Okinawa Research Articles

Relationship between the Number of Deaths Due to Renal Failure and Air Temperature Parameters in Hokkaido and Okinawa Prefectures, Japan.

Background: The aim of the present study was to investigate the relationship between the number of deaths due to renal failure and air temperature parameters in Hokkaido (the northernmost region) and Okinawa (the southernmost region) prefectures, Japan. Methods: Monthly data on the number of deaths due to renal failure between January 2008 and December 2016 and annual population data were collected from the Hokkaido and Okinawa official prefecture websites. Air temperature parameters were obtained from the Japan Meteorological Agency. The relationship between the number of deaths due to renal failure and air temperature parameters was evaluated by an ecological study. Results: The number of deaths due to renal failure (per 100,000 people/month) in Hokkaido and Okinawa were 2.28 ± 0.30 and 1.17 ± 0.31. In Hokkaido, the number of deaths due to renal failure negatively correlated with air temperature parameters in both sexes. The number of deaths due to renal failure was significantly higher in January than from June to September in all subjects. However, in Okinawa, no significant difference was observed among months. Conclusions: The present results suggest that the relationship between the number of deaths due to renal failure and air temperature parameters differs between Hokkaido and Okinawa.

A Longitudinal Study on the Relationship of Oral Health at 4 Years of Age with That in Adulthood.

This longitudinal study aimed to clarify the relationship of oral health in infancy with that in adulthood among participants who were the subjects of the oral health promotion project (OHPP) conducted in Miyako Island, Okinawa Prefecture, Japan, since 1984. Twenty-seven subjects, around 35 years of age, were examined for dental caries, periodontal diseases (community periodontal index), dental plaque, occlusion, and bite-force and compared with those at 4 and 13–15 years of age. The dental caries status and maximum bite force in adulthood was significantly reflected for those at 4 and 13–15 years of age (p < 0.05). CPI in adulthood was related to the dental caries status at 4 and 13–15 years of age but not to the gingival score at 4 years of age, and it was weakly related to the gingival score at 13–15 years (r = 0.264, p > 0.05). Most of the normal occlusion at 4 years of age became normal permanent occlusion in adulthood (88.9%). Most of the cases involving the discrepancy factor retained the same condition in both the deciduous and permanent dentitions (83.3%) (p < 0.001). Those who participated in the OHPP soon after birth showed significantly fewer DMFT (p < 0.05) compared with those who did not. This study revealed that oral health at 4 years of age was related to that in adulthood, suggesting that fostering good oral health soon after birth is of great importance.

Color morphs of the coral, Acropora tenuis, show different responses to environmental stress and different expression profiles of fluorescent-protein genes.

Corals of the family Acroporidae are key structural components of reefs that support the most diverse marine ecosystems. Due to increasing anthropogenic stresses, coral reefs are in decline. Along the coast of Okinawa, Japan, three different color morphs of Acropora tenuis have been recognized for decades. These include brown (N morph), yellow green (G), and purple (P) forms. The tips of axial polyps of each morph exhibit specific fluorescence spectra. This attribute is inherited asexually, and color morphs do not change seasonally. In Okinawa Prefecture, during the summer of 2017, N and P morphs experienced bleaching, in which many N morphs died. Dinoflagellates (Symbiodiniaceae) are essential partners of scleractinian corals, and photosynthetic activity of symbionts was reduced in N and P morphs. In contrast, G morphs successfully withstood the stress. Examination of the clade and type of Symbiodiniaceae indicated that the three color-morphs host similar sets of Clade-C symbionts, suggesting that beaching of N and P morphs is unlikely attributable to differences in the clade of Symbiodiniaceae the color morphs hosted. Fluorescent proteins play pivotal roles in physiological regulation of corals. Since the A. tenuis genome has been decoded, we identified five genes for green fluorescent proteins (GFPs), two for cyan fluorescent proteins (CFPs), three for red fluorescent proteins (RFPs), and seven genes for chromoprotein (ChrP). A summer survey of gene expression profiles under outdoor aquarium conditions demonstrated that (a) expression of CFP and REP was quite low during the summer in all three morphs, (b) P morphs expressed higher levels of ChrP than N and G morphs, (c) both N and G morphs expressed GFP more highly than P morphs, and (d) GFP expression in N morphs was reduced during summer whereas G morphs maintained high levels of GFP expression throughout the summer. Although further studies are required to understand the biological significance of these color morphs of A. tenuis, our results suggest that thermal stress resistance is modified by genetic mechanisms that coincidentally lead to diversification of color morphs of this coral.

Characterization of Erwinia sp. causing black rot of papaya (Carica papaya) first recorded in Okinawa Main Island, Japan

AbstractSince 2002, papaya black rot has been spreading over several islands of Okinawa Prefecture, Japan. To devise a prevention strategy for the disease, microbiological research on the pathogen was conducted. Twelve strains were isolated from papaya infected with black rot showing symptoms such as water‐soaked lesions on stems and petioles, black spots on fruits, and rotted leaves turning yellow with necrotic spots. Through Koch's postulates, we confirmed that the isolated strains caused papaya black rot. Bacteriological assays showed that the strains have characteristics different from the type strains of Erwinia mallotivora, E. papayae, and E. psidii. Moreover, 16S rDNA sequence similarity searches showed that the isolated strains had less than 98.6% similarity with type strains. Additionally, phylogenetic analysis of 16S rDNA sequences suggested that the isolated strains were possibly a novel species belonging to the genus Erwinia, as the strains formed an independent cluster and had low sequence similarity with the type strains. Earlier studies indicated that papaya black rot is caused by E. cypripedii. Therefore, we propose to add the Erwinia sp. isolated in this study to the list of papaya black rot pathogens.

&lt;i&gt;Benedenia akajin&lt;/i&gt; n. sp. (Monogenea: Capsalidae) from Leopard Coral Grouper &lt;i&gt;Plectropomus leopardus&lt;/i&gt; Reared in Okinawa Prefecture, Japan

The grow-out stage of leopard coral grouper Plectropomus leopardus reared in land-based tanks in Okinawa Prefecture, Japan, were often heavily infected with capsalid monogeneans, up to a few millimeters in size, on the fins and skin. ​Morphological investigation revealed that the parasite belongs to Benedenia (Monogenea: Capsalidae). ​Benedenia akajin n. sp. is proposed here and described morphologically, based on the unique structures in the vaginal duct with a thick-walled distal one-third, the penis with a teat-shaped tip and the testes smaller than the germarium. ​A positive relationship between the lengths of three haptoral sclerites (anterior sclerites and anterior and posterior hamuli) and body length indicates that these taxonomically important structures keep growing as the parasite ages. ​Molecular analyses showed that the present species is most closely related to B. epinepheli and B. sargocentron, with the highest 28S rDNA identity of 98.1%, but no identical sequences were found in the database. ​Both morphological and molecular evidences suggest Benedenia akajin n. sp. as an undescribed species, and this new skin fluke deserves further investigations for the stable aquaculture of P. leopardus.

Contested memory of Okinawa’s colonial and war past: history teaching in and beyond formal education

ABSTRACT This paper investigates the different ways in which the Battle of Okinawa in World War II is presented in and beyond formal education, using narratives and photos in Japan’s state-authorized history textbooks and at a local museum. Specifically, this study examines 15 upper secondary school textbooks issued by six publishing companies from across the political spectrum and analyzes the narratives and photos used in these textbooks to depict and explain the Battle of Okinawa, together with the digital archives and official guidebook of the Okinawa Prefectural Peace Memorial Museum (OPPMM). The arguments and findings are three-fold. First, despite the line-by-line scrutiny of textbook contents by the state, individual textbooks show different narratives of the battle, and the monolithic view regarding the “Japanese textbook” is not sustained. Second, there are general differences of the battle’s presentations between the school textbooks as a group and the OPPMM. Third, a crucial gap between them in presenting the Battle of Okinawa and World War II is in the perception of the “enemy”. This gap needs to be understood, as the museum’s presentation implies, with a prolonged relationship of contestation between Okinawa and “mainland Japan”, dating back to the late 19th century.

Geomorphology and its Formation of Nagashima Limestone Cave off the Henoko-Zaki, Nago City, Okinawa Prefecture, Japan

Geomorphology and its Formation of Nagashima Limestone Cave off the Henoko-Zaki, Nago City, Okinawa Prefecture, Japan

Genetic diversity and genomic inbreeding in Japanese Black cows in the islands of Okinawa Prefecture evaluated using single-nucleotide polymorphism array.

Maintaining genetic diversity and inbreeding control are important in Japanese Black cattle production, especially in remote areas such as the islands of Okinawa Prefecture. Using a single-nucleotide polymorphism (SNP) array, we evaluated the genetic diversity and genomic inbreeding in Japanese Black cows from the islands of Okinawa Prefecture and compared them to those from other locations across Japan. Linkage disequilibrium decay was slower in cows in the islands of Okinawa Prefecture. The estimated effective population size declined over time in both populations. The genomic inbreeding coefficient (FROH ) was estimated using long stretches of consecutive homozygous SNPs (runs of homozygosity; ROH). FROH was higher in the cows on the islands of Okinawa Prefecture than on other locations. In total, 818 ROH fragments, including those containing NCAPG and PLAG1, which are major quantitative trait loci for carcass weight in Japanese Black cattle, were present at significantly higher frequencies in cows in the islands of Okinawa Prefecture. This suggests that the ROH fragments are under strong selection and that cows in the islands of Okinawa Prefecture have low genetic diversity and high genomic inbreeding relative to those at other locations. SNP arrays are useful tools for evaluating genetic diversity and genomic inbreeding in cattle.

Production of Carotenoids from Cultivated Seaweed.

Cladosiphon (C.) okamuranus, a brown alga endemic to the Nansei Islands, Japan, has been conventionally ingested as food. Nowadays, it is a major aquatic product of the Okinawa Prefecture with an annual production of around 20,000 tons. The life cycle of C. okamuranus comprises the macroscopic sporophyte (algal body) generation and the microscopic gametophyte generation. The germlings in the latter generation can proliferate when floating in seawater. This floating form has been exploited in techniques involved in the commercial production of C. okamuranus seedlings.Brown algae contain fucoxanthin, a carbonyl carotenoid known to have anticancer, anti-obesity, and antidiabetic effect in addition to the anti-oxidation effect. We found that the fucoxanthin content of cultivated floating form of C. okamuranus discoid germlings becomes up to 50 times that of the mature alga. Since the discoid germlings repeatedly grow like microorganisms, although they are large algae, they are utilized to produce fucoxanthin. We optimize the culture conditions by changing the temperature, light intensity, photoperiod, light wavelength, and nutrient salt conditions for optimal fucoxanthin productivity. The cultivation has been successful to industrial plant scale, culminating in the use of 1 ton of cultivating medium.In brown algal cells, fucoxanthin is primarily found bound to the photosynthetic pigment-protein complexes known as fucoxanthin-chlorophyll protein (FCP). Consequently cultivated floating form of C. okamuranus also shows high content of FCP. Isolation and characterization of pigments bound to the FCP were determined precisely, and ultrafast spectroscopies were applied to elucidate the photosynthetic function of fucoxanthin bound to the pigment-protein complexes. This cultivation method has also been applied to the other edible brown algae. We found that the optimal cultivation conditions as well as the yields of fucoxanthin and FCP highly depend on the species.The floating form cultivation was also applied to a large-sized edible green alga, Codium intricatum, which is uniquely producing a carbonyl carotenoid, siphonaxanthin. This has several anti-disease effects and is also a primal photosynthetic pigment which is found bound to photosynthetic antenna complex usually called siphonaxanthin-chlorophyll protein (SCP). We are working on the improvement of productivity, scale-up of production, and development of cultivation technology of new macro algae.

Downsizing of Sugarcane Harvesting and Transportation System on Minami Daitojima and Kita Daitoujima Islands in Okinawa Prefecture

沖縄県南北大東島におけるサトウキビ収穫・運搬作業体系のダウンサイズモデルについて，シミュレーションの手法によりその経済性等を分析した．老朽化した現行の作業機の代替えを進めるにあたっては，運搬トラックが収穫機の伴走を兼ねる大型，中型のモデルやハイダンプ式の伴走・搬出機を用いる中型モデル等を中心に進めることが有利であり，現行の作業料金を維持できる可能性がある．単収や作業能率の向上は，コストの低減につながり，製糖工場のプラントの処理量をコントロールできる技術や仕組みがあれば，より自由度の高い作業体系が構築できると考えられる．シーズンを通して各作業機の1台当りの処理量を増やすことや，アイドリング時間を減らす方向で種々の対策を講ずることが重要である．

Downsizing of Sugarcane Harvesting and Transportation System on Minami Daitojima and Kita Daitoujima Islands in Okinawa Prefecture

機械作業による土壌の圧密がサトウキビの初期生育や根群の発達に及ぼす影響について解明するため，土壌密度を4水準設けたルートボックス試験を行った．サトウキビの根群の発達や根量は，土壌密度が高いほど抑制される傾向となったのに対し，仮茎長と茎径は土壌密度と明確な関係は見られず，地下部と地上部では異なる結果となった．圧密された土壌では，灌漑水の浸入能が低いため上層部で停滞し，根域も比較的上層部に集中していることから，水分の吸収において有利に作用したと考えられる．土壌圧密がマイナス要因ばかりではないとの報告も散見されることから，温暖期での再評価試験が必要である．

Characterization of Macroscopic Colony-Forming Filamentous Cyanobacteria from Okinawan Coasts as Potential Sources of Bioactive Compounds

Marine macroscopic colony-forming filamentous (MMCFF) cyanobacteria are considered as prolific producers of bioactive compounds. Thus, knowledge of the diversity of MMCFF cyanobacteria as related to bioactive compound production has become very important. However, basic taxonomic studies of MMCFF cyanobacteria are lacking. Many cyanobacterial taxa are still misidentified or undescribed. In this study, a total of 32 cyanobacterial colonies from nine coastal regions of Okinawa Prefecture were investigated for a diversity assessment. A polyphasic approach including morphological and molecular studies based on 16S rRNA gene sequences was performed to characterize Okinawan MMCFF cyanobacteria. Both morphological and molecular phylogenetic results showed that MMCFF cyanobacteria from Okinawan coasts are very diverse. We found morphotypes of Lyngbya-like, Phormidium-like, and Leptolyngbya-like groups among Okinawan cyanobacterial samples. Genetically, samples were distributed in various clades in the phylogenetic tree, including within Moorena, Okeania, Caldora, Neolyngbya, Dapis, as well as several unknown clades. In addition, cytotoxic activities of three samples from Kiyan coast were tested against HeLa cells. All three crude extracts of these samples showed strong cytotoxic activity with IC50 < 1μg/ml.

Ontological Security and Critical Gubernatorial Elections in Okinawa -The Paradoxical Dynamics of Trust in the Japanese Government-

Ontological Security and Critical Gubernatorial Elections in Okinawa -The Paradoxical Dynamics of Trust in the Japanese Government-

Disappearance of summer influenza in the Okinawa prefecture during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic.

Since the Okinawan islands are located in the southernmost part of Japan, where the climate is subtropical, several episodes of influenza epidemics occur during the summer season. More recently, we have demonstrated that summer influenza epidemics occur every year. After the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) began in January 2020, measures to avoid disease transmission have been widely promoted in Japan, such as the use of masks, handwashing, remote work, and cancellation of large events. These measures might also have reduced the spread of other infectious diseases, such as the seasonal influenza. Based on this background, we evaluated weekly influenza activity in the 2019/2020 season. After the SARS-CoV-2 pandemic, the summer influenza in the Okinawa prefecture disappeared in 2020. The reasons for the disappearance of summer influenza in Okinawa are discussed herein.

Population Structure and Reproductive Biology of the Endangered Crab Deiratonotus japonicus (Brachyura, Camptandriidae) Surveyed for Nine Years in the Kita River, Japan

Deiratonotus japonicus (D. japonicus) is known as a near-threatened species, because of the changing conditions of its habitat. This species resides in isolated locations and in upstream, brackish waters from Kanagawa Prefecture to Okinawa Prefecture in Japan. In this study, we investigated the population structure and reproductive biology of D. japonicus in the Kita River, Japan. The distribution, sex ratio, breeding season, and fecundity were assessed at bimonthly intervals during spring low-tide periods from May 2001 to November 2008 and from November 2014 to January 2016 for approximately nine years. A total of 3525 crabs were collected during the sampling period: 1806 (51.2%) males, 1240 (35.2%) non-ovigerous females, and 479 (13.6%) ovigerous females. The overall sex ratio (1:0.95) did not differ significantly from the expected 1:1 ratio. The mean maximum density was 26.1 and 36.5 indiv./m2 for the first and second sampling periods, respectively, in the sampling station 5.2 km from the Kita River mouth, and all individuals were typically found approximately 4.4–6.8 km (13.2 ± 7.8 indiv./m2) from the Kita River mouth. Carapace width (CW) ranged from 2.6 to 13.5 mm in males and from 2.8 to 13.4 mm in females and was significantly different between the two sexes (p &lt; 0.05). Ovigerous females were found almost throughout the entire sampling period, with breeding peaks between July and September. The smallest ovigerous female had a CW of 3.9 mm. The seasonal frequency distribution suggested the continuous recruitment of young juveniles (CW &lt; 3.9 mm) throughout the year, with peaks from September to November. The mean fecundity was 1008.3 ± 183.1 (8.3 ± 1.6 mm) eggs. Egg number in relation to CW was calculated by the formula egg number (EN) = 110.36 × CW + 90.96 (R2 = 0.948, n = 41, p &lt; 0.0001). Regression analysis showed that fecundity was closely associated with female CW. Our results indicate that the performance of reproductive biology depends not only on continuous breeding but also on recruitment throughout the year in our study area.

Detection of Mycoplasma wenyonii and "Candidatus Mycoplasma haemobos" from Japanese Black breeding cows in Kyushu and Okinawa region, southern part of Japan.

This study aimed to elucidate the epidemiological status of hemoplasma infection and investigate the interaction between Theileria orientalis and hemoplasmas in Japanese Black breeding cows raised in the Kyushu and Okinawa regions. Blood samples were collected from 400 cows from 80 different farms in eight prefectures (five samples per farm and 10 farms per prefecture). Mycoplasma wenyonii (Mw), “Candidatus Mycoplasma haemobos” (CMh), and T. orientalis were examined by polymerase chain reaction (PCR) assay using whole blood samples. PCR results showed that 91.5% (366/400) of cows were positive for bovine hemoplasma: 40.3% were infected with Mw only, 9.5% with CMh only, and 41.8% with both species. T. orientalis was detected in 36% (144/400) of cows. The infection rate of T. orientalis was higher in the grazing group (P<0.001) than in the housed group, while the rate of CMh infection was higher (P<0.05) in the housed group than in the grazing group, suggesting that not only the tick but also other arthropod vectors may contribute to hemoplasma transmission. Although the cows with hemoplasma dual infection showed higher (P<0.05) white blood cell counts compared with hemoplasma-negative cows, there was no difference in hematologic parameters related to the anemia between the hemoplasma-positive and -negative animals. This may indicate that Japanese Black cattle could have resistance to the anemia caused by infection with hemoplasma.

Two species of Dioncopseudobenedenia Yamaguti, 1965 (Monogenea: Capsalidae) from Naso unicornis (Forsskål) (Acanthuridae) and Coryphaena hippurus Linnaeus (Coryphaenidae) in western Japan, with a description of D. elongata n. sp. from N. unicornis.

Three species of Dioncopseudobenedenia Yamaguti, 1965 (Monogenea: Capsalidae: Benedeniinae) have been described, all found parasitising Naso spp. (Acanthuridae) and Siganus lineatus (Siganidae), in Hawaii, the Great Barrier Reef, and New Caledonia in the Pacific. In this paper, D. elongata n. sp. is described, found parasitising the gills of N. unicornis (Forsskål) caught off Okinawa-jima Island. Dioncopseudobenedenia kala Yamaguti, 1965 is also reported, found parasitising the gills of N. unicornis, and those of a new host, the common dolphinfish Coryphaena hippurus Linnaeus (Coryphaenidae), off Okinawa and Kochi prefectures, Japan. The new species differed from known species in both nuclear (28S rDNA and ITS1-5.8S-ITS2) and mitochondrial DNA (cox1) sequences. Morphologically, the new species differed from other species of Dioncopseudobenedenia in possessing a longer accessory sclerite and a thick, short penis. No species of Dioncopseudobenedenia have been detected during past examinations of C. hippurus; this instance was probably an accidental infection. A key for identification of the species of Dioncopseudobenedenia is also provided herein.

沖縄県初記録のアヤメイズハナダイ（ハタ科ハナダイ亜科）および本種の標徴に関する再評価

沖縄県初記録のアヤメイズハナダイ（ハタ科ハナダイ亜科）および本種の標徴に関する再評価

Hougo and Somayama of Okinawa seen in the aspect of Fengshui

Hougo and Somayama of Okinawa seen in the aspect of Fengshui

Potential curing and beneficial effects of Ooitabi (Ficus pumila L.) on hypertension and dyslipidaemia in Okinawa.

BackgroundOver 30% of the population of Okinawa Prefecture have a high body mass index. The incidence of hypertension and dyslipidaemia has also increased in recent years. We found that Ooitabi (Ficus pumila L.), a plant native to Okinawa, was useful for hypertension. During ancient times, the extracts of Ooitabi leaves were used for making Ishimaki tea in some areas of Okinawa Prefecture. The plants in Okinawa are rich in antioxidants, and four flavonoid glycosides, including rutin, have been identified in Ooitabi.MethodsIn the present study, we conducted clinical verification tests on the effects of drinking Ishimaki tea on outpatients with hypertension and dyslipidaemia. Of 3814 Japanese patients who underwent medical check‐ups in Okinawa, 38 individuals with high blood pressure, dyslipidaemia, liver dysfunction and gout visited our hospital as outpatients and were asked to drink Ishimaki tea.ResultsAfter 3 months, there were significant reductions in body mass index, systolic and diastolic blood pressure, total cholesterol, low‐density lipoprotein cholesterol, γ‐glutamyltrans peptidase, uric acid and ratio of blood vessel insulin resistance.ConclusionsOoitabi extract can lower blood pressure and improve lipid abnormalities and has likely contributed to the well‐known health and longevity of the population in Okinawa.