Factors inducing morphological transition in harmful algal bloom-forming species Phaeocystis globosa with emphasis on predator chemical cue

The microalga Phaeocystis globosa is recognized as a harmful alga and also one of the few keystone phytoplankton genera that shape the structure and function of marine ecosystems. P. globosa possess a complex polymorphic life cycle, exhibiting phase alternation between free-living cells of approximately 3–6 μm in diameter and gelatinous colonies(palmelloid stage) reaching several millimeters. The knowledge on the factors that induced the morphological transition of P. globosa in the last two dec...     

Molecular identification of bloom-forming species Phaeocystis globosa(Prymnesiophyta)and its dispersal based on rDNA ITS sequence analysis

Abstract-The colony-forming Phaeocystis species are causative agents of dense bloom occurrences incoastal waters worldwide. It is difficult to separate them because of the different morphologies associatedwith their colonial stages. In this study we applied molecular approaches to analyze the genetic variationof Phaeocystis globosa and Phaeocystis pouchetii from several geogrtaphic regions, and to assist in tracingthe dispersal of bloom-forming Phaeocystis species in coastal waters of China. The Sequences of the inter-nal transcribed sacers (ITS1 and ITS2) of rDNA and the 5.8S ribosomal RNA gene of Phaeocystisstrains were determined. Sequence comparison shows that P.globosa was the most divergent toP. pouchetii, exhibiting sequence divergence higher than 0.08. However, lower genetic divergences ex-isted between strains of P.globosa. The sequence comparison of the Phaeocystis rDNA ITS clearlyshows that the species isolated from the southeast coast of China is identified as P. globosa rather thanP. cf. po     

Paraconchoecia diacanthus n. sp., a new species of planktonic Ostracoda

Ｐａｒａｃｏｎｃｈｏｅｃｉａｄｉａｃａｎｔｈｕｓｎ．ｓｐ．,ａｎｅｗｓｐｅｃｉｅｓｏｆｐｌａｎｋｔｏｎｉｃＯｓｔｒａｃｏｄａ￥ＣｈｅｎＲｕｉｘｉａｎｇａｎｄＬｉｎＪｉｎｇｈｏｎｇ（ＲｅｃｅｉｖｅｄＡｐｒｉｌ１６,１９９３１ａｃｃｅｐｔｅｄＪｕｌｙ２０...     

Fracture activity: A possible triggering mechanism for slope instabilities in the Eastern Atlantic?

The largest known submarine slope instabilities occur on gently inclined slopes or in the deep sea. The sedimentation rates are mostly too low to induce an excess pore-water pressure sufficient to create failure. A possible triggering mechanism for these instabilities is additional horizontal ground acceleration caused by earthquakes. Old zones of weakness, represented by fracture zones, can be reactivated by isostatic movements and induce seismic activity. The distribution of some major slope instabilities and the trend of fracture zones in the Eastern Atlantic are compared and Fracture activity is suggested as the main triggering mechanism for these slope instabilities.     

Tritonia iocasica sp. nov., a new tritoniid species from a seamount in the tropical Western Pacific (Heterobranchia: Nudibranchia)

During an expedition to a seamount at Caroline Plate in the tropical Western Pacific, a new species of Tritonia was sampled from the upper bathyal zone at depth...     

Fracture activity: A possible triggering mechanism for slope instabilities in the Eastern Atlantic?

The largest known submarine slope instabilities occur on gently inclined slopes or in the deep sea. The sedimentation rates are mostly too low to induce an excess pore-water pressure sufficient to create failure. A possible triggering mechanism for these instabilities is additional horizontal ground acceleration caused by earthquakes. Old zones of weakness, represented by fracture zones, can be reactivated by isostatic movements and induce seismic activity. The distribution of some major slope instabilities and the trend of fracture zones in the Eastern Atlantic are compared and Fracture activity is suggested as the main triggering mechanism for these slope instabilities.     

褐斜鲽(Plagiopsetta glossa)线粒体基因组特征及重排机制研究

冠鲽科(Samaridae)隶属于鲽形目(Pleuronectiformes), 包含冠鲽属(Samaris)、沙鲽属(Samariscus)和斜鲽属(Plagiopsetta)。目前研究表明, 冠鲽(Samaris cristatus)和满月沙鲽(Samariscus latus)的线粒体基因组结构都有重排, 并且两者的基因数量也有差别。为检测斜鲽属鱼类中是否也有不同的特征结构, 我们选用褐斜鲽(Plagiopsetta glossa)作为代表种进行斜鲽属鱼类线粒体基因组特征分析, 同时与冠鲽属及沙鲽属鱼类的线粒体基因组特征进行对比。分析显示, 褐斜鲽的线粒体基因组全长为18723bp, 包括39个基因: 13个蛋白基因、24个tRNA基因、2个rRNA基因、2个控制区、1个轻链复制起点和比典型基因组多的13个间隔子。和经典鱼类的线粒体基因组相比, 褐斜鲽和满月沙鲽都多了tRNA-Cys和tRNA-Tyr两个tRNA, 冠鲽只多了tRNA-Cys, 且3个种类都多了一个控制区, 但褐斜鲽与满月沙鲽的基因排列顺序相同。褐斜鲽线粒体基因的重排导致不同位置的6个tRNA形成了六连体基因簇“tRNA-Cys₁-Tyr₁- Ser1-Lys-Arg-Ser2”, “ND5-ND6-Glu-Cytb-Thr”则位于六连体之后, 但这11个基因相对的排序没有发生变化。采用双复制随机丢失模型(double replications and random loss, DRRL)对褐斜鲽基因的重排现象进行分析, 认为该鱼类基因数量、排列顺序以及比典型基因组多13个间隔子等特征为该模型提供了新的依据。     

Two new marine benthic diatom species of Hippodonta (Bacillariophyceae) from the coast of China: H . nanjiensis sp. nov. and H . qingdaoensis sp. nov.

The diversity and distribution of Hippodonta species on the coast of China are largely unknown due to limited investigations. In this paper, we report the detai...     

Karlodinium elegans sp. nov. (Gymnodiniales,Dinophyceae), a novel species isolated from the East China Sea in a dinofl agellate bloom

Abstract On May 24–29,2019,a harmful algal bloom occurred in Pingtan coastal areas,Fujian,southeast China,and caused mass mortality of cage-cultured fi sh.Two clonal cultures of an unknown naked dinofl agellate were set up from seawater samples taken during the bloom.The cultures were examined for morphological features,ultrastructure characters,photosynthetic pigments,the large subunit(LSU)of the rRNA gene,and the internal transcribed spacer(ITS)sequences,as well as acute toxicity analysis.The cell was unarmored,small-sized,and ovoid,and was characterized by elaborate striations on the epicone and hypocone.The nucleus was large,ellipsoid to oval or kidney-shaped,and centrally located in the cell.A long linear apical groove originated above the sulcus in the ventral epicone and extended to the dorsal side.An elongate,slit-like“ventral pore”was located on the left of the epicone,well away from the apical groove.The chloroplasts were yellowish brown,numerous,band like,and irregularly distributed in the cell periphery.Fucoxanthin was the main accessory pigment composition.Phylogeny topology reconstructed on partial LSU rDNA showed that the unknown dinofl agellate branched as a sister species to Karlodinium sp.(strain IFR981&IFR797,from France)and Karlodinium corrugatum(strain KDGSO08,from Australia),with genetic divergences of 0.6%and 3.3%,respectively.Based on the morphological and molecular phylogenetic analysis,we describe the novel dinofl agellate as Karlodinium elegans sp.nov.A toxicity assay revealed that the clonal culture of K.elegans(strain PTB601)had no adverse eff ect on brine shrimp(Artemia salina)and marine medaka(Oryzias melastigma),indicating it may not be a toxic species.     

Morphological and ecological parallels between sublittoral and abyssal foraminiferal species in the NE Atlantic: a comparison of Stainforthia fusiformis and Stainforthia sp.

Dead specimens of a minute fusiform rotaliid foraminifer are common in the 28–63 μm fraction of multiple corer samples from a 4850 m-deep site on the Porcupine Abyssal Plain (PAP). Their test morphology is remarkably similar to small specimens of Stainforthia fusiformis (Williamson, 1858), a species which is well known from coastal settings (intertidal to outer shelf) around NW Europe and North America. A detailed comparison of the PAP form with typical individuals of S. fusiformis from Norwegian waters (55–203 m depth), however, reveals slight but consistent morphological differences. The PAP specimens are smaller (test length 40–140 μm) than those from Norway (test length 80–380 μm), the chambers tend to be rather less elongate, the density of pores in the test wall is much lower, and there are differences in apertural features. We therefore conclude that the diminutive abyssal form is a distinct species, here referred to as Stainforthia sp. This interpretation is consistent with increasing evidence for genetic differentiation in deep-sea organisms, particularly along bathymetric gradients. Stainforthia sp. was previously illustrated by Pawlowski as Fursenkoina sp. and appears to be widespread and abundant in the abyssal North Atlantic (>4000 m depth). Stainforthia fusiformis, on the other hand, is most abundant in continental shelf and coastal settings. It extends onto the continental slope in the North Atlantic but has not been reported reliably from depths greater than about 2500 m.We suggest that the striking morphological convergence between these two species reflects the adoption of similar ecological strategies in widely separated habitats. Both are enrichment opportunists, a life-style which may explain the rather broad bathymetric range of Stainforthia fusiformis. This is a dominant species in organically-enriched and sometimes extremely oxygen-depleted environments on the continental shelf, and is a rapid coloniser of formerly azoic habitats. Live specimens of the abyssal form are typically found embedded within phytodetrital aggregates (organic material derived from primary production in the euphotic zone). It is presumably the availability of these organic-rich microhabitats, which enables this species to survive in the otherwise oligotrophic deep sea.     

海洋烷烃降解菌Alcanivorax sp.A-11-3的分离鉴定及其降解酶基因研究

从马六岬海峡的表层海水中分离到一株石油降解菌A-11-3.经16S rDNA Blast结果表明其与Alcanivorax borkumensis SK2具有最高相似性为96%,该菌可能是食烷菌属的一个新种.该菌具有很强的石油降解能力.结果表明,A-11-3对烷烃的降解范围较宽,能以C8～C36的烷烃为唯一碳源和能源生长;在7d内该菌对柴油的降解率达到49.5%.此外,还从菌株中克隆到了大小为426bp的烷烃羟化酶基因alkB片段和843bp的P450 烷烃羟化酶基因的部分序列.序列分析表明,alkB片段编码的氨基酸序列与A. borkumensis SK2T的AlkB1和AlkB2的同源性分别为57.75%和40.14%;该菌的P450与SK2菌株的P450具有最高同源性,为87%.研究结果对于海洋石油降解微生物生态研究及石油污染生物修复技术开发有参考价值.     

On a new species of deep-water Siphonophora, Lensia multicristoides sp. nov. from middle South China Sea

-In this paper, a new species of deep-water Siphonophora, Lensia multicristoides sp. nov., collected from the middle South China Sea is described and compared with some similar species in the genus.     

Characterization of bacterial symbioses in Myrtea sp. (Bivalvia: Lucinidae) and Thyasira sp. (Bivalvia: Thyasiridae) from a cold seep in the Eastern Mediterranean

Cold seeps have recently been discovered in the Nile deep‐sea fan (Eastern Mediterranean), and data regarding associated fauna are still scarce. In this study, two bivalve species associated with carbonate crusts and reduced sediment are identified based on sequence analysis of their 18S and 28S rRNA‐encoding genes, and associated bacterial symbioses are investigated using 16S rRNA gene sequencing and microscopy‐based approaches. The specimens are closely related to Myrtea spinifera and Thyasira flexuosa, two species previously documented at various depths from other regions but not yet reported from the Eastern Mediterranean. Both species harbour abundant gammaproteobacterial endosymbionts in specialized gill epithelial cells. The Myrtea‐associated bacterium is closely related to lucinid symbionts from both deep‐sea and coastal species, whereas the Thyasira‐associated bacterium is closely related to the symbiont of a T. flexuosa from coastal waters off the U.K. An epsilonproteobacterial sequence has also been identified in Thyasira which could correspond to a helicoid‐shaped morphotype observed by electron microscopy, but this was not confirmed using fluorescent in situ hybridization. Virus‐like particles were observed within some symbionts in Thyasira, mostly in bacteriocytes localized close to the ciliated zone of the gill filament. Overall, results indicate that very close relatives of shallow species M. spinifera and T. flexuosa occur at cold seeps in the Eastern Mediterranean and harbour chemoautotrophic symbioses similar to those found in their coastal relatives.     

Reactive iron in Black Sea Sediments: implications for iron cycling

The distribution of reactive iron in sediments of the northwestern shelf, the shelf edge and the abyssal part of the Black Sea has been studied. In the euxinic Black Sea, iron sulfides (pyrite and iron monosulfide) are formed in the upper part of the anoxic water column and sink to the deep-sea floor where they are buried in the sediment. This flux of iron sulfides from the water column is reflected in enhanced concentrations of highly reactive iron and a high degree of pyritization (0.57–0.80) for the deep-water sediments of the Black Sea. The iron enrichment of deep-water sediments is balanced by a loss of highly reactive iron from the oxic continental shelf. Calculations from a numerical diagenetic model and reported in situ flux measurements indicate that the dissolved iron flux out of the shelf sediments is more than sufficient to balance the enrichment in reactive iron in deep-sea sediments, and that the majority of the dissolved iron efflux is redeposited on the continental shelf. This iron mobilization mechanism likely operates in most shelf areas, but its net effect becomes only apparent when reactive iron is trapped in sulfidic water bodies as iron sulfides or when iron is incompletely oxidized in low oxygen zones of the ocean and transported over long distances.     

中国东南沿海小头虫科(环节动物:多毛类)一新种

中蚓虫是小头虫科较为常见的属,中国海区的样品过去常被鉴定为加洲中蚓虫Mediomastus californiensis Hartman。本研究中,来自东南沿海四个不同海区的118条中蚓虫样品被鉴定为一个新的种类,在此给出具体描述。这个新种具有如下特征：（1）第1至9刚节表皮双环型,刚毛束位于体节中间位置,而后的刚节多环型,刚毛束位于体节后半部;（2）后腹区具有疣足突起;（3）前4个胸刚节仅具双羽型翅毛状刚毛,其它体节仅具巾钩刚毛;（4）胸区巾钩刚毛的柄长且直,巾长为宽的3至5倍;（5）腹区巾钩刚毛不同于胸区,较短且具收缩部;（6）甲基绿染色模式独特。这个研究表明了中国海区的中蚓虫可能被误鉴定为加洲中蚓虫,而这个新种M.chinensis sp.nov.在东南沿海广为分布。