Okinawa Island Research Articles

A new species of Leptoplectus Casey from Ryukyu Islands, Japan, with comments on morphology of integumental structures in Euplectitae (Coleoptera, Staphylinidae, Pselaphinae).

Leptoplectus kijimunaa Jałoszyński Nomura, sp. n. is described, based on a series of specimens collected on Okinawa Island, Japan. Morphological structures of the new species are illustrated in detail and compared to known characters of all remaining 14 congeners. As the diagnosis of Leptoplectus remains unclear, character variability within known species is discussed. It is concluded that within Palaearctic region, the bilobed labrum is a reliable character to distinguish this genus from other Euplectini. The placement of Labroplectus Kurbatov, treated as incertae sedis within the tribe Trichonychini in the latest edition of the Catalogue of Palaearctic Coleoptera, is verified and it is concluded that it should be maintained in Euplectini. An identification key to genera of northeastern Asian Euplectini is given. We also comment on outdated and inaccurate morphological nomenclature still broadly used in descriptions of new Pselaphinae taxa.

Fine-Scale Genetic Structure and Demographic History in the Miyako Islands of the Ryukyu Archipelago

The Ryukyu Archipelago is located in the southwest of the Japanese islands and is composed of dozens of islands, grouped into the Miyako Islands, Yaeyama Islands, and Okinawa Islands. Based on the results of principal component analysis on genome-wide single-nucleotide polymorphisms, genetic differentiation was observed among the island groups of the Ryukyu Archipelago. However, a detailed population structure analysis of the Ryukyu Archipelago has not yet been completed. We obtained genomic DNA samples from 1,240 individuals living in the Miyako Islands, and we genotyped 665,326 single-nucleotide polymorphisms to infer population history within the Miyako Islands, including Miyakojima, Irabu, and Ikema islands. The haplotype-based analysis showed that populations in the Miyako Islands were divided into three subpopulations located on Miyakojima northeast, Miyakojima southwest, and Irabu/Ikema. The results of haplotype sharing and the D statistics analyses showed that the Irabu/Ikema subpopulation received gene flows different from those of the Miyakojima subpopulations, which may be related with the historically attested immigration during the Gusuku period (900 − 500 BP). A coalescent-based demographic inference suggests that the Irabu/Ikema population firstly split away from the ancestral Ryukyu population about 41 generations ago, followed by a split of the Miyako southwest population from the ancestral Ryukyu population (about 16 generations ago), and the differentiation of the ancestral Ryukyu population into two populations (Miyako northeast and Okinawajima populations) about seven generations ago. Such genetic information is useful for explaining the population history of modern Miyako people and must be taken into account when performing disease association studies.

Plant indicator species for the conservation of priority forest in an insular forestry area, Yambaru, Okinawa Island

ABSTRACT Degradation of old-growth forests is an important issue for global biodiversity conservation. Robust indicator species greatly facilitate the identification of old-growth forests requiring protection. Understanding why particular species are associated with priority forests is necessary for assessing the reliability of indicator species. Here, we surveyed the vegetation of 69 sites in Yambaru forests (Okinawa Island) varying in forest age and analyzed the relationships between the dominance of vascular species and three criterion parameters (forest age and species richness (SR) of epiphytes and endangered plants). Eleven species showing significant positive correlations with three parameters were designated as potential candidate indicator species, ten of which were woody species. Of the above eleven candidate indicator species, Distylium racemosum was considered one of the most useful indicator species because it can be easily identified in the field and its ecological characteristics are well documented. Regarding three woody traits – sprouting ability, annual growth rate and wood density – which are expected as the cause of indexing, endangered SR increased when tree species with low sprouting ability and high wood density were dominant, and epiphyte SR increased when tree species with low annual growth rate and high wood density were dominant. These woody species traits were associated with forest age and could explain why D. racemosum is an indicator of priority forest. These results suggest that large trees with such woody characteristics are effective indicators of priority forests.

Final yield of the brown alga Cladosiphon okamuranus (Chordariaceae, Phaeophyceae) may depend on nursery quality

SUMMARYCladosiphon okamuranus (Chordariaceae, Phaeophyceae) production is an important economic activity in the islands of Okinawa, Japan, and has been unstable for the past decade. Local producers surmise that unstable yields are related to highly localized environmental conditions. We report that the differential yields of C. okamuranus harvested from experimental nets during the 2019 season at two adjacent nurseries (less than 40 m apart), which were designated as a poor or good nursery by local producers, were 137 and 253 kg (wet weight), respectively. In fact, nutrient conditions between the poor and good nursery were slightly different, although involvement of some unsurveyed environmental factors cannot be excluded at present. Additionally, we report on a thallus shearing phenomenon that led to the catastrophic loss of thalli from the cultivation nets.

Landscape and the crisis of representation in Nakae Yūji’s Panari nite (1986)

ABSTRACT In Japan, the ideological implications of landscape were hotly discussed throughout the 1970s. In his response to this discussion, the film scholar and critic Hasumi Shigehiko characterized ‘landscape’ as a cultural apparatus that dictates one’s perception of the physical world. A comparable view on landscape can be found in Panari nite (On an Offshore Island, Nakae Yūji, 1986), which evinces a critical engagement with landscape through drawing on the mythologized life of Vincent van Gogh in Arles. As with the Dutch artist, who sought an imagined Japan in southern France, the film’s protagonist, a painter from Tokyo, carries along his fantasies when he comes to an island in subtropical Okinawa, where he confronts the devastating gap between reality and representation. Through analysis of the film, I will assess Hasumi’s formative influence upon Nakae, arguing that the film employs Hasumi’s critical approach to landscape in order to counter the dominant stereotype of Okinawa as an exotic Other within Japan’s national boundary.

COOPERATIVE SUCCESSION: STRATEGIC MILITARY BASE REALIGNMENT IN OKINAWA

Since the Battle of Okinawa and the end of World War II, Okinawa Island, one of the five main islands of Japan, has been a critical strategic location for the United States Armed Forces. Approximately 70% of the U.S. military bases in Japan are located on Okinawa Island. The bases cover one-fifth of the total Island area and expose Okinawa to various social–ecological vulnerabilities. Being unconstrained by the military base border, the social-ecological impacts of this highly militarized reality could be observed across the Island, and contaminates and disturbs ecological systems crucial for local residents and wildlife. Within the context of the ongoing debate over the military realignment on Okinawa Island, this study responds to the aforementioned challenges by proposing a landscape-based alternative realignment strategy. In particular, with the upcoming 50th anniversary of Okinawa’s reversion to Japan in 2022, this work outlines four strategies for establishing an ecological symbiosis between nature, the indigenous Okinawan, and the U.S. military bases, and strengthening self-sustainability on a militarized island landscape.

Aspects of the biology of two Nemipterus species in coastal waters around Okinawa Island, Ryukyu Archipelago

Aspects of the biology of two <i>Nemipterus</i> species in coastal waters around Okinawa Island, Ryukyu Archipelago

Power Generation Performance of a Pilot-Scale Reverse Electrodialysis Using Monovalent Selective Ion-Exchange Membranes.

Reverse electrodialysis (RED) is a promising process for harvesting energy from the salinity gradient between two solutions without environmental impacts. Seawater (SW) and river water (RW) are considered the main RED feed solutions because of their good availability. In Okinawa Island (Japan), SW desalination via the reverse osmosis (RO) can be integrated with the RED process due to the production of a large amount of RO brine (concentrated SW, containing ~1 mol/dm3 of NaCl), which is usually discharged directly into the sea. In this study, a pilot-scale RED stack, with 299 cell pairs and 179.4 m2 of effective membrane area, was installed in the SW desalination plant. For the first time, asymmetric monovalent selective membranes with monovalent selective layer just at the side of the membranes were used as the ion exchange membranes (IEMs) inside the RED stack. Natural and model RO brines, as well as SW, were used as the high-concentrate feed solutions. RW, which was in fact surface water in this study and close to the desalination plant, was utilized as the low-concentrate feed solution. The power generation performance investigated by the current-voltage (I–V) test showed the maximum gross power density of 0.96 and 1.46 W/m2 respectively, when the natural and model RO brine/RW were used. These are a 50–60% improvement of the maximum gross power of 0.62 and 0.97 W/m2 generated from the natural and model SW, respectively. The approximate 50% more power generated from the model feed solutions can be assigned to the suppression of concentration polarization of the RED stack due to the absence of multivalent ions.

First records of Pseudanthias rubrolineatus (Fourmanoir and Rivaton, 1979) (Serranidae: Anthiadinae) from the Okinawa Islands, Ryukyu Islands, southern Japan, with morphological comparison with a closely related species, P. georgei (Allen, 1976)

First records of <i>Pseudanthias rubrolineatus</i> (Fourmanoir and Rivaton, 1979) (Serranidae: Anthiadinae) from the Okinawa Islands, Ryukyu Islands, southern Japan, with morphological comparison with a closely related species, <i>P. georgei</i> (Allen, 1976)

A Study on Cone Karst Landforms at Yamazato, Motobu, Okinawa Island

A Study on Cone Karst Landforms at Yamazato, Motobu, Okinawa Island

Reproductive patterns and early life history of the Indian mackerel Rastrelliger kanagurta in the coastal waters of Okinawa Island, Ryukyu Archipelago, Japan

Reproductive patterns and early life history of the Indian mackerel <i>Rastrelliger kanagurta</i> in the coastal waters of Okinawa Island, Ryukyu Archipelago, Japan

Preliminary report on diatoms attached to pumice clasts that originated from the 2021 eruption of the Fukutoku-Oka-no-Ba submarine volcano and drifted to Okinawa Island, southwestern Japan

Preliminary report on diatoms attached to pumice clasts that originated from the 2021 eruption of the Fukutoku-Oka-no-Ba submarine volcano and drifted to Okinawa Island, southwestern Japan

Life history traits of the bigeye scad, Selar crumenophthalmus, in the coastal waters of Okinawa Island, southwestern Japan

Life history traits of the bigeye scad, <i>Selar crumenophthalmus</i>, in the coastal waters of Okinawa Island, southwestern Japan

Historical investigation into articles on alien species introduced around 1910, particularly Shozaburou Watase’s introduction of the mongoose to the Okinawa Islands, Japan

Historical investigation into articles on alien species introduced around 1910, particularly Shozaburou Watase’s introduction of the mongoose to the Okinawa Islands, Japan

Topography formation in the Central and Southen Parts of Okinawa Island and the Nakagusuku Bay

Topography formation in the Central and Southen Parts of Okinawa Island and the Nakagusuku Bay

Further new species of the plant bug genus Campylomma Reuter from the Oriental Region (Heteroptera: Miridae: Phylinae: Nasocorini)

• Three new Oriental species of Campylomma are described. • Two of these were found to uniquely inhabit Hibiscus tiliaceus flower or leaf buds in urbanized zones. • The present result could contribute to the further biodiversity researches in the Oriental Region. The fauna of the nasocorine plant bug genus Campylomma Reuter from the Oriental Region, including subtropical Japanese Ryukyu Islands (Okinawa Island of Southwest Islands-group) and Taiwan is updated. Three new species are herein described, C. astica n. sp. (from Okinawa and Taoyuan, Taiwan) , C. hibiscicola n. sp. (Bangkok, Thailand) and C. nanrenana n. sp. (Pingtung, Taiwan). Of these, C. astica and C. hibiscicola , were observed to have cryptic habitat-preference, inhabiting bracts, stipules or flower buds of the sea (or coastal) hibiscus, Hibiscus tiliaceus (L.) (Malvaceae), planted for landscaping at urbanized zones. An updated checklist of the 22 Oriental Campylomma species is provided.

Two cases studies of Model Predictive Control approach for hybrid Renewable Energy Systems

&lt;abstract&gt;&lt;p&gt;This work presents a load frequency control scheme in Renewable Energy Sources(RESs) power system by applying Model Predictive Control(MPC). The MPC is designed depending on the first model parameter and then investigate its performance on the second model to confirm its robustness and effectiveness over a wide range of operating conditions. The first model is 100% RESs system with Photovoltaic generation(PV), wind generation(WG), fuel cell, seawater electrolyzer, and storage battery. From the simulation results of the first case, it shows the control scheme is efficiency. And base on the good results of the first case study, to propose a second case using a 10-bus power system of Okinawa island, Japan, to verify the efficiency of proposed MPC control scheme again. In addition, in the second case, there also applied storage devices, demand-response technique and RESs output control to compensate the system frequency balance. Last, there have a detailed results analysis to compare the two cases simulation results, and then to Prospects for future research. All the simulations of this work are performed in Matlab®/Simulink®.&lt;/p&gt;&lt;/abstract&gt;

Sugarcane Dry Matter Production estimating with the Evapotranspiration in the Southern Region of Okinawa Island

Sugarcane Dry Matter Production estimating with the Evapotranspiration in the Southern Region of Okinawa Island

Unique Evolution of Hyla hallowellii Among Amphibians of the Central Ryukyus, Japan (Anura: Hylidae).

Fauna of the Central Ryukyus includes a high percentage of endemic species, and Hallowell's tree frog Hyla hallowellii Thompson, 1912 is one of such elements, occurring in a total of eight islands in the Amami and Okinawa Island groups. Using samples representing all of these eight island populations, we studied variations in morphology, karyotype, allozyme, and mtDNA, to clarify the pattern of geographic differentiation of H. hallowellii and consider factors for its formation. We could not clearly discriminate one population from another in morphology, nor could we find any interpopulation difference in karyotype. From genetic analyses, using allozymes and cyt b, we found low overall differentiations among populations. However, the southern populations from Okinawajima and Yoronjima were genetically nearly identical with the northern Amamioshima population. From that group the geographically intermediate Tokunoshima and Kakeromajima populations showed prominent differentiations. These patterns of geographical differentiation greatly differ from those known in other amphibian species of the Central Ryukyus, and suggest that H. hallowellii has evolutionary history unique to the species.

A new species of Egglestonichthys (Teleostei, Gobiiformes, Gobiidae) from Okinawa Island, Japan.

Egglestonichthys fulmensp. nov. (Teleostei: Gobiidae) is described on the basis of a single specimen (21.7 mm in standard length) collected from 250 m depth off Okinawa Island, Ryukyu Islands, Japan. The new species is characterized by the following combination of characters: anal-fin rays I, 9; pectoral-fin rays 17, lower rays not free from membrane; longitudinal scale series 25; transverse scales 8; pre-dorsal-fin scale rows 8; cheek and opercle naked; pelvic frenum absent; caudal fin lanceolate, its length 32.2% of SL; interorbital width very narrow, 1.2% of HL (much narrower than pupil diameter); no spicules or odontoid processes on outer surface of gill arches; and body whitish, upper half with broken zigzag pattern of bright yellow patches and associated scattered black melanophores in fresh specimens (melanophores retained in preserved specimens). Several characters, including pectoral-fin ray count, interorbital width, and coloration uniquely distinguish the new species from congeners.