Southwestern Islands Of Japan Research Articles

Analysis of the occurrence of the fall armyworm, Spodoptera frugiperda, in the winter season on the southwestern islands of Japan using the insect's strontium radiogenic isotope ratio (87Sr/86Sr)

AbstractSpodoptera frugiperda, an invasive pest insect that targets maize and other crops, first arrived in Japan in the summer of 2019. This species occurs year‐round in East Asian subtropical regions such as southern mainland China and the island of Taiwan, where the mean air temperature in the coldest month is above 10°C. Adults are similarly found throughout the year on the southwestern islands of Japan. Trap monitoring there showed continuous or intermittent S. frugiperda catches in the three winter seasons since 2019. However, it was difficult to distinguish between immigrants arriving from these neighbouring areas and local individuals occurring on each Japanese island. In this study, the possible natal origin of captured insects on five small islands (Yonagunijima, Taramajima, Okinawajima, Amamioshima and Tanegashima) was determined by investigating the strontium radiogenic isotope ratios (87Sr/86Sr) and comparing them with those of reference hosts and insects. Since trapping data and the 87Sr/86Sr values of trapped insects didn't support S. frugiperda's winter breeding on the northernmost island, Tanegashima, further analysis was limited to the four southern islands. The 87Sr/86Sr values of reference host plants and reared insects on the four islands ranged from 0.70929 to 0.71009, while those of catch insects ranged from 0.70885 to 0.71090. The 87Sr/86Sr values of the catch insects and the reference on the four islands did not differ significantly. In addition, the monthly averages of daily mean air temperature in January and February 2020–2022 were above 10°C, and the wind direction at the surface was mostly from the northeast or northwest. These pieces of evidence, together with winter host availability, suggested that S. frugiperda occurs year‐round on the islands. In other words, the year‐round occurrence area of S. frugiperda in East Asia extends to the Japanese southwestern islands below Amamioshima Island.

Spatio-temporal distribution of adults and eggs of the West Indian sweetpotato weevil Euscepes postfasciatus (Coleoptera: Curculionidae) on sweet potato stems

The West Indian sweetpotato weevil, Euscepes postfasciatus, a serious pest of sweet potatoes, is being eradicated by sterile insect technique (SIT) in the south-western islands of Japan. Information on the diurnal movement of the target pests on host plants and where mating and egg-laying behavior occurs on the host is important for the application of SIT, which eradicates the target pest through mating of released sterile males and wild females. However, little such information is available on this species. In this study, male and female adults were released on host plants to examine the diurnal distribution on seedlings according to sex, as well as the sites where mounting behavior and egg laying occurs. The results showed that females left the host plant more frequently at night, whereas males were more likely to remain on the host plant at night. Both males and females stayed on the nodes of the host plant during the daytime. Mounting behavior also tended to occur more often at nodes. Furthermore, compared to unmated females, mated females stayed at the vertical top of the seedlings. However, it was found that eggs were often laid close to the roots rather than at the top of the vertical stems, even when the seedlings were placed upside down. The results of previous studies and this study will be discussed from the perspective of the application of SIT against E. postfasciatus.

Cultural transmission of traditional songs in the Ryukyu Archipelago.

Geographic patterns of cultural variations are affected by how cultural traits are transmitted within and between populations. It has been argued that cultural traits are transmitted in different manners depending on their characteristics; for example, words for basic concepts are less liable to horizontal transmission between populations (i.e., borrowing) than other words. Here we examine the geographic variation of traditional songs in the Ryukyu Archipelago, southwestern islands of Japan, to explore cultural evolution of music with a focus on different social contexts in which songs are sung. Published scores of 1,342 traditional songs are coded using the CantoCore song classification scheme and distances between the songs are calculated from the codings. Neighbor-Net graphs of regions/islands are generated on the basis of the musical distances, and delta scores are obtained to examine the treelikeness of the networks. We also perform analysis of molecular variance (AMOVA) to evaluate the extent of musical diversification among regions/islands. Our results suggest that horizontal transmission between populations has played a greater role in the formation of musical diversity than that of linguistic diversity in the Ryukyu Archipelago and that the social context in which songs are sung has an effect on how they are transmitted within and between populations. In addition, we compare the observed patterns of song diversity among regions/islands with those of lexical and mitochondrial-DNA (mtDNA) diversity, showing that the variation of songs sung in the "work" context are associated with the linguistic variation, whereas no association is found between the musical and genetic variation.

Isolation of Culicoides- and Mosquito-Borne Orbiviruses in the Southwestern Islands of Japan Between 2014 and 2019.

The circulation of arboviruses in livestock ruminants has often gone unrecognized owing to the fact that a significant percentage of arboviruses probably induce subclinical infections and/or negligible symptoms in infected animals. To determine the current situation of arbovirus circulation in the Yaeyama Islands, attempts to isolate viruses from bovine blood samples collected between 2014 and 2019 have been made. In total, 308 blood samples were collected during the study period, and 43 of them induced cytopathic effects (CPEs) in cell cultures. The identification of the CPE agents was performed by reported RT-PCR assays and a high-throughput analysis with a next-generation sequencing platform. The obtained viruses consisted of an orthobunyavirus (Peaton virus), Culicoides-borne orbiviruses (bluetongue virus serotypes 12 and 16, epizootic hemorrhagic disease virus [EHDV] serotypes 5, 6, and 7, D'Aguilar virus, and Bunyip Creek virus), and potential mosquito-borne orbiviruses (Yunnan orbivirus, Guangxi orbivirus, and Yonaguni orbivirus). Most of the orbiviruses were recovered from washed blood cells with mosquito cell cultures, suggesting that this combination was more efficient than other combinations such as plasma/blood cells and hamster cell lines. This marked the first time that the isolation of EHDV serotypes 5 and 6 and three potential mosquito-borne orbiviruses was recorded in Japan, showing a greater variety of orbiviruses on the islands than previously known. Genetic analysis of the isolated orbiviruses suggested that the Yaeyama Islands and its neighboring regions were epidemiologically related. Some of the viruses, especially the potential mosquito-borne orbiviruses, were isolated during several consecutive years, indicating their establishment on the islands.

Pseudoexfoliation syndrome and relating factors in a rural Japanese population: the Kumejima Study.

To report the prevalence of pseudoexfoliation (PEX) syndrome and glaucoma associated with PEX (PEX-G) and their relating factors of them in a south-western island of Japan. A population-based survey of all residents aged≥40years was conducted in Kumejima, Okinawa, Japan, and 3762 subjects (participation rate, 81.2%) underwent detailed ophthalmic examinations. Presence of PEX material on the lens capsule, iris surface and/or pupillary margin was determined by slit-lamp biomicroscopy. Glaucoma was diagnosed according to the criteria of the International Society of Geographical and Epidemiological Ophthalmology. In subjects aged≥40years, prevalence rates of PEX syndrome, PEX without glaucoma and PEX-G in at least one eye were 1.5% (95% confidence interval [CI]: 1.0-1.9%), 1.3% (95% CI: 0.9-1.7%) and 0.1% (95% CI: 0.0-0.2%), respectively, excluding eyes after cataract surgery; and 2.8% (95% CI: 2.3-3.3%), 2.2% (95% CI: 1.8-2.6 %) and 0.4% (95% CI: 0.2-0.6%), respectively, including eyes after cataract surgery. Cataract surgery had been performed in 61% of subjects with PEX in at least one eye; presence of PEX showed no significant effects on the intraocular pressure (IOP). A multivariate analysis showed that PEX was associated with older age (p<0.0001, odds ratio: 1.10 [95% CI: 1.07-1.13]) and working outdoors (p=0.0395, odds ratio: 2.18 [95% CI: 0.99-4.82]). The prevalence rates of PEX syndrome and PEX-G in a south-western island of Japan were reported. PEX showed no significant effect on IOP, and age and working outdoors were significantly related with PEX.

Notes on the feeding habits of the Okinawan fishing spider, Dolomedes orion (Araneae: Pisauridae), in the southwestern islands of Japan

Fishing spiders, Dolomedes Latreille, 1804 (Pisauridae), are thought to be important predators in semi-aquatic ecosystems, but relatively few studies have investigated feeding ecology of Asian species. Here, we report on the diet of the Okinawan fishing spider, Dolomedes orion Tanikawa, 2003, the largest cursorial spider in Japan, based upon field observations on Amami Oshima Island in Kagoshima Prefecture and a literature review. A total of 13 predation events were observed in field surveys and 10 records were found in the literature. Together, these indicate the consumption of a broad range of food items from arthropods to vertebrates, e.g., insects, harvestman, conspecific spiders, crustaceans (freshwater crab and prawn), two species of endemic frogs (Rana ulma, Odorrana narina), and an Okinawa tree lizard (Japalura polygonata polygonata). Because this species has substantial energy demands for growth, large prey items such as crustaceans and vertebrates seem to be its primary food resources with 10 of 23 prey items [= 43%] belonging to these two large-sized prey groups.

南西諸島で生産された暖地型牧草によるサイレージ調製 : I.ローズグラス及びネピアグラスサイレージの品質に対する各種処理の影響

南西諸島で生産された暖地型牧草によるサイレージ調製 : I.ローズグラス及びネピアグラスサイレージの品質に対する各種処理の影響

南西諸島で生産された暖地型牧草によるサイレージ調製 : II.ローズグラスとスタイロ並びにサイラトロの混合がサイレージの品質に及ぼす影響

南西諸島で生産された暖地型牧草によるサイレージ調製 : II.ローズグラスとスタイロ並びにサイラトロの混合がサイレージの品質に及ぼす影響

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XIII.島尻マージにおけるFeとZn,および国頭マージにおけるMoとMnの施与効果

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XIII.島尻マージにおけるFeとZn,および国頭マージにおけるMoとMnの施与効果

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XI.国頭および島尻マージにおける暖地型マメ科およびイネ科牧草の燐施与に対する生育反応

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XI.国頭および島尻マージにおける暖地型マメ科およびイネ科牧草の燐施与に対する生育反応

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : VI.サイラトロと数種暖地型イネ科牧草との混播栽培における可消化乾物収量と乾物消化率

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : VI.サイラトロと数種暖地型イネ科牧草との混播栽培における可消化乾物収量と乾物消化率

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XII.国頭および島尻マージにおける有効態燐酸定量法の比較

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XII.国頭および島尻マージにおける有効態燐酸定量法の比較

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XIV.暖地型マメ科・イネ科18草種の生育におよぼす土壌pHの影響

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XIV.暖地型マメ科・イネ科18草種の生育におよぼす土壌pHの影響

持続的な周年利用草地のための造成技術と維持管理 : 南西諸島での事例を中心に( 最新の持続的な草地管理技術)

持続的な周年利用草地のための造成技術と維持管理 : 南西諸島での事例を中心に( 最新の持続的な草地管理技術)

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : VIII.暖地型マメ科牧草スタイロ(Stylosanthes spp.)とイネ科牧草との混播栽培における可消化乾物収量

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : VIII.暖地型マメ科牧草スタイロ(Stylosanthes spp.)とイネ科牧草との混播栽培における可消化乾物収量

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : IV.永年生暖地型マメ科牧草8種とローズグラスとの混播栽培における乾物生産量の比較

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : IV.永年生暖地型マメ科牧草8種とローズグラスとの混播栽培における乾物生産量の比較

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XVI. 南西諸島北部における数種暖地型マメ科牧草及びローズグラスの単播及び混播栽培における乾物生産量と窒素収量

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : XVI. 南西諸島北部における数種暖地型マメ科牧草及びローズグラスの単播及び混播栽培における乾物生産量と窒素収量

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : IX.暖地型マメ科牧草の追播によるマメ科イネ科混播草地の造成

南西諸島における暖地型マメ科牧草の実用栽培に関する研究 : IX.暖地型マメ科牧草の追播によるマメ科イネ科混播草地の造成

Interisland variegation of venom [Lys49]phospholipase A2 isozyme genes in Protobothrops genus snakes in the southwestern islands of Japan

Protobothrops tokarensis (Pt), a Crotalinae snake, inhabits only Takarajima and Kodakarajima islands of the Tokara Islands located in the immediate north of Amami-Oshima island of Japan. Kodakarajima P. tokarensis venom gland cDNA library gave four types of phospholipase A2 (PLA2) cDNAs encoding neutral [Asp49]PLA2, basic [Asp49]PLA2, highly basic [Asp49]PLA2, and [Lys49]PLA2. As the amino acid sequences encoded by their open reading frames (ORFs) were identical to those of PLA2, PLA-B, PLA-N, and BPI (a [Lys49]PLA2), respectively, from Amami-Oshima P. flavoviridis (Pf) venom, they were named PtPLA2, PtPLA-B, PtPLA-N, and PtBPI. Chromatography of P. tokarensis venom gave three PLA2 isozymes, PtPLA2, PtPLA-B, and PtBPI. However, BPII and BPIII ([Lys49]PLA2s) expressed in Amami-Oshima P. flavoviridis venom were not found in P. tokarensis venom. Genomic polymerase chain reaction (PCR) for P. tokarensis liver DNAs with the unique primers gave PtBPI gene. Notably it was found that LINE (long interspersed nuclear element)-1 fragment is inserted into second intron of PtBPI gene. The LINE-1 fragment may prevent duplication of PtBPI gene and thus formation of plural [Lys49]PLA2 genes in P. tokarensis genome. The interisland variegation of venom [Lys49]PLA2 isozyme genes in Protobothrops genus snakes in the southwestern islands of Japan is discussed.

Conservation of landscape and culture in southwestern islands of Japan

Conservation of landscape and culture in southwestern islands of Japan