently. ORF55, but not ORF42, was polyubiquitinated, suggesting that an unidentified regulatory mechanism may be present. A recombinant virus with an ectopic stop codon in ORF42 exhibited normal replication of genomic DNA, but fewer virus particles were released with the recombinant than with the wild-type virus. A unique R136Q mutation in ORF42, which is found in a KSHV strain that is prevalent on Miyako Island, Okinawa Prefecture, Japan, further increased the expression of ORF42 and ORF55 when these proteins were expressed simultaneously. However, the ORF42 R136Q mutation did not affect the localization pattern of ORF42 itself or of ORF55. In addition, experiments with a recombinant virus possessing the ORF42 R136Q mutation showed lower levels of production of the mutant virus than of the wild-type virus, despite similar levels of genome replication. We suggest that the R136Q mutation in ORF42 plays an important role in ORF55 protein expression and virus production.

Region-Specific Genetic Diversity of Black Rats (Rattus rattus Complex) in Southeast and East Asia Shaped by Rapid Population Expansion Events.

Among the six mitochondrial DNA lineages of the black rat (Rattus rattus Complex; RrC), lineages II and IV are widespread in Southeast and East Asia. This study explored their demographic history using 17 new sequences from the Miyako Islands in the Ryukyu archipelago, together with 178 publicly available cytochrome b sequences. We defined six and two haplotype groups showing rapid population expansion signals in Lineages II and IV, respectively. The six haplotype groups of Lineage II were represented by haplotypes from 1) Myanmar/Bangladesh/Northeast India, 2) Laos, 3) Thailand, 4) Indonesia/Philippines, 5) Vietnam/southern China, and 6) the Ryukyu archipelago. These expansion times were estimated using time-dependent evolutionary rates to be 115,300 years ago (ya), 128,500 ya, 9600 ya, 10,600 ya, 7200 ya, and 1400 ya, respectively, although all had large confidence intervals. The two groups of Lineage IV were recovered from the mainland and islands of Southeast Asia with predicted expansion times of 197,000 ya and 5800 ya, respectively. These results suggest that climatic fluctuations during the last 200,000 years of the Quaternary, affected the population dynamics in subtropical areas at different times. Furthermore, the results of the younger rapid expansion events of RrC suggest the possibility of agricultural advancement and dispersal of Neolithic farmers to different areas within the mainland and islands of Southeast Asia during the Holocene. A subset of rats from the Miyako Islands were found to have the same lineage IV haplotypes as those in Southeast Asia, suggesting a recent introduction of these new lineages.

Fecal DNA analysis coupled with the sighting records re-expanded a known distribution of dugongs in Ryukyu Islands after half a century

DNA analysis of large herbivore feces samples collected from seagrass beds at two distant sites (Irabu Island in Miyako Islands and Kushi in Okinawa Island) in the Ryukyu Islands proved that some of these feces were from dugongs, which had been treated in recent studies as extinct in this region since the last stranding of a deceased individual in 2019. In addition, local knowledge of sightings of animals thought to be dugongs and confirmed cases of dugong feeding trails since 2010 were compiled to estimate its recent distribution. This is the first scientific report on the presence of this mammal in the Ryukyu Islands within the last four years, and particularly in the Miyako Islands within the last half-century. As the Ryukyu Islands are known to be the northern limit of the dugong’s fragmented distribution in East Asia, conservation efforts are therefore needed.

An ancient genome perspective on the dynamic history of the prehistoric Jomon people in and around the Japanese archipelago

The Jomon people were prehistoric residents of the Japanese archipelago who occupied the region from ca. 16,500 to 2,300 years before present (BP). While recent accumulation of ancient genomes and genome-wide data of the Jomons has substantially enhanced our understanding of their genetic profiles and contribution to present-day populations, their genetic history in the Jomon-period archipelago, spanning over 14,000 years in time and 2,000 km in distance, remains scarcely investigated. Here we report multiple findings illuminating the Jomon genetic history based on the analysis of the genetic relationship between published ancient genome-wide data of 23 Jomon and Jomon-like individuals. First, the Initial Jomon individual from Shikoku, dated to ca. 9,000 BP, forms a common outgroup to the remaining later Jomon individuals, suggesting a population turnover in western Japan. Second, genetically Jomon-like individuals outside the Jomon archaeological context, found in the Miyako Island in Ryukyu and the Yokjido island in the southern coast of Korea, show the closest genetic affinity with the Late Jomon individual from Shikoku, narrowing down their sources in space and time. This study highlights a dynamic history of the Jomon people in and out of the Japanese archipelago and calls for a large-scale investigation of the ancient Jomon genomes.

First record of Macrobrachium mammillodactylus (Thallwitz, 1891) (Crustacea, Decapoda, Palaemonidae) from Japan

Knobtooth Prawn, Macrobrachium mammillodactylus (Thallwitz, 1891), is an amphidromous freshwater prawn that occurs in the tropics of the western Pacific Ocean. Here, we report a new record of this species from Miyako Island, in the Ryukyu Archipelago, Japan. The obtained specimens were mature, suggesting that they had overwintered. This record updates the northern limit of M. mammillodactylus and suggests an expansion of the range of this species.

A new species of free-living marine nematode, Fotolaimus cavus sp. nov. (Nematoda, Oncholaimida, Oncholaimidae), isolated from a submarine anchialine cave in the Ryukyu Islands, southwestern Japan

Fotolaimus cavussp. nov. was described from a submarine anchialine cave called Akuma-no-yakata on the Shimoji Island, Miyako Island Group, Ryukyu Islands, southwestern Japan. This is the first free-living marine nematode isolated from a submarine cave in Japan, and the third species of the genus Fotolaimus. This new species differs from its congeners by its small body size, wide amphids, long buccal cavity, long conico-cylindrical tail, and proximally curved gubernaculum. We provide amended dichotomous keys to genera in the subfamily Oncholaiminae and species in Fotolaimus. We also analyzed partial DNA sequences encoding ribosomal small subunit RNA and cytochrome c oxidase subunit I from Fotolaimus cavussp. nov. and six other species of Oncholaimidae collected from Japanese waters. The phylogenetic tree based on the ribosomal small subunit RNA sequences using maximum likelihood analysis suggested a close relationship between Fotolaimus and Wiesoncholaimus as well as Oncholaimus. The topology of the tree was similar to those from previous studies; however, it suggested a new phylogenetic position of Adoncholaimus as a sister clade for Viscosia and Oncholaimus.

Recent Relative Sea‐Level Changes Recorded by Coral Microatolls in Southern Ryukyus Islands, Japan: Implication for the Seismic Cycle of the Megathrust

AbstractThe seismic hazard related to megathrust earthquakes in the Ryukyus (southern Japan) is poorly constrained as no large earthquake has been reported there. The Meiwa tsunami impacted the coasts of the Yaeyama and Miyako islands in 1771 but its origin is still debated. Global Navigation Satellite Systems measurements indicate that strain is accumulating along the plate interface but the observation period is short. It is thus crucial to gain information on the seismic potential of the megathrust. The islands of the Ryukyu archipelago are located in a tropical region and surrounded by reefs where numerous microatolls are growing. They preserved the record of variations of the relative sea‐level in their skeleton. We mapped seven sites over five islands and subsequently selected and sampled eight slabs of modern microatolls. The corals have emerged slowly at a rate of 0.7–2.8 mm/yr due to the long‐term interseismic loading on the megathrust up to 40 km in deep. The coupling rate estimated from elastic back‐slip models ranges between 10% and 100%. We also identified multi‐decadal relative sea‐level changes of a few cm/yr, likely due to very long duration slow‐slip events (SSE) along the shallow or deep parts of the megathrust. Those SSEs occur each 10–40 years and have accommodated 50% of the convergence rate in the last 250 years. Our study provides new constraints on the seismic cycle of the Ryukyu megathrust and on the seismic hazard in this region and suggests that a large megathrust earthquake could occur in the area in the future.

Heterogeneity of hydrological connectivity in coral limestone groundwater pool from vertical, spatial and temporal tracing of groundwater chemicals and isotopes

Carbonate aquifers are critical for the health and well-being of human communities. Despite considerable efforts on the structure of karst aquifers, the variable and invisible flow paths or the vertical and spatial heterogeneity of karst systems remain too complex to be fully understood. An artificially constructed small limestone aquifer with an extensive network of observation wells in the Miyako Island, Japan, provides a unique opportunity to illustrate the vertical and spatial hydrological connectivity for water movement and storage. Water chemical data at two different depths over six years, including electrical conductivity (EC), dissolved oxygen (DO), oxidation–reduction potential (ORP), major ions (Na+, K+, Ca2+, Mg2+, SO42−, and HCO3−), δ18O and δ2H capture water mixing processes during groundwater recharge in the aquifer influenced by irrigation pumping and recharge by precipitations throughout drying and wetting cycles. Results suggest that the intensive weathering of coral limestone under the impact of agricultural fertilization, as indicated by high EC values and high concentrations of Ca2+ and HCO3−. The high DO and low ORP values imply a lack of organic decomposition activity, which is typical in the karst groundwater condition. More importantly, groundwater recharge in the small aquifer was found to be influenced by following three processes. Spatially, both Cl− and NO3−−N indicate the large heterogeneity of water mixing as rainfall or drainage water percolates differently to various parts of the aquifer. Vertically, there are apparent differences in the concentration of Cl− and NO3−−N between the top and bottom layers in several wells, suggesting that, even within a single well, the vertical profile can be weakly connected between the top and the bottom layers. The bottom layer should have been recharged by lateral water inflow from fractures or conduits. And thirdly, the even distribution of Cl− over the long precipitation season from October 2016 and March 2021 and another nearly even distribution of NO3−−N in the low fertilization season in March 2021, demonstrate that the aquifer system is basically connected and porous. In summary, the insights gained from our study reveal that: 1) coral limestone can be treated as a well-developed porous aquifer and 2) the hydrological connectivity is highly heterogeneous and influenced by rock properties, including formation structure, degree of weathering, and clay content. Such findings are essential for understanding the hydrogeological properties of coral limestone aquifers globally.

Epidemiology of Subarachnoid Hemorrhage in Isolated Islands in Japan: A Population-based Study in the Miyako Islands.

The Miyako Islands (with a population of approximately 50,000) are located in southwestern Japan, with a subtropical oceanic climate. This isolated location permitted a retrospective population-based epidemiological study of subarachnoid hemorrhage. We retrospectively enrolled 110 consecutive patients from 2010 to 2019 using the subarachnoid hemorrhage database at Okinawa Miyako Hospital, which is the only local facility with neurosurgeons. We calculated the incidence of subarachnoid hemorrhage standardized to the entire Japanese population. The seasonal distribution of subarachnoid hemorrhage onset and patients' epidemiological characteristics were also investigated. The standardized annual incidence of subarachnoid hemorrhage was 21.4 per 100,000 population, as reported previously in Japan. The patients' mean age was 62.1 ± 15.4 years, and women constituted 60.9%. Anterior communicating artery aneurysms were most common. The endovascular treatment for ruptured aneurysms was increasing as standard levels in Japan. The rates of symptomatic vasospasm and secondary hydrocephalus requiring additional neurosurgical treatment were 2.7% and 19.1%, respectively. The mortality rate was 23.6%. The percentage of patients with a modified Rankin scale score of 0-2 at discharge was 55.5%. There were no differences in the frequency of subarachnoid hemorrhage associated with seasonal distribution or climatic factors. The incidence, baseline characteristics, and clinical outcomes of subarachnoid hemorrhage in the Miyako Islands were similar to those in other regions of Japan. There are preferable epidemiological backgrounds for further practical clinical research.

New sea spider species (Pycnogonida: Austrodecidae) from a submarine cave in Japan

Abstract We describe a new sea spider species, Pantopipetta hosodai sp. nov., based on one juvenile female collected from a submarine cave (‘Akumanoyakata’ Cave) in Shimojijima Island, Miyako Island Group, Ryukyu Islands, southwestern Japan. It was collected from the second slope zone of the cave, 80–100 m from the entrance, no light, low salinity and with rocky substrate. This is the first record globally of a Pantopipetta species from a submarine cave and anchialine environment. Pantopipetta hosodai sp. nov. resembles Pantopipetta auxiliata, Pantopipetta lenis and Pantopipetta oculata in having auxiliary claws, but differs from them in having a palp with three short distal articles, lateral processes without dorsodistal tubercles, coxae 1 and 3 of legs 1–3 each with one long dorsal tubercle and one dorsodistal tubercle bearing a seta on each femur. Features of the palp appear to delineate two species groups in Pantopipetta, i.e. (1) those having four small distal articles, and a small, basal palp article between the lateral cephalon process and longest palp article (eight-articulate palp) and (2) those having three small distal articles, and lacking the small basal article (six-articulate palp), but further detail examination of the described species is needed. We discuss the diagnostic characters separating Pantopipetta and Austrodecus and the generic affiliation of Austrodecus aconae. Few pycnogonids from marine or anchialine caves have been identified to species, and it is generally unknown whether cave-dwelling pycnogonids tend to be troglobites.

Groundwater Management in an Uncommon and Artificial Aquifer Based on Kc Approach and MODIS ET Products for Irrigation Assessment in a Subtropical Island

Groundwater is a critical resource in remote and isolated islands where rainfall hardly provides a continuous and even water supply. In this paper, in a very rare and uncommonly found artificial aquifer on Miyako Island, far away from the main continent of Japan, with limited experimental results of evaluations of crop water requirement, MODIS ET together with crop ETc estimated from Kc coefficient from the nearest island were compared to determine the reliability of the MODIS ET and FAO-56-based ETc value. The testified Kc approach for sugarcane ET was used to assess the risk of irrigation water shortages using historical metrological data and to predict the future risk of irrigation agriculture under different scenarios of GCM models. It was shown that FAO-56-based ETc and MOD16A2 were both applicable for crop evapotranspiration on the island. Then, the response of groundwater storage to gross irrigation water requirement was analyzed to clarify the effect of irrigation on groundwater storage and the risk of groundwater depletion under current and future climatic conditions. Results showed that the construction of the dam efficiently secured the irrigation of sugarcane. Using historical climatic data (1951–2021), the influence of estimated irrigation water requirements on groundwater showed that in 296 out of 852 months, irrigation was heavily required. Over a 71 year period, there was absolutely no water for irrigation four times, or nearly once every 18 years. Under the future projected climate from four bias-corrected GCM models with two emission scenarios (2022–2100), the risk of groundwater depletion both in terms of frequency and duration will increase. Therefore, there is a need for either improvement of irrigation water management or additional construction of artificial aquifers on the island. The study proved the value of ET derived from remote sensing in areas lacking the support of experimental results. The methodology developed in the study can be potentially used to evaluate long-term irrigation demand and groundwater management over dry periods for engineering design or dam construction globally.

Meteorological and demographic factors associated with the onset of acute appendicitis in rural islands of Japan

Emergency surgery and hospitalisation has become a burden in rural areas owing to a shortage of surgeons. Acute appendicitis is a common emergency disease. Understanding the aetiology of acute appendicitis could predict emergency surgeries to optimise resource allocation in rural areas. Several studies have pointed out that some meteorological factors are associated with acute appendicitis; however, there is no consensus about these factors. With the geographical advantages, homogenous meteorological effects, and overwhelming medical data collection in the area, this study aimed to explore meteorological and demographic factors associated with acute appendicitis by focusing on the onset day of acute appendicitis. Miyako islands is in southern Japan and it has a subtropical climate. Okinawa Miyako prefectural Hospital (OMH) is the only hospital in the area that conducts emergency surgery. A total of 212 acute appendectomy cases collected over 6 years were analysed for sex, age, onset date, pathology type, perforation, and fecaliths. Meteorological factors (air pressure, air temperature, humidity, precipitation, wind speed, sunlight hours, and lunar age) on the onset day of acute appendicitis were analysed. Significant differences between air temperature 6 and 7 days before onset and the onset day were observed. Higher air temperature, compared to the average value, was significant in acute appendicitis cases. Pathological types were associated with age group, perforation, and fecaliths. Age group was also associated with existing perforation. Increase in temperature throughout the week prior to onset could be an anticipating factor for the onset of acute appendicitis. The meteorological and demographic features associated with the onset of acute appendicitis could become keys to evaluating acute appendicitis risk in the future and contribute to reasonable allocation of scarce surgical resources to rural areas.

Comparison of mortality and feeding behavior of the false cleanerfish Aspidontus taeniatus and the lance blenny A. dussumieri regarding the effects of mimicry.

The online version contains supplementary material available at 10.1007/s10164-022-00769-8.

A new shrimp of the genus Odontozona Holthuis, 1946 (Decapoda: Stenopodidea: Stenopodidae) from a submarine cave of the Ryukyu Islands, Indo-West Pacific.

A new species of the stenopodid shrimp genus Odontozona Holthuis, 1946 is described and illustrated on the basis of single specimen recently collected from a submarine cave at Shimoji-jima Island, Miyako Island Group, Ryukyu Islands, southwestern Japan. Odontozona ganzu sp. nov. appears to be unique within the genus Odontozona by lacking transverse row of posterior small spines on sixth pleuron. General morphology of the new species is also similar to O. stigmatica Saito, Okuno Anker, 2017 described from Ishigaki-jima Island, Ryukyu Islands, West Pacific, but differs from it by a combination of morphological characters, viz., lacking the cincture of small spines on the posterior margin of the carapace, the distinct transverse carina on the third pleuron, as well as the lateral teeth of the uropodal endopod. This study increases the total number of the described species in the genus Odontozona to 23, 11 of which occur the Indo-West Pacific.

First records of the lace bug genus Lasiacantha Stål, 1873 (Hemiptera, Heteroptera, Tingidae) from Japan

The lace bug genus Lasiacantha Stål, 1873 (Hemiptera, Heteroptera, Tingidae, Tinginae, Tingini) is widely distributed in the Old World; however, no species has been recorded in Japan. To date, L. altimitrata (Takeya, 1933) has been reported in China and Taiwan. Here, I report Lasiacantha and L. altimitrata from Japan for the first time, based on materials collected from Ishigaki and Miyako islands in the Ryukyu Islands. In Japan, this lace bug is found in grasslands near beaches. Miyako Island is the easternmost locality for L. altimitrata.

Can Third-Party-Ownership Business Model Overcome Barriers to Adopt Rooftop Solar Pv-Battery Systems? Implications from the Case of Miyako Island, Japan

Can Third-Party-Ownership Business Model Overcome Barriers to Adopt Rooftop Solar Pv-Battery Systems? Implications from the Case of Miyako Island, Japan

Analyses of Cemented and Un-cemented Sand Layers and Spring Water, Collected from Yoshino Coast, Southeast of Miyako Island, Okinawa

Analyses of Cemented and Un-cemented Sand Layers and Spring Water, Collected from Yoshino Coast, Southeast of Miyako Island, Okinawa