Okinawa-jima Island Research Articles

A new species of Homalernis Meyrick, 1908 (Lepidoptera, Tortricidae, Tortricinae) represents the first record of the tribe Schoenotenini in Japan

Homalernis fluctuosa Suzuki & Jinbo, sp. nov., is described and illustrated from Honshu, Shikoku, Kyushu, Tsushima Island, Amamiooshima Island, and Okinawajima Island, Japan. This is not only the first record of the genus Homalernis but also of the tribe Schoenotenini from warm temperate zones in the Palaearctic region. The association of males and females of the new species was confirmed based on the mitochondrial gene cytochrome oxidase submit 1 (COI). We discuss the taxonomic positions of two alleged Homalernis species from Malaysia and the taxonomic position of Homalernis within Schoenotenini.

Tribasodes kamedai Nomura is not a strictly cavernicolous species (Coleoptera: Staphylinidae: Pselaphinae)

Tribasodes kamedai Nomura, 2012 was described based on specimens collected in a limestone cave in Okinawa-jima Island. We demonstrate that this species is not a strict troglobite, but presumably a trogloxene, as it was recently collected in new localities from forest leaf litter and hollow trees. Tribasodes kamedai is redescribed in detail, with the first illustrations of female genitalia, notes on interspecific variability, and new distributional records.

Genetic and Morphological Studies on Goniurosaurus kuroiwae (Squamata: Eublepharidae), with a Description of a New Species from the Northern Part of Okinawajima Island, Ryukyu Archipelago, Japan

Genetic and Morphological Studies on Goniurosaurus kuroiwae (Squamata: Eublepharidae), with a Description of a New Species from the Northern Part of Okinawajima Island, Ryukyu Archipelago, Japan

Description of a new species, Pseudodiscocotyla mikiae n. sp. (Monogenea: Discocotylidae) parasitic on gills of Pristipomoides filamentosus from off Okinawa-jima island in Japan, with redescription of Pseudodiscocotyla opakapaka.

Two species of Pseudodiscocotyla Yamaguti, 1965 (Monogenea: Discocotylidae) were collected from crimson jobfish Pristipomoides filamentosus (Valenciennes) (Perciformes: Lutjanidae) off Okinawa-jima island, southern Japan. Pseudodiscocotyla opakapaka is redescribed and represents the first Japanese record. A new species, Pseudodiscocotyla mikiae n. sp., differs from Ps. opakapaka in the absence of spines around the male genital pore, the shape of the vaginal pore, the presence of spines inside the vaginal pore, and the shape of the clamp. The locations of the male genital atrium and the vaginal pore in both species were similar, and the observed armament differences of the male copulatory organ are therefore presumed to establish reproductive isolation. The phylogenetic trees for the Mazocraeidea based on the partial 28S rDNA sequences were created using new sequences of Pseudodiscocotyla mikiae n. sp., and Discocotylidae formed a sister group with the species Diclidophoridae, Macrovalvitrematidae, and Plectanocotylidae. Pristipomoides filamentosus is widely distributed across the Indo-Pacific, and Pseudodiscocotyla mikiae n. sp. could share the distribution of the host.

Age, growth and maturation of the brown surgeonfish Acanthurus nigrofuscus at Okinawa-jima Island, Japan

Age, growth and maturation of the brown surgeonfish Acanthurus nigrofuscus at Okinawa-jima Island, Japan

Fish mortality following sudden cold snap in Okinawa-jima Island, Japan

Fish mortality following sudden cold snap in Okinawa-jima Island, Japan

The genus Anacaena Thomson from the Ryukyu Archipelago of Japan (Coleoptera, Hydrophilidae)

We review the genus Anacaena Thomson, 1859 from the Ryukyu Archipelago, southern Japan. Three aquatic species are recognised: A. torikaiisp. nov. from Amami-ôshima Island, A. okinawanasp. nov. from Okinawa-jima Island and Kerama Islands, and A. kumejimanasp. nov. from Kumejima Island. All three species are very similar, with the morphology of the aedeagus being essential for a reliable identification. Dorsal colouration is also useful as a diagnostic character, despite some variation within species. We observe a possible geography-based variation between A. okinawana from Okinawa-jima I. and the neighbouring Kerama Is., but we treat both populations as conspecific based on genital morphology. Anacaena kumejimana and A. okinawana share many morphological characters possibly indicating their close relationship. We compare the endemism of aquatic Hydrophilidae in the Ryukyu Archipelago to that in other groups of aquatic beetles: the proportion of endemic species is higher in aquatic Hydrophilidae than in Dytiscidae, but much lower than in stream-inhabiting Hydraenidae and Elmidae. A list of Japanese species of Anacaena and a key to the Japanese species of the genus are provided.

Geographic Variation in Skull Morphology of the Japanese Crocodile Newt, Echinotriton andersoni (Amphibia: Urodela: Salamandridae), Inferred from Geometric Morphometrics

The Anderson's crocodile newt, Echinotriton andersoni, is an endangered species distributed in the islands of Central Ryukyus, Japan. This species is well known to show high intraspecific genetic variation among islands, but its morphological variation has not been explored. We examined the skull variation in this species including enigmatic specimens collected from Taiwan by using geometric morphometrics, and found sexual differences and geographic variation mainly between the Okinawa group (Okinawajima Island) and the Amami Group (Amamioshima and Tokunoshima Islands). We further found close resemblance between the Taiwanese specimens and the female specimens from Amamioshima Island.

Taxonomic revision and re-description of Ateuchosaurus pellopleurus (Hallowell, 1861) (Reptilia, Squamata, Scincidae) with resurrection of A. okinavensis (Thompson, 1912)

The scincid lizard Ateuchosaurus pellopleurus (Hallowell, 1861) has been recognized as a single species widely distributed in the Osumi, Tokara, Amami, and Okinawa Groups of the Ryukyu Archipelago, southern Japan. However, a recent molecular phylogenetic study suggested that this skink should be divided into two species: one distributed in the Osumi to Amami Groups, and another distributed in the Okinawa Group. For A. pellopleurus, two extant syntypes collected from an island of the Amami Group were confirmed. Therefore, we identified the species in the Osumi to Amami Groups as A. pellopleurus sensu stricto by designating one of the syntypes as the lectotype for this species. For the species in the Okinawa Group, we resurrected A. okinavensis (Thompson, 1912), of which the type locality is on Okinawajima Island in the Okinawa Group. Ateuchosaurus pellopleurus and A. okinavensis can be differentiated by the following characteristics: usually separated frontonasal and frontal, 8–14 subdigital scales on the fourth toe (mode = 11), and usually two or three pairs of dorsal median scale rows with black stripes in A. pellopleurus; usually fused frontonasal and frontal, 10–16 subdigital scales on the fourth toe (mode = 13), and usually no stripe on the dorsal scales or a pair of dorsal median scale rows with black stripes in A. okinavensis.

Two new species of the snake eel genus Bascanichthys (Anguilliformes: Ophichthidae) from the northwestern Pacific.

Two new species of the elongate snake eel genus Bascanichthys are described from the northwestern Pacific. Bascanichthys kabeyawan sp. nov. is described based on a single specimen collected from estuary of southern Taiwan. It is characterized by having head 4.6% TL; tail 52.3% TL; body depth at gill opening 1.1% TL; predorsal-fin length 58.4% HL; snout length 10.9% HL; body bicolored, head without bands; lateral-line pores anterior to anus 104; vertebral formula 4-103-224. Bascanichthys ryukyuensis sp. nov. is described based on two specimens collected from the shallow water of Okinawa-jima Island, Ryukyu Islands of southern Japan. It is characterized by having head 3.7-4.3% TL; tail 43.3-44.2% TL; predorsal-fin length 40.7-45.4% HL; snout length 11.3-13.1% HL; body pale brown, head without distinct dark bands after preservation; lateral-line pores anterior to anus 114-118; total vertebrae 207-216, mean vertebral formula 2-116-212; and dorsal-fin origin before middle of head.

Food Habits of the Taiwan Beauty Snake, Elaphe taeniura friesi, as an Introduced Species on Okinawajima Island

The Taiwan beauty snake, Elaphe taeniura friesi, has established a stable population in the central part of Okinawajima Island, and there are concerns about the negative effects of the snakes' predation on the native fauna. Thus, we examined the stomachs of 239 E. t. friesi specimens collected on Okinawajima Island from July 2018 to November 2019. Stomach contents were identified to the species level whenever possible based on morphological observations and/or DNA analyses. Of the 239 snake specimens, 39 (12 males, 16 females, and 11 juveniles) had contents in their stomach, including 67 prey items, 75% of which were mammals (Muridae and Soricidae) and the rest of which were birds (Pycnonotidae, Cisticolidae, and Columbidae). Rattus rattus occurred most frequently; 25 of the 39 snakes examined had this species in their stomachs. All avian prey items detected were nestlings and eggs. Twelve snakes had multiple prey items in their stomach, including in most cases either nestlings of passerine birds or infants or subadults of R. rattus. Therefore, E. t. friesi is an endotherm consumer that occasionally preys on nestlings and infant rats. These food habits suggested that E. t. friesi uses various habitats, from the humus layer on the ground to the branches of trees, for foraging. Several endangered endemic rodent and bird species exist in the northern area of Okinawajima Island; thus, our results provide a warning about potential negative impact on such animals when E. t. friesi expands its range to the northern part of the island.

Diversity and distribution of air-breathing sea slug genus Peronia Fleming, 1822 (Gastropoda: Onchidiidae) in southern Japanese waters.

Species of the genus Peronia Fleming, 1822, are air-breathing onchidiid sea slugs that inhabit intertidal reef flats of temperate to tropical zones. In the Ryukyu Islands of southern subtropical Japan, Peronia species are a traditional food source for local people. To date, there have been three species recorded around Okinawajima Island; P. verruculata and P. peronii, along with recently described P. okinawensis, which was described as possibly endemic to Okinawajima Island. This study aimed to map the distribution ranges of these three Peronia species within the Ryukyu Islands using molecular analyses in order to understand the specific distribution of each species. Since Peronia species are generally indistinguishable by gross external morphology, a DNA barcoding approach was employed to identify specimens. The molecular data showed that there are four species present in the Ryukyu Islands. P. verruculata (unit #1 sensu Dayrat et al., 2020) was dominant at almost all locations, while P. peronii was present in much lower numbers than P. verruculata, but found across a relatively wide range in the Ryukyu Islands. We newly record P. okinawensis and P. setoensis from Amami Oshima Island and from several places around Okinawajima Island, and also identified high levels of genetic variation within P. setoensis. Peronia okinawensis and P. setoensis have been thought to be endemic to Okinawajima Island and to Honshu, mainland Japan, respectively. However, as both species were observed around Okinawajima and Amami Oshima islands, other islands of the Ryukyus are also likely to harbor these species, and their distribution ranges are wider than previously thought. Based on the results from molecular analyses, we provide general descriptions of each species. Sizes of specimens were consistently smaller for P. setoensis and relatively larger for P. peronii specimens. On the other hand, P. verruculata and P. okinawensis had similar size ranges, but P. okinawensis had comparatively much more distinct papillae. This study revealed that the Ryukyu Islands are the only region currently known with four sympatric Peronia species, and this work provides a basis for future research on these Peronia species throughout the northwest Pacific Ocean, representing the first step in more effective management of the local Peronia fisheries in the Ryukyu Islands.

First Record of the Black-Bearded Tomb Bat Taphozous melanopogon Temminck, 1841 (Chiroptera: Emballonuridae) from Japan

A bat was rescued from Okinawajima Island, Ryukyu Archipelago, Japan in November 2021. Observing the external characteristics, we identified it as the black-bearded tomb bat, Taphozous melanopogon Temminck, 1841, which is mainly distributed in tropical Asia. To our knowledge, this is the first record of this species in Japan. However, we infer that it was accidentally only visiting and not established on Okinawajima Island.

Ixodid ticks recovered from various animals on Okinawajima Island, Japan, in the period 2016–2021

Ixodid ticks recovered from various animals on Okinawajima Island, Japan, in the period 2016–2021

The first record of Anatrachyntis lunulifera ( ) (Lepidoptera: Cosmopterigidae) in the Ryukyus, Japan

Anatrachyntis lunulifera (Meyrick, 1935) (Lepidoptera: Cosmopterigidae) is distributed in the Pacific region, for example, in Fiji and the Marquesas Islands, and larvae of this species feed on the male inflorescence of Pandanus species. In our study, A. lunulifera was collected from Pandanus odorifer (Forssk.) Kuntze in Amami oshima Island, Okinawa-jima Island, and Miyako-jima Island, the Ryukyus, Japan. This article is the first report of A. lunulifera from Japan, North Pacific. In this study, we have redescribed and illustrated the adult, male and female genitalia of A. lunulifera, and illustrated those of A. incertulella (Walker, 1864), another Pandanus feeder occurring together with A. lunulifera in the Ryukyus, for comparison.

Did food resource shortage cause Ryukyu-ayu extinction on Okinawa-jima Island? A clue based on morphological approach

Did food resource shortage cause Ryukyu-ayu extinction on Okinawa-jima Island? A clue based on morphological approach

Mammal and bird species using cavities among forests of different ages on Okinawajima Island in the Ryukyu Archipelago, Japan

ABSTRACT Various animals use tree cavities in the northern forest of Okinawajima Island in the Ryukyu Archipelago. However, the cavity characteristics and forest types used by cavity users are not well known. The aim of this study was to reveal the cavity users in natural forests of different ages in northern Okinawajima Island. Camera trap surveys were conducted to identify the utilization of cavities in four Castanopsis sieboldii dominated forests; one 40-year-old, one 70-year-old, and two mature forests. Only a few cavities were recorded in the 40-year-old forest and these locations were limited to the lower part of the trees. Consequently, cavity users were limited to two ground-foraging bird species. In contrast, cavities of various sizes were located at various heights above the ground in the other three types of forests, although endangered mammals such as Ryukyu long-furred rat (Diplothrix legata) and Ryukyu tube-nosed bat (Murina ryukyuana) only used cavities in mature forests. The greatest number of cavity-using bird species were recorded in the 70-year-old forest, and a Ryukyu robin (Larvivora komadori) built a nest in a cavity. These results show that mature forests provide various types of cavities with various functions which are important for diverse animal taxa, and that cavity users differ among forests of different ages. Furthermore, it was observed that cavity availability and use does not recover in 70 years. Cavity users should be considered in forest management not only in the core area, but also in the buffer zone of the protected areas in the future.

Four-Year Field Survey of Black Band Disease and Skeletal Growth Anomalies in Encrusting Montipora spp. Corals around Sesoko Island, Okinawa

The Indo-Pacific zooxanthellate scleractinian coral genus Montipora is the host of many coral diseases. Among these are cyanobacterial Black Band Disease (BBD) and Skeletal Growth Anomalies (GAs), but in general data on both diseases are lacking from many regions of the Indo-Pacific, including from Okinawa, southern Japan. In this study, we collected annual prevalence data of Black Band Disease (BBD) and Skeletal Growth Anomalies (GAs) affecting the encrusting form of genus Montipora within the shallow reefs of the subtropical Sesoko Island (off the central west coast of Okinawajima Island) from summer to autumn for four years (2017 to 2020). In 2020 Montipora percent coverage and colony count were also assessed. Generalized Linear Models (GLM) were used to understand the spatial and temporal variation of both BBD and GAs in the nearshore (NE) and reef edge (RE) sites, which revealed higher probability of BBD occurrence in RE sites. BBD prevalence was significantly higher in 2017 in some sites than all other years with site S12 having significant higher probability during all four surveyed years. In terms of GAs, certain sites in 2020 had higher probability of occurrence than during the other years. While the general trend of GAs increased from 2017 to 2020, it was observed to be non-fatal to colonies. In both diseases, the interaction between sites and years was significant. We also observed certain BBD-infected colonies escaping complete mortality. BBD progression rates were monitored in 2020 at site S4, and progression was related to seawater temperatures and was suppressed during periods of heavy rain and large strong typhoons. Our results suggest that higher BBD progression rates are linked with high sea water temperatures (SST > bleaching threshold SST) and higher light levels (>1400 µmol m−2 s−1), indicating the need for further controlled laboratory experiments. The current research will help form the basis for continued future research into these diseases and their causes in Okinawa and the Indo-Pacific Ocean.

Taxonomy and phylogeny of the genus Melita (Crustacea: Amphipoda: Melitidae) from the West Pacific Islands, with descriptions of four new species

The amphipod genus MelitaLeach, 1814 (Amphipoda: Melitidae) is a predominantly marine group with a cosmopolitan distribution in both circumtropical and temperate waters. However, records of Melita from inland waters such as fresh and brackish waters are limited. In this study, four new species of Melita are described from inland waters in the Ogasawara and Ryukyu Islands, West Pacific: M. nunomurai sp. nov. from Hahajima Island, Ogasawara Islands; M. ogasawaraensis sp. nov. from Anijima, Chichijima, and Hahajima Islands, Ogasawara Islands; M. miyakoensis sp. nov. from Miyakojima Island, Ryukyu Islands; and M. okinawaensis sp. nov. from Okinawajima Island, Ryukyu Islands. Molecular phylogenetic analyses based on nuclear and mitochondrial DNA sequences reveal that M. ogasawaraensis sp. nov. and M. nunomurai sp. nov. are recovered as the sister taxon of M. miyakoensis sp. nov. and M. choshigawaensis, respectively. These results suggest multiple colonisations of the Ogasawara Islands by Melita species. The present study revealed a high species diversity of Melita in the inland waters of the islands of West Pacific. We further discuss the phylogeny among genera of Melitidae.

Capsalids (Platyhelminthes: Monogenea) from marine fishes off Okinawa in Japan with the proposal of two new genera.

Molecular studies of the Capsalidae suggested that the genus Benedenia is polyphyletic, but a taxonomic organization of the genus that reflects molecular data has not yet been proposed. As a result of molecular analysis (28S rDNA, ITS1-5.8S-ITS2, and cox1 data) including specimens of Benedeniinae newly obtained from Okinawa-jima Island in Japan, two new genera and the revival of Tareenia independent to the genus Benedenia are proposed. Gracilobenedenia n. gen. is distinguished from the other genera of Benedeniinae based on morphological characteristics. This new genus comprises 6 species: G. lutjani n. comb. (type species), G. anticavaginata n. comb., G. rohdei n. comb., G. beverleyburtonae n. comb., G. kuremibai n. gen., n. sp., and G. hichi n. gen., n. sp. Armatobenedenia n. gen. is a monotypic genus for A. armata n. comb. The present molecular phylogenetic analysis showed the independence of Tareenia, and it can be morphologically separated from the other benedeniines. Four species including two new species obtained from Okinawa-jima Island are reported: G. kuremibai n. sp., G. hichi n. sp., G. lutjani n. comb., and Metabenedeniella parva. Furthermore, in the species identification and phylogenetic analysis of capsalids, the usefulness of not only the 28S rDNA but also ITS and the cox1 regions was suggested. These genes were evaluated the efficacy of those regions in DNA barcoding, and the ITS and cox1 regions shown to be useful for DNA barcoding in capsalids compared to the 28S rDNA sequence.