Amami-Oshima Island Research Articles

A case study of feral cat predation on a weaning juvenile of the Amami rabbit as revealed by a camera trap survey in Amami-Oshima Island in Japan

A case study of feral cat predation on a weaning juvenile of the Amami rabbit as revealed by a camera trap survey in Amami-Oshima Island in Japan

付加体中の現地性緑色岩（奄美大島の名瀬層） —泥質岩の化学組成—

付加体中の現地性緑色岩（奄美大島の名瀬層） —泥質岩の化学組成—

A Record of Fairy Pitta <i>Pitta nympha</i> on Amami-Oshima Island, Kagoshima, Southwestern Japan

A Record of Fairy Pitta <i>Pitta nympha</i> on Amami-Oshima Island, Kagoshima, Southwestern Japan

Monthly occurrence and feeding habits of larval and juvenile Ryukyu-ayu Plecoglossus altivelis ryukyuensis in an estuarine lake and coastal area of the Kawauchi River, Amami-oshima Island, southern Japan

We examined monthly occurrence patterns and feeding habits of larvae and juveniles of the critically endangered Ryukyu-ayu Plecoglossus altivelis ryukyuensis in the lower reach of the Kawauchi River, Amami-oshima Island, southern Japan, for two successive years. The study area was classified into a brackish lake (Lake Uchiumi) and a coastal zone (Sumiyo Bay) based on monthly variations in water temperature and salinity. Larvae and juveniles occurred from December to April in the first year and from January to February in the second year, respectively. Smaller-sized and earlier developmental-staged P. altivelis ryukyuensis individuals tended to emerge in larger numbers in Lake Uchiumi than in Sumiyo Bay. The present data suggest that Lake Uchiumi, where the physical environment is characterized by lower temperature and salinity than in Sumiyo Bay, would be suitable as a nursery ground for this fish, especially for earlier developmental-staged larvae. No individuals ≥25.0 mm body length, which is the size at which they begin their upstream migration, occurred in Lake Uchiumi or Sumiyo Bay in April or May, when upstream migration is assumed to reach a peak based on previous studies, in either year. The peak of upstream migration, therefore, may have occurred several months earlier in the years covered in this study due to higher water temperature than in typical years. To assess the feeding habits of this fish, the gut contents were observed. In both areas, copepods were abundant in P. altivelis ryukyuensis diet with calanoids and Oithona spp. being the most abundant. The diet composition differed between Lake Uchiumi and Sumiyo Bay and clearer ontogenetic variation in the composition of the diet was observed in Lake Uchiumi. Small individuals fed on tintinnid ciliates, but the proportion of these organisms in the diet gradually decreased with growth. Large individuals fed exclusively on harpacticoid copepods and insects including demersal species. Overall, larval and juvenile P. altivelis ryukyuensis exhibited a generalist feeding habit that tended to increase with growth. It is indispensable to adequately manage the environmental conditions in the lower reach of the Kawauchi River, especially Lake Uchiumi, to conserve P. altivelis ryukyuensis population.

The Occurrence and Individual Identification Study of Indo-Pacific Bottlenose DolphinsTursiops aduncusin the Waters Around Amami Oshima Island, Southern Japan: A preliminary Report

Abstract. Surveys for the occurrence, distribution, and individual identification of Indo-Pacific bottlenose dolphins Tursiops aduncus were conducted around Amami Oshima Island, Kagoshima Prefecture, Japan from 2007 to 2013. The dolphins were primarily distributed in the areas where the survey effort was concentrated, particularly in Oshima Strait and on the western coast of the Island. In total, 33 groups of dolphins were encountered with a median group size of 8 (range: 1–50 individuals). The group size in Oshima Strait was significantly smaller than that recorded off the western coast. A total of 100 individuals were identified from photographs taken by the survey cruise and local residents with the cumulative number of identified individuals increasing over time and with no indication of saturation being reached. Thus, the population size of Indo-Pacific bottlenose dolphins in the waters around Amami Oshima Island was probably larger than that indicated by the present study; hence, photo-identificatio...

Song-count surveys and population estimates reveal the recovery of the endangered Amami Thrush Zoothera dauma major, which is endemic to Amami-Oshima Island in south-western Japan

SummaryThe Amami Thrush, Zoothera dauma major, is an endemic subspecies of the Eurasian Scaly Thrush that is distributed only on Amami-Oshima Island in south-western Japan. This bird was formerly considered to be a distinct species (Z. major) and was listed on the IUCN Red List as ‘Critically Endangered’ based on the small population size estimated in the early 2000s. To re-evaluate the conservation status of this bird, we estimated the number of singing males from song-count surveys conducted by an NPO with public participation from 2007 to 2013. An estimation that applied a distance sampling method revealed the number of singing males to be 945–1,858 up to 2012. A sudden increase in song counts was recorded in 2013, and the estimate increased to 2,512 in 2013. Based on the assumption that the sex ratio does not deviate from 1:1, simply doubling the number was considered to produce the estimated population size (number of males and females that are capable of breeding). The present study also confirmed that the Amami Thrush was more abundant in older forest with less open habitat, suggesting that forest maturity is an important factor for thrush abundance. The relative density of the invasive small Indian mongoose Herpestes auropunctatus probably affected thrush abundance before the early 2010s prior to mongoose eradication efforts. Our results suggest that thrush recovery was likely associated with forest regeneration and mongoose eradication. However, it is important to continue population monitoring approaches including public participation to promote further conservation of the Amami Thrush.

A new <I>Chinattus</I> species (Araneae: Salticidae) from Amami-Oshima Island, Japan

A new salticid species of the genus Chinattus is described as Chinattus falco sp. nov. For the present, this species is known from only Amami-Oshima Island, Japan. The new species can be distinguished from other congeners by the male palp with not-hooked retrolateral tibial apophysis and epigyne with slender scape.

First Record of <i>Mimobdella japonica</i> (Hirudinida: Arhynchobdellida: Salifidae) from Hachijojima Island, Izu Islands, Japan, with a Comment on the Genetic Diversity of the Species

Three specimens of the predatory salifid leech Mimobdella japonica Blanchard, 1897 were collected from Hachijojima island, Izu Islands, Japan. This species was previously known only from Okinawajima and Amamioshima islands in the Ryukyu Islands, Japan; this is the first record of this species from the Izu Islands. A morphological description based on these specimens is presented here. In addition, we evaluated the genetic diversity of this species based on sequences of cytochrome c oxidase subunit I, tRNACys, tRNAMet, 12S rRNA, tRNAVal, 16S rRNA, tRNALeu, and NADH dehydrogenase subunit 1 obtained from specimens of M. japonica collected recently from all three islands. The only difference noted among them was a unique ND1 sequence detected from two specimens collected on Okinawajima. The possibility of human-mediated introduction of M. japonica to one or more of these islands is discussed.

Relationships between capture-site characteristics and capture levels of the invasive mongoose on Amami-Oshima Island, Japan

We used a generalized linear model (GLM) to investigate environmental characteristics of capture sites of the invasive small Indian mongoose (Herpestes auropunctatus) on Amami Island, Japan. Data were collected from 2002 to 2011, from an area with the lowest mongoose density. Data on capture levels and environmental factors were obtained within 1 × 1 km grid cells. In addition, we developed an evaluation map that predicts the occurrence of mongooses throughout the island by extrapolating the 2011 results, in which the last mongoose appearance was confirmed. We found that environmental characteristics of capture sites drastically changed during the final stage of the eradication project. From 2002 to 2010, mongooses were captured in grid cells with many gentle ridges. In 2011, when mongoose density became exceedingly low, mongooses seem to have survived in the grid cells with abundant steep ridges, where it was difficult to establish traps. Therefore, environmental factors affected capture levels and the density of the mongoose population. The evaluation map predicts that mongooses could survive on the southwest and southeast island peninsulas. This evaluation map will be helpful in allocating limited labor and financial resources toward the most effective capture strategies. This study suggests that an analysis of pest management data is an important step in the eradication of mongooses. Our results can contribute to long-term projects in invasive pest management not only for the mongoose population on Amami Island, but also for other invasive species globally.

Population genetics analysis of East Asian Passiflora virus on Amami Oshima Island

East Asian Passiflora virus (EAPV) is a member of the genus Potyvirus in the family Potyviridae. In this study, we collected 15 isolates of EAPV from two different areas (the Yuwan area of Uken village and the Sumiyo town of Amami city) on Amami Oshima Island, Japan. The sequences of polyproteins from 10 isolates and the NIb and CP regions of five isolates were determined. The nucleotide and amino acid sequence identities of polyproteins within each population were very high, and those between isolates from both areas were also high. However, five characteristic nonsynonymous substitutions were uniformly observed in the P3 and CP regions of Sumiyo isolates. Recombination analysis revealed that there was no evidence of recombination in any of the isolates from Amami Oshima Island. The selection pressure analysis showed that as a whole, the EAPVs of both populations underwent negative selection but the extent of the negative selection varied. These results were supported by a neutrality test. The gene differentiation and gene flow analysis suggested that the Sumiyo and Yuwan populations were differentiated clearly and gene flow occurred only infrequently. These results were supported by phylogenetic analysis. It was concluded that the two populations evolved independently in each respective area.

Morphological Variation in the Sperm Head of Ryukyu Long-Furred Rat,Diplothrix legata

Ryukyu long-furred rats (Diplothrix legata) are large rodents distributed only on three small islands in Japan: Amami-Oshima Island, Tokuno-shima Island, and Okinawa-jima Island (Iwasa 2009). These rats are an endangered species (Ministry of Environment, Japan 2012; IUCN 2014), and little is known about their ecological and physiological characteristics (Iwasa 2009). For the management or conservation of the Ryukyu longfurred rats, it is important to know such information. Reproductive traits are important features to consider the maintenance of populations of an endangered species from standpoint of conservation biology. The relationships between sperm morphology and inbreeding have been reported for endangered mammals (O’Brien et al. 1987; Gomendio et al. 2000; Gage et al. 2006). The ­individual­coefficient­of­inbreeding­is­inversely­related­ to morphologically normal spermatozoa frequency in the endangered gazelles (Gazella cuvieri); this species has a­ high­ inbreeding­ level,­with­ inbreeding­ coefficients­ of­ approximately 0.15 (Gomendio et al. 2000). Males with few normal form spermatozoa are known to have low fertility (Kruger et al. 1988; Guzick et al. 2001). Mammalian­ spermatozoa­ have­ species-specific­ morphology.­ The sperm head of domestic mammals, including bull, stallion,­ pig,­ and­ dog,­ is­ generally­ flattened­ and­ ovalshaped (Masuda 1995). In contrast, most rodents have falciform sperm head with an apical hook, and many morphological sperm variations among species have been reported (Breed and Yong 1986; Breed 2004). For example, the laboratory mouse (Mus musculus) and the striped field­mouse­(Apodemus agrarius) have two ventral processes in the sperm head, which are absent in the laboratory rat (Rattus norvegicus; Lee and Mori 2006). Furthermore, the desert mouse (Pseudomys desertor) has three apical hooks in the sperm head, whereas only one hook is present in most other species (Breed 1983). However, the sperm morphology of Ryukyu long-furred rats has not yet been reported. Therefore, this study aimed to investigate the morphology of spermatozoa in Ryukyu long-furred rats by using phase-contrast and scanning electron microscopy.

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.

Discovery of the genus Leptophion Cameron, 1901, from Japan and the Palaearctic region, with description of two new species (Hymenoptera: Ichneumonidae: Ophioninae)

The genus Leptophion Cameron, 1901, which belongs to the subfamily Ophioninae Shuckard, 1840, is recorded from Japan and the Palaearctic region for the first time based on two new species, L. parvus sp. nov. from Amamioshima Island and L. septentrionis sp. nov. from Yakushima and Amamioshima Island. A key to the Japanese and Taiwanese species is also provided.

Clarification and Application of Inundation Processes in Basins with Insufficient Observation Devices Installed

Torrential rain possibly due to climate change has begun causing disasters annually, with water and sediment resulting from heavy rainfall in relatively narrow upper basins often arising in short periods. Because most of these basins are traversed by class B rivers administered by local governments, data on disasters are not accumulated comprehensively. Targeting the Sumiyo River basin on Amami Oshima Island, this study involved field surveys and numerical simulations to clarify inundation features in areas short on data based on hearings from investigation results. Calculation results have reproduced water levels, together with hearing results, including the initial inundation process in which rain water flowed directly from mountain slopes and later inundation processes mainly caused by overtopping and dike breach on the Sumiyo River. (Note that river bed fluctuations and dike breach progress are to be addressed in the future.)

Growth of Mangrove Forests and the Influence on Flood Disaster at Amami Oshima Island, Japan

“Mangrove” is the generic name for plants growing on tropical and subtropical tidal flats. The mangrove is used for many things, including disaster protecting land from high waves and tides and tsunamis, cleaning rivers and drainage containing soil and sand, and providing a variety of organisms with living space. Climate change and rising sea levels are threatening the future of the mangrove. Developing effective ways to conserve mangroves is thus needed, but more must be known about how the mangrove’s ecology and how it develops. It has been pointed out, for example, that mangroves increased flooding by the Sumiyo River in Amami Oshima. We studied ways to develop the mangrove at the Sumiyo River mouth in Amami Oshima and its influence in local flooding, finding that the current mangrove forest had little influence on flooding and that sediment deposition accelerating in Sumiyo Bay due to a sea dike could enlarge the mangrove forest in future.

Book Review Satoshi SUYAMA (2014): Regional characteristics of Amami Oshima island: from various viewpoints of undergraduate students

Book Review Satoshi SUYAMA (2014): Regional characteristics of Amami Oshima island: from various viewpoints of undergraduate students

Food Availability for Larvae of Plecoglossus altivelis ryukyuensis in the Yakugachi River of Amami-oshima Island, Japan

Food Availability for Larvae of Plecoglossus altivelis ryukyuensis in the Yakugachi River of Amami-oshima Island, Japan

Large-diameter trees as a potential indicator of a subtropical evergreen broadleaf forest of high conservation value on Amami Oshima Island

Large-diameter trees as a potential indicator of a subtropical evergreen broadleaf forest of high conservation value on Amami Oshima Island

Stranding record of two species of Epitoniidae in Amami-Oshima Island

Stranding record of two species of Epitoniidae in Amami-Oshima Island

Distribution of Parasitic Nematodes in Japan with Host–Parasite Relationship of Lizards ofPlestiodon(Reptilia: Squamata: Scincidae)

ABSTRACT: Four Japanese species of Plestiodon (Reptilia: Scincidae, formerly Eumeces): Plestiodon japonicus, Plestiodon finitimus, Plestiodon latiscutatus, and Plestiodon oshimensis oshimensis collected from Honshu, Shikoku, and Kyushu of the Japanese main islands and Amamioshima Island of the Ryukyus, Japan, were examined to make a more exact list of the parasitic nematodes and to reveal their distribution patterns. Six nematode species were found, including 2 species of Heterakidae (Meteterakis japonica and Meteterakis amamiensis), 1 species of Rhabdiasidae (Kurilonema markovi), 1 species of Trichostrongylidae (Oswaldocruzia socialis), 1 species of Cosmocercidae (Cosmocercidae gen. sp.), and 1 species of Pharyngodonidae (Pharyngodonidae gen. sp.). Six new hosts were recorded and 19 new localities were reported. Meteterakis amamiensis and K. markovi were distributed on both sides of Watase's line, which is known as a geographical distribution boundary between the Oriental and Palaearctic regions in Japan...