Ishigaki-jima Island Research Articles

Molecular Phylogenetic Analysis of Caridina weberi Species Group around Japan, with the First Record of Caridina tupaia de Mazancourt, Marquet & Keith, 2019 (Crustacea: Decapoda: Atyidae) from Japan

Recently, numerous new species of Caridina weberi species group were described from around Polynesia. This study reports the molecular phylogenetic data of the Japanese specimens belonging to C. weberi species group based on the mitochondrial 16S rRNA and cytochrome c oxidase subunit I gene. The results suggested that C. laoagensis Blanco, 1939, C. macrodentata Cai & Shokita, 2006, C. multidentata Stimpson, 1860, C. prashadi Tiwari & Pillai, 1971 and C. tupaia de Mazancourt, Marquet & Keith, 2019 are distributed in Japan. This is the first record of C. tupaia on Ishigaki-jima Island, Ryukyu Archipelago, southern Japan and the northernmost record of this shrimp. Attempted to find C. okinawa, belonging to C. weberi species group, for the first time in about 50 years, but there were no Atyid shrimps in its type locality. Based on the data of mitochondrial DNA fragments, we suggest that if the divergence estimate in C. weberi species group exceed 3% for 16S rRNA, it may be an interspecific variation. We also reveal the existence of two unnamed species which had been identified as C. macrodentata and C. multidentata. Caridina multidentata is known to be distributed in Japan (type locality), Taiwan, Fiji and Madagascar, however East Asian and Malagasy samples were shown to be distinct species, their divergence estimates were more than 10% for 16S rRNA. We also provide the key to the Japanese species of C. weberi species group.

A new shrimp of the genus Odontozona Holthuis, 1946 (Decapoda: Stenopodidea: Stenopodidae) from a submarine cave of the Ryukyu Islands, Indo-West Pacific.

A new species of the stenopodid shrimp genus Odontozona Holthuis, 1946 is described and illustrated on the basis of single specimen recently collected from a submarine cave at Shimoji-jima Island, Miyako Island Group, Ryukyu Islands, southwestern Japan. Odontozona ganzu sp. nov. appears to be unique within the genus Odontozona by lacking transverse row of posterior small spines on sixth pleuron. General morphology of the new species is also similar to O. stigmatica Saito, Okuno Anker, 2017 described from Ishigaki-jima Island, Ryukyu Islands, West Pacific, but differs from it by a combination of morphological characters, viz., lacking the cincture of small spines on the posterior margin of the carapace, the distinct transverse carina on the third pleuron, as well as the lateral teeth of the uropodal endopod. This study increases the total number of the described species in the genus Odontozona to 23, 11 of which occur the Indo-West Pacific.

First report of the genus Thirumalaia Zettel amp; Laciny, 2021 (Hemiptera: Veliidae) in the Ryukyu Islands, Japan, with the description of a new species.

The genus Thirumalaia Zettel Laciny, 2021 (Veliidae: Microveliinae) was recently established with one Indian species. Here, a new species, T. kaara sp. nov., from Ishigaki-jima Island and Iriomote-jima Island, Ryukyu, Japan is described. Additionally, the distribution of the genus is updated and laboratory rearing information of the immature stages of T. kaara sp. nov. are provided.

Quarter-Century (1993–2018) Nesting Trends in the Peripheral Populations of Three Sea Turtle Species at Ishigakijima Island, Japan

Three sea turtle species (loggerhead [Caretta caretta], green [Chelonia mydas], and hawksbill [Eretmochelys imbricata] turtles) have nesting sites at Ishigakijima Island, which is located in the southwestern part of Japan. This island is known as the geographic southern (low-latitude) limit of north Pacific loggerhead turtles' nesting sites and close to the northern (high-latitude) limit of northwest Pacific green and hawksbill turtles' nesting sites. Our 26-yr nesting survey (1993–2018) revealed that the number of nesting events of loggerhead turtles decreased (with a temporal increment between 2006 and 2008), while the other study reported that the entire Japanese loggerhead nesting population continued to increase substantially from 2006 to, at least, 2012. In contrast, the green turtle population increased gradually, with fluctuations. Hawksbill turtles had several nests annually. The sea surface temperature during the nesting season was significantly related to the annual number of nesting events in loggerhead turtles but not in green and hawksbill turtles. Thus, warming temperature may have caused a reduction in the nesting population of loggerhead turtles at Ishigakijima Island, which is the southern limit of their nesting distribution.

Gravity Measurement of Nagura River Basin, in the Western part of Ishigakijima Island, Japan

Gravity Measurement of Nagura River Basin, in the Western part of Ishigakijima Island, Japan

Discovery of the Masson Pine Moth, <i>Dendrolimus punctatus</i>, from Japan with Taxonomic Notes on <i>D. superans,</i> <i>D. spectabilis</i>, and <i>D. okinawanus</i>（Lepidoptera: Lasiocampidae）

The masson pine moth, Dendrolimus punctatus（Walker）（Lepidoptera: Lasiocampidae）, is a notorious pest of pine trees in Asian countries and was recorded in Japan for the first time from Ishigakijima Island and Iriomotejima Island. We performed taxonomic studies involving the male and female genitalia and clarified the distinguishable features among the following four Japanese species of the genus Dendrolimus: D. superans（Butler）, D. spectabilis（Butler）, D. okinawanus Sonan, and D. punctatus based on many specimens including the lectotype of D. punctatus. As for DNA barcoding, five of the analyzed Japanese haplotypes from Ishigakijima Island and Iriomotejima Island and three of the Chinese haplotypes registered in GenBank as D. punctatus belonged to the same clade in the NJ tree. The intraspecific divergence value within D. punctatus was higher than the interspecific divergence value between D. okinawanus and D. spectabilis. In addition, we revealed that D. punctatus induced severe damage in Pinus luchuensis Mayr on Ishigakijima Island in 2016.

Japanese Species of the Genus <i>Lasconotus</i> (Coleoptera: Zopheridae: Colydiinae), with Description of a New Species from Ishigaki-jima Island, the Ryukyu Islands

A new species of the genus Lasconotus Erichson, 1845 from Ishigaki-jima Island, Southwest Japan, is described. Lasconotus akitai sp. nov. is compared with the three previously known species of Lasconotus in Japan: L. niponius (Lewis, 1879), L. okadai Aoki, 2011, and L. sculpturatus (Sharp, 1885). The new species is characterized by small body size, large eyes, antennal segments III and IV same in size, four sharp ridges on pronotum, and bubble-shaped sculpture on ventral side of body. A key to the four Japanese Lasconotus-species is also given.

Recruitment to adult habitats in terrestrial hermit crabs on the coast of Ishigakijima Island, Ryukyu Archipelago, Japan

AbstractTerrestrial hermit crabs in the family Coenobitidae (genera Coenobita and Birgus) are distributed in tropical and subtropical regions. They occupy various habitats ranging from shore to inland forests, and the two shore‐dwelling species, Coenobita rugosus and C. violascens, possess different distributional characteristics on Ishigakijima Island, Ryukyu Archipelago, Japan. Coenobita rugosus is distributed throughout the coast of the island and is abundant in beach areas, whereas C. violascens has mainly been found in river mouth areas. However, very little is known about the habitats used by the early life stages of coenobitid crabs because identifying the species of recently landed early juveniles is difficult. We tested whether the species compositions of early juveniles of coenobitids differed between beach and river mouth sites on Ishigakijima Island. We collected and identified the early stage coenobitids using PCR–RFLP techniques. A total of 576 early juveniles of five Coenobita species were collected, of which 0.7% were C. brevimanus, 7.3% were C. cavipes, 0.2% were C. purpureus, 70.1% were C. rugosus, and 21.7% were C. violascens. The early juveniles of Birgus latro were not found. The early juveniles of C. rugosus occurred at both beach and river mouth sites, and they were abundant at beach sites. The early juveniles of C. violascens were only found at river mouth sites. These findings indicate that C. rugosus and C. violascens complete their life cycles on land near the localities where they land. The early juveniles of the inland‐dwelling species, C. cavipes, were also mainly collected from river mouth sites, which suggested that juveniles of C. cavipes selected landing sites near river mouth areas and then migrated into the inland forests, passing through riverside areas. Our results highlighted the importance of river mouth areas for recruitment to adult habitats by some coenobitid species.

First record of the thread-legged assassin bug genus Proguithera from Japan, with description of a new species (Hemiptera: Heteroptera: Reduviidae).

The thread-legged assassin bug genus Proguithera Wygodzinsky, 1966 of the emesine tribe Leistarchini (Hemiptera: Heteroptera: Reduviidae) is recorded from Japan for the first time, and a new species P. kiinugama sp. nov., the third representative of this genus, is described based on specimens from Ishigaki-jima Island in the Ryukyu Islands. This new species can be distinguished from its congeners primarily by the absence of a median longitudinal sulcus on the anterior pronotal lobe, forewing with an incomplete cross vein connecting the M+Cu vein and a submarginal vein basad of the discal cell, and the anteroventral series of the profemur consisting of about 30 spine-like setae.

High levels of genetic diversity and gene flow in the endangered goby Hypseleotris cyprinoides on Okinawajima Island, Ishigakijima Island and Luzon Island

High levels of genetic diversity and gene flow in the endangered goby <i>Hypseleotris cyprinoides</i> on Okinawajima Island, Ishigakijima Island and Luzon Island

Phylogeographic Study of Whip Scorpions (Chelicerata: Arachnida: Thelyphonida) in Japan and Taiwan.

Whip scorpions (Thelyphonida), comprising an order in the class Arachnida, are distributed from tropical to temperate zones. Two species occur exclusively in Japan and Taiwan, but the border of their distributional ranges is ambiguous in the Central Ryukyus (Japan). We collected new specimens from the Central Ryukyus and revealed that the border of distribution of the two species lies between the Central and Southern Ryukyus, i.e., the Kerama Gap. Moreover, the estimated divergence time (15.8 Mya) of the two species, based on the mitochondrial COI gene, was older than the recently estimated time (1.55 Mya) of formation of the Kerama Gap. These results highlight the risks of a priori assumption solely on the basis of geological data for applying it as a calibration point to some terrestrial animals in this region. Typopeltis stimpsonii was genetically divided into four lineages, two of which turned out to be endemic to the Okinawa Islands. All specimens from the main island of Japan and Shikoku were in one lineage, which was also found in the Amami Islands and Hachijojima Island. This suggests that these specimens may have been dispersed by human activity. Typopeltis crucifer included five genetic lineages. Species collected from Ishigakijima and Iriomotejima Islands were genetically diversified not between the borders of these islands but within Ishigakijima Island. This study also suggests that phylogenetic diversity of the species in the Southern Ryukyus have increased through two times of invasions from Taiwan.

Use of the clover Trifolium repens by the pierid butterfly Eurema hecabe from Ishigakijima Island

Use of the clover Trifolium repens by the pierid butterfly Eurema hecabe from Ishigakijima Island

Molecular phylogeographic analysis of East Asian cryptoperlan stoneflies (Insecta: Plecoptera, Peltoperlidae)

Cryptoperlan stoneflies inhabit the headwaters or upper stream areas of rivers. A molecular phylogeographic study of cryptoperlans in the Japanese archipelago and on Taiwan Island has been conducted. Altogether the mtDNA 16S rRNA region of 71 individuals from 61 populations, the mtDNA COI region of 76 individuals from 41 populations, and the nDNA Histone 3 region of 56 individuals from 52 populations were sequenced and analyzed. The respective ML, NJ, MP and Bayesian dendrograms were proposed from the sequencing data for the 16S rRNA region (362-bp), the COI region (540-bp), and the Histone 3 region (322-bp), estimated using Yoraperla uenoi as an outgroup. Based upon those data and the resulting dendrograms, it has become clear that the cryptoperlan stoneflies of the Japanese archipelago and those of Taiwan Island comprise two major clades. The first of these two major clades consists of a number of OTUs [operational taxonomic units: Cryptoperla japonica (Honshu, Shikoku and Kyushu Islands) + C. ishigakiensis (Ishigaki-jima Island) + Cryptoperla spp. (Okinawa-jima and Taiwan Islands)]. The other clade consists of the species Cryptoperla kawasawai inhabiting only Shikoku Island. Of particular note, C. kawasawai was observed to be significantly genetically differentiated from all other cryptoperlans examined. Yet, despite the fact that the specimens of C. japonica were taken from a very broad range of populations, their genetic diversity was relatively low, similar to that of C. kawasawai, which inhabits only a limited region within Shikoku Island. Furthermore, even the species C. kawasawai was revealed to be composed of two significantly genetically differentiated subclades. It is considered that this genetic structure among cryptoperlans largely reflects the geological history from the middle to upper Miocene Epoch (i.e., Tortonian stage) of the Japanese archipelago and Taiwan Island.

南琉球弧・石垣島の弱変成付加複合体（富崎層）における 層序と放散虫年代

南琉球弧・石垣島の弱変成付加複合体（富崎層）における 層序と放散虫年代

Dietary Habits of the Introduced Cane Toad Bufo marinus (Amphibia: Bufonidae) on Ishigakijima, Southern Ryukyus, Japan1

ABSTRACT We examined dietary habits of the introduced cane toad Bufo marinus at three sites representing different types of habitats (pond, forest, and rice paddy) on Ishigakijima Island, southern Ryukyus, Japan. Stomach contents analysis revealed that the toad mostly utilizes terrestrial arthropods, of which hymenopterans (mostly ants), adult coleopterans, hemipterans, and araneans dominated in the frequency of occurrence, hymenopterans in the numerical proportion, and larval lepidopterans, adult coleopterans, and larval dipterans in the volumetric proportion. Comparisons in taxonomic composition of the toad's stomach contents and pitfall and sweeping net samples suggested ignorance or avoidance of Amphipoda by the toad. Our results suggest the possibility of considerable predation pressure of B. marinus upon the native arthropods, and ants in particular, on Ishigakijima Island.

Low Genetic Diversity of Oval Squid, Sepioteuthis cf. lessoniana (Cephalopoda: Loliginidae), in Japanese Waters Inferred from a Mitochondrial DNA Non-coding Region1

Genetic diversity and population structure of Japanese populations of the oval squid, Sepioteuthis cf. lessoniana, were compared with populations from Taiwan and Vietnam using nucleotide sequences of the mitochondrial DNA non-coding region 2. In total, 402 nucleotide sequences representing 242 individuals from Japanese waters (Ishikawa, Japan Sea coast of Honshu; Tokushima, eastern Shikoku; Nagasaki, western Kyushu; and Okinawajima and Ishigakijima Island, in the Ryukyu Archipelago) and the East and South China Seas (Keelung, northern Taiwan; Vietnam, Gulf of Tonkin) were examined. Among the 29 haplotypes recognized, haplotype no. 1 was shared by more than 75% of individuals from Japanese localities, whereas it was found in less than 13% of specimens from the East and South China Seas populations. Conversely, the East and South China Seas populations included more than 30% individuals with haplotype no. 2, whereas less than 10% of haplotype no. 2 individuals were from Japanese localities. The differences of haplotype and nucleotide diversities between pooled Japanese populations (0.2639, 0.23%) and the East and South China Seas populations (0.7900, 1.01%) indicate that S. cf. lessoniana from Japanese waters exhibits lower genetic diversity. An analysis of molecular variance between the Japanese populations and the East and South China Seas populations was highly significant. A minimum spanning tree of 29 haplotypes and an Unweighted Pair Group Method with Arithmetic mean (UPGMA) tree based on pairwise F ST comparisons also supported the separation between Japanese and the East and South China Seas populations. We suggest that the Kuroshio Current physically limits gene flow and has thus caused the differences in genetic diversity among the populations examined.

Morphological and molecular characterization of a new genus and new species of parazoanthid (Anthozoa: Hexacorallia: Zoantharia) associated with Japanese Red Coral

The Order Zoantharia has long been taxonomically neglected primarily due to difficulty in examining the internal morphology of sand-encrusted zoanthids. However, recent work using molecular markers has shown an unexpectedly high diversity of previously “hidden” taxa (families and genera) within Zoantharia (=Zoanthidea, Zoanthiniaria). In this study, unidentified sediment-encrusting zoanthid specimens (n = 8) were collected from living Japanese Red Coral Paracorallium japonicum (Family Coralliidae) during precious coral harvesting by Remotely Operated Vehicle (ROV) and manned submersible (February 2004–January 2006) at depths of 194–250 m at six locations between Ishigaki-jima Island and Kikai-jima Island, southern Japan. DNA sequences (mitochondrial 16S ribosomal DNA [mt 16S rDNA], cytochrome oxidase subunit I [COI], nuclear internal transcribed spacer of ribosomal DNA [ITS-rDNA]) unambiguously place these specimens in a previously undescribed, new monophyletic lineage within the family Parazoanthidae. Corallizoanthus tsukaharai, gen. n. et sp. n. is the first reported zoanthid species associated with the family Coralliidae and unlike other described gorgonian-associated zoanthids (Savalia spp.) does not secrete its own hard axis. Morphologically, C. tsukaharai sp. n. is characterized by generally unitary polyps and bright yellow external coloration.

Description of the male ofUpogebia miyakeifrom Ryukyu Islands, Japan (Decapoda: Thalassinidea: Upogebiidae)

The small upogebiid shrimp,Upogebia miyakei, was originally described from a female collected from Ishigaki-jima Island, Ryukyu Islands, southern Japan. However, no male specimen has been reported since the discovery of the holotype. During surveys at Iriomote-jima Island and its type locality, both females and males ofU. miyakeiwere collected from the intertidal zone. Based on this material a full description of the male is given, and comparison with the female reveals the sexual dimorphic characteristics. The palm of the first pereiopod of male specimens is about 1.5 times wider than that of females. In male specimens, one or two spines are present on the dorsal margin of the palm of the first pereiopod, while three to six sharp spines are found on female specimens. This species is compared here withUpogebia lincolnifrom Java, Indonesia.

Uranium-series dates of fossil hermatypic corals in Ishigaki-jima Island, Okinawa Prefecture, and their significance

This study provides new uranium-series dates of the Ryukyu Group in Ishigaki-jima Island, South Ryukyu Arc (SRA). Two fossil hermatypic coral samples taken from coral limestone in the northern and southern parts of the island were dated as 118.5±2.0 ka and 119.9±2.0 ka, respectively, which correlates to oxygen isotope stage 5.5. This fact suggests that a reef complex was formed during isotope stage 5.5 in Ishigaki-jima Island, just like in Hateruma-jima and Yonaguni-jima Islands, SRA. The dated coral in the northern part was collected at an elevation of 1.3 m. It is, therefore, inferred that the northern part of the island was tectonically stable since isotope stage 5.5. On the other hand, the dated corals in the southern part was collected at an elevation of 15 m, which indicated that the southern part of Ishigaki-jima has been uplifted at rate of about 0.10 m/ky since isotope stage 5.5. Our data clearly show that the western part of SRA has been situated in the tectonic setting of uprift for the last 125 ky.

サンゴ礁海域を対象とした写真測量（測深）法の開発

A nearshore zone characterized by coral reef has so much potential for fish habitat, marine activity and other ecological and recreational functions. However, a subaerial survey with high special resolution is still hard to conduct in the nearshore zone yet especially in depths shallower than several meters. Therefore, an aerial photogrammetry method is applied to a nearshore survey at Yoshiwara beach in Ishigakijima Island, Okinawa. The method uses a digital still camera with nearly 8 mega pixels of resolution and a series of aerial photographs of carbonate beach and coral reef which were taken from a Japan Coast Guard (JCG) helicopter. The original digital photograph is then modified to an orthogonal image by using some new techniques. In addition, a set of nearshore topography data surveyed by an aerial laser system had been applied as a reference data. The resulting map shows a typical character of real coral reef topography although there are some inconsistencies. Thus, in general the current method can be applicable to a nearshore survey with good cost performance.