Okinawa Main Island Research Articles

Visit to valuable water springs (94) Valuable water springs in central part of Okinawa main island

Visit to valuable water springs (94) Valuable water springs in central part of Okinawa main island

沖縄本島地域における市街地分布に着目した土地利用基本計画の土地利用規制の評価

沖縄本島地域における市街地分布に着目した土地利用基本計画の土地利用規制の評価

Notes on some plant-inhabiting fungi collected from the Nansei Islands (3)

In this paper, four plant-inhabiting fungi newly collected from the Nansei Islands, Japan, are reported. Among them, Phaeodiscula tremae Sawada from Tokunoshima Island was transferred to the genus Capnodiastrum and given a new name C. sawadae, because in the genus Capnodiastrum, the specific epithet tremae has already been used for the different South American species. Nyssopsora formosana on Koelreuteria formosana and Pestalotiopsis fici on Ardisia quinquegona collected in Okinawa Main Island and Pseudocercospora acaciaeconfusae on Acacia confusa collected in Okinoerabu Island were newly recorded from Japan.

Sequence homogeneity of the ψserA-trmU-tufB-secE-nusG-rplKAJL-rpoB gene cluster and the flanking regions of ‘Candidatus Liberibacter asiaticus’ isolates around Okinawa Main Island in Japan

In Japan and Southeast Asia, ‘Candidatus Liberibacter asiaticus’ (Las) is the dominant causal agent of citrus greening (huanglongbing) disease. Using PCR techniques, we determined the 11168-nucleotide sequence of the ψserA-trmU-tufB-secE-nusG-rplKAJL-rpoB gene cluster and the flanking regions for 51 Japanese, four Taiwanese, four Indonesian, and three Vietnamese isolates of Las. The sequence is identical in 62 isolates collected from Japan, Taiwan, Indonesia, and Vietnam, except for nucleotide substitutions at 11 positions. Some Las isolates from Sakishima Islands near Taiwan had unique nucleotide mutations, but all Las isolates around Okinawa Main Island were homologous. On the basis of the pattern of single nucleotide polymorphisms (SNPs) of the 11 nucleotide substitutions, the 62 Las isolates from Japan, Taiwan, Indonesia, and Vietnam could be divided into 12 pattern groups, and the 51 Japanese isolates consisted of six patterns. The results suggested that one unique genetic group is dominant around Okinawa Main Island, whereas several different are commonly distributed around islands near Taiwan.

Notes on some plant-inhabiting fungi collected from the Nansei Islands (2)

In this paper, four fungi collected in Nansei Islands are reported. One is Strasseria garciniae, which must be transferred to the genus Phyllosticta. This fungus was collected in Okinawa Main Island and Iriomote Island. The other three fungi are newly added to the Japanese fungal flora. Phyllosticta ghaesembillae on Codiaeum variegatum and Cercospora asplenii on Asplenium antiquum were collected in Yoron Island. The last one, Coniella australiensis on Eucalyptus robusta was collected in Okinawa Main Island. Their morphology and symptoms on the host plant are described, with some mycological notes.

Notes on some plant-inhabiting fungi collected from the Nansei Islands (2)

In this paper, four fungi collected in Nansei Islands are reported. One is Strasseria garciniae, which must be transferred to the genus Phyllosticta. This fungus was collected in Okinawa Main Island and Iriomote Island. The other three fungi are newly added to the Japanese fungal flora. Phyllosticta ghaesembillae on Codiaeum variegatum and Cercospora asplenii on Asplenium antiquum were collected in Yoron Island. The last one, Coniella australiensis on Eucalyptus robusta was collected in Okinawa Main Island. Their morphology and symptoms on the host plant are described, with some mycological notes.

Notes on some plant-inhabiting fungi collected from the Nansei Islands (3)

In this paper, four plant-inhabiting fungi newly collected from the Nansei Islands, Japan, are reported. Among them, Phaeodiscula tremae Sawada from Tokunoshima Island was transferred to the genus Capnodiastrum and given a new name C. sawadae, because in the genus Capnodiastrum, the specific epithet tremae has already been used for the different South American species. Nyssopsora formosana on Koelreuteria formosana and Pestalotiopsis fici on Ardisia quinquegona collected in Okinawa Main Island and Pseudocercospora acaciaeconfusae on Acacia confusa collected in Okinoerabu Island were newly recorded from Japan.

Descriptive analysis of the prevalence and the molecular epidemiology of Mycobacterium avium complex-infected pigs that were slaughtered on the main island of Okinawa

Recent genetic studies have revealed that several epidemiological factors affect Mycobacterium avium complex (MAC) infection in pig populations. However, mechanisms underlying the spread of MAC infection among hog farms have not been clarified. In consideration of this situation, we cross-sectionally investigated the mechanisms underlying the spread of MAC on the island of Okinawa. Pigs slaughtered (n=706,763) and 331 hog farms on Okinawa were surveyed during the years 2002-2004. Two outbreaks of MAC infection were occurred in several farms during survey period. Bacteria were isolated from randomly selected pigs and genotype of isolates was determined by using genetic finger printing methods with the insertion sequence (IS) 1245 restriction fragment length polymorphism (RFLP). Most isolates had large numbers of IS1245 copies, while strains with low copy numbers of IS1245 and isolates without IS1245 were seen in few farms. MACs strains were repeatedly isolated from pigs of the affected farms during the survey period. Those farms with an identical pig rearing systems showed synchronic changes in the prevalence of MAC infection. An industrial farm without an outbreak had an independent pig flow, but maintained distinct MAC strains. Multivariate analysis did not reveal independent factors for the prevalence of the MAC infection. These findings suggest that there were three clusters distinguished genetically in the main island of Okinawa, which were potentially spread by common pig flow. However, the outbreaks occurred because of unspecified conditions on each farm environment.

Introduction and Molecular Characterization of Tomato yellow leaf curl virus in Okinawa, Japan

Tomato yellow leaf curl disease (TYLCD) caused by Tomato yellow leaf curl virus (TYLCV) has been identified in Okinawa Prefecture, a subtropical region in Japan, for the first time in 2007. Infected tomato plants were collected from Tomigusuku City, Uruma City, Yomitan-son, and Nakijin-son on the main island of Okinawa. The complete nucleotide (nt) sequence of the TYLCV-Israel[Japan:Tomigusuku:2007] (TYLCV-IL[JR:Tom:07]) isolate obtained from Tomigusuku was determined. The sequence comparison with four representative TYLCV isolates in Japan showed that TYLCV-IL[JR:Tom:07] was most closely related to TYLCV-Israel[Japan:Tosa:2005] (TYLCV-IL[JR:Tos:05]), a member of the Israel strain of TYLCV (TYLCV-IL). The phylogenetic relationship analyses were performed based on determined partial nucleotide sequences of approximately 1,400 nt of 14 other isolates collected from 7 distinct locations. All the Okinawa isolates were separated into the cluster including TYLCV-IL[JR:Tos:05] and at least 2 distinct isolates of the TYLCV-IL were introduced onto the main island of Okinawa. These results indicated that the introduction of TYLCV into Okinawa might have been caused by domestic transportation of infected plants.

An Oral History Narrative Based on Life Story Materials of a Female Cotton-Mill Worker Born in the main island of Okinawa

An Oral History Narrative Based on Life Story Materials of a Female Cotton-Mill Worker Born in the main island of Okinawa

複数調査データを用いた沖縄本島内の観光交通分析手法に関する研究

複数調査データを用いた沖縄本島内の観光交通分析手法に関する研究

Population history of the northern and central Nansei Islands (Ryukyu island arc) based on dental morphological variations: gene flow from North Kyushu to Nansei Islands

This study investigates dental morphological variations among the modern inhabitants of Tanegashima Island and Okinawa Main Island of the Nansei Islands (Ryukyu island arc), which is the southern gateway of the Japanese archipelago. Temporal variations within Tanegashima Island and regional variations of the northern half of the Nansei Islands were used to study population history. The late Aeneolithic Yayoi to protohistoric Kofun populations (c. 0–700 AD) of Tanegashima was found to be similar to the native Japanese populations, such as the Neolithic Jomonese (c. 10000–300 BC) and Hokkaido Ainu; however, the modern population of Tanegashima was similar to the migrant Japanese populations such as the post-Jomon people (c. 300 BC–present time) of the Japanese main islands. Using statistically sufficient materials, this study confirmed that a substantial change had occurred from the prehistoric to the modern period in Tanegashima Island. It is suggested that temporal change occurred in Tanegashima over approximately 1000 years after substantial change (c. 300 BC) in the Japanese main islands. The delay in temporal change in Tanegashima indicates that dispersal of migrant populations from northern Kyushu to its southern end occurred at a time remarkably later than the northeastward dispersal of migrant populations to central Honshu Island. Furthermore, the geographical cline extending from North Kyushu to Okinawa Main Island via Tanegashima Island suggests southward gene flow from North Kyushu to the central Nansei Islands via the northeast end of the Nansei Islands.

Vegetation change in the main island of Okinawa, southern Japan from late Pliocene to early Pleistocene

Samples were taken from five outcrops that formed from late Pliocene to early Pleistocene on the main island of Okinawa. The five sites are located in Sonan, Yabu, Oyakawa, Akakimata and Goga. The age of Sonan and Yabu is ca. 1.0–0.8 Ma, that of Oyakawa is ca. 1.5 Ma, that of Akakimata is ca. 1.7 Ma and that of Goga predates ca. 1.9 Ma. Pollen analysis of these sediments revealed the following types occur together: the coniferous trees of Pinus subgen. Haploxylon and Cryptomeria, the deciduous broadleaved trees of Ulmus, Zelkova, Liquidamber and Lagerstroemia, and the evergreen broadleaved trees of Castanopsis and Symplocos. This pollen profile is similar to that of the last interglacial period in the Japanese mainland. The coniferous trees of Abies, Tsuga, Pinus subgen. Haploxylon, Keteleeria and Cryptomeria appear until the late Pliocene. Presently these taxa are not present on the Ryukyu Islands. Abies, Tsuga and Keteleeria pollen disappeared by the end of the Pliocene (1.78 Ma). The climate became cold rapidly and many Tertiary plants disappeared from late Pliocene to early Pleistocene in the Japanese main islands, as well as on the main island of Okinawa. At ca. 1.7 Ma, Lagerstroemia pollen suddenly increased. Tectonic activity was rapid and the other vegetation species could not adapt. Subsequently, ca. 1.5 Ma, Pinus subgen. Haploxylon, Ulmus, Zelkova and Cryptomeria pollen increased. This period is associated with regression and the climate was cool and wet. Pinus subgen. Diploxylon and evergreen broadleaved tree pollen grains increased, ca. 1.0–0.8 Ma, and the climate was warm. Subsequently, the climate became similar to the present climate in the main island of Okinawa. The formation of the modern evergreen broadleaved forest, dominated by Castanopsis sieboldii, dated from ca. 0.8 Ma.

Sporadic Cases and an Outbreak of Leptospirosis Probably Associated with Recreational Activities in Rivers in the Northern Part of Okinawa Main Island

In the summer of 2003, sporadic cases and an outbreak of human leptospirosis probably related to recreation in rivers occurred in the northern part of Okinawa Main Island. Sixteen of 22 suspected cases were definitely diagnosed as leptospirosis by serological test or isolation. The infective leptospiral serovar in 14 cases was presumed to be Hebdomadis. Transmission was thought to occur by exposure to river water that was contaminated by the urine of infected animals. The findings indicate that recreation in rivers in this area is a significant risk factor for infection with leptospires.

Termitomyces eurrhizus collected from the main island of Okinawa

<i>Termitomyces eurrhizus</i> collected from the main island of Okinawa

The Role of the Bridge Connecting the Islands of Hamahiga and Okinawa

This study has been conducted on the island of Hamahiga, Katsuren-cho, Okinawa Prefecture in Japan since the latter half of the 1950's to observe the dynamics of population and to determine various factors that have caused changes and differences among different settlements on the island in relation to the changes in the industrial structure. The construction of Hamahiga Bridge in 1997 connected the island and the main island of Okinawa, which resulted in an increased number of households and population of Hamahiga island. The residents of the island who have moved in after the completion of Hamahiga Bridge were interviewed to confirm their attributes, occupations, types or category of moving in, and types of houses. The results of our studies may be summarized as follows:(1) The island of Hamahiga was designated as a source of supply of vegetables for the United States military installations in Okinawa in the 1950's. A horticulture cooperative society, which collectively shipped all vegetables including watermelon, green pepper, and onion for individual farmers to the military bases, was established in each settlement on the island. However, less expensive vegetables have been imported to Okinawa from Taiwan since the 1960's and replaced the most of Hamahiga-made vegetables for the U. S. military bases. The farmers on Hamahiga inevitably faced difficulties due to the reclined demand for their vegetables and being small sized farmers. Many farmers also did not have sugarcane fields to compensate decreased demand for other vegetables. Therefore, many farmers had to turn to other sources of income such as construction labor in the central district of the main island of Okinawa.(2) As a result, the population of Hamahiga Island decreased approximately 20% every five (5) years in the 1960's, 1970's and 1980's. The downsizing of the population was especially obvious in the settlement of Higa-district where most of the residents depended on farming to make their livings. Besides, the residents of Higa-district were known for emigration to other countries and did not traditionally have strong attachment to the island or desire to keep their houses on the island. Thus, these economical and mental factors resulted in a relatively greater number of households to move out of the island of Hamahiga in those days. On the contrary, the populations of both Hama settlement and Kaneku settle ments were relatively well maintained since a number of residents were engaged in fishery.(3) The outflow of population from the island of Hamahiga has slowed down since the 1980's, however it varied from one settlement to another. Young residents of Hama-district have been engaging with seaweed (called Mozuku) farming since the latter half of the 1970's. The business of seaweed farming has been successful and profitable especially since 1980. The fishery industry has grown to support the fishermen on the island financially, which promoted participation of young generations into this industry since economic stability was promised and sustained development was expected.(4) Upon the completion of Hamahiga Bridge in 1997 connecting the island and the main island of Okinawa, former residents of the island began to return to Hamahiga. At least one resident was added to approximately 1/4 of all households on Hamahiga during the five years period following the construction of Hamahiga Bridge. The bridge evidently made it possible for the residents of Hamahiga to go to work on the main island of Okinawa on daily basis enhancing its population increase.(5) The interview of the households in the settlements of Hama-district and Higa-district whose family members moved in showed opposite results. Many of the residents in Hama who returned to the settlement were relatively young and they came back with their wives and children, whereas residents who came back to Higa-district were mainly older people with or without their wives.(6) The comparis

Experimental studies on rain splash erosion of forest soils after clearing in Okinawa using an artificial rainfall apparatus

The main island of Okinawa, in southwestern Japan, is characterized by a subtropical climate, coral reefs, and “reddish soils,” which contain Acrisols and Cambisols (FAO/UNESCO classifications). Recently, due to soil erosion on hilly lands, the coral reefs have been damaged by an inflow of reddish soil. Forest clearing is thought to one of the factors increasing rain splash erosion rates on hilly lands, because it is believed that clearing disturbs the forest floor and causes the supply of litter to stop. After clearing, A0, A and B horizons will be denuded, one after the other, by rain splash. In this study, we measured rain splash erosion rates of undisturbed samples of A0, A and B horizons using an artificial rainfall apparatus. The results of experiments on rain splash erosion clarified several aspects of the erosion process in a clearing site. First, it was found that the rain splash erosion rates were higher in fresh litter than in decomposed litter, in decomposed litter than in the A horizon, and in the A horizon than in the B horizon. Thus, the erosion rate increases with soil depth. Secondly, surface-gleyed red and yellow soils are mostly vulnerable to rain splash erosion. The erosion rates of these soils are two to three times higher than those of the red soil and the yellow soils. Thirdly, the erosion rates are affected mainly by bulk density and saturated hydraulic conductivity, not by clay ratio and dispersion ratio. Lastly, the difference between erosion rates of surface-gleyed red and yellow soils and other soils will be even greater if a soil crust has formed, because the formation of a soil crust increases the rain splash erosion rate.

CHANGES IN HTLV-I POSITIVE RATES AMONG PREGNANT WOMEN IN OKINAWA PRIOR TO THE EFFECTS OF MEASURES INTRODUCED TO PREVENT VERTICAL TRANSMISSION THROUGH BREAST MILK FEEDING

Objectives: Human T cell leukemia virus type-I (HTLV-I) is a causative agent of human T-cell leukemia and HTLV-I associated myelopathy (HAM/TSP). HTLV-I carriers are often infected vertically, especially via mother's milk. Since 1985, clinical measures have been adopted at a hospital in Okinawa to prevent vertical infections.Methods: We examined HTLV-I antibodies in all of the women (total 11, 506) who gave birth after 24 gestational weeks at a hospital on the Okinawa main island from January 1985 to December 1999.Results: The positive rate among all pregnant women was always higher than that among primipara alone. Both figures decreased over the period studied, but the primiparity rate (36-39%) did not change significantly. The percentage of HTLV-I positive primipara pregnant women among the HTLV-I positive total was close to the primiparity rate from 1985 to 1988, but it was considerably lower than the overall primiparity rate thereafter (22-26%).Conclusions: Preventive measures against HTLV-I infection did not contribute to the decrease in HTLV-I positive mothers before 1999 because these measures were adopted from 1985, and so there must be other reasons for the decrease in HTLV-I positive rate. Further studies on social factors and by year of birth are needed to identify factors influencing HTLV-carrier ratios among pregnant women.

ENVIRONMENTAL CONSERVATION MEASURES IN CONSTRUCTION OF POWER PLANT

The seawater pumped- storage pilot plant (maximum output 30MW) was recently completed in Okinawa Prefecture, Japan. The site is located in the northern part of Okinawa Main Island, where the rich environment still remains. Many valuable, even endangered species are also found on and nearby the plant site. However, the land is covered with thick layer of red soil making a serious impact on the coral reefs when discharged. The point of environmental conservation measures was, therefore, that both the protection of valuable species and the prevention of sediment yield of red soil should be taken into great account during the plant construction and after its completion as well.As for the actual countermeasures, small plastic fences and trapezoid-shaped gutters were installed around the construction site so that small animals could not intrude into the site and could easily bail out when trapped in the gutters. Sediment yield was also effectively reduced throuh catch drains, weirs, and sedimentation ponds. Environmental monitoring was carried out over the construction period. The plant site was fully restored to the native condition after its completion.

New genomospecies related to Borrelia valaisiana, isolated from mammals in Okinawa archipelago, Japan.

In 2000 and 2001, a survey was conducted of Borrelia isolated from various mammals in the southernmost islands of Japan, including Okinawa (main island), Izena, Iriomote and Ishigaki. Isolates obtained from the ear tissues of Suncus murinus (10 isolates), Mus calori (four isolates), Rattus norvegicus (one isolate) and Crocidura watasei (one isolate), were characterized by RFLP of the 5S-23S rDNA intergenic spacer and sequence analysis of the intergenic spacer, 16S rDNA and flagellin gene. While these isolates showed identical RFLPs to Borrelia valaisiana found in Korea, Taiwan and the southern and central parts of China, their RFLP patterns differed from those of B. valaisiana found in European countries, and strain Am501 isolated from Ixodes columnae in Japan. It was found that these isolates clustered with each other on a phylogenetic tree based on flagellin gene and 16S rDNA sequences, but were relatively divergent from the European B. valaisiana and strain Am501. These findings suggest that these isolates found in East Asia should be classified as a new genomospecies of Borrelia burgdorferi sensu lato.