Ecological aspects of a silicified bivalve fauna from the Silurian of Gotland

The silicified Wenlockian (Silurian) bivalve fauna from MÖllbos, Gotland, is part of a life assemblage. The vast number of shells show unusual phenomena, e.g. shell repair, pearl and tumour formation, etc. A number of shells contain epibionts and bored, round holes. Presumptive predators of the bivalve community are discussed. Size-frequency distribution of the two most abundant species possibly reflects age classes. The fauna, comprising eleven species, is dominated by deposit-feeders (90 %). They exhibit niche diversification, including at least three different feeding levels within the sediment.     

Palaeozoic calcareous plankton: evidence from the Silurian of Gotland

In order to investigate whether or not equivalents to modern calcareous plankton existed in Palaeozoic times, extremely well-preserved successions have to be investigated. The Silurian strata on Gotland (Sweden) are exceptionally well preserved because they have not experienced deep burial conditions and tectonic stress, due to their position on the stable Baltic Shield. Scanning electron microscope investigations of polished, slightly etched rock surfaces revealed the presence of a variety of calcareous micro- and nannofossils. Among these organisms, many can be termed 'calcispheres' (60–100 µm in diameter), whereas others due to their size range (nannofossils) are informally termed herein as 'nannospheres' (10–25 µm in diameter). The systematic attribution of these fossils is unknown ( incertae sedis ). Mesozoic calcispheres are usually attributed to calcareous cysts of dinoflagellates following comparisons of ultrastructure with modern species. The abundance of different calcispheres in the Silurian sediments of Gotland and the observation that many of the calcareous microfossils occur in distinctly different facies as well as their spherical shape indicate that they probably belong to calcareous micro- and nannoplankton. We therefore conclude that calcareous plankton most probably existed already during the Palaeozoic, but can only be observed under conditions of exceptional preservation.     

Enigmatic polychaete jaws from the Silurian of Gotland, Sweden

The jaws of the new polychaetaspid polychaete, Oenonites? honki, from the Silurian of Gotland, Sweden, differ from most Palaeozoic polychaete jaws. They exhibit enigmatic microstructural features in that they appear rough and give a corroded, or weathered impression. The altered microstructure of the jaws suggests a jaw chemistry and/or composition differing in some way from that of the co‐occurring polychaete taxa. The jaws appear to have limited preservational potential and/or were particularly susceptible to secondary processes, resulting in microstructural alteration. Commonly, a row of distinct pits occurs on the outer face, especially of the first right maxillae (MIr). Because these pits are interpreted as associated with the dentary, the term ‘denticle marks’ is suggested. The pits may be the result of primary or secondary physical wear, or, more probably, secondary chemical alteration of localized mineral deposits. The primary function of such mineral deposits was to harden those parts of the surface that were exposed to great stress. The restricted occurrence of O.? honki, coupled with occasional increases in abundance (especially in the Halla Formation, unit b), indicates a preference for shallow marine, high‐energy environments, particularly in reefal pockets with calcilutitic sediments. Highest frequency coincides with faunas characteristically containing a few labidognath species also displaying high frequencies.     

Radial perforations in crinoid stems from the Silurian of Gotland

Radiating intracolumnal canals are a characteristic feature of large (diameter 10 mm or more) crinoid stems from the Silurian of Gotland. They are found in nodals as well as in internodals where the columnal height exceeds one millimetre. They were formed secondarily in the median and distal portions of crinoid stems with pseudocirriferous holdfasts. Intercolumnal canals are found in the distal parts of stems with true cirri regardless of the size of the stem. It is suggested that these canals played an important role in crinoid physiology. The crinoids are believed to have sustained a large proportion of their tissues through cutaneous digestion and uptake of dissolved substances from the surrounding sea water. The intra- and intercolumnal canals increased the surface of the axial canal in relation to volume. They provided a connection between the axial canal and the surrounding sea water, thus facilitating nutrient transport to the tissues.     

Large dwellers of the Silurian Halysites biostrome: rhizosessile life strategies of cystiphyllid rugose corals from the Llandovery of Gotland

An exceptionally well‐preserved, unusual biostrome composed of the framebuilding cateniform tabulate coral Halysites catenularius (Linnaeus, 1767) bears an assemblage of the relatively large solitary cystiphyllid rugosan Cystiphyllum visbyense Wedekind, 1927. The corallites of solitary cystiphyllids are embedded within the ranks of the halysitid colonies, which developed on a soft, muddy substrate and in relatively turbid water. The cystiphyllid larvae successively settled mostly on the ranks of halysitid colonies and on colonies of the tiny phaceloid rugose coral Nanophyllum ramosum Johannessen, 1995, whereas calice‐in‐calice recruitment was not successful for these cystiphyllid corals. Further growth of C. visbyense was supported by rhizoid structures, which were most frequently developed on the cardinal (convex) side of the corallite. The process of formation of the rhizoid structures is here discussed and explained in detail, showing that they were formed by the extension of the basal ectodermal tissue of the polyp. The cystiphyllids, which settled on the walls of living corallites of halysitid colonies, used sweeper tentacles to kill the smaller polyps of the colony to maintain the space around them and expand. Hence, they ultimately used the halysitid colonies only as a hard substrate to stabilize their position on the soft muddy sediment.     

FTIR characterisation of the chemical composition of Silurian miospores (cryptospores and trilete spores) from Gotland, Sweden

To better understand the biological affinities of cryptospores, micro-FTIR (Fourier transform infrared) spectroscopy analysis has been carried out on isolated specimens from the Upper Silurian of Gotland. The geobiochemical results have been compared to spectra of trilete spores, chitinozoans and leiospheres from the same sample. The palynomorphs are all very well preserved as attested by their pale yellow to orange colour indicative of a low thermal maturity. Micro-FTIR spectroscopy indicates that cryptospores display very similar spectra to those of the trilete spores, which are composed of sporopollenin characterised by absorption bands from aliphatic C-H in methylene (CH₂) and methyl (CH₃) groups, aromatic (C=C and C-H) groups and C=O groups of carboxylic acids. The sporopollenin composition of the cryptospore wall observed here is additional evidence demonstrating the embryophytic affinity of the cryptospores. In addition, several variations in other bands in the spectra of the different miospore morphospecies are evidenced and may be linked to their biological affinity or palaeoecological history.     

Development of facies and C/O-isotopes in transects through the Ludlow of Gotland: Evidence for global and local influences on a shallow-marine environment

Summary The Silurian of Gotland is characterized by repeated changes in depositional facies development. The deposition of uniform sequences of micritic limestones and marls was interrupted four times by the growth of reef complexes and the formation of expanded carbonate platforms. Coinciding with these, often abrupt, facies changes extinction events occurred which predominantly affected nektonic and planktonic organisms. Ratios of carbon- and oxygen-isotopes covary with the facies development. Periods in which the deposition of limestonemarl alternations prevailed are characterized by relatively low C- and O-isotope values. During periods of enhanced reef growth isotope values are high. For these changes,Bickert et al. (1997) assume climatic changes between humid “H-periods”, with estuarine circulation systems and cutrophic surface waters with decreased salinity in marginal seas, and arid “A-periods”, with an antiestuarine circulation and oligotrophic, stronger saline surface waters. In order to separate local and regional influences on the isotopic development from the global trend, the interactions between facies formation and isotope record have to be clarified. For this purpose, the patterns of isotope values in the upper part of the Silurian sequence on Gotland (upper Wenlock —upper Ludlow) has been determined and stratigraphically correlated along four transects through different facies areas. Facies formation during this time interval was investigated by differentiation and mapping of twelve facies complexes in the southern part of Gotland. These include shelf areas, reef complexes with patch reefs and biostromes, backreef facies, and marginal-marine deposits. The good correspondence between the carbon-isotope records of the four transects suggests that local environmental conditions in the different facies areas did not influence the δ¹³C values. Therefore, a supra-regional or even global mechanism for the C-isotope variations is likely. In contrast to carbon istopes, the oxygen-isotope values of the four transects generally show parallel trends, but higher variabilities and in parts distinctly deviating developments with a trend to more negative values. These are interpreted as an effect of local warming in small shallow-water areas which developed during arid periods in reef complexes and backreef areas. The boundaries between A-periods and H-periods, as defined by δ¹³C values, which are interpreted as isochrones, can be mapped. From the upper Homerian to the Pridolian six parastratigraphic isotope zones are defined which only partly match the stratigraphic division ofHede (1942, 1960). The isotope stratigraphy results in an improved correlation between the shallow and marginal-marine areas in the eastern part of Gotland and the uniform shelf areas at the west coast of the island. Furthermore, a detailed relationship between the development of carbon and oxygen isotope ratios, the carbonate facies formation, and the succession of palaeontological events could be observed. At the transition from H-periods to A-periods, major extinction events occurred prior to the first increase of δ¹³C and δ¹⁸O values. Extinction events affected conodonts, graptolites, acritarchs, chitinozoans, and vertebrates and resulted in impoverished nektonic and planktonic communities. The reef-building benthos was less affected. Parallel to a first slight increase of isotope values, facies began to change, and reefs developed in suitable locations. The subsequent rapid increase of C- and O-isotope values occurred contemporarily with strong facies changes and a short-term drop of sea-level. Oligotrophic conditions in the later stages of A-periods led to strong reef growth and to an expansion of carbonate platforms. The transitions from A-periods to H-periods were more gradual. The δ¹³C values decreased slowly, but reef growth continued. Later the reefs retreated and were covered by the prograding depositional facies of shelf areas. The diversity of planktonic and nektonic communities increased again. The close relationship between facies formation, palaeontological events and isotope records in the Silurian suggests common steering mechanisms but gives no indication of the causes for the repeated extincion events related to H-period/A-period transitions. Especially the observation, that strong extinctions occurred prior to changes of isotope values and facies, points to causes that left no signals in the geological record. Hypothetical causes like collapse of trophical nets, anoxias, or cooling events are not evident in the sediment record or do not fit into the regular succession of period transitions.     

Cementing strophomenide brachiopods from the Silurian of Gotland (Sweden): Morphology and life habits

Dorsal valves of the cementing strophomenide brachiopods Leptaenoidea silurica Hedström and Liljevallia gotlandica Hedström are described for the first time, and it is shown that both these species could also live ambitopically. The lower Wenlock Scamnomena rugata (Lindström) represents young individuals of the ambitopic variant of Leptaenoidea silurica, and is placed in synonymy, resulting in the valid name for the taxon being Leptaenoidea rugata. The range of this species now spans the whole Wenlock, from the upper Visby Formation to the Klinteberg Formation, and possibly even into the Ludlow. Ambitopic gerontic specimens of L. rugata develop very thick shells, in which the ventral valves have strong curvature, and become deeper not by geniculation but by successive mantle retractions and subsequent re-growth, in a way similar to that of atrypides. This shape was probably an adaptation to “floating” on softer substrates. The thickened gerontic dorsal valves have well-developed lophophoral support, showing the shape of the lophophore, which comprises two branches that curve inwards and then backwards; the lophophore was probably ptycholophous and similar to that in living members of the Thecideidina. Ambitopic specimens of Liljevallia could grow to a much larger size than cementing forms, where the dorsal valves have very large, posterior-facing cardinal process lobes and deeply impressed muscle fields and anterior scars. The presence of a ventral process and long, posteroventrally elongated cardinal process lobes, and the absence of dental plates reveals that Liljevallia was probably an early member of the Douvillinidae and is thus removed from the Leptaenoideidae.     

Gonad pouches in a new clam-like monoplacophoran from the Silurian of Sweden

Beyrichidiscus fecundatus n. gen. n. sp. is described from the Upper Silurian of Gotland, Sweden. The minute, isostrophically coiled mollusc exhibits profound allometry and is considered to have been a monoplacophoran on the basis of functional interpretation of apertural structures. A clam-like, semi-infaunal mode of life is suggested. A pair of prominent lateral swellings in the adult shell are interpreted as reflecting the location of the gonads.     

Coralline red algae from the Silurian of Gotland indicate that the order Corallinales (Corallinophycidae,Rhodophyta) is much older than previously thought

Aguirrea fluegelii gen. et sp. nov. (Corallinales, Corallinophycidae, Rhodophyta) is described from the mid‐Silurian of Gotland Island, Sweden (Högklint Formation, lower Wenlock). The holotype is of dimerous construction and includes a uniporate conceptacle with a sporangium, thus providing evidence that taxa of the Corallinales/Corallinaceae existed at least 300 million years earlier than previously documented. Aguirrea fluegelii cannot be unequivocally placed in any of seven currently recognized lineages/subfamilies/groups of the Corallinaceae as not all diagnostic characters are preserved, and thus is accorded incertae sedis status within the family Corallinaceae and order Corallinales. Extant evolutionary history studies of Corallinophycidae involving molecular clocks now require updating using new calibration points to take account of the much earlier unequivocal mid‐Silurian record of uniporate conceptacle‐bearing taxa of Corallinales/Corallinaceae as well as the parallel record of Graticula, a genus attributed to the Sporolithales.     

The fish swimming trace Undichna unisulca from the Silurian of Sweden: probably the oldest vertebrate locomotion trace fossil

The fish swimming trace Undichna unisulca is reported from a sandstone block collected from the Upper Silurian (Ludlow) Burgsvik Formation of Gotland, Sweden. It represents the oldest record of a vertebrate trace (apart from coprolites), predating previous finds from the Lower Devonian by at least 10 Ma. A thelodont or acanthodian fish may have produced the sinusoidal trails with the aid of their caudal or anal fins while browsing slowly over the sediment whilst searching for food.     

Anatomy and Morphology of Pinnatiramosus,a New Plant from the Middle Silurian (Wenlockian) of China

A new genus and species Pinnatiramosus qianensis is described from the Xiushan Formation of Middle Silurian (Wenlockian)in the north of Guizhou, China. This plant consists of a prostrate axis and erect pinnate branching system. Conductin gbundle is comprised of tubular cells with scalariform or alternate simple pits. Pinnatiramosus gen. nov. Diagnosis: Plant cylindrical, differentiated into erect branches and prostrate axes; erect branches much branched, consisting of regular or irregular pinnate lateral branches; laterals opposite or alternate, with basal parts constricted and acute or blunt apices. Conducting bundle comprised of longitudinally aligned tubes with secondary thickening. Reproductive structures nor seen. Derivation of name: Pinnatus (Latin)=pinnate and ramosus (Latin)=ramose, referred to the external morphology of the plant. Pinnatiramosus qianensis sp. nov. Diagnosis: Characters described as the genus. Prostrate axes at least 400 mm in length and 3–6 mm in diameter, produced erect longer branches and downward shorter branches; erect branches up to 200 mm long and vary from 1.0 to 2.5mm in diameter, branched at least six orders, with lateral branches unequally developed, long laterals scattered among short ones; lateral branches oppositely or alternately arranged on main axis, 1–3 mm: apart; ultimate bran- ches 0.4–0.8 mm in diameter, with acute or blunt apex; borne at angles of 40–70˚ with main axis. Conducting bundle ca. 1/4 of the axis diameter, composed of tubular elements with secondary thickening; tubes range from 15–54μm in diameter, with blunt end wall; secondary wall averages 4.86 μm in thickness, ranging 2.5–6.6 μm, with scalariform and alternate pits. Derivation of name: Qian is the abbreviation for Guizhou province from where the plants are found. In this paper, is made the comparison of this new plant with fossil and living algae as well as early vascular plants on the basis of its external morphology and internal structure According to the comparison, Pinnatiramosus belongs to one of specialized plants with tracheophyte- like conducting tissue. Some interesting opinions are here provided as follows: (i) Silurian is, an important age of plant evolution. During this period certainly coexist not only various algae and undoubted vascular plants but also a group of interesting plants that were just immigrating from aquatic to terrestrial environments. (ii) The transmigration of algae from water to land occurred along several different evolutionary lines. Accompanying changes of these algae on morphology and anatomy were adapted to terrestrial environments. (iii) Pinnatiramosus represents a group of new plants with remarkably nontracheophyte morphology but tracheophyte- like anatomy. (iv) The tracheid-like tubes, macerated out of Silurian rocks, derived more probably from non-vascular plants such as Pinnatiramosus, Prototaxitesor Nematothallus than from vascular plants.     

Cardiolinka bohemica (Barrande, 1881) – A first representative of the Late Silurian Bohemian type Bivalvia fauna from the northern Arabian Plate,Southeast Turkey

The Rheic Ocean was a major oceanic domain between Baltica, Laurentia, Perunica and Gondwana in Ordovician-Silurian times. The cosmopolitan nepiomorphian bivalves Praecardioidei Newell, 1965 and Antipleuroidei Kříž, 2007 are characteristic of the Silurian of Perunica, peri-Gondwana, and Baltica, and occur also in Laurentia and Siberia. The Bohemian-type bivalve Cardiolinka Kříž, 1981 (Nepiomorphia Kříž, 2007, Cardiolidae Hoernes, 1884), from the Late Silurian of the Bahar-1 well core, has been found for the first time in southeastern Turkey. The strata containing the species Cardiolinka bohemica (Barrande, 1881) occur in the middle part of the Dadaş Formation in the interior Petroleum District X-Siirt of the northern parts of the Arabian Plate. The cosmopolitan species C. bohemica was until now known from the Latest Ludlow to Pridoli of the Prague Basin, France, Carnic Alps, Sardinia, East European Platform (Poland), eastern Serbia, Moesian Platform, and Arctic Canada. The new surprising subsurface data on C. bohemica in Diyarbakır-Bismil area (southeastern Turkey) therefore represent another piece of evidence in favour of strong faunistic affinity between Perunica, peri-Gondwanan Europe and the northern Gondwana margin.     

Origin of the Retiolitidae: insights from a new graptolite genus from the early Silurian of Arctic Canada

Isolated specimens of Hercograptus introversus n. gen., n. sp. show features characteristic of the Retiolitidae, such as partial periderm reduction, and extended ancora lists and a reticulum that are attached to the thecal margins, on a rhabdosome that, in most other respects, resembles Pseudorthograptus. This newly discovered graptolite provides support for the hypothesis that Pseudoretiolites is the first-evolved retiolitid, since they share a similar ancora type and unique thecal style. It is also clear that the suite of features that normally distinguish the Retiolitidae did not all evolve simultaneously. It is proposed that development of a complete thecal framework of lists, permitting complete periderm reduction, should be the character used to distinguish the Retiolidae from the Petalolithidae. Unusual apertural modifications, such as strong introversion, lateral lappets, and a short, free dorsal wall suggest that Hercograptus may be an offshoot of the lineage leading from Pseudorthograptus to Pseudoretiolites.     

Phaenocompsopogon pustulatus n.gen.n. sp., a calcareous alga from the lacustrine rotliegend of the Saar-Nahe Basin (SW-Germany)

Summary Phaenocompsopogon pustulatus n. gen. n. sp. is a calcareous freshwater alga, probably of rhodophycean affinity. The fossils are mainly known from one locality in the Lower Permian of the Saar-Nahe Basin. The algal remains form a packstone in the Reckweilerhof-Bank of the Altenglan Formation. The simple thallus branches irregularly y-shaped and is covered with abundant pustules. An axial canal is characteristic, as are distinct cell features of an inner and outer cortex surrounding a structureless medulla. Most fossils are silicified and often three-dimensionally preserved. The algae lived in a wave-dominated environment, probably in offshore shallow water. The limited occurrence suggests special ecological restrictions.     

Paleoecologic,temporal, and spatial analysis of early Silurian Reefs of the Chicotte Formation,Anticosti Island,Quebec, Canada

Summary Reefs of the Lower Silurian Chicotte Formation are the largest and most faunally diverse known on Anticosti Island, Quebec. They reach up to 25 m in thickness and 250 m in diameter and are present predominantly at two intervals, forming a lower and upper reef cluster. Remnants of bioherms are represented on the present-day wave-cut terrace as 60 to 100 m diameter, subcircular erosional depressions known as Philip structures or as outcrop. The bioherms were relatively low structures, with approximately 3 to 5 m maximum synoptic relief, some of which developed on hardgrounds and possible paleokarst surfaces of crinoidal wackestone and packstone. Dominant skeletal framework builders and sediment producers within all of the reefs are laminar to low domical stromatoporoids, colonial cerioid and fasciculate rugose corals, colonial tabulate corals, and cryptostome bryozoans. Vertical zonation of reef biota is evident within well-exposed reefs of the lower reef cluster. Three to four stages are recognizable:1) a low-diversity tabulate coral-dominatedpioneering community including large tabulate coral colonies (halysitids and favositids), and few stromatoporoids (clathrodictyids, ecclimadictyids), fasciculate rugosans, large generally monotypic stalked crinoids, and shelly benthos (brachiopods, few ostracodes and trilobites);2) an intermediate- to high-diversity, mixed tabulate coral-stromatoporoid-dominatedreef-core community;3) a slightly lower diversity stromatoporoid-tabulate coral-dominatedclimax community with laminar coenitids and alveolitids; and,4) in a few localities, a capping, low-diversity tabulatecoral-dominated (alveolitid and coenitid), and stromatoporoid-bearing community comprising laminar forms. Amelioration of Early Silurian climates, following Late Ordovician glaciation, allowed gradual reestablishment of extensive shallow-water reef growth, by mainly new and increasingly diverse genera and species of metazoans. Reef development within the Chicotte Formation coincided with global, widespread development of latest Llandovery and earliest Wenlock reefs in subtropical to tropical areas. Chicotte reefs have broad characteristics, in terms of overall biotic composition, vertical successions recognized, and paleogeographic setting, similar to those of equivalent and slightly younger age from intracratonic settings in Baltica (Gotland, Sweden and Estonia) and central and northern Laurentia (Midcontinent, U.S.A.; Hudson Bay, Canada; and North Greenland, Denmark).     

Aerobic nitrogen fixation is confined to a subset of cells in the non-heterocystous cyanobacterium Symploca PCC 8002

Symploca PCC 8002 Kützing is a filamentous cyanobacterium that lacks the specialized cells, known as heterocysts, that protect nitrogenase from O₂ in most aerobic N₂-fixing cyanobacteria. Nevertheless, Symploca is able to carry out N₂ fixation in the light under aerobic conditions. When cultures were grown under light/dark cycles, nitrogenase activity commenced and increased in the light phase and declined towards zero in the dark. Immunolocalization of dinitrogenase reductase in sectioned Symploca trichomes showed that the enzyme was present only in 9% of the cells. These cells lacked any obvious mechanical protection against atmospheric O₂ and their ultrastructural characteristics were similar to those of cells that did not contain any dinitrogenase reductase. The nitrogenase-containing cells possessed carboxysomes that were rich in ribulose-1,5-bisphosphate carboxylase/oxygenase and phycoerythrin, a light harvesting pigment of PS II. This indicates that these cells had a capacity for both N₂ fixation and photosynthesis. The significance of the localization pattern for dinitrogenase reductase is discussed in the context of N₂ fixation in Symploca PCC 8002.     

Mitochondrial genome of the colorless green alga Polytomella capuana: a linear molecule with an unprecedented GC content

One common observation concerning mitochondrial genomes is that they have a low guanine and cytosine content (GC content); of the complete mitochondrial genome sequences currently available at the National Center for Biotechnology Information (NCBI) (July 2007), the GC content ranges from 13.3% to 53.2% and has an average value of 38%. Here, we present the GC-rich mitochondrial genome (57% GC) of the colorless green alga Polytomella capuana. The disproportion of GC among the different regions of the P. capuana mitochondrial DNA (mtDNA) suggests that a neutral process is responsible for the GC bias. We propose that a biased gene conversion mechanism resulted in the GC-rich state of the P. capuana mtDNA. In addition, our analysis indicates that the P. capuana mitochondrial genome is a single 13-kb linear molecule with telomeres, which have a closed (hairpin-loop) conformation: a novel terminal structure among described linear green-algal mtDNAs. Furthermore, using a series of GC-rich inverted repeats found within the P. capuana mitochondrial genome, we describe recombination-based scenarios of how intact linear mtDNA conformations can be converted into the fragmented forms found in other Polytomella taxa.     

Ectomycorrhizal fungi of the Seychelles: diversity patterns and host shifts from the native Vateriopsis seychellarum (Dipterocarpaceae) and Intsia bijuga (Caesalpiniaceae) to the introduced Eucalyptus robusta (Myrtaceae), but not Pinus caribea (Pinaceae)

Ectomycorrhizal (ECM) fungi form highly diverse communities in temperate forests, but little is known about their community ecology in tropical ecosystems. Using anatomotyping and rDNA sequencing, ECM fungi were identified on root tips of the introduced Eucalyptus robusta and Pinus caribea as well as the endemic Vateriopsis seychellarum and indigenous Intsia bijuga in the Seychelles. Sequencing revealed 30 species of ECM fungi on root tips of V. seychellarum and I. bijuga, with three species overlapping. Eucalyptus robusta shared five of these taxa, whereas P. caribea hosted three unique species of ECM fungi that were likely cointroduced with containerized seedlings. The thelephoroid (including the anamorphic genus Riessiella), euagaric, boletoid and hymenochaetoid clades of basidiomycetes dominated the ECM fungal community of native trees. Two species of Annulatascaceae (Sordariales, Ascomycota) were identified and described as ECM symbionts of V. seychellarum. The low diversity of native ECM fungi is attributed to deforestation and long-term isolation of the Seychelles. Native ECM fungi associate with exotic eucalypts, whereas cointroduced ECM fungi persist in pine plantations for decades.     

Human fibrinogen gel formed by the action of a cell surface polysaccharide obtained from a Staphylococcus

An alkali-stable polysaccharide (called compact-colony forming active substance; substance 1) obtained from the cell surface of a strain of Staphylococcus epidermidis caused gel formation of human fibronogen, with no release of fibrinopeptides. Substance 1 possessed neither esterase nor caseinolytic activities; no inhibition of gel formation was shown by dinitrofluorophosphate. Heparin and galactose prevented gel formation of fibrinogen with substance 1. With the addition of early- and late-fibrinogen or fibrin degradation products into the fibrinogen sample, no prolongation of the gel formation time was observed. This substance is, therefore, assumed to nonenzymatically induce gel formation with fibrinogen, a process resembling paracoagulation.