A phylogeny of Cenozoic macroperforate planktonic foraminifera from fossil data

We present a complete phylogeny of macroperforate planktonic foraminifer species of the Cenozoic Era (∼65 million years ago to present). The phylogeny is developed from a large body of palaeontological work that details the evolutionary relationships and stratigraphic (time) distributions of species‐level taxa identified from morphology (‘morphospecies’). Morphospecies are assigned to morphogroups and ecogroups depending on test morphology and inferred habitat, respectively. Because gradual evolution is well documented in this clade, we have identified many instances of morphospecies intergrading over time, allowing us to eliminate ‘pseudospeciation’ and ‘pseudoextinction’ from the record and thereby permit the construction of a more natural phylogeny based on inferred biological lineages. Each cladogenetic event is determined as either budding or bifurcating depending on the pattern of morphological change at the time of branching. This lineage phylogeny provides palaeontologically calibrated ages for each divergence that are entirely independent of molecular data. The tree provides a model system for macroevolutionary studies in the fossil record addressing questions of speciation, extinction, and rates and patterns of evolution.     

srDna-based taxonomic affinities of algal symbionts from a planktonic foraminifer and a solitary radiolarian

Planktonic sarcodines (acantharia, radiolaria, and planktonic foraminifera) are oceanic amoeboid protozoa that often harbor a variety of microalgae as intracellular symbionts. The identity and function of these endosymbiotic algae have intrigued and perplexed biologists for more than a century. The most conspicuous and well‐studied symbiotic algae of planktonic foraminifera and radiolaria are dinoflagellates, but a variety of nondinoflagellate taxa have also been reported. Ultrastructural features have been used to characterize some of these nondinoflagellate algae, but rarely has this led to clear taxonomic affiliations. We analyzed the nuclear small subunit ribosomal DNA (srDNA) isolated from the symbionts of the spinose planktonic foraminiferan Globigerinella siphonifera d'Orbigny (=Globigerinella aequilateralis Brady) and a solitary radiolarian (Spongodrymus sp. Haeckel) in order to determine the identity of these symbionts. The small coccoid algae isolated from G. siphonifera correspond to the Type I symbionts described by Faber et al. (1988) . Phylogenetic analysis of the srDNA sequences places these symbionts within the prymnesiophyte (haptophyte) lineage, closer to Prymnesium Conrad than to Phaeocystis Lagerheim. To our knowledge, this is the first confirmed case of a symbiotic prymnesiophyte. In addition, we were able to examine the level of sequence heterogeneity between symbionts isolated from different individuals of a single host species. The three isolates in this study had srDNA sequences that were almost identical, indicating that the three were all of the same species. Very green symbiotic algae were isolated from three solitary radiolaria identified as species of Spongodrymus. The symbiont srDNA sequences from the three individual hosts were identical to each other, again implicating a single species of algae in that symbiotic association. These symbionts are prasinophytes most closely related to the clade containing Tetaselmis convolutae Norris, Hori et Chihara. Tetraselmis convolutae is the algal symbiont of the marine flatworm, Convolutae roscoffensis Graff.     

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No previous study of plankton in lakes has estimated the relative contribution of ciliated protozoa to the biomass of the total plankton community, including phytoplankton. In a series of south-central Ontario lakes, ciliates comprise on the order of 5 to 10% of the total planktonic biomass of these relatively oligotrophic lakes and exist there in densities of 20–40 ml⁻¹. Therefore, ciliates constitute an important component of lake ecosystems that should not be ignored in limnological studies of zooplankton abundance and distribution.     

Factors Controlling the Planktonic Community in the Shallow-Lake of Créteil,France

A two-year study on the seasonal pattern of plankton was performed in a shallow, polymictic, eutrophic lake. Autogenic successions typical of stratified lakes did not occur. Only small edible algae developed throughout the two years and Cyanophyceae rarely appeared, and did not bloom. Algal sequences depended on wind-induced periodic mixing of water. The seasonal pattern of Rotifers varied greatly from year to year and some species depended on sporadic increases of algae. In contrast, the seasonal pattern of microcrustacea was more regular. Resting stages played an important role in zooplankton development in this variable environment. Successful fish reproduction depended a great deal on climatic conditions. The changes from year to year in predation pressure from young fish appeared to be an important factor controlling zoo-plankton structure.     

广西北部湾茅尾海夏冬季浮游细菌群落结构及其影响因子

海洋浮游细菌在生物地球化学循环过程中具有不可替代的作用。为解析广西北部湾茅尾海夏冬季浮游细菌群落结构及其关键环境影响因子，于2017年6月(夏季)和2017年12月(冬季)在该海域设置7个站点，采集0.5m处表层海水样品，利用16S核糖体RNA (16S rRNA)基因高通量测序技术，分析茅尾海浮游细菌群落结构与多样性。结果表明：茅尾海海域浮游细菌隶属于11个门、36个纲、86个目、188个科和506个属；主要浮游细菌类群为变形菌门(Proteobacteria, 52.47%)、厚壁菌门(Firmicutes, 17.34%)、放线菌门(Actinobacteria, 16.39%)、拟杆菌门(Bacteroidetes, 7.54%)和蓝细菌门(Cyanobacteria, 5.38%),共占浮游细菌总丰度的99.12%。北部湾茅尾海夏季浮游细菌群落Chao 1指数和Richness指数均显著(P<0.05)高于冬季。主坐标分析(PCoA)和相似性分析(ANOSIM)结果表明，不同季节浮游细菌群落结构存在极显著差异(R=0.586,P<0.001)。在目分类水平上进行组...     

Le Campanien-Maastrichtien du bassin des Aurès,Algérie : biostratigraphie,paléoenvironnements et leurs implications

An integrated study of the lithological, micropaleontoligical, sedimentological and statistical data has been done on samples taken from four geological sections (El Gaaga, Tighanimine and El Kantara) spread in different sea areas. This allowed to redefine the stratigraphy of the studied area to provide information about the benefits of some kinds of foraminifera, planktonic and ostracods in knowing the palaeoenvironment and identifying the types referring to the latter during the late cretaceous. The late creataceous appeared in Aures in a form of two hills separated by a light lowness. This morphology corresponds generally to the tripartite composition of the Campanian-Manstrichtian with lower member of limestone-marl (Haraoua Member), a median marl member (Akhdar Member) and an upper member of massive limestones (Ncham member). The regularity of this trilogy changed in the anticline of Dj. El Azereg through a reduction, visibly affecting the tree members. The study of the foraminifera in the late cretaceous (Campanian-Manstrichtian) in the Aures proved the existence of 141 species (48 planktonic and 93 benthic foraminifera). Applying the concepts of biostratigraphy mainly on the foraminifera allowed to distinguish different bizones, ranging from lower Campanian of El Gaaga and El Kantara cuts (Globotruncanita elevata biozone) and Maastrichtian (Contusotruncana contusa biozone). The biostratigraphical framework is thus relatively precise and helps precising for instance the position of some inconsistent boundaries.