Weno Island Research Articles

Reproductive condition of the black-lip pearl oyster Pinctada margaritifera during the lunar phase.

This study analyzed the relationship between the lunar phase and the reproductive cycle of Pinctada margaritifera inhabiting Weno Island, Chuuk Lagoon, Micronesia. We measured indicators of maturity (gonadosomatic index [GSI]and sexual maturation-related genes) and investigated changes in the gonadal maturity stages (GMS) of P. margaritifera over lunar cycle. GSI was higher around the full moon. GMS of P. margaritifera were classified as the early gametogenesis stage, ripe and spawning stage, and spent and degenerating stage. A large percentage of oysters was observed in the ripe and spawning stage at the first quarter moon in female and the full moon in male as well as in the spent and degenerating stages at the third quarter moon in both sexes. In addition, the expression of doublesex- and mab-3-related transcription factor 2 (DMRT2) in the male P. margaritifera black-lip pearl oyster was the highest during the full and third quarter moon phases, whereas no difference in expression was observed with the lunar phase in females. In contrast, the expression of vitellogenin (VTG) was the highest in female P. margaritifera during the first and third quarters. No difference in expression was observed according to the lunar phase in males. The results suggest that the lunar phase directly affects the expression of sexually mature gonads in P. margaritifera black-lip pearl oyster.

Estimation of the Benthic Habitat Zonation by Photo-Quadrat Image Analysis along the Fringing Reef of Weno Island, Chuuk, Micronesia

Benthic habitat zonation is described from in situ observations and seabed photographs taken from the coastal area of Weno Island, Chuuk, Micronesia. Habitat groups, types, and boundaries are defined by visible substratum characteristics (i.e., in situ and by digital imaging of photo-quadrats along transect lines), and by cluster and ordination analyses using relative coverage percentage of identified classification categories. The statistical similarity between habitat groups is determined by Analysis of similarity (ANOSIM). Benthic habitat groups with significant influence on the determination of habitat type are isolated by the similarity percentage (SIMPER) test. In addition to the standard practices of using transect lines and collecting data in accordance with the already well-implemented and thoroughly-tested benthic habitat classification scheme for tropical reef monitoring, we applied simple statistics that enable comparative data interpretation. Our simple, repeatable methods provide a framework for benthic habitat-related monitoring research that allows the comparison of results across regions.

The reproductive cycle of the humbug damselfish Dascyllus aruanus according to the changes in lunar phase in Micronesia

The moon is known to be an environmental factor that controls the reproductive cycle of fish, and fish have evolved a variety of reproduction patterns depending on the lunar phase. In this study, we examined the relationship between lunar phases and the reproductive cycle of the humbug damselfish Dascyllus aruanus inhabiting Weno Island, Chuuk Lagoon, Micronesia. We divided the one-month lunar cycle into eight phases, and measured the features of moonlight (peak wavelength and intensity) and indicators of fish maturity [gonadosomatic index (GSI) and sex hormones] in relation to the eight lunar phases. In addition, we investigated the daily rhythms of sex hormones in fish ovaries during the full moon phase. The results showed that the peak wavelength of moonlight was 430 nm (blue wavelength region) regardless of the lunar phase, and that moonlight intensity was highest during a full moon at 02:00. Furthermore, the GSI and sex hormones were both higher around the full moon phase. These findings support the hypothesis that humbug damselfish spawn once a month and that this event occurs at full moon, which is the phase of the moon with the strongest intensity. Based on these findings, we predict that blue wavelength, the dominant wavelength of moonlight, is one of the environmental factors influencing the monthly spawning of D. aruanus.

Mallacoota carinacera sp. nov., a new amphipod species of the family Maeridae (Hadzioidea, Senticaudata) from Micronesia

Mallacootacarinacerasp. nov., a new amphipod species of the family Maeridae, collected from Weno Island, Chuuk, Federated States of Micronesia, is described for the first time, with a detailed description and illustrations, and characteristic features between related species are discussed.

미크로네시아 웨노섬 서식 망그로브 식물의 분류 및 항산화 활성

Mangrove plants serve as a sink of heavy metals and contain phenolic compounds at a high level. Therefore, with mangrove plants, recent studies to develop phytoremediation and natural antioxidants have been conducted in the commercial and academic fields. In the present study, six mangroves in Weno Island of Micronesia were investigated for their phylogenetic relationship and antioxidant activities. First, to determine the phylogenetic relationship among them, rbcL (large subunit of ribulose-bisphosphate carboxylase), one of the chloroplast genes, was used as a molecular marker. According to the data, Xylocarpus, Sonneratia and Rhizophora showed close similarity but not Excoecaria. The levels of phenolic compounds in the bark were abundant in R. apiculata and X. granatum, accounting for 1.10 mM/mg, while R. stylosa and S. alba contained the low amounts, representing 0.73 mM/mg and 0.72 mM/mg, respectively (p<0.05). In addition, bark extracts from R. apiculata, X. granatum, X. moluccensis, and E. agallocha had high antioxidant activities through the DPPH radical scavenging activity and ABTS analysis, whereas S. alba showed the lowest activities. These results suggest that the bark of R. apiculata can be used as a good source for the development of natural antioxidants.

Quantification of eggs and sperm in the Black-lip pearl oyster Pinctada margaritifera using an enzyme-linked immunosorbent assay (ELISA)

We have developed immunological probes to quantify eggs and sperm of the Black-lip pearl (BLP) oyster Pinctada margaritifera. The western blot assay revealed that the polyclonal antibodies developed in this study specifically recognized only egg and sperm proteins. These polyclonal antibodies also showed high sensitivities to the antigens, detecting 0.31–10 μg/ml of the egg or sperm proteins in an indirect enzyme-linked immunosorbent assay (ELISA). Accordingly, we used an indirect ELISA to quantify the eggs and sperm in BLP oysters collected in December 2009 from Weno Island in Micronesia and in May 2010 from Tahiti. The gonad somatic index (GSI), a ratio of gonad weight to somatic tissue weight, of the females collected from Weno Island ranged from 3.6 to 18.4 %, while the GSI of the females collected from Tahiti ranged from 5.6 to 12.6 %. Similarly, the GSI of the male BLP oysters from Weno Island ranged from 0.8 to 8.5 %, while the GSI of the males from Tahiti ranged from 4.8 to 7.5 %. These results lead to the conclusion that the immunological probes developed in this study can be successfully applied to quantify BLP oyster gonadal tissues and that these probes can be used in studies of BLP oyster reproductive ecology based on their sensitivity, rapidity, and affordability.

Bacillus solimangrovi sp. nov., isolated from mangrove soil

Two novel bacterial strains, GH2-4T and GH2-5, were isolated from mangrove soil near the seashore of Weno island in Chuuk state, Micronesia, and were characterized by a polyphasic approach. The two strains were strictly aerobic, Gram-staining-positive, motile, endospore-forming rods that were catalase- and oxidase-positive. Colonies were circular, convex, stringy and transparent yellowish (GH2-4T) or opaque whitish (GH2-5). The 16S rRNA gene sequences of the two isolates were identical. The most closely related strains in terms of 16S rRNA gene sequence similarity were Bacillus kochii WCC 4582T, B. horneckiae DSM 23495T, B. azotoformans LMG 9581T, B. cohnii DSM 6307T and B. halmapalus DSM 8723T (95.6, 95.4, 95.4, 95.2 and 95.2% similarity, respectively). The partial groEL sequence of strain GH2-4T was identical to that of strain GH2-5 and showed <85% similarity to those of the most closely related strains. The isolates grew at pH 5-12 (optimal growth at pH 9), at 10-40 °C (optimum 30-35 °C) and at 0-9% (w/v) NaCl (optimum 1-3% NaCl). The cell-wall peptidoglycan of strains GH2-4T and GH2-5 contained meso-diaminopimelic acid and cell-wall hydrolysates contained ribose as a major sugar. The DNA G+C content was 36 mol%, and DNA-DNA relatedness between the isolates and five related reference strains was 20-24%. Strain GH2-4T exhibited 81% DNA-DNA relatedness with strain GH2-5. The major cellular fatty acids of both strains were iso-C15:0, iso-C16:0, iso-C14:0 and anteiso-C15:0 and the predominant menaquinone was MK-7. On the basis of the evidence from this polyphasic study, strains GH2-4T and GH2-5 (=KCTC 33143=JCM 18995=DSM 27084) represent a novel species of the genus Bacillus, for which the name Bacillus solimangrovi sp. nov. is proposed; the type strain is GH2-4T (=KCTC 33142T=JCM 18994T=DSM 27083T).

Mosquitoes collected on Weno Island, Romanum Island and Piis-Paneu Island, Chuuk State, the Federated States of Micronesia (Diptera: Culicidae)

Mosquito larval surveys were carried out on Weno Island, Romonum Island and Piis Island in August 2011. Larvae were collected from 133 natural and artificial habitats. A total of 1,761 larvae belonging to nine species including one unidentified species were collected. On Weno Island, eight species, Aedes hensilli， Ae. albopictus， Ae. lamelliferus, Aedes sp.， Culex quinquefasciatus， Cx. carolinensis， Cx. annulirostris and Lutzia vorax, were collected. On Romonum Island， four species, Ae. scutoscriptus， Ae. hensilli， Cx. quinquefasciatus and Cx. carolinensis were collected. On Piis Island, six species, Ae. scutoscriptus， Ae. hensilli， Aedes sp.， Cx. quinquefasciatus， Cx. carolinensis and Cx. annilirostris, were collected. Distributions of Ae. hensilli and Ae. albopictus were confirmed in this survey. To prevent the outbreak of dengue fever, environmental management should focus on the destruction, alternation, disposal or recycling of containers that produce the greater number of adult Aedes mosquitoes.

마이크로네시아 웨노섬 연안 서식지 분포의 현장조사와 위성영상 분석법 비교

The aim of this study is to suggest an optimal survey method for coastal habitat monitoring around Weno Island in Chuuk Atoll, Federated States of Micronesia (FSM). This study was carried out to compare and analyze differences between in situ survey (PHOTS) and high spatial satellite imagery (Worldview-2) with regard to the coastal habitat distribution patterns of Weno Island. The in situ field data showed the following coverage of habitat types: sand 42.4%, seagrass 26.1%, algae 14.9%, rubble 8.9%, hard coral 3.5%, soft coral 2.6%, dead coral 1.5%, others 0.1%. The satellite imagery showed the following coverage of habitat types: sand 26.5%, seagrass 23.3%, sand + seagrass 12.3%, coral 18.1%, rubble 19.0%, rock 0.8% (Accuracy 65.2%). According to the visual interpretation of the habitat map by in situ survey, seagrass, sand, coral and rubble distribution were misaligned compared with the satellite imagery. While, the satellite imagery appear to be a plausible results to identify habitat types, it could not classify habitat types under one pixel in images, which in turn overestimated coral and rubble coverage, underestimated algae and sand. The differences appear to arise primarily because of habitat classification scheme, sampling scale and remote sensing reflectance. The implication of these results is that satellite imagery analysis needs to incorporate in situ survey data to accurately identify habitat. We suggest that satellite imagery must correspond with in situ survey in habitat classification and sampling scale. Subsequently habitat sub-segmentation based on the in situ survey data should be applied to satellite imagery.

마이크로네시아 웨노섬의 맹그로브 숲에 서식하는 고둥류 및 집게의 영양원에 대한 이해

Carbon cycling and productivity within Weno Island of Micronesia enclosed by the coral reef may be likely self-maintained and insignificantly affected by the open ocean. Therefore, it is important to understand the role of the mangrove known as providing the organic matter and habitats for many organisms in this enclosed area. In order to trace the nutritional source of fauna (mostly invertebrates) in the mangrove forest of Weno island, we analyzed the fatty acid (FA) and carbon and nitrogen stable isotopes of potential nutritional sources (mangrove leaf & pneumatophore, seagrass leaf & root, surface sediment, and particulate organic matter (POM) in water) and consumers (4 gastropods and anomura). The mangrove and seagrass contained the abundance of 18:2<TEX>${\omega}$</TEX>6, and 18:3<TEX>${\omega}$</TEX>3, whereas FAs associated with phytoplankton and bacteria were accounted for a high proportion in the surface sediment and POM. FA composition of consumers was found to be similar to those of the surface sediment, mangrove, and seagrass. These were also confirmed through the mixing model of stable isotope for contribution of nutritional sources to consumers. Overall results with the feeding types of investigated mangrove fauna indicate that investigated mangrove fauna obtained their nutrition from the various sources, i.e. the mangrove for Littorina cf. scabra, the microalgae for Strombus sp., and omnivorous Pagurus sp. and Terebralia cf. palustris. However, it is obvious that the nutrition of most species living in the mangrove ecosystem is highly dependent on the mangrove, either directly or indirectly. More detail food-web structure and function of the mangrove ecosystem would be established with the analysis of additional fauna and flora.

카드뮴과 구리에 노출된 Rhizophora stylosa 의 phytochelatin synthase 1 유전자 클로닝 및 발현

망그로브 생태계는 수생태계로 유입되는 중금속을 받아들이는 기능을 가지고 있다. 중금속에 오염된 퇴적물에 노출됨에도 불구하고 망그로브는 중금속에 내성을 가지고 있다. 이 연구에서 우리는 망그로브로부터 중금속 저항성 관련 유전자를 클로닝하고, 중금속 노출에 유전자 발현 변화를 분석하였다. 미크로네시아 축라군의 웨노섬에서 채취한 Rhizophora stylosa의 잎과 뿌리조직으로부터 CTAB 방법을 이용하여 RNA를 분리하였고, gene specific primers를 이용하여 phytochelatin synthase 1(PCS1) 유전자를 클로닝하였다. R. stylosa 태생종자를 100 ppb의 Cd과 10 ppb의 Cu에 노출하였을 때 각각 1.91배 및 2.72배 발현이 증가하였다. 이러한 결과는 PCS1 유전자의 발현분석이 망그로브 생태계의 건강성을 평가하기 위한 좋은 도구가 될 수 있음을 나타낸다. The mangrove ecosystems have the capacity to act as a sink of heavy metals entering aquatic ecosystems. Despite their potential exposure to metal contaminated sediments, mangroves appear to be highly tolerant to heavy metals. In this study, we cloned metal tolerance gene from mangrove plant. Using CTAB method, RNA were isolated from leaves and root tissue of Rhizophora stylosa habitated at Weno island in Micronesia Chuuk lagoon using CTAB method and phytochelatin synthase 1 (PCS1) gene was cloned using gene specific primers. Expression of PCS1 gene was increased 1.91 fold and 2.72 fold in mangrove propagules exposed to 100 ppb Cd and 10 ppb Cu, respectively. These results indicate that expression of PCS1 gene are promising tools for health assessment of mangrove ecosystem.

고해상도 위성영상을 이용한 산호초 서식환경 모니터링 : 축라군 웨노섬을 중심으로

The distribution of coral reefs can be an indicator of environmental or anthropogenic impacts. Here, we present a habitat map of coral reefs developed using high-spatial satellite images. The study area was located on the north-eastern part of Weno island, in the Chuuk lagoon of Federated States of Micronesia. Two fieldwork expeditions were carried out between 2007 and 2008 to acquire optical and environmental data from 121 stations. We used an IKONOS image obtained in December 2000, and a Kompsat-2 image obtained in September 2008 for the purpose of coral reef mapping. We employed an adapted version of the object-based classification method for efficient classification of the high-spatial satellite images. The habitat map generated using Kompsat-2 was 72.22% accurate in terms of comparative analysis with in-situ measurements. The result of change detection analysis between 2000 and 2008 showed that coral reef distribution had decreased by 6.27% while seagrass meadows had increased by 8.0%.

Carlia ailanpalai (Reptilia: Scincidae): An Invasive Species of Lizard in the Federated States of Micronesia

Distribution of the introduced scincid lizard Carlia ailanpalai Zug in the Federated States of Micronesia (FSM) is reviewed. It is common in open grassy areas but seldom occurs in mature forest. Preliminary surveys indicate that it is well established in Yap, though less frequently encountered at increasing distance from Colonia, the main settlement, and it is unrecorded in the extreme northern and southern parts of Yap. It is the most common species of lizard in open, grassy, ruderal habitats throughout Weno Island, Chuuk, being nearly the only species encountered in the commercial district, but it is unknown elsewhere in Chuuk State. The only record for Kosrae is a single specimen collected in 1988 (first record for the FSM), but there is no evidence of an established population. There are no records for Pohnpei State. Guam is likely the primary source for the Yap and Chuuk populations (and Kosrae specimen), but the time of initial introduction is unknown. Carlia ailanpalai appears to have spread rapidly, at least on Weno, Chuuk, where it has become the predominant lizard in open habitats islandwide, possibly since the late 1960s. How C. ailanpalai interacts with other species in the FSM requires further study, but preliminary surveys of distribution and relative abundance suggest that it has a negative impact on populations of Emoia jakati and, to a lesser extent, on other Emoia species as well. Populations of C. ailanpalai in the FSM meet the criteria for invasive species status as it is defined by numerous U.S. government agencies and international conservation groups.

마이크로네시아 축 주의 석호환경 내 동물플랑크톤 군집: 종조성 및 개체수

Mesozooplankton samples were collected to investigate the spatial distribution in the Chuuk lagoon of the Federated States of Micronesia through three surveys from 2002 to 2004. Average temperature was in August 2002, in October 2003 and in July 2004 at a water depth of 2rn. Average salinity was 33.95 psu in August 2002, 33.56 psu in October 2003 and 33.77 psu in July 2004. Total rnosozooplankton consisted of 70 taxa during the study period, among which copepods were the most diverse group. Foraminiferans, radiolarians, copepods and appendicularians, which comprised about 70% of total zooplankton abundance, were important components in the zooplankton community. Within the copepod group, Acartia spp., Centropages spp. and Undinula spp. were dominant in August 2002, Acartia spp., Centropages spp., and Oithona spp. in October 2003, and Acartia spp., Undinula spp., and Oithona spp. in July 2004. Total zooplankton abundance was high around Weno Island, while low in stations located in the northern part of Weno Island. High abundances of appendicularians were found in the southern part of weno Island as well as around Weno Island. Appendicularians foraminiferans, radiolarians, Sagitta spp. and immature copepods accounted for most of the distribution pattern of the mesozzoplankton community throughout the study area. These results suggest that appendicularians may be potential food items for fish larvae around Weno Island in the Chuuk lagoon states.