Okinawa Island Research Articles

Stable carbon and nitrogen isotopic compositions of ambient aerosols collected from Okinawa Island in the western North Pacific Rim, an outflow region of Asian dusts and pollutants

Stable carbon (δ13C) and nitrogen (δ15N) isotope ratios were measured for total carbon (TC) and nitrogen (TN), respectively, in aerosol (TSP) samples collected at Cape Hedo, Okinawa, an outflow region of Asian pollutants, during 2009–2010. The averaged δ13C and δ15N ratios are −22.2‰ and +12.5‰, respectively. The δ13C values are similar in both spring (−22.5‰) and winter (−22.5‰), suggesting the similar sources and/or source regions. We found that δ13C from Okinawa aerosols are ca. 2‰ higher than those reported from Chinese megacities probably due to photochemical aging of organic aerosols. A strong correlation (r = 0.81) was found between nss-Ca and TSP, suggesting that springtime aerosols are influenced from Asian dusts. However, carbonates in the Asian dusts were titrated with acidic species such as sulfuric acid and oxalic acid during atmospheric transport although two samples suggested the presence of remaining carbonate. No correlations were found between δ13C and tracer compounds (levoglucosan, elemental carbon, oxalic acid, and Na+). During winter and spring, coal burning is significant source in China. Based on isotopic mass balance, contribution of coal burning origin particles to total aerosol carbon was estimated as ca. 97% in winter, which is probably associated with the high emissions in China. Contribution of NO3− to TN was on average 45% whereas that of NH4+ was 18%. These results suggest that vehicular exhaust is an important source of TN in Okinawa aerosols. Concentration of water-soluble organic nitrogen (WSON) is higher in summer, suggesting that WSON is more emitted from the ocean in warmer season whereas inorganic nitrogen is more emitted in winter and spring from pollution sources in the Asian continent.

Discovery of Iron Grapnel Anchors in Early Modern Ryukyu and Management of Underwater Cultural Heritage in Okinawa, Japan

The Yarabuoki underwater site contains seven iron grapnel anchors and Early Modern Okinawan ceramic jars and is dated to the 16th–19th centuries. The site lies at a depth of 12–32 m off the western coast of Ishigaki Island in Okinawa, Japan. Based on underwater archaeological and broadband multibeam surveys, as well as historical research of the artefacts and Early Modern Ryukyuan shipping, we discuss the possible anchor and vessel types in Ryukyu and Eastern Asia in Early Modern times. We also discuss the efficacy of low-cost ROV for assisting surveys in shallow-water environments and the value of educational programmes for promoting the management and conservation of underwater cultural heritage.

Female defence polygyny and plasticity in the mating system of the demersal triggerfish Rhinecanthus aculeatus (Pisces: Balistidae) from Okinawa Island

The prevalence of a haremic mating system type with parental care is one of the main characteristics of the modern triggerfish family (Balistidae). In addition, intraspecific modifications of the mating system in relation to environmental conditions have been recognized. Thirteen months of observation of mating units in a natural population of Rhinecanthus aculeatus from Okinawa Island, Japan, revealed that the mating system in this species involved a mixture of polygyny, monogamy, and potential promiscuity in solitary females. Females defended individual, multi-purpose territories, while males engaged in female defence (“female defence polygyny”) using displays and overt aggressions that advertised that territories were occupied. Male size was strongly linked to access to multiple females (i.e. polygyny). Plasticity in the mating system was related to male–male competition and the ability of females to reject males. An increase in the proportion of monogamous pair territories over the course of the reproductive season was positively correlated with the adult sex ratio (increased male density relative to females), and facultative monogamy was enhanced under a less female-biased sex ratio. A comparison between female and male mating success (number of matings) and the adjustment of the mating status over time revealed that polygyny was advantageous and the optimal mating system for males. Females achieved higher number of matings when pairing with larger males, but mating success was not negatively affected by the actual mating status, and females did not attempt to escape polygyny. Polygyny is therefore considered as the primary mating system in R. aculeatus.

Branching Pattern Modeling for Psychotoria species and Their Deterministic Algorithm

Back Ground: The branching patterns and the subsequent elongations of two shrub Psychotria species, Pyschotoria rubra and Psychotoria manillensis, in Okinawa Island, the Ryukyu Islands, Japan, were examined by Watanabe. His results showed that Hamilton’s classication for Psychotria species in the South American continent is also applicable to the same species in Okinawa Island. After Watanabe’s research, the author of the present paper introduced branching pattern models for same species to simulate their branching patterns theoretically. He also determined the branching pattern models in earlier growth stages and calculated their occurrence probabilities. To proceed with the analyses, a systematic construction of the branching pattern models has been required. Aims: To rene our earlier branching pattern models of P. rubra and P. manillensis in view of vector representation and to introduce a deterministic algorithm which produces the branching pattern models systematically.

Okinawa as Transported Landscape: Understanding Japanese Archaeological Remains on Tinian Using Ryūkyū Ethnohistory and Ethnography

abstract: The two islands of Okinawa and Tinian in the western Pacific are often linked in the modern archaeological literature by a common ethnic heritage in the early twentieth century, with Okinawan culture serving as a template for interpreting the archaeological remains of the Japanese sugarcane plantation era in Tinian. Tens of thousands of Okinawans immigrated to Tinian and other Commonwealth of the Northern Mariana Islands to be tenant farmers or contract laborers on the plantations between the 1920s and 1944, when they could no longer leave. Structural and functional parallels do indeed exist between the architectural remains of many farmsteads of the plantation era on both islands. The extent to which these archaeological remains on Tinian reflect a “transported landscape” from Okinawa versus a Japanese colonial construct is explored, using the vehicle of Okinawan ethnohistory and ethnography.

Contamination Status of PCBs and Organochlorine Pesticides in the Okinawa Island, Japan: Utilization of Small Indian Mongoose (<i>Herpestes auropunctatus</i>) as a Bioindicator

Contamination Status of PCBs and Organochlorine Pesticides in the Okinawa Island, Japan: Utilization of Small Indian Mongoose (<i>Herpestes auropunctatus</i>) as a Bioindicator

Larval development and distributional pattern of the painted sweetlip Diagramma pictum in Nakagusuku Bay, Okinawa Island, Ryukyu Archipelago

Larval development and distributional pattern of the painted sweetlip <i>Diagramma pictum</i> in Nakagusuku Bay, Okinawa Island, Ryukyu Archipelago

Relationship between seagrasses, reef corals and substrates at Bise moat in Okinawa Island, southern Japan

Relationship between seagrasses, reef corals and substrates at Bise moat in Okinawa Island, southern Japan

沖縄における陸水の特徴（I）

沖縄における陸水の特徴（I）

Occurrence and genetics of black‐eyed migratory locusts, Locusta migratoria (Orthoptera: Acrididae)

AbstractBlack‐eyed Locusta migratoria appeared in albino locusts as a result of crossing between a short‐winged strain originating from Tsushima Island, Japan, and an albino strain originating from Okinawa Island. The black eye trait was recessive to the white eye trait because the crosses between black‐ and white‐eyed albino locusts produced only individuals with white eyes in the F1 generation. In the F2 generation, black‐ and white‐eyed individuals appeared in a ratio of 1:3, indicating that the black eye trait was controlled by a simple Mendelian unit. The black eye trait showed no genetic association with other traits including wing morph, adult body dimensions and classical morphometric ratios such as hind femur length / head width and forewing length / hind femur length.

Hands-on Fieldwork Education for Tourism in Okinawa Island

Hands-on Fieldwork Education for Tourism in Okinawa Island

Nectar foraging behavior by Japanese White-Eyes on Golden Trumpet Trees in Okinawa Island, southern Japan

Nectar foraging behavior by Japanese White-Eyes on Golden Trumpet Trees in Okinawa Island, southern Japan

沖縄の陸水の特徴（II）石垣島の降水の水蒸気および酸性物質の起源

沖縄の陸水の特徴（II）石垣島の降水の水蒸気および酸性物質の起源

A comparative study of craniofacial measurements between Ryukyuan and mainland Japanese females using lateral cephalometric images

Using lateral cephalometric images, we compared the skeletal and soft tissue configurations of Ryukyuan and mainland Japanese females. We collected lateral cephalometric images of 30 females each from Okinawa Island and mainland Japan. Sixty landmarks were plotted on each image. Then, based on the coordinates of the landmarks, 68 distances and 34 angles were calculated according to orthodontic and anthropometric methods. We confirmed that the Ryukyuans have a smaller height in the upper and midfacial region than the mainland Japanese. Moreover, our findings indicate that, compared with the mainland Japanese females, the Ryukyuan females clearly have the following features: (1) a shallower mandibular notch, (2) an anterior-inclined symphysis of mandible, and (3) a smaller depth from upper lip to incisors. We also found that an anterior-inclined mandibular corpus and incisors are associated with a smaller distance between the surfaces of the upper lip and teeth and with a more protruded lip shape.

沖縄本島中部地区市町村子宮頸がん検診への LBC 全面導入効果

沖縄本島中部地区市町村子宮頸がん検診への LBC 全面導入効果

エクセルギー効率を用いた沖縄本島小河川の河川生態環境評価

エクセルギー効率を用いた沖縄本島小河川の河川生態環境評価

A variety of trees to create a forest soil and mountainous topography of Okinawa Island

A variety of trees to create a forest soil and mountainous topography of Okinawa Island

Four Cytotoxic Spongian Diterpenes from the Sponge Dysidea cf. arenaria.

Chemical analysis of the sponge Dysidea cf. arenaria from Irabu Island provided four new diterpenes 1-4. Their structures were elucidated by NMR and other spectroscopic analyses. All the metabolites retained the spongian skeleton and an isovalerate ester, but were different from those previously isolated from a specimen of Okinawa Island, implying geographic variation. The cytotoxicity of compounds 1-4 to NBT-T2 cells was evaluated and their IC50 values were 3.1, 1.9, 8.4, and 3.1 µM, respectively.

An Epidemiological Analysis of Summer Influenza Epidemics in Okinawa.

Objective This study evaluates the difference between winter influenza and summer influenza in Okinawa. Methods From January 2007 to June 2014, weekly rapid antigen test (RAT) results performed in four acute care hospitals were collected for the surveillance of regional influenza prevalence in the Naha region of the Okinawa Islands. Results An antigenic data analysis revealed that multiple H1N1 and H3N2 viruses consistently co-circulate in Okinawa, creating synchronized seasonal patterns and a high genetic diversity of influenza A. Additionally, influenza B viruses play a significant role in summer epidemics, almost every year. To further understand influenza epidemics during the summer in Okinawa, we evaluated the full genome sequences of some representative human influenza A and influenza B viruses isolated in Okinawa. Phylogenetic data analysis also revealed that multiple H1N1 and H3N2 viruses consistently co-circulate in Okinawa. Conclusion This surveillance revealed a distinct epidemic pattern of seasonal and pandemic influenza in this subtropical region.

New records of the rare calcareous sponge Paragrantia waguensis Hôzawa, 1940.

Paragrantia waguensis Hôzawa is reported from coastal reefs of the island of Okinawa. This rare species was previously known only from Central Japan, Mie Prefecture. It has peculiar apopylar tetractine spicules, so far unique among Calcarea. We present in situ images of the species and a full description including SEM images of skeletal structure and spicule complement. The status of Paragrantia as a separate genus of the family Grantiidae distinct from Grantia Fleming is confirmed on the basis of a morphological and molecular comparison with the European type species of Grantia, Grantia compressa (Fabricius).