Ultrastructure and phylogeny of Glugea arabica n. sp. (Microsporidia), infecting the marine fish Epinephelus polyphekadion from the Red Sea

A new microsporidian species, Glugea arabica n. sp., is reported infecting the intestinal wall of the marine teleost Epinephelus polyphekadion (=microdon) collected from the Red Sea coast off Saudi Arabia, and described on the basis of microscopic and molecular procedures. Spherical blackish xenomas formed parasitophorous vacuoles completely packed with several parasitic developmental stages, including spores. The nuclei were monokaryotic in all developmental stages. Spores were ellipsoidal to pyriform and measured 6.3 ± 0.3 (5.9–6.6) μm in length and 3.3 ± 0.4 (2.9–3.7) μm in width. A lamellar polaroplast surrounded the uncoiled portion of the polar filament, which extended into the spore's posterior pole and formed 27–29 coils organized in three or four rows. The posterior vacuole, located at the spore's posterior pole, appeared surrounded by the polar filament coils and displayed an irregular matrix composed of light material, in which was located the posterosome. Molecular analysis of the rRNA genes, including the ITS region, was performed using maximum parsimony, neighbor-joining and maximum likelihood methodologies. The ultrastructural features observed, in combination with the molecular data analysed, suggests the parasite to be a new species of the genus Glugea.     

Contrasted levels of genetic diversity in a benthic Mediterranean octocoral: Consequences of different demographic histories?

Understanding the factors explaining the observed patterns of genetic diversity is an important question in evolutionary biology. We provide the first data on the genetic structure of a Mediterranean octocoral, the yellow gorgonian Eunicella cavolini, along with insights into the demographic history of this species. We sampled populations in four areas of the Mediterranean Sea: continental France, Algeria, Turkey, and the Balearic and Corsica islands. Along French coasts, three sites were sampled at two depths (20 and 40 m). We demonstrated a high genetic structure in this species (overall F_ST = 0.13), and most pairwise differentiation tests were significant. We did not detect any difference between depths at the same site. Clustering analyses revealed four differentiated groups corresponding to the main geographical areas. The levels of allelic richness and heterozygosity were significantly different between regions, with highest diversity in Algeria and lowest levels in Turkey. The highest levels of private allelic richness were observed in Algeria followed by Turkey. Such contrasted patterns of genetic diversity were not observed in other Mediterranean octocorals and could be the result of different evolutionary histories. We also provide new empirical evidence of contrasting results between tests and model‐based studies of demographic history. Our results have important consequences for the management of this species.     

Inhibition of replicative DNA synthesis in nuclei of Strongylocentrotus intermedium urchin embryo by 2′,3′-dideoxy-3′-aminonucleoside 5′-triphosphates

2′,3′-Dideoxy-3′-aminonucleoside 5′-triphosphates have been shown to be inhibitors of replicative DNA synthesis in isolated nuclei of sea urchin embryo. These compounds inhibit the Okazaki fragment synthesis. The effect of 2′,3′-dideoxy-3′-aminothymidine 5′-triphosphate and arabinothymidine 5′-triphosphate is reversible when adding the corresponding substrate for DNA synthesis, 2′-deoxythymidine 5′-triphosphate.     

菲律宾海北部底质沉积中的深海介形类

对琉球群岛东侧的菲律宾海北部海区(27.0°-30.0°N,129.5°-135.5°E)水深1 666 m至6 616 m的123个表层沉积物样品进行了定量微体古生物学研究.仅在38个样品中发现介形类,主要分布在4 000 m以浅水深区.初步鉴定有21属35种,其中Krithe在样品中的出现率和丰度最高,其次常见的还...     

Regulatory contribution of heterotrimeric G-proteins to oocyte maturation in the sea urchin

Regulation of animal oocyte maturation is hypothesized to involve heterotrimeric G-proteins. It is difficult to test this hypothesis though without knowing what G-proteins are present in these cells and where are they localized. We set out to test the hypothesis that G-proteins regulate maturation in the sea urchin oocyte by identifying resident G-proteins in oocytes and eggs, and then investigating their function. We find four families of G-protein alpha-subunits (Galphai, Galphaq, Galphas, and Galpha12) present in both oocytes and eggs of the sea urchin. Three of them, Galphai, Galphaq, and Galphas are present on the plasma membrane of the oocyte, while the fourth is located on cytoplasmic vesicles. Upon oocyte maturation, these proteins remain in eggs, and continue to be expressed in embryonic tissues. To test the functional contribution of the G-proteins to the regulation of oocyte maturation, we employ specific intervening reagents, including antibodies and competitor peptides to each Galpha subunit, and specific Galpha toxins. We find that Gi is a main candidate for a positive regulator of sea urchin oocyte maturation. These studies provide a foundation to further test specific hypotheses of the G-protein mediated regulation of oocyte maturation, fertilization, and early development in the sea urchin.     

金门岛北部海域浮游植物的季节变动及与环境的关联

采用2013—2014年四季度月在金门岛北部海域获取的浮游植物及环境因子监测数据, 分析该区浮游植物的群落结构和季节变化及其与温度、盐度、悬浮物、营养盐、叶绿素等的关系, 初步探讨涉海工程建设对浮游植物群落的潜在影响。结果显示, 鉴定出的浮游植物隶属3门43属82种(不含未定种), 群落构成以硅藻为主, 其次是甲藻, 蓝藻仅1种。物种组成的季节差异较大, 3月物种贫乏, 1月次之, 7月和11月最丰富。四季丰度平均为47.09×103 cells/L, 1月丰度最高, 7月次之, 11月最低, 3月高于11月少许。四季优势种均为硅藻, 13个优势种分别为柔弱几内亚藻(Guinardia delicatula)、短角弯角藻(Ecampia zoodicaus)、骨条藻(Skeletonema spp.)、具槽帕拉藻(Paralia sulcata)、微小海链藻(Thalassiosira exigua)、标志星杆藻(Asterionella notula)、旋链角毛藻(Chaetoceros curvisetus)、新月菱形藻(Nitzchia closterium)、派格棍形藻(Bacillaria paxillifera)、异常角毛藻(Chaetoceros abmormis)、小细柱藻(Leptocylindrus minutum)、宽角曲舟藻(Pleurosigma angulatum)和美丽曲舟藻(Pleurosigma formosum)。不同季节优势种有一定程度交错, 仅在单季占优的有6种, 有2/3在3个以上季节出现, 具槽帕拉藻、骨条藻为四季优势种。浮游植物物种多样性和均匀度总体较好, 群落结构稳定。与毗邻海区相比, 本区物种丰富度偏低, 丰度高于毗邻海区, 种类组成相似, 优势种却有较大差别。Pearson相关分析表明, 溶解无机氮及活性磷酸盐仅在1月与丰度存在极显著的正相关, 是促使丰度为四季最高的原因。涉海工程施工产生的悬浮物和冲击波是影响浮游植物群落的主要因素, 大量海洋工程建设案例表明, 施工期造成的浮游植物丰度下降趋势和优势种更替混乱在工程结束后能得以恢复。     

Tolerance of Pinus taeda and Pinus serotina to low salinity and flooding: Implications for equilibrium vegetation dynamics

Questions: 1. Do pine seedlings in estuarine environments display discrete or continuous ranges of physiological tolerance to flooding and salinity? 2. What is the tolerance of Pinus taeda and P. serotina to low salinity and varying hydrologic conditions? 3. Are the assumptions for ecological equilibrium met for modeling plant community migration in response to sea‐level rise? Location: Albemarle Peninsula, North Carolina, USA. Methods: In situ observations were made to quantify natural pine regeneration and grass cover along a salinity stress gradient (from marsh, dying or dead forest, to healthy forest). A full‐factorial greenhouse experiment was set up to investigate mortality and carbon allocation of Pinus taeda and P. serotina to low‐salinity conditions and two hydrology treatments over 6 months. Treatments consisted of freshwater and two salinity levels (4 ppt and 8 ppt) under either permanently flooded or periodically flushed hydrologic conditions. Results: Natural pine regeneration was common (5–12 seedlings per m²) in moderate to well‐drained soils where salinity concentrations were below ca. 3.5 ppt. Pine regeneration was generally absent in flooded soils, and cumulative mortality was 100% for 4 and 8 ppt salinity levels under flooded conditions in the greenhouse study. Under weekly flushing conditions, mortality was not significantly different between 0 and 4 ppt, confirming field observations. Biomass accumulation was higher for P. taeda, but for both pine species, the root to shoot ratio was suppressed under the 8 ppt drained treatment, reflecting increased below‐ground stress. Conclusions: While Pinus taeda and P. serotina are commonly found in estuarine ecosystems, these species display a range of physiological tolerance to low‐salinity conditions. Our results suggest that the rate of forest migration may lag relative to gradual sea‐level rise and concomitant alterations in hydrology and salinity. Current bioclimate or landscape simulation models assume discrete thresholds in the range of plant tolerance to stress, especially in coastal environments, and consequently, they may overestimate the rate, extent, and timing of plant community response to sea‐level rise.     

Oceanography and reefs of recent and Paleozoic tropical epeiric seas

Summary The Java Sea, one of the few modern tropical epeiric seas, is used as an analogue to examine oceanography, stratigraphy, and reefs of Devonian strata in the Appalachian and Michigan Basins. Nearshore patch reefs and offshore “pinnacle” reefs occur in both the Java Sea and the Emsian-Eifelian Onondaga Formation in the Appalachian Basin. Nearshore patch reefs also occur in the Eifelian Formosa Reef Limestone in the Michigan Basin. The Java Sea is characterized by quasi-estuarine circulation, in which runoff and rainfall exceed evaporation. Nutrient and organic matter influx from land and from estuarine upwelling contribute to organic rich facies during transgressions and sea level highstands. Similarly, we propose that high runoff from the Appalachian Mountains and from the Laurentian craton contributed to slightly reduced salinity in the Appalachian basin, including possible density stratification during Middle Devonian highstands. By contrast, the Michigan Basin was characterized by antiestuarine circulation, in which evaporation exceeded combined runoff and rainfall. Contemporaneous Emsian-Eifelian strata in the Michigan Basin are dolomite and dolomitic limestone, rather than cherty and muddy limestone typical of the Appalachian basin. Reef composition generally reflects oceanographic circulation regime within the epicontinental seas we examine. Nearshore reefs of the modern Java Sea and the Onondaga Formation (Appalachian Basin) are dominated by multilobate submassive, dendroid, and phaceloid corals, and virtually no platy corals or tabular stromatoporoids. Multilobate and phaceloid corals are better able to accommodate muddy sedimentation. By contrast, offshore pinnacle reefs of the Java Sea and nearshore reefs of the Formosa Reef Limestone are dominated by platyAcropora (modern) or tabular and laminar stromatoporoids (Devonian). The scarcity of tabular stromatoporoids, and the dominance of phaceloid corals and dendritic branching corals, in the Onondaga Formation (Appalachian Basin) are herein explained by localized high productivity conditions driven by quasi-estuarine circulation, rather than cool water. Quasi-estuarine circulation or localized topographic upwelling leading to highly productive coastal environments may be responsible for other Paleozoic examples of apparent cool-water carbonate deposition within the tropics, including the Ordovician of Eastern Canada.     

Ross Sea Mollusca from the Latitudinal Gradient Program: R/V Italica 2004 Rauschert dredge samples

Information regarding the molluscs in this dataset is based on the Rauschert dredge samples collected during the Latitudinal Gradient Program (LGP) on board the R/V “Italica” in the Ross Sea (Antarctica) in the austral summer 2004. A total of 18 epibenthic dredge deployments/samplings have been performed at four different locations at depths ranging from 84 to 515m by using a Rauschert dredge with a mesh size of 500μm. In total 8,359 specimens have been collected belonging to a total of 161 species. Considering this dataset in terms of occurrences, it corresponds to 505 discrete distributional records (incidence data). Of these, in order of abundance, 5,965 specimens were Gastropoda (accounting for 113 species), 1,323 were Bivalvia (accounting for 36 species), 949 were Aplacophora (accounting for 7 species), 74 specimens were Scaphopoda (3 species), 38 were Monoplacophora (1 species) and, finally, 10 specimens were Polyplacophora (1 species). This data set represents the first large-scale survey of benthic micro-molluscs for the area and provides important information about the distribution of several species, which have been seldom or never recorded before in the Ross Sea. All vouchers are permanently stored at the Italian National Antarctic Museum (MNA), Section of Genoa, enabling future comparison and crosschecking. This material is also currently under study, from a molecular point of view, by the barcoding project “BAMBi” (PNRA 2010/A1.10).     

Description of Ganymedes yurii sp. n. (Ganymedidae), a New Gregarine Species from the Antarctic Amphipod Gondogeneia sp. (Crustacea)

A novel species of aseptate eugregarine, Ganymedes yurii sp. n., is described using microscopic and molecular approaches. It inhabits the intestine of Gondogeneia sp., a benthic amphipod found along the shore of James Ross Island, Weddell Sea, Antarctica. The prevalence of the infection was very low and only a few caudo‐frontal syzygies were found. Morphologically, the new species is close to a previously described amphipod gregarine, Ganymedes themistos, albeit with several dissimilarities in the structure of the contact zone between syzygy partners, as well as other characteristics. Phylogenetic analysis of the 18S rDNA from G. yurii supported a close relationship between these species. These two species were grouped with other gregarines isolated from crustaceans hosts (Cephaloidophoroidea); however, statistical support throughout the clade of Cephaloidophoroidea gregarines was minimal using the available dataset.