Okinawa Island Research Articles

Balancing timber production and habitat conservation of Okinawa Rails (Gallirallus okinawae): Application of a harvest scheduling optimization model in subtropical forest in Okinawa, Japan

Finding the right balance between timber production and the management of forest-dependent wildlife species, present a difficult challenge for forest resource managers and policy makers in Okinawa, Japan. A possible explanation of this can be found in the unique nature of the forest management area which is populated with various kinds of rare and endangered species. This issue has been brought to light as a result of the nomination of northern Okinawa Island in 2018 as a candidate for World Natural Heritage site. The nomination has raised public awareness to the possibility of conflicting management objectives between timber extraction and the conservation of habitat for forest-dependent wildlife species. Managing exclusively for one objective over the other may fail to meet the demand for both forest products and wildlife habitat, ultimately jeopardizing the stability of human and wildlife communities. It is therefore important to achieve a better balance between the objective of timber production and conservation of wildlife habitat. Despite the significance of this subject area, current ongoing discussions on how to effectively manage for forest resources, often lack scientific basis to make sound judgement or evaluate tradeoffs between conflicting objectives. Quantifying the effect of these forest management activities on wildlife habitat provides useful and important information needed to make forest management and policy decisions. In this study we develop a spatial timber harvest scheduling model that incorporates habitat suitability index (HSI) models for the Okinawa Rail (Gallirallus okinawae), an endangered avian species found on Okinawa, Japan. To illustrate how the proposed coupling model assembles spatial information, which ultimately aids the study of forest management effects on wildlife habitat, we apply these models to a forest area in Okinawa and conduct a simple simulation analysis.

Shedding Light on Specificity: Population Genomic Structure of a Symbiosis Between a Coral Reef Fish and Luminous Bacterium.

All organisms depend on symbiotic associations with bacteria for their success, yet how these interspecific interactions influence the population structure, ecology, and evolution of microbial symbionts is not well understood. Additionally, patterns of genetic variation in interacting species can reveal ecological traits that are important to gene flow and co-evolution. In this study, we define patterns of spatial and temporal genetic variation of a coral reef fish, Siphamia tubifer, and its luminous bacterial symbiont, Photobacterium mandapamensis in the Okinawa Islands, Japan. Using restriction site-associated sequencing (RAD-Seq) methods, we show that populations of the facultative light organ symbiont of S. tubifer exhibit genetic structure at fine spatial scales of tens of kilometers despite the absence of physical barriers to dispersal and in contrast to populations of the host fish. These results suggest that the host’s behavioral ecology and environmental interactions between host and symbiont help to structure symbiont populations in the region, consequently fostering the specificity of the association between host generations. Our approach also revealed several symbiont genes that were divergent between host populations, including hfq and a homolog of varS, both of which play a role in host association in Vibrio cholerae. Overall, this study highlights the important role that a host animal can play in structuring the distribution of its bacterial symbiont, particularly in highly connected marine environments, thereby promoting specificity of the symbiosis between host generations.

<p><strong>Emended description and new localities of <em>Oxygyne shinzatoi </em>(Burmanniaceae/Thismiaceae), with discussion of phylogenetic relationships of <em>Oxygyne </em>from Japan and Africa</strong></p>

During a recent survey, Oxygyne specimens were discovered in three lowland evergreen forests on Okinawa Island, Japan. After morphological investigation, we identified the specimens as O. shinzatoi. Intriguingly, the colour of the specimens from one of the localities was significantly different from that of specimens collected from both the type and two of the new localities. Furthermore, morphological analysis also revealed clear differences between specimens collected from the type locality, including the type specimen, and previous descriptions of O. shinzatoi. Therefore, an amended description of O. shinzatoi is provided, based on the type and newly collected specimens. Phylogenetic relationships of Oxygyne from Japan and western Central Africa are also discussed, with consideration of the characteristics of newly discovered colour variation.

First record of Larsonella pumilus (Teleostei: Gobiidae) from Japan, with phylogenetic placement of the genus Larsonella.

During a survey of deep-sea fauna, using a Remotely Operated Vehicle, a single specimen (21.6 mm in standard length) of Larsonella pumilus (Larson Hoese, 1980) was collected at a depth of 214 m off the coast of Okinawa Island, Japan. It represents the first record of this species from Japan. The collection site was far deeper than previous reports for this species. This suggests that the main habitat of L. pumilus is deeper than previously recognized and it may explain the paucity of records of this species. As the previously available morphological description of L. pumilus was based on only a single specimen (holotype), this new specimen is described herein. Its morphology corresponds closely to the original description of the holotype, except that faint melanophores are arranged radially around the eyes and scattered on the trunk and the fins. Mitochondrial genome sequences of L. pumilus and 19 related species demonstrate close relationships between L. pumilus and the genus Priolepis. These data also indicate that the genus Priolepis is not monophyletic.

Elemental compositions and sizes of carbonaceous fly ash particles from atmospheric deposition collected at Cape Hedo, Okinawa, Japan: Implications for their long-range transportation and source region variation

Spheroidal carbonaceous particles (SCPs) are a type of carbonaceous fly ash resulting from high-temperature industrial fossil fuel combustion. In this study, we examined the fluxes, elemental compositions (18 elements including silicon, sulfur, and aluminum but not carbon) and sizes of dry-deposited SCPs in the atmosphere at Cape Hedo (the northernmost part of Okinawa Island) to assess the temporal variation. The study site at Cape Hedo is suitable for investigating atmospherically deposited SCPs, particularly for evaluating their long-range transportation, because Cape Hedo is situated in an outflow region of East Asian pollutants. High SCP fluxes mostly occurred in autumn and winter when air masses came from the Asian continent. Additionally, we determined the temporal variations in the elemental compositions and the sizes of the SCPs during four week-long sampling periods and these results suggest that the high SCP fluxes were due to the transportation of the particles from the Asian continent to the study site. The potential source regions of the particles during respective periods are very consistent with the backward air mass trajectories. Results of our study would imply that sources of the SCPs deposited in the area changed temporarily, and that coarse particulate-pollutants such as SCPs were transported from the eastern Asian continent to Okinawa Island during the periods under specific meteorological conditions. Our findings suggest that the examination of SCPs from atmospheric deposition can contribute to the assessment of atmospheric transportation, specifically for particulate pollutants in the atmospheric boundary layer.

Characteristics of upper-tropospheric outflow-layer clouds of Typhoon Francisco (2013) observed by hydrometeor videosonde

Ice crystals in upper-tropospheric outflow layers of typhoons are an important factor in determining typhoon intensity and track through radiative cooling of the secondary circulation. Quantitative representation of ice crystal distribution is fundamental for accurate reproduction of typhoon intensity and track in cloud-resolving numerical models. This study used hydrometeor videosondes (HYVISs) released from Okinawa Island (Japan) to conduct microphysical observations of ice crystals in the outflow layer of Typhoon Francisco (2013). During the approach of the typhoon center, seven HYVISs were released between 02:53 JST October 23, 2013 and 13:33 JST October 24, 2013 at distances of between 230 and 550 km from the typhoon center (r = 230 and 550 km). The observation site was located at the downshear left flank, and at least three HYVISs were released within 100 km of active convection in the eyewall from which outflow-layer clouds extended. During the observations, the central pressure of the typhoon increased slightly from 945 to 960 hPa. Ice particles were observed at heights of 7–14 km. The numbers of ice particles tended to decrease with distance from the typhoon center. The maximum number concentrations of ice crystals were 180 and 20 L −1 at r = 230 and 550 km, respectively. Ice particles with diameter of a few tens of micrometers were found dominant. Large particles with diameter > 100 μm were restricted to just outside the eyewall and the inner-core precipitation region. Ice supersaturation layers with thickness > 2 km were present from r = 230 to 360 km, i.e., reasonably close to the typhoon center. In addition, supercooled liquid droplets were observed in areas with relative humidity >95% in two profiles (r = 260 and 290 km). Conversely, there was no ice supersaturation layer in the outermost profile at r = 550 km. Saw-like radar echo patterns were common along the bottom of outflow-layer clouds, below which a considerably drier layer was evident. Saturation ratio minima relative to ice within the dry layer were 0.01–0.34 (for relative humidities of 1%–31%). It was considered that ice particles formed in the upper levels of rainbands near the typhoon center, and that they were sublimated in both the dry layer below the outflow layer and the ice subsaturation area in the outermost region of the typhoon, which resulted in decreased number concentrations of ice particles. • Upper-tropospheric outflow-layer clouds of Typhoon Francisco (2013) were observed. • Microphysical quantities of ice particles were measured throughout the outflow layer. • Dissipation process of ice particles was clarified. • Supercooled water droplets existed in the outflow-layer clouds of the typhoon. • A saw-like radar echo pattern was found along the bottom of the outflow-layer clouds.

Horizontal and vertical movement patterns of sunfish off eastern Taiwan

The horizontal and vertical movements of two large sunfishes (TL > 200 cm) were investigated using pop-up satellite archival tags off eastern Taiwan in 2017–2018. One tag attached to Mola mola popped-up in the South China Sea after 148 days at-liberty and another on M. alexandrini was recovered after 18 days. The most probable track, estimated by the Kalman filter with matching sea surface temperature, suggested that M. mola moved in a northerly direction to the East China Sea, went southward back to Taiwan with the tag detaching near the coast of Miyakojima and Okinawa Island, Japan. During these movements, the fish experienced thermal fronts and moved against the prevailing current. Both fish exhibited distinct diel oscillations in their vertical movements. During daytime periods, tagged fish spent most of their time (>72%) below the thermocline and occasionally ascended to the surface and experienced water temperatures of 12–16 °C. During nighttime periods, vertical movements were confined to the mixed layer with water temperatures ranging from 18 to 24 °C. Depth patterns were different between December and May when descending dives were correlated with strength of the thermocline. These movements suggested that sunfish shifted their horizontal and vertical patterns in response to changing ambient water temperature, thermocline structure, and prey availability.

Detecting inter- and intra-island genetic diversity: population structure of the endangered crocodile newt, Echinotriton andersoni, in the Ryukyus

The endangered crocodile newt, Echinotriton andersoni, is a relatively large species of the family Salamandridae and is distributed on six islands in the central part of the Ryukyu Archipelago, Japan. Because of an originally small distribution range and recent habitat loss, this species has been steadily declining in number. To elucidate fine-scale population structure, which is essential for effective conservation management, we analyzed genetic diversity and gene flow based on nine microsatellite loci. Our results identified three different island groups (Amamioshima, Tokunoshima, and Okinawajima) and multiple genetic assemblages within the Amami and Okinawa island groups. The gross genetic variation within each island was positively correlated with island size. Population structure followed a latitudinal cline and isolation by distance, even among geographically isolated islands. In northern Okinawajima, relatively complex genetic structure was observed. This unexpected population structure seems to reflect historical migration and distribution expansion through the formation of land bridges and shifted coastlines in the Pleistocene. We also found that small islands showed little genetic variation (Ukeshima, Sesokojima, and Tokashikijima). In particular, our findings revealed that the Tokashikijima population is at greater risk for extinction than the other populations because it has the smallest effective population size.

Distribution pattern of Termitomyces types symbiotic with the fungus‐growing termite Odontotermes formosanus on Okinawa Island

AbstractFungus‐growing termites (subfamily Macrotermitinae) cultivate the symbiotic basidiomycete fungus Termitomyces in their fungus comb to digest cellulosic materials and to supply nitrogen‐rich fungal diet. In Japan, the fungus‐growing termite Odontotermes formosanus is found on the Yaeyama Islands and Okinawa Island, Okinawa Prefecture. Odontotermes formosanus is thought to have been recently and artificially introduced to Okinawa Island as its distribution is discontinuous and restricted to small areas. Previous DNA analyses revealed that two types of Termitomyces, namely Termitomyces sp. Type A and Termitomyces sp. Type B, whose fruiting bodies correspond to Termitomyces microcarpus‐like pseudorhiza‐lacking small mushroom and Termitomyces intermedius, respectively, are cultivated by O. formosanus on the Yaeyama Islands. However, information about the Termitomyces types cultivated by O. formosanus on Okinawa Island is limited. To define the fungal types cultivated by O. formosanus on Okinawa Island, I developed a diagnostic polymerase chain reaction method using primer sets specific to the nuclear ribosomal DNA sequences consisting of the internal transcribed spacers (ITS1 and ITS2) and 5.8S rDNA of Termitomyces not using fungal mycelium, but using the termite gut metagenome including fungal DNA as a template. The results indicated that the same two Termitomyces types from Iriomote Island are cultivated by O. formosanus on Okinawa Island. The distribution pattern of Termitomyces types on Okinawa Island showed that Termitomyces sp. Type A is limited to the mountainous side of Sueyoshi Park, despite Termitomyces sp. Type B being widely distributed in the area in which O. formosanus is found. This finding implies that O. formosanus on Okinawa Island was recently introduced from Iriomote Island to Sueyoshi Park.

「奄美・沖縄」の世界自然遺産登録と持続可能な観光への提言

「奄美・沖縄」の世界自然遺産登録と持続可能な観光への提言

Zooxanthellate, Sclerite-Free, and Pseudopinnuled Octocoral Hadaka nudidomus gen. nov. et sp. nov. (Anthozoa, Octocorallia) from Mesophotic Reefs of the Southern Ryukyus Islands

Shallow water coral reefs are the most diverse marine ecosystems, but there is an immense gap in knowledge when it comes to understanding the diversity of the vast majority of marine biota in these ecosystems. This is especially true when it comes to understudied small and cryptic coral reef taxa in understudied ecosystems, such as mesophotic coral reef ecosystems (MCEs). MCEs were reported in Japan almost fifty years ago, although only in recent years has there been an increase in research concerning the diversity of these reefs. In this study we describe the first stoloniferous octocoral from MCEs, Hadaka nudidomus gen. nov. et sp. nov., from Iriomote and Okinawa Islands in the southern Ryukyus Islands. The species is zooxanthellate; both specimens host Cladocopium LaJeunesse & H.J.Jeong, 2018 (formerly Symbiodinium ‘Clade C’) and were collected from depths of ~33 to 40 m. Additionally, H. nudidomus gen. nov. et sp. nov. is both sclerite-free and lacks free pinnules, and both of these characteristics are typically diagnostic for octocorals. The discovery and morphology of H. nudidomus gen. nov. et sp. nov. indicate that we still know very little about stoloniferous octocoral diversity in MCEs, their genetic relationships with shallower reef species, and octocoral–symbiont associations. Continued research on these subjects will improve our understanding of octocoral diversity in both shallow and deeper reefs.

Expanding walls and shrinking beaches: loss of natural coastline in Okinawa Island, Japan.

Okinawa is the largest and most populated island of the Ryukyu Archipelago in southern Japan and is renowned for its natural resources and beauty. Similar as to what has been happening in the rest of the country, Okinawa Island has been affected by an increasing amount of development and construction work. The trend has been particularly acute after reversion to Japanese sovereignty in 1972, following 27 years of post-war American administration. A coastline once characterized by extended sandy beaches surrounded by coral reefs now includes tracts delimited by seawalls, revetments, and other human-made hardening structures. Additionally, part of coastal Okinawa Island was obtained by land-filling shallow ocean areas (land reclamation). Nevertheless, the current extension of the artificial coastline, as well as the level of fragmentation of the natural coastline are unclear, due to the lack of both published studies and easily accessible and updated datasets. The aims of this research were to quantify the extension of coastline alterations in Okinawa Island, including the amount of land-filling performed over the last 41 years, and to describe the coastlines that have been altered the most as well as those that are still relatively pristine. The analyses were performed using a reference map of Okinawa Island based on GIS vector data extracted from the OpenStreetMap (OSM) coastline dataset (average node distance for Okinawa Island = 24 m), in addition to satellite and aerial photography from multiple providers. We measured 431.8 km of altered coastline, equal to about 63% of the total length of coastline in Okinawa Island. Habitat fragmentation is also an issue as the remaining natural coastline was broken into 239 distinct tracts (mean length = 1.05 km). Finally, 21.03 km2 of the island’s surface were of land reclaimed over the last 41 years. The west coast has been altered the most, while the east coast is in relatively more natural conditions, particularly the northern part, which has the largest amount of uninterrupted natural coastline. Given the importance of the ecosystem services that coastal and marine ecosystems provide to local populations of subtropical islands, including significant economic income from tourism, conservation of remaining natural coastlines should be given high priority.

Clinical characteristics with long-term follow-up of four Okinawan families with moderate hearing loss caused by an OTOG variant

We describe the clinical features of four Japanese families with moderate sensorineural hearing loss due to the OTOG gene variant. We analyzed 98 hearing loss-related genes in patients with hearing loss originally from the Okinawa Islands using next-generation sequencing. We identified a homozygous variant of the gene encoding otogelin NM_001277269(OTOG): c.330C>G, p.Tyr110* in four families. All patients had moderate hearing loss with a slightly downsloping audiogram, including low frequency hearing loss without equilibrium dysfunction. Progressive hearing loss was not observed over the long-term in any patient. Among the three patients who underwent newborn hearing screening, two patients passed the test. OTOG-associated hearing loss was considered to progress early after birth, leading to moderate hearing loss and the later stable phase of hearing loss. Therefore, there are patients whose hearing loss cannot be detected by NHS, making genetic diagnosis of OTOG variants highly useful for complementing NHS in the clinical setting. Based on the allele frequency results, hearing loss caused by the p.Tyr110* variant in OTOG might be more common than we identified. The p.Tyr110* variant was reported in South Korea, suggesting that this variant is a common cause of moderate hearing loss in Japanese and Korean populations.

Estimating Tsunami Economic Losses of Okinawa Island with Multi-Regional-Input-Output Modeling

Understanding the impacts of tsunamis, especially in terms of damage and losses, is important for disaster mitigation and management. The aim of this study is to present our estimations of the potential losses from tsunami damage on Okinawa Island. We combine the use of a tsunami hazard map and our proposed economic loss model to estimate the potential losses that would be sustained by Okinawa Island in the event of a tsunami. First, to produce the tsunami hazard map, we calculated tsunami flow characteristics using the mathematical model TUNAMI-N2 and incorporating 6 earthquake fault scenarios around the study area. The earthquake scenarios are based on historical records along the Ryukyu Trench and the Okinawa. The resulting inundation map is overlaid with economic land use type and topography maps to identify vulnerable regions, which are then employed to compute potential economic losses. Second, we used our proposed economic model for this study area to calculate the potential losses that would be sustained in these vulnerable regions. Our economic model extends the multi-regional-input-output (MRIO) model, where the economic values of industrial sectors are scaled to correlate with land use and topography types (coastal and inland areas) to calculate losses through the Chenery–Moses estimation method. Direct losses can be estimated from the total input of the MRIO table, while indirect losses are computed from the direct losses and interaction parameter of the MRIO table. The interaction parameter is formed by linear programming and calculated using the Leontief methodology. Our results show that the maximum total damaged area under the 6 earthquake scenarios is approximately 30 km2. Inundation ranging from 2.0 to 5.0 m in depth covers the largest area of approximately 10 km2 and is followed by areas with inundation depths of 1.0–2.0 m and >5.0 m. Our findings show that direct losses will occur, while indirect losses are only approximately 56% that of direct losses. This approach could be applied to other areas and tsunami scenarios, which will aid disaster management and adaptation policies.

Large-scale extermination of introduced mangroves to conserve <i>Scartelaos histophorus</i> of Nakagusuku Bay, Okinawa Island

Large-scale extermination of introduced mangroves to conserve <i>Scartelaos histophorus</i> of Nakagusuku Bay, Okinawa Island

Supplementary descriptions of Pergalumna amamiensis Aoki, 1984 (Acariformes, Galumnoidea) from Ryukyu Islands.

A species of oribatid mites, Pergalumna amamiensis was collected from Amami-Ohshima Island, Ishigaki Island, and Okinawa Island, Southwestern Japan. The specimens were studied in detail, and supplementary descriptions are provided; these include features of the rostrum, the subcapitulum and the surface pattern of pteromorphs. The main morphological traits for this species are summarized as follows; body length 519-570 μm, body width 363-410 μm, rostral tip pointed, sensillus with a long stalk covered by minute barbs, porose areas Aa bulbous, porose areas A1, A2, and A3 circular, surface of pteromorphs ornamented by fine granular structure and dense wrinkles, fine granular structure on prodorsum, subcapitulum, genital plates and anal plates, median pore on the notogaster represented as single pore.

Seafloor Stereo Map of Coastal Areas for Geomorphological Studies

Abstract. Topographical anaglyph maps produced from digital elevation model (DEM) are an easy and practical means of inland topography and seafloor observations (Goto, 2016). Since the 2000s, several coastal DEMs surveyed by multi-beam sound systems have been stored, though submarine topographic features have been popularly represented by contour lines in the previous century. Various DEM-based visual maps including shaded relief or stereo maps with contour lines have been adapted to observe inland topography (Awata, 2017); however, they have been rarely used to express slope shade with contour lines in coastal areas. Since the development of submarine topography above −120 m has become relevant for sea-level changes after the last glacial age, deep-sea features such as cliffs and terraces could provide essential information on topographical evolution and crustal movement. Therefore, we produced a stereo image map of slope shade and contour lines in a coastal area based on DEM. Although Louis Ducas du Hauron patented the original idea of producing anaglyphs in 1891(Waker and Dodge, 2001), anaglyph seafloor maps expressing slope shade and contour lines from DEM are new as well as are effective for understanding the geomorphic features of submerged terraces and the broad deformation of the oceanic bed because they enable us to identify small topographic features, such as submerged coral crests and height differences in the wide area. We studied the area around Inazejima and Iheyajima islands distributed in the north of Okinawa prefecture, southwest Japan. We found it difficult to understand the active tectonics of Nansei–Shoto arc based on only the isolated small islands; thus, we focused on the submerged marine terraces widely developed around these islands to reveal the depth distribution of paleo-shorelines. The Japan Coast Gard (JCG) conducted a multi-beam survey along the northwestern coast of Okinawa island from 2008 to 2012 (Yasuhara, 2013). The JAMSTEC (2016) stored and disseminated information for the rock and sediment core samples as well as the results of the multi-beam survey on their website, “Data and Sample Research System for Whole Cruise Information in JAMSTEC.” We retrieved these data from the JCG and JAMSTEC to generate 1.44-smesh (approximately 44 m) and 2-s-mesh (approximately 65 m) seafloor DEMs, respectively. We combined these DEMs with a 500-m-mesh DEM (J-EGG500) published by JCG, which were subsequently overlapped in a decreasing resolution. We imported these seafloor DEMs into Simple DEM Viewer® to produce an anaglyph map that was overlapped onto the black and white slope shading base map and contour lines for stereoscopic analysis with red-cyan glasses. Interpretation of the map revealed that the several submerged marine terraces were distributed around the islands, and the NWW-trending active faults cut and deformed these terraces in the southwest off the coast of Izena island. Stereoscopic analysis with contour lines enabled us to obtain the height difference of the submerged terraces between the west and east sides of Iheya island, which were estimated to have formed during the last glacial age based on the terrace platform depth.

A new species of the flower bug genus Orius Wolff (Hemiptera: Anthocoridae) cryptically inhabiting Hibiscus tiliaceus L. (Malvaceae).

A new species of the anthocorid genus Orius Wolff (subgenus Heterorius Wagner), O. (H.) hibiscus sp. n., is described, based on specimens recently found from the coastal area of Okinawa Island, Ryukyus, Japan. This new species, evidently most related to Orius (Heterorius) strigicollis (Poppius), was found to prefer cryptic habitat, or bract and flower bud of Hibiscus tiliaceus (L.) (Malvaceae) planted at urbanized zones in Naha City. Diagnostic characters of the new species are described, comparing with those of other Japanese members of Heterorius, based on detailed observation using a SEM. An updated checklist and revised key are provided to aid in identification of all known Japanese Orius species.

Long-Term Observation of Atmospheric Speciated Mercury during 2007–2018 at Cape Hedo, Okinawa, Japan

The concentrations of atmospheric gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (particles with diameter smaller than 2.5 μm; PBM2.5) were continuously observed for a period of over 10 years at Cape Hedo, located on the north edge of Okinawa Island on the border of the East China Sea and the Pacific Ocean. Regional or global scale mercury (Hg) pollution affects their concentrations because no local stationary emission sources of Hg exist near the observation site. Their concentrations were lower than those at urban and suburban cities, as well as remote sites in East Asia, but were slightly higher than the background concentrations in the Northern Hemisphere. The GEM concentrations exhibited no diurnal variations and only weak seasonal variations, whereby concentrations were lower in the summer (June–August). An annual decreasing trend for GEM concentrations was observed between 2008 and 2018 at a rate of −0.0382 ± 0.0065 ng m−3 year−1 (−2.1% ± 0.36% year−1) that was the same as those in Europe and North America. Seasonal trend analysis based on daily median data at Cape Hedo showed significantly decreasing trends for all months. However, weaker decreasing trends were observed during the cold season from January to May, when air masses are easily transported from the Asian continent by westerlies and northwestern monsoons. Some GEM, GOM, and PBM2.5 pollution events were observed more frequently during the cold season. Back trajectory analysis showed that almost all these events occurred due to the substances transported from the Asian continent. These facts suggested that the decreasing trend observed at Cape Hedo was influenced by the global decreasing GEM trend, but the rates during the cold season were restrained by regional Asian outflows. On the other hand, GOM concentrations were moderately controlled by photochemical production in summer. Moreover, both GOM and PBM2.5 concentrations largely varied during the cold season due to the influence of regional transport rather than the trend of atmospheric Hg on a global scale.

Thirteen cases of pulmonary dirofilariasis in a single institution in Okinawa Island

Pulmonary dirofilariasis is an infection caused by Dirofilaria immitis, which is an endemic parasite in Japan. We experienced 13 surgical cases of pulmonary dirofilariasis in our hospital. Of the 13 patients, 61.5% were men. The responsible lesions were located in the right lung in all cases, and 76.9% of them were in the lower lobe. Histologically, 12 cases showed necrotic nodules with peripheral granuloma with worms inside the pulmonary artery. One case did not show a necrotic nodule but showed only thickening and hyalinization of the pulmonary artery wall with a degenerated worm inside. Eosinophils were found histologically in all cases. Thirteen cases of dirofilariasis in one institution seem to be the largest number in Japan, based on previous reports. One reason for this increased prevalence may be the hot and humid climate of our prefecture considering the ecology of the mosquito as a vector. Elastic staining and eosinophils in peripheral granulomatous areas can contribute to the diagnosis when the worms are degenerated.