Iriomote Island Research Articles

A new species of the genus Paradistomum (Platyhelminthes: Trematoda) from Iwasaki's snail-eating snake Pareas iwasakii, with a note on morphological variations of Paradistomum megareceptaculum (Tamura, 1941).

Dicrocoeliid trematodes were detected from Iwasaki's snail-eating snake Pareas iwasakii in Iriomote Island, Okinawa Prefecture, Japan, and described as a new species Paradistomum dextra n. sp. in the present study. This new species can be distinguished from the type series of the other members of the genus based on size of eggs and morphological characteristics of body, oral and ventral suckers, and reproductive organs. However, the new species was hard to distinguish from Paradistomum megareceptaculum infecting snakes in Japan, including Iriomote Island where is the type locality of the new species, because it is closely similar to some part of the broad range of morphological variations in P. megareceptaculum. On the other hand, a partial sequence of 28S ribosomal DNA clearly distinguished these two species. Moreover, the new species' host snake Pareas iwasakii is reported to exclusively feed on land snails while host snakes of P. megareceptaculum feed on small vertebrates, indicating that the new species is also ecologically different from P. megareceptaculum. We also redescribed P. megareceptaculum based on adults sampled in this study and past studies to record the morphological variations of this species.

Seasonal diet partition among top predators of a small island, Iriomote Island in the Ryukyu Archipelago, Japan

Small islands tend to lack predators because species at higher trophic levels often cannot survive. However, two exceptional top predators—the Iriomote cat Prionailurus bengalensis iriomotensis, and the Crested Serpent Eagle Spilornis cheela perplexus—live on the small Iriomote Island in the Ryukyu Archipelago. To understand how these predators coexist with limited resources, we focused on their seasonal diets between which conflicts are considered to occur. To compare the diets, we used DNA metabarcoding analysis of faecal samples. In the summer, we identified 16 unique prey items from Iriomote cat faecal samples and 15 unique prey items from Crested Serpent Eagle faecal samples. In the winter, we identified 37 and 14, respectively. Using a non-metric multidimensional scaling and a permutational multivariate analysis of variance, our study reveals significant differences in the diet composition at the order level between the predators during both seasons. Furthermore, although some prey items at the species-to-order level overlapped between them, the frequency of occurrence of most prey items differed in both seasons. These results suggest that this difference in diets is one of the reasons why the Iriomote cat and the Crested Serpent Eagle are able to coexist on such a small island.

Morphological and molecular characterization of Desmicola ryukyuensis n. sp. (Nematoda: Oxyuridomorpha: Thelastomatidae) from the wood-feeding cockroach Panesthia angustipennis yayeyamensis Asahina, 1988 (Blattaria: Blaberidae) in the Ryukyu Archipelago, Japan.

Desmicola ryukyuensis n. sp. (Nematoda: Oxyuridomorpha: Thelastomatidae) is described from the wood-feeding cockroach Panesthia angustipennis yayeyamensis Asahina, 1988 (Blattaria: Blaberidae) in Iriomote Island, Japan. The males of D. ryukyuensis n. sp. are similar to D. lamdongensis Sokolova, 2019 but differ by the length of the spicule and the extension of the lateral alae. The females of D. ryukyuensis n. sp. resemble those of D. ornata Jex, Schneider, Rose & Cribb, 2005, but can be differentiated by the shape of the sensilla in the interlabial space and the presence of lateral alae in D. ryukyuensis n. sp. that are absent in D. ornata. The females of D. ryukyuensis n. sp. are similar to D. lamdongensis. However, they differ in the morphology of the lips and the size of the eggs. The phylogeny of D. ryukyuensis n. sp. is inferred by the D2-D3 domains of the 28S rDNA. The new species forms a clade with another sequence of an unidentified Desmicola species from a Vietnamese wood-feeding cockroach.

Characteristics of spider assemblages of subtropical rice paddy fields in the Yaeyama Islands, Japan

Spiders are important natural enemies of rice pests in paddy fields. To estimate their roles, it is essential to understand their functional diversity. However, little is known about the spider fauna of paddy fields in subtropical regions. Here, we investigated spider diversity and species composition in paddy fields in the Yaeyama Islands, in subtropical Japan. We collected 1489 individuals of at least 42 species in 13 families and 7 guilds from rice paddies on Ishigaki, Iriomote, and Yonaguni islands by net sweeping during the first and second crops from 2013 to 2015. The Tetragnathidae (39%), Araneidae (35%), and Thomisidae (18%) were the most abundant families, comprising > 90% of total abundance. Orb web weavers (73%) and ambush hunters (19%) were the most abundant guilds. The most common species were Neoscona theisi (Walckenaer, 1841) (Araneidae) (n = 352), Tetragnatha javana (Thorell, 1890) (Tetragnathidae) (n = 294), and Tetragnatha nitens (Audouin, 1826) (Tetragnathidae) (n = 94). The results show that the species composition of spiders in subtropical paddy fields is more similar to that in tropical paddy fields in Asia than to that in temperate paddy fields in mainland Japan. Ordination analysis showed that the composition of spiders on Ishigaki island varies greatly with season and year. This study makes a valuable contribution to knowledge of the comprehensive diversity of subtropical spiders associated with rice paddy fields in Japan.

The hard tick fauna (Acari: Ixodida) of the Iriomote cat (<I>Prionailurus bengalensis iriomotensis</I>) in Iriomote Island, Okinawa Prefecture, Japan: a literature review with emphasis on need for surveillance of tick-borne pathogens

The hard tick fauna (Acari: Ixodida) of the Iriomote cat (<I>Prionailurus bengalensis iriomotensis</I>) in Iriomote Island, Okinawa Prefecture, Japan: a literature review with emphasis on need for surveillance of tick-borne pathogens

Relationship between herbivory and leaf traits in mangroves on Iriomote Island, southern Japan

Relationship between herbivory and leaf traits in mangroves on Iriomote Island, southern Japan

Suitability and Energy Sustainability of Atmospheric Water Generation Technology for Green Hydrogen Production

This research investigated the suitability of air-to-water generator (AWG) technology to address one of the main concerns in green hydrogen production, namely water supply. This study specifically addresses water quality and energy sustainability issues, which are crucial research questions when AWG technology is intended for electrolysis. To this scope, a reasoned summary of the main findings related to atmospheric water quality has been provided. Moreover, several experimental chemical analyses specifically focused on meeting electrolysis process requirements, on water produced using a real integrated AWG system equipped with certified materials for food contact, were discussed. To assess the energy sustainability of AWGs in green hydrogen production, a case study was presented regarding an electrolyzer plant intended to serve as energy storage for a 2 MW photovoltaic field on Iriomote Island. The integrated AWG, used for the water quality analyses, was studied in order to determine its performance in the specific island climate conditions. The production exceeded the needs of the electrolyzer; thus, the overproduction was considered for the panels cleaning due to the high purity of the water. Due to such an operation, the efficiency recovery was more than enough to cover the AWG energy consumption. This paper, on the basis of the quantity results, provides the first answers to the said research questions concerning water quality and energy consumption, establishing the potential of AWG as a viable solution for addressing water scarcity, and enhancing the sustainability of electrolysis processes in green hydrogen production.

Simulated distributions of pumice rafts in Japan following eruptions at volcanic islands and submarine volcanoes

Voluminous pumice rafts produced by the 2021 phreatomagmatic eruption of Fukutoku-Oka-no-Ba, a submarine volcano located in the Izu-Bonin Islands, reached many Japanese ports and islands, damaging fisheries and hindering marine traffic and trade. This event emphasized the necessity for governments and stakeholders to develop plans in advance and prepare disaster mitigation measures before an eruption. To investigate when and to what extent pumice might intersect trade routes and arrive at islands after future eruptions, we conducted particle tracking simulations of eruptions at major volcanic islands and submarine volcanoes near Japan using the velocity field from the ocean reanalysis dataset. Seven major volcanoes that have produced pumice rafts in the past century were selected: the submarine volcano NNE of Iriomote Island, Izu-Tobu Volcanoes, Miyakejima, Bayonnaise Rocks, Nishinoshima, Kaitoku Seamount, and Fukutoku-Oka-no-Ba. We partly reproduced the distribution of pumice arrivals recorded after the 1986 Fukutoku-Oka-no-Ba eruption, demonstrating the potential effectiveness of the simulations. We report likely pumice raft arrivals and drifting durations for the investigated eruptive scenarios, which may aid future risk assessments for pumice arrivals.

Resurrection and emended description of Gastrodia foetida (Orchidaceae)

This paper presents a re-evaluation of the taxonomic identity of Gastrodia foetida based on molecular and morphological data. The taxon was described from Iriomote Island, Ryukyu Islands, Japan, and has often been treated as a synonym of G. nipponica from Wakayama Prefecture, Honshu, Japan. In contrast, we showed that the genetic divergence between G. foetida and G. nipponica is much more significant than that between G. foetida and G. takeshimensis. Additionally, G. foetida can be distinguished from G. nipponica by a few morphological traits, particularly a more dilated column toward a little below the middle. Therefore, we propose that G. foetida is recognized as a distinct species based primarily on molecular phylogenetic evidence followed by morphological evidence. Our investigation strongly suggested that these species exhibit distinct geographic separation: G. nipponica is restricted in mainland Japan (north of the Ryukyu Islands), whereas G. foetida is mainly distributed on the more southern areas (the Ryukyu Islands and possibly Taiwan).

Potential seed dispersal agents of Monoon liukiuense on Iriomote Island, Japan

Abstract Monoon liukiuense (Annonaceae) is an endangered tree species distributed in Iriomote Island and Hateruma Island in the Ryukyu (Nansei) Islands, Japan, and in Orchid Island (Lanyu) in Taiwan. While its habitat is confined to small areas surrounded by human-altered landscapes, the matured trees bear abundant fruits, and many offspring grow under the mother trees. M. liukiuense is hypothesised to have lost effective seed dispersers. To test this hypothesis, fate of its seeds and the behaviour of frugivores were observed using time-lapse photography during three fruiting seasons from June 2015 to August 2016 in Iriomote Island, Japan. Although several animal taxa were observed to consume the fruit pulp, only two volant animals, namely the Yaeyama flying fox and large-billed crow, were proposed as seed dispersal agents for M. liukiuense. The present study shows that an average of 82% of the fruits in the canopies fell directly beneath the fruiting trees and an average of 90% of the seeds on the forest floor remained in their original positions. These results suggest that M. liukiuense has lost most of its seed dispersal agents and the chance to expand its distribution.

North-to-South diversity of lipomycetaceous yeasts in soils evaluated with a cultivation-based approach from 11 locations in Japan.

To understand the species distribution, diversity, and density of lipomycetaceous yeasts in soil based on their north-to-south location in Japan, 1146 strains were isolated from soil samples at 11 locations from Hokkaido to Okinawa Prefecture and taxonomically characterized. Lipomycetaceous yeast strains were isolated efficiently from soil by selecting watery mucoid-like colonies on agar plates with nitrogen-depleted medium. Twenty-four (80%) of the 30 known species of the genus Lipomyces were isolated from the soil samples collected in Japan, including species recently proposed. Among the species isolated, L. starkeyi was the most predominant in Japan, except on Iriomote Island, Okinawa, and accounted for 60-98% of the isolated strains. Lipomyces yarrowii was the dominant species on Iriomote Island (64%). The second most dominant species were L. chichibuensis in Saitama Prefecture and L. doorenjongii from Yamaguchi to Okinawa Prefecture. The species diversity of lipomycetaceous yeasts was in Japan and the significant correlation with the latitude of the sampling sites was revealed.

History and issues of setting target values for tourism management in Iriomote Island

History and issues of setting target values for tourism management in Iriomote Island

「奄美大島，徳之島，沖縄島北部及び西表島」—「島」の世界自然遺産の特徴

「奄美大島，徳之島，沖縄島北部及び西表島」—「島」の世界自然遺産の特徴

奄美大島・徳之島・沖縄島北部及び西表島の世界自然遺産登録の経緯とその課題

奄美大島・徳之島・沖縄島北部及び西表島の世界自然遺産登録の経緯とその課題

Taxonomy of Perissosega Krombein (Hymenoptera: Chrysididae, Amiseginae), with description of a new species from Japan.

Perissosega sulcata sp. nov. is newly described on the basis of the two females collected from Iriomote Island, the Ryukyus, Japan. A new combination is proposed for Calosega flavipes (Kimsey, 1995), comb. nov. from Perissosega Krombein, 1983. The diagnostic characters of Calosega Terayama, 1999 and Perissosega are revised.

Rapid recovery of coral communities from a mass bleaching event in the summer of 2016, observed in Amitori Bay, Iriomote Island, Japan

Devastating bleaching of coral communities at Amitori Bay, Iriomote Island, Japan, occurred in 2016 during the third global mass bleaching event in 2014–2017. The present study documented changes in coral communities in Amitori Bay from just before until after the 2016 bleaching event (2016–2020), by measuring coral cover and recruitment at nine sites (with two additional sites in 2018) in the bay. Spawning rates of acroporid corals were also monitored from 2017 to 2019 by visual observation and using bundle collectors to observe how long the effect of bleaching persisted. Reductions of 64.7 and 89.5% from 2016 to 2017 were observed in cover and recruitment of all coral families, respectively. Coral cover of all coral families recovered to pre-bleaching levels by 2020 and recruitment in 2020 was about two times greater than the pre-bleaching level. These results mirrored those of acroporids. Spawning rates of Acropora corals increased significantly from 40.6% in 2017 to 90.0% in 2019. Recovery of coral cover 4 years after the severe bleaching event was likely related to regrowth of remnants and of surviving juveniles of < 5 cm. The sudden increase in recruitment was likely driven by a combination of larval supply from other populations, increased numbers of reproductive adults, increases in spawning rates, and increased larval retention in the bay due to wind conditions in 2020. This study suggests that coral communities as in Amitori Bay will be critical for local-scale community persistence, serving as both source and sink populations.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00227-022-04091-2.

The First Record of the Fairy Pitta &lt;i&gt;Pitta nympha&lt;/i&gt; from Iriomote Island, Japan

The First Record of the Fairy Pitta &lt;i&gt;Pitta nympha&lt;/i&gt; from Iriomote Island, Japan

Two new species and a new genus of ray spiders (Araneae, Theridiosomatidae) from the Ryukyu Islands, southwest Japan, with notes on their natural history.

This paper provides descriptions of two new theridiosomatid species, Theridiosomanigrivirgatum sp. nov. and Sennintanikawai gen. nov., sp. nov. from the Ryukyu Islands, southwest Japan, with photographs and illustrations of both sexes. Sennin gen. nov. is a troglophilic genus composed of two species, S.tanikawai sp. nov. (Iriomote Island, Japan) and S.coddingtoni (Zhu, Zhang & Chen, 2001), comb. nov. (southern China). Zomadibaiyin Miller, Griswold & Yin, 2009, which recently joined the Japanese fauna, was morphologically reexamined based on specimens from the Ryukyus, and taxonomic features of Zoma males were reassessed. A distributional map of theridiosomatid spiders in the Ryukyus is also provided, including T.dissimulatum Suzuki, Serita & Hiramatsu, 2020, and T.alboannulatum Suzuki, Serita & Hiramatsu, 2020 with their habitat types, web morphology, and web-building behavior in detail.

Correction to: Arbuscular mycorrhizal fungal communities of a mangrove forest along a salinity gradient on Iriomote Island

Correction to: Arbuscular mycorrhizal fungal communities of a mangrove forest along a salinity gradient on Iriomote Island

Parameterization of Mangrove Root Structure of Rhizophora stylosa in Coastal Hydrodynamic Model

Mangroves are able to attenuate tsunamis, storm surges, and waves. Their protective function against wave disasters is gaining increasing attention as a typical example of the green infrastructure/Eco-DRR (Ecosystem-based Disaster Risk Reduction) in coastal regions. Hydrodynamic models commonly employed additional friction or a drag forcing term to represent mangrove-induced energy dissipation for simplicity. The well-known Morison-type formula (Morison et al. 1950) has been considered appropriate to model vegetation-induced resistance in which the information of the geometric properties of mangroves, including the root system, is needed. However, idealized vegetation configurations mainly were applied in the existing numerical models, and only a few field observations provided the empirical parameterization of the complex mangrove root structures. In this study, we conducted field surveys on the Iriomote Island of Okinawa, Japan, and Tarawa, Kiribati. We measured the representative parameters for the geometric properties of mangroves, Rhizophora stylosa, and their root system. By analyzing the data, significant correlations for hydrodynamic modeling were found among the key parameters such as the trunk diameter at breast height (DBH), the tree height H, the height of prop roots, and the projected areas of the root system. We also discussed the correlation of these representative factors with the tree age. These empirical relationships are summarized for numerical modeling at the end.