Das Wachstum silurischer Sphaerellarien und ihre späteren chemischen Umwandlungen

The discovery of well preserved Radiolaria (Sphaerellaria) embedded in Silurian Kieselschiefer offered the possibility to find out a lot of information about the ontogenetic connections between the skeletons as well as about diagenetic transformations. Only spherical Radiolaria with centripetal growth tendency can be found. The question about the origin of the SiO₂, the Kieselschiefer consists of, cannot be answered from the results.     

Video plankton recorder reveals high abundances of colonial Radiolaria in surface waters of the central North Pacific

Colonial spumellarian Radiolaria are heterotrophic protiststhat form large (up to several meters in length), gelatinousstructures in the surface waters of all tropical and subtropicaloceanic ecosystems. These species are morphologically and trophicallycomplex and some, but not all, produce silica skeletal structuresof considerable paleontological significance. Skeletonless speciesof Radiolaria are poorly sampled by plankton nets, which canseverely damage these delicate organisms. Therefore, abundancesof colonial Radiolaria typically have been underestimated inquantitative studies of zooplankton abundance and biomass. Herewe document the abundances of colonial Radiolaria in the centralNorth Pacific based on analysis of video images from a miniaturizedvideo plankton recorder. We observed abundances of radiolariancells in colonies that exceeded previous reports of total Radiolariaby more than ten-fold, and counts of skeleton-bearing Radiolariaby more than two to three orders of magnitude. Biomass (carbon)within these colonies was similar to or greater than the totalradiolarian biomass (i.e. including all solitary species) previouslyreported for the Pacific. Symbiont productivity within colonialRadiolaria was estimated to constitute a modest but significantfraction of total primary productivity (up to     

Radiolaria divided into Polycystina and Spasmaria in combined 18S and 28S rDNA phylogeny

Radiolarians are marine planktonic protists that belong to the eukaryote supergroup Rhizaria together with Foraminifera and Cercozoa. Radiolaria has traditionally been divided into four main groups based on morphological characters; i.e. Polycystina, Acantharia, Nassellaria and Phaeodaria. But recent 18S rDNA phylogenies have shown that Phaeodaria belongs within Cerocozoa, and that the previously heliozoan group Taxopodida should be included in Radiolaria. 18S rDNA phylogenies have not yet resolved the sister relationship between the main Radiolaria groups, but nevertheless suggests that Spumellaria, and thereby also Polycystina, are polyphyletic. Very few sequences other than 18S rDNA have so far been generated from radiolarian cells, mostly due to the fact that Radiolaria has been impossible to cultivate and single cell PCR has been hampered by low success rate. Here we have therefore investigated the mutual evolutionary relationship of the main radiolarian groups by using the novel approach of combining single cell whole genome amplification with targeted PCR amplification of the 18S and 28S rDNA genes. Combined 18S and 28S phylogeny of sequences obtained from single cells shows that Radiolaria is divided into two main lineages: Polycystina (Spumellaria+Nassellaria) and Spasmaria (Acantharia+Taxopodida). Further we show with high support that Foraminifera groups within Radiolaria supporting the Retaria hypothesis.     

Skeletal morphogenesis in some living collosphaerid Radiolaria

Two major patterns of shell morphogenesis occurring in varying proportions among species were identified by examining skeletons from five species of living collosphaerid, colonial Radiolaria: Collosphaera huxleyi, Acrosphaera cyrtodon, Acrosphaera spinosa, Siphonosphaera tubulosa and Siphonosphaera socialis. Skeletons possessing large open-lattice structures characterized by ellipsoidal to polygonal pores separated by narrow bars are produced by repeated subdivision of large pores into smaller pores. A bridge-like bar grows across the pore and subdivides it into two or more smaller pores. In skeletons with small, nearly circular pores and occasionally elongated tubular rims, the pores appear to be developed by rim thickening. Silica is deposited at the perimeter of the pore, thus decreasing its diameter and increasing the bar width between pores. In some species exhibiting intermediate types of skeletal morphology, there appears to be varying amounts of both bridge growth and rim growth. These data are used to explore possible phylogenetic pathways for a variety of collosphaerid species and to elucidate the processes of skeletal deposition in Radiolaria.     

DNA metabarcoding focused on difficult-to-culture protists: An effective approach to clarify biological interactions

DNA metabarcoding on a single organism is a promising approach to clarify the biological interactions (e.g., predator–prey relationships and symbiosis, including parasitism) of difficult-to-culture protists. To evaluate the effectiveness of this method, Radiolaria and Phaeodaria, which are ecologically important protistan groups, were chosen as target taxa. DNA metabarcoding on a single organism focused on the V9 region of the 18S rRNA gene revealed potential symbionts, parasites and food sources of Radiolaria and Phaeodaria. Previously reported hosts and symbionts (parasites) were detected, and newly recognized combinations were also identified. The contained organisms largely differed between Radiolaria and Phaeodaria. In Radiolaria, members of the same order tended to contain similar organisms, and the taxonomic composition of possible symbionts, parasites, and food sources was fixed at the species level. Members of the same phaeodarian family, however, did not contain similar organisms, and body part (i.e., the central capsule or the phaeodium) was the most important factor that divided the taxonomic composition of detected organisms, implying that the selection of appropriate body part is important when trying to ascertain contained organisms, even for unicellular zooplankton. Our results show that DNA metabarcoding on a single organism is effective in revealing the biological interactions of difficult-to-culture protists.     

Molecular phylogeny of solitary shell-bearing Polycystinea (Radiolaria)

The phylogeny of the Family Spongodiscidae (polycystine Radiolaria), which includes Dictyocoryne profunda Ehrenberg, Dictyocoryne truncatum (Ehrenberg) and Spongaster tetras Ehrenberg, was examined using 18S ribosomal DNA (small-subunit ribosomal DNA) sequence analysis. Three types of tree construction methods, the neighbor joining (NJ), maximum parsimony (MP), and maximum likelihood (ML) methods, were used to infer the phylogenetic relationships of the polycystine and acantharian Radiolaria among eukaryotes. The obtained 18S rDNA molecular phylogenetic tree argues for the monophyly of the two groups. Furthermore, the Polycystinea is divided into at least two distinct lineages consisting of: (1) colonial and skeletonless Polycystinea, including Thalassicollidae, Collospaeridae, and Sphaerozoidae; and (2) shell-bearing solitary Polycystinea, including Spongodiscidae. The Polycystinea thus show a paraphyly among Radiolaria. Moreover, the monophyly of the clade including the acantharians and the spongodiscid polycystines was supported by bootstrap values, which were 94%, 53%, and 59% in the NJ, MP, and ML analyses, respectively. This lineage is characterized by having latticed or spongy skeletons of different chemical composition, namely SiO₂ (Class Polycystinea) or SrSO₄ (Class Acantharea). According to the present taxonomic scheme, the Acantharea and the Polycystinea have not been placed in different classes, but the results of our molecular study show the opposite. We therefore suggest, based on the monophyly of the two clades, that a new taxonomic group of Radiolaria can be established. Our molecular data also suggest that the currently used radiolarian taxonomic system may need serious revisions.     

Radiolaria: Sinking population,standing stock,and production rate

A method is presented for estimating sinking population, rate of production, and residence time in the living zone for Radiolaria. This method employs vertical flux measurements from PARFLUX sediment traps and laboratory sinking speed measurements of the radiolarian skeletons.The estimated population sinking through the oceanic water column is approximately equal to the standing stock at several hundred meters depth reported from direct measurements by other workers. The rate of production of total Radiolaria was estimated to be approximately 80 shells m^?3 day^?1 in the western equatorial Atlantic (E) and central Pacific (P₁) stations and 230 shells m^?3 day^?1 in the Panama Basin (PB). The production of Nassellaria is greater than that of the other suborders. The average residence time for Radiolaria in the living zone (0–200 m) was estimated to be between 16 and 42 days.     

The Radiolarian biotic response to Oceanic Anoxic Event 2 in the southern part of the Northern proto-Atlantic (Demerara Rise, ODP Leg 207)

Rare Radiolaria occur in the Upper Cenomanian-Lower Turonian part of finely laminated black shales recovered from Sites 1258 and 1261 of Demerara Rise (Ocean Drilling Program Leg 207, western tropical Atlantic, off Surinam). The observed fauna are of a low diversity, with up to 12 species co-occurring in a single sample and 49 species identified in total in both sites. Nassellarians and “Spumellarians” are equally represented in the assemblages. Diverse species of Stichomitra and Theocampe are particularly common, including the two new species described herein: Theocampe costata and T. demeraraense. Radiolarian preservation is on average moderate to poor, suggesting substantial influence of diagenetic alterations to species diversity. The few well-preserved assemblages can potentially provide better information about Cenomanian-Turonian Radiolarian biodiversity, but given their low abundance in the processed sediment samples, the diversity sampled during this study is considered to be an underestimate of the original Radiolarian diversity at Demerara. However, the abundance and diversity of Theocampe in Upper Cenomanian levels is noteworthy. Given the earliest known occurrence of the genus from Upper Albian sediments of the Deep Ivorian Basin it is likely that it originated and diversified in the opening Equatorial Atlantic Gateway. Based on the stable carbon isotope curve, the OAE-2 interval is clearly identified in the sedimentary sequence of both studied sites and helps to specify the known age range of three species (Acanthocircus hueyi, Archaeospongoprunum bipartitum and Rhopalosyringium hispidum). The most intriguing result of this study is the paucity of Radiolaria within the OAE-2 interval of the deeper site (1258) and the total absence of this micro-zooplankton group in the OAE-2 interval of the proximal site (1261). Radiolaria are the most abundant and diverse at the distal Site 1258, below OAE-2, while the proximal Site 1261 contains very few Radiolaria. The opposite pattern is observed above OAE-2 (few Radiolaria at site 1258, more abundant at site 1261). The paucity or absence of Radiolaria within the OAE-2 interval may be due to the upward excursion of the chemocline in the southern part of the Northern proto-Atlantic. Upwelling of deep warm waters may have fuelled primary productivity (sulfate-reducing bacteria) but prevented at the same time micro-zooplankton survival and proliferation after intensification of euxinic conditions in the surface waters.     

Phylogenetic position of the small solitary phaeodarians (Radiolaria) based on 18S rDNA sequences by single cell PCR analysis

Within the holoplanktonic protists group Radiolaria, the Class Phaeodarea is today represented by several hundreds species. The phaeodarian skeletons consist of opaline silica as well as organic matter and are very fragile and vulnerable to dissolution. Their tests are therefore rarely found in the fossil records; this has caused uncertainty with regard to their phylogenetic evolution. In this study, small, solitary phaeodarian species, namely, Protocystis xiphodon (Haeckel), Challengeron diodon Haeckel and Conchellium capsula Borgert were examined using molecular techniques in order to clarify the phylogenetic position of the Phaeodarea. The phylogenetic trees obtained from the neighbor-joining, maximum-parsimony and maximum-likelihood methods of analysis showed that all phaeodarians formed a monophyletic group within the Phylum Cercozoa. This result contradicts Haeckel's classical taxonomy, wherein the phaeodarians were grouped along with the polycystines, i.e., nassellarians and spumellarians, and the acantharians under the common name “Radiolaria”. Within the cercozoan clade, the Phaeodarea were closely related to the euglyphid and pseudodifflugid testate amoebae and the desmothoracid heliozoans. The tests and skeletons of both the phaeodarians and the euglyphid testate amoebae resemble each other in their chemical composition and construction. The similarities in the morphologic features may suggest that they are sisters as the Phylum Cercozoa in which leading from molecular methods.     

Evolution of elongation factor-like (EFL) protein in Rhizaria is revised by radiolarian EFL gene sequences

Elongation factor 1α (EF-1α) and elongation factor-like (EFL) proteins are considered to carry out equivalent functions in translation in eukaryotic cells. Elongation factor 1α and EFL genes are patchily distributed in the global eukaryotic tree, suggesting that the evolution of these elongation factors cannot be reconciled without multiple lateral gene transfer and/or ancestral co-occurrence followed by differential loss of either of the two factors. Our current understanding of the EF-1α/EFL evolution in the eukaryotic group Rhizaria, composed of Foraminifera, Radiolaria, Filosa, and Endomyxa, remains insufficient, as no information on EF-1α/EFL gene is available for any members of Radiolaria. In this study, EFL genes were experimentally isolated from four polycystine radiolarians (i.e. Dictyocoryne, Eucyrtidium, Collozoum, and Sphaerozoum), as well as retrieved from publicly accessible expressed sequence tag data of two acantharean radiolarians (i.e. Astrolonche and Phyllostaurus) and the endomyxan Gromia. The EFL homologs from radiolarians, foraminiferans, and Gromia formed a robust clade in both maximum-likelihood and Bayesian phylogenetic analyses, suggesting that EFL genes were vertically inherited from their common ancestor. We propose an updated model for EF-1α/EFL evolution in Rhizaria by incorporating new EFL data obtained in this study.     

Diversity and ecology of Radiolaria in modern oceans

Among the many inhabitants of planktonic communities, several lineages have biomineralized intricate skeletons. These have existed for millions of years and include the Radiolaria, a group of marine protists, many of which bear delicate mineral skeletons of different natures. Radiolaria are well known for their paleontological signatures, but little is known about the ecology of modern assemblages. They are found from polar to tropical regions, in the sunlit layers of the ocean down to the deep and cold bathypelagic. They are closely involved in the biogeochemical cycles of silica, carbon and strontium sulfate, carrying important amounts of such elements to the deep ocean. However, relatively little is known on the actual extent of genetic diversity or biogeographic patterns. The rapid emergence and acceptance of molecular approaches have nevertheless led to major advances in our understanding of diversity within and evolutionary relationships between major radiolarian groups. Here, we review the state of knowledge relating to the classification, diversity and ecology of extant radiolarian orders, highlighting the substantial gaps in our understanding of the extent of their contribution to marine biodiversity and their role in marine food webs.     

Ultrastructure of a colonial radiolarian Collozoum inerme and a cytochemical determination of the role of its zooxanthellae

Collozoum inerme (Müller) is a colonial Radiolarian containing numerous cells bound in a common gelatinous matrix. The cells do not possess a skeleton as observed in many unicellular Radiolaria, but the cytoplasmic organization is similar. The cells are multinucleate and a complex system of cellular processes containing mitochondria, Golgi, and numerous vacuoles radiate out from the nuclear region. The endoplasm is connected to the ectoplasm across a double membrane boundary by thin cytoplasmic strands called fusules whose structure resemble those in unicellular Radiolaria. The ectoplasm contains a lacy network of vacuoles containing an osmiophilic substance. Rhizopodia emerge from the ectoplasmic sheath. Some are thin and densely granular. Larger diameter rhizopodia, containing less dense cytoplasm, sequester the zooxanthellae which present a typical dinoflagellate fine structure. Some of the zooxanthellae are apparently cultivated since they are sometimes observed dividing and persist in large numbers when colonies are cultivated under illumination for several weeks in the laboratory. However, colonies maintained in the dark have a decline in number of zooxanthellae and light microscopic examination shows they are being drawn into the ectoplasm of the radiolarian cells. Electron microscopic examination of zooxanthellae drawn into the ectoplasm sheath indicates they are digested. C. inerme is a remarkable example of a simple cellular aggregate that has exploited its colonial habit to culture algae and use them as food thus possibly enhancing the viability of the colony.     

Radiolarian biogeography in surface sediments of the eastern Indian Ocean

We analyzed recurrent groups of Radiolaria in 74 core top samples from a transect through the eastern Indian Ocean in order to supplement our previous results from the western Indian Ocean (Johnson and Nigrini, 1980). We now identify six distinct recurrent groups and nine radiolarian assemblages in the combined data set of 120 samples; this extended sample coverage has led to several re-interpretations of the oceanographic significance of the radiolarian distribution patterns. Assemblage boundaries closely reflect the presence of major oceanographic fronts and surface currents including the South Equatorial Divergence, Subtropical Gyre, Subtropical Convergence, and Antarctic Convergence. At least four major aspects of the assemblages in the eastern transect are notably different from those in the western transect, leading to a marked east-west asymmetry in faunal distribution patterns across the Indian Ocean. The assemblage formerly associated with strong upwelling near the Arabian Peninsula is present throughout the Bay of Bengal as well, and is interpreted to reflect high salinity and low oxygen in the subsurface waters of the Indian Ocean north of the Equator. A new assemblage has been identified associated with the westward-flowing Pacific water into the eastern Indian Ocean in low latitudes, and may be a potential stratigraphic and paleoclimatic marker for times of low sea level when this westward near-surface flow was shut off (i.e., glacial maxima). An extensive region in the core of the subtropical gyre between 25°S and 35°S is relatively barren of Radiolaria, yet is marked by a characteristic assemblage distributed asymmetrically, perhaps reflecting the lack of a strong boundary current off the west coast of Australia. Assemblage boundaries in the vicinity of the eastward circumpolar flow are not strictly zonal, and may indicate significant deviations from the mean eastward flow as a necessary condition for conservation of potential vorticity when the flow encounters topographic irregularities.     

Phylogenetic relationships and evolutionary patterns of the order Collodaria (Radiolaria)

Collodaria are the only group of Radiolaria that has a colonial lifestyle. This group is potentially the most important plankton in the oligotrophic ocean because of its large biomass and the high primary productivity associated with the numerous symbionts inside a cell or colony. The evolution of Collodaria could thus be related to the changes in paleo-productivity that have affected organic carbon fixation in the oligotrophic ocean. However, the fossil record of Collodaria is insufficient to trace their abundance through geological time, because most collodarians do not have silicified shells. Recently, molecular phylogeny based on nuclear small sub-unit ribosomal DNA (SSU rDNA) confirmed Collodaria to be one of five orders of Radiolaria, though the relationship among collodarians is still unresolved because of inadequate taxonomic sampling. Our phylogenetic analysis has revealed four novel collodarian sequences, on the basis of which collodarians can be divided into four clades that correspond to taxonomic grouping at the family level: Thalassicollidae, Collozoidae, Collosphaeridae, and Collophidae. Comparison of the results of our phylogenetic analyses with the morphological characteristics of each collodarian family suggests that the first ancestral collodarians had a solitary lifestyle and left no silica deposits. The timing of events estimated from molecular divergence calculations indicates that naked collodarian lineages first appeared around 45.6 million years (Ma) ago, coincident with the diversification of diatoms in the pelagic oceans. Colonial collodarians appeared after the formation of the present ocean circulation system and the development of oligotrophic conditions in the equatorial Pacific (ca. 33.4 Ma ago). The divergence of colonial collodarians probably caused a shift in the efficiency of primary production during this period.     

Fine Structure of Yellow-Brown Symbionts (Prymnesiida) in Solitary Radiolaria and Their Comparison with Similar Acantharian Symbionts1

Yellow-brown, algal symbionts varying in diameter from approximately 5 μ m to 20 μ m, associated with solitary Radiolaria with spongiose skeletons (i.e. Spongodrymus sp.), exhibit fine structural features resembling the Prymnesiida (botanical class, Prymnesiophyceae). A large central vacuole is surrounded by a thin layer of cytoplasm containing plastids with lamellae composed of three thylakoids and granular pyrenoids with internal tubules immersed between the thylakoids. The pyrenoids lack internal thylakoid membranes. The nucleus is surrounded by a dilated cisterna of the nuclear envelope that also encloses the plastids and gives rise to saccules of the endoplasmic reticulum. The algal symbionts appear coccoid; hence no flagella nor surface scales were observed. The symbiont fine structure is compared to similar yellow-brown symbionts associated with Acantharia. Thus far, three kinds of algal symbionts have been observed to be associated with solitary Radiolaria: dinoflagellate, prasinomonad, and this apparent prymnesiomonad.     

Worldwide Distribution Patterns of the Planktonic Shelled Protists Radiolaria (Polycystina) and Foraminifera: Similarities and Contrasts

Paleontological Journal - Planktonic Foraminifera and Polycystina (Radiolaria) depict roughly similar—but not identical—worldwide distribution patterns. Discrepancies affect both cold-...     

苏皖地区早志留世坟头组腹足类

记述苏皖地区坟头组腹足类１１属１２种,其中Ｕｍｂｏｎｅｌｌｉｎａ ｃｆ．ｇｌｏｂｕｌｏｓａ Ｙｕ,Ｒａｐｈｉｓｔｏｍｉｎａ ｒｈｏｍｂｉｓｔｏｍａ Ｙｕ,Ｔｒｏｃｈｏｎｅｍａ ｃｆ．ｆｒａｇｉｌｅ Ｕｌｒｉｃｈ ｅｔ Ｓｃｏｆｉｅｌｄ常见于西南地区早志留世秀山组、上翁项群及石牛栏组。坟头组上段所产的三叶虫Ｃｏｒｏｎｃｅｐｈａｌｕｓ,Ｋａｉｌｉａ;头足类Ｓｉｃｈｕａｎｏｃｅｒａｓ;腕足类Ｓａｌｏｐｉ     

Comparisons of the Fungal and Protistan Communities among Different Marine Sponge Holobionts by Pyrosequencing

To date, the knowledge of eukaryotic communities associated with sponges remains limited compared with prokaryotic communities. In a manner similar to prokaryotes, it could be hypothesized that sponge holobionts have phylogenetically diverse eukaryotic symbionts, and the eukaryotic community structures in different sponge holobionts were probably different. In order to test this hypothesis, the communities of eukaryota associated with 11 species of South China Sea sponges were compared with the V4 region of 18S ribosomal ribonucleic acid gene using 454 pyrosequencing. Consequently, 135 and 721 unique operational taxonomic units (OTUs) of fungi and protists were obtained at 97 % sequence similarity, respectively. These sequences were assigned to 2 phyla of fungi (Ascomycota and Basidiomycota) and 9 phyla of protists including 5 algal phyla (Chlorophyta, Haptophyta, Streptophyta, Rhodophyta, and Stramenopiles) and 4 protozoal phyla (Alveolata, Cercozoa, Haplosporidia, and Radiolaria) including 47 orders (12 fungi, 35 protists). Entorrhizales of fungi and 18 orders of protists were detected in marine sponges for the first time. Particularly, Tilletiales of fungi and Chlorocystidales of protists were detected for the first time in marine habitats. Though Ascomycota, Alveolata, and Radiolaria were detected in all the 11 sponge species, sponge holobionts have different fungi and protistan communities according to OTU comparison and principal component analysis at the order level. This study provided the first insights into the fungal and protistan communities associated with different marine sponge holobionts using pyrosequencing, thus further extending the knowledge on sponge-associated eukaryotic diversity.     

Small-subunit ribosomal RNA gene sequences of Phaeodarea challenge the monophyly of Haeckel's Radiolaria

In his grand monograph of Radiolaria, Ernst Haeckel originally included Phaeodarea together with Acantharea and Polycystinea, all three taxa characterized by the presence of a central capsule and the possession of axopodia. Cytological and ultrastructural studies, however, questioned the monophyly of Radiolaria, suggesting an independent evolutionary origin of the three taxa, and the first molecular data on Acantharea and Polycystinea brought controversial results. To test further the monophyly of Radiolaria, we sequenced the complete small subunit ribosomal RNA gene of three phaeodarians and three polycystines. Our analyses reveal that phaeodarians clearly branch among the recently described phylum Cercozoa, separately from Acantharea and Polycystinea. This result enhances the morphological variability within the phylum Cercozoa, which already contains very heterogeneous groups of protists. Our study also confirms the common origin of Acantharea and Polycystinea, which form a sister-group to the Cercozoa, and allows a phylogenetic reinterpretation of the morphological features of the three radiolarian groups.     

Trimeridianellidae nov. fam., a Triassic spumellarian radiolarian family with simple initial skeleton and pyloniacean mode of growth

Based on several samples of Middle and Late Triassic age, the authors describe a new family of spumellarian Radiolaria – Trimeridianellidae Dumitrica and Tekin, characterized by a three-fold symmetry, a first shell of triangular prism type with 6 primary rays originated at the edges of two bases of the prism, or 3 meridian arches with 3 equatorial rays, and growth of pyloniacean type. The family comprises 4 monospecific new genera (Enneacladus Dumitrica, Endoprisma Dumitrica, Trimeridianella Dumitrica and Tekin, and Tristylopyle Dumitrica), 4 new species and one left in open nomenclature. In spite of their spotty occurrences and low diversity, the authors attempt to trace the evolution of the family, which is considered to be the result of heterochrony in ontogenetic growth, mostly of paedomorphic type. The family seems to be related to the Middle Triassic family Patruliidae Dumitrica with which it shares in common the simple microsphere with 6 primary rays and the pyloniacean mode of growth.