Scotia Arc Acari: antiquity and origin

The Scotia Arc comprises South Georgia, South Sandwich, South Orkney and South Shetland Islands together with the Antarctic Peninsula. Free-living Acari of the Scotia Arc contain immigrant and endemic elements. Transport of immigrant species to and within the Maritime Antarctic has been via Holocene storms and ocean currents. Most immigrants are Gamasida, Oribatida and Acaridida while Actinedida dominate the endemic element. Immigrant species on South Georgia share common 'sub-Antarctic' affinities with South Indian and, to a lesser extent, South Pacific Ocean island faunas. In contrast, immigrants to the rest of the Scotia Arc and Bouvetøya on the mid-Atlantic Ridge, form a robust 'Maritime Antarctic' Province group. The endemic component is of largely Tertiary origin and, like that of Continental Antarctica, dominated by a few cosmopolitan families and genera of Actinedida. There are no bona fide pan-Antarctic species and little evidence that Continental and Maritime Antarctic faunas have a common ancestry, indeed the Continental endemic fauna is entirely montane while that of Maritime Antarctica is coastal. The presence of common Maritime Antarctic/South Pacific island genera corroborate the Antarctic Peninsula as being derived from a South Pacific island archipelago which collided with Continental Antarctica during the Tertiary period.     

Assessment of the habitat conditions of a rare and endangered inland saline wetland community with Bolboschoenus maritimus (L.) Palla dominance in Southeastern Europe: the effects of physical–chemical water and soil properties

Wetlands Ecology and Management - Continental inland saline wetlands are among the most endangered habitats in Europe. In the Danube-Tisza-Danube canal network (Serbia, Southeastern Europe), which...     

Historical biogeography and ecology of a Continental Antarctic mite genus, Maudheimia (Acari, Oribatida): evidence for a Gondwanan origin and Pliocene-Pleistocene speciation

Of the eight genera (30 species) of extant Acari in Continental (= East) Antarctica, the genus Maudheimia Dalenius & Wilson, 1958 (Oribatida; Maudheimiidae) is uniquely endemic. A Gondwanan origin is proposed for the genus based on antiquity, inferred from endemism, a widespread distribution throughout Continental Antarctica and a limited dispersal capacity. Adaptation for a high montane epilithic existence, a necessity for the origination and long-term persistence in Antarctica, is inferred from the life history, physiology and ecology of Maudheimia. Phylogenetic analysis placed all four Maudheimia species in a single (generic) clade with the following structure (M. pelronia Wallwork, 1962 (M. tanngardenensis Coctzee, 1997 (M. manhalli Coetzee, 1997 (M. wilsoni Dalenius & Wilson, 1958)))). Geographical distributions of the Maudheimia species, in relation to their phylogenetic relationships, support the hypothesis that post-Gondwanan speciation occurred as a consequence of isolation during glaciation of Antarctica.     

Does distance from the sea affect a soil microarthropod community?

Coastal sand dunes are dynamic ecosystems characterized by strong abiotic gradients from the seashore inland. Due to significant differences in the abiotic parameters in such an environment, there is great interest in biotic adaptation in these habitats. The aim of the present study, which was conducted in the northern Sharon sand-dune area of Israel, was to illustrate the spatial changes of a soil microarthropod community along a gradient from the seashore inland. Soil samples were collected from the 0–10 cm depth at five locations at different distances, from the seashore inland. Samples were taken from the bare open spaces during the wet winter and dry summer seasons. The soil microarthropod community exhibited dependence both on seasonality and sampling location across the gradient. The community was more abundant during the wet winter seasons, with an increasing trend from the shore inland, while during the dry summers, such a trend was not observed and community density was lower. The dominant groups within soil Acari were Prostigmata and Endeostigmata, groups known to have many representatives with adaptation to xeric or psammic environments. In addition, mite diversity tended to be higher at the more distant locations from the seashore, and lower at the closer locations, a trend that appeared only during the wet winters. This study demonstrated the heterogeneity of a soil microarthropod community in a coastal dune field in a Mediterranean ecosystem, indicating that the gradient abiotic parameters also affect the abundance and composition of a soil microarthropod community in sand dunes.     

Endolithic microbial composition in Helliwell Hills,a newly investigated Mars-like area in Antarctica

The diversity and composition of Antarctic cryptoendolithic microbial communities in the Mars-analogue site of Helliwell Hills (Northern Victoria Land, Continental Antarctica) are investigated, for the first time, applying both culture-dependent and high-throughput sequencing approaches. The study includes all the domains of the tree of life: Eukaryotes, Bacteria and Archaea to give a complete overview of biodiversity and community structure. Furthermore, to explore the geographic distribution of endoliths throughout the Victoria Land (Continental Antarctica), we compared the fungal and bacterial community composition and structure of endolithically colonized rocks, collected in >30 sites in 10 years of Italian Antarctic Expeditions. Compared with the fungi and other eukaryotes, the prokaryotic communities were richer in species, more diverse and highly heterogeneous. Despite the diverse community compositions, shared populations were found and were dominant in all sites. Local diversification was observed and included prokaryotes as members of Alphaproteobacteria and Crenarchaeota (Archaea), the last detected for the first time in these cryptoendolithic communities. Few eukaryotes, namely lichen-forming fungal species as Lecidella grenii, were detected in Helliwell Hills only. These findings suggest that geographic distance and isolation in these remote areas may promote the establishment of peculiar locally diversified microorganisms.     

Low cyanobacterial diversity in biotopes of the Transantarctic Mountains and Shackleton Range (80-82°S), Antarctica

The evolutionary history and geographical isolation of the Antarctic continent have produced a unique environment rich in endemic organisms. In many regions of Antarctica, cyanobacteria are the dominant phototrophs in both aquatic and terrestrial ecosystems. We have used microscopic and molecular approaches to examine the cyanobacterial diversity of biotopes at two inland continental Antarctic sites (80-82°S). These are among the most southerly locations where freshwater-related ecosystems are present. The results showed a low cyanobacterial diversity, with only 3-7 operational taxonomic units (OTUs) per sample obtained by a combination of strain isolations, clone libraries and denaturing gradient gel electrophoresis based on 16S rRNA genes. One OTU was potentially endemic to Antarctica and is present in several regions of the continent. Four OTUs were shared by the samples from Forlidas Pond and the surrounding terrestrial mats. Only one OTU, but no internal transcribed spacer (ITS) sequences, was common to Forlidas Pond and Lundstr?m Lake. The ITS sequences were shown to further discriminate different genotypes within the OTUs. ITS sequences from Antarctic locations appear to be more closely related to each other than to non-Antarctic sequences. Future research in inland continental Antarctica will shed more light on the geographical distribution and evolutionary isolation of cyanobacteria in these extreme habitats.     

Belemnite battlefields

Mass accumulations of belemnite rostra ('belemnite battlefields') are common in Mesozoic sediments, and accumulations of belemnoids are also known from older rocks. Many Recent teuthid species suffer mortality immediately after spawning, and some authors have suggested that belemnite accumulations record a similar phenomenon. Conversely, it is clear that many belemnite battlefields actually formed in an environment of net sediment loss, with current alignment and winnowing. A proposed model for the production of belemnite battlefields involves five possible pathways: post-spawning mortality, catastrophic mass mortality, predation concentration, stratigraphical condensation, and resedimentation. Although accumulations that have not been reworked are rare, it is possible to recognise the generating agents of belemnite accumulations through their intrinsic features. A genetic classification of belemnite battlefields, based on the identified pathways, is tested through field examples in Britain and Antarctica, as well as through published examples. □ Belemnites, fossil accumulations, palaeoecology, Mesozoic, Antarctica, Yorkshire.     

Tertiary climatic evolution and vegetation history in the Southeast Indian Ocean region

The broad trends of climatic evolution in the Southeast Indian Ocean region during the Tertiary have become clearer with the accumulation of data from Legs 28 and 29 of the Deep Sea Drilling Project. The same events which are reflected in the deep-sea sediments clearly influenced the major continental areas of Australia and Antarctica and the vegetation which covered those regions. In this review, data relating to sea-surface temperatures, to land and sea positions, and to the extent of the Antarctic ice-cap, are used to derive climatic models for the Palaeocene to latest Miocene interval: the models are correlated with vegetation history deciphered from palynological data.For most of the Palaeocene, Australia and Antarctica were joined, and lay in high southern latitudes. Sea-surface temperatures were relatively high, and there is no evidence for Antarctic ice. The postulated atmospheric circulation patterns suggest a zone of westerly winds confined to 60–80°S, and, north of that, a wide zone of erratic circulation, with deep inland penetration of rain-bearing winds. Palynological evidence from Australia indicates rainforest in the southeast, with an extension to presently arid inland South Australia.In the Eocene, Australia and Antarctica were separated by a wide gulf; water temperatures were high — in the vicinity of 20°C on the Campbell Plateau — and evidence for Antarctic ice development is meagre. Atmospheric circulation was probably sluggish, with patterns similar to those of the Palaeocene. Vegetational data show the spread of rainforest communities across Australia from the east to the southwest, and locally, inland to central Australia. Vegetation zonation appears to have been minimal on that continent. In Antarctica, late Eocene vegetation was poorly diversified.For the Oligocene, evidence for a pronounced temperature drop is both isotopic and sedimentological, and includes the first record of ice-rafting near Antarctica. Intensification of atmospheric circulation seems likely. The vegetation records suggest lowered floristic diversity in Australia, and the persistence of vegetation, again of low diversity, in Antarctica into the late Oligocene.For the Miocene, the marine record suggests the development of a major Antarctic ice-cap; in consequence, atmospheric circulations continued to intensify. Continued northward drift of Australia meant increasing aridity in regions to the north and northwest; the south and east were watered by rain-bearing westerly systems and by embryonic Trade Winds. Vegetation data in Australia suggest rainforest cover in the southeast and on the east coast, and, in the middle Miocene, the development of grasslands in interfluvial areas in the central part of the continent. The latest Miocene was marked by an intense and sudden chilling which is clearly documented in Southern Ocean sediments. This event must have caused marked precipitation decrease in much of Australia, and may coincide with the disappearance of pollen of the Nothofagus brassi type from regions west of the Great Dividing Range, although age control of this event is poor.     

Anatomically preserved leaves of the conifer Notophytum krauselii (Podocarpaceae) from the Triassic of Antarctica

Permineralized leaves of the Triassic podocarpaceous conifer Notophytum krauselii are described from the Fremouw Formation of Antarctica. The leaves are elongate and apetiolate with 8-12 parallel veins. The adaxial epidermis consists of rows of rectangular to pentagonal cells; the abaxial epidermis is papillate. Longitudinally oriented stomata occur on both surfaces. An adaxial palisade layer is present and auxiliary sclereids are common in the mesophyll. The vascular bundles have a weakly defined sheath and are flanked by transfusion tracheids. Bundles in the basipetal area of the leaf are capped by sclerotic tissue and subtended by resin canals. These leaves are superficially similar to those of the extant podocarp genus Nageia, but probably represent a distinct acquisition of this leaf type within the Podocarpaceae. Notophytum leaves are similar to the common compression fossil Heidiphyllum elongatum and may be closely related or even conspecific. Evidence from Antarctica suggests that Heidiphyllum and the seed cone Telemachus were produced by the same plant, and may be closely related to several other early Mesozoic conifers with multiveined leaves.     

Fossil fungi with suggested affinities to the Endogonaceae from the Middle Triassic of Antarctica

Documented fossil evidence of zygomycetous fungi is rare. A conspicuous fungal fossil, Jimwhitea circumtecta gen. et sp. nov., occurs in permineralized peat from the Middle Triassic of Antarctica. The fossil is interpreted as a mantled zygosporangium that buds from a macrogametangium subtended by a sac-like macrosuspensor. The macrogametangium is united at its tip with a microgametangium which is subtended by a micro-suspensor. This configuration is strikingly similar to the zygosporangium-gametangia complexes seen in certain modern Endogonaceae. Co-occurring with J. circumtecta are isolated propagules closely resembling the zygosporangium of J. circumtecta and a portion of a sporocarp containing zygosporangia embedded in a gleba. Several of the sporangia are borne on ovoid or elongate structures, which we interpret as gametangia. These fossils offer an exceptionally detailed view of the morphology and reproductive biology of early Mesozoic zygomycetes.     

Antarctic terrestrial life--challenging the history of the frozen continent?

Antarctica is a continent locked in ice, with almost 99.7% of current terrain covered by permanent ice and snow, and clear evidence that, as recently as the Last Glacial Maximum (LGM), ice sheets were both thicker and much more extensive than they are now. Ice sheet modelling of both the LGM and estimated previous ice maxima across the continent give broad support to the concept that most if not all currently ice-free ground would have been overridden during previous glaciations. This has given rise to a widely held perception that all Mesozoic (pre-glacial) terrestrial life of Antarctica was wiped out by successive and deepening glacial events. The implicit conclusion of such destruction is that most, possibly all, contemporary terrestrial life has colonised the continent during subsequent periods of glacial retreat. However, several recently emerged and complementary strands of biological and geological research cannot be reconciled comfortably with the current reconstruction of Antarctic glacial history, and therefore provide a fundamental challenge to the existing paradigms. Here, we summarise and synthesise evidence across these lines of research. The emerging fundamental insights corroborate substantial elements of the contemporary Antarctic terrestrial biota being continuously isolated in situ on a multi-million year, even pre-Gondwana break-up timescale. This new and complex terrestrial Antarctic biogeography parallels recent work suggesting greater regionalisation and evolutionary isolation than previously suspected in the circum-Antarctic marine fauna. These findings both require the adoption of a new biological paradigm within Antarctica and challenge current understanding of Antarctic glacial history. This has major implications for our understanding of the key role of Antarctica in the Earth System.     

The Acari of fresh- and brackish water habitats in the Antarctic and sub-Antarctic regions

Neither the benthic Halacaroidea nor nektonic Hydrachnidia, characteristic of temperate and tropical freshwater mite faunas are represented among the twenty four species and sub-species of Acari recorded from the Antarctic and sub-Antarctic. The mites collected from the streams, lakes or brackish/freshwater pools of the region are either terrestrial species blown by wind into freshwater or interlopers from the marine littoral which have invaded coastal brackish pools.The present study reports on new collections of mites obtained from lakes and pools at a number of locations from both Continental and Maritime Antarctica, as well as from several sub-Antarctic islands. It reviews all published records for the region and the combined fauna is then compared with that of temperate and tropical regions.     

Dissemination and survival of non-indigenous bacterial genomes in pristine Antarctic environments

Continental Antarctic is perceived as a largely pristine environment, although certain localized regions (e.g., parts of the Ross Dependency Dry Valleys) are relatively heavy impacted by human activities. The procedures imposed on Antarctic field parties for the handling and disposal of both solid and liquid wastes are designed to minimise eutrofication and contamination (particularly by human enteric bacteria). However, little consideration has been given to the significance, if any, of less obvious forms of microbial contamination resulting from periodic human activities in Antarctica. The predominant commensal microorganism on human skin, Staphylococcus epidermidis, could be detected by PCR, in Dry Valley mineral soils collected from heavily impacted areas, but could not be detected in Dry Valley mineral soils collected from low impact and pristine areas. Cell viability of this non-enteric human commensal is rapidly lost in Dry Valley mineral soil. However, S. epidermidis can persist for long periods in Dry Valley mineral soil as non-viable cells and/or naked DNA.     

Factors regulating summer phytoplankton in a highly eutrophic Antarctic lake

Lakes from Maritime Antarctica are regarded as systems generally inhabited by metazoan plankton capable of imposing a top-down control on the phytoplankton during short periods, while lakes from Continental Antarctica lacking these communities would be typically controlled by scarcity of nutrients, following a bottom-up model. Otero Lake is a highly eutrophic small lake located on the NW of the Antarctic Peninsula, which has no metazoan plankton. During summer 1996, we studied the density, composition and vertical distribution of the phytoplankton community of this lake with respect to various abiotic variables, yet our results demonstrated neither light nor nutrient limitation of the phytoplankton biomass. Densities of heterotrophic nanoflagellates (HNAN) and ciliates from three different size categories were also studied. Extremely low densities of HNAN (0–155 ind. ml^–1) could be due to feeding competition by bacterivore nanociliates and/or predation by large ciliates. A summer bloom of the phytoflagellate Chlamydomonas aff. celerrima Pascher reached densities tenfold those of previous years (158.10³ ind. ml^–1), though apparently curtailed by a strong peak of large ciliates (107 ind. ml^–1) which would heavily graze on PNAN (phototrophic nanoflagellates). Top-down control can thus occur in this lake during short periods of long hydrologic residence time.     

Structurally preserved sphenophytes from the Triassic of Antarctica: reproductive remains of Spaciinodum

Permineralized cones found organically attached to Spaciinodum collinsonii stems are described from the early Middle Triassic silicified flora from the Fremouw Formation of Antarctica, and the species diagnosis is emended to include the reproductive specimens. The apical cones are organized into internodal and leaf-bearing nodal regions. Nodal septations span the central pith and cortex, and thin fimbrils subdivide the internodal areas into smaller chambers. The vascular system consists of 31-33 continuous bundles that do not alternate in position between successive nodes and internodes. Simple sporangia are associated with the cortical chambers and occur in one whorl on the axis. Spores are small, lack elaters, and have no discernible ultrastructure preserved, and they are interpreted to be immature. The Antarctic cones are different in structure from typical cones of modern and fossil members of Equisetales; however, they share similarities with some morphologically aberrant cones of extant Equisetum and several Late Paleozoic and Mesozoic compression-impression fossils. Spaciinodum is now the most complete anatomically described Mesozoic sphenophyte.     

Facies characterization of mid-mesozoic deep-water sediments by quantitative analysis of siliceous microfaunas

Summary Quantitative approaches to the analysis of Late Mesozoic radiolarian faunas are rare and often poorly defined. In order to overcome preservational and taxonomic biases, general information indices were tested for their paleoecologic potential. 300 samples from different Tethyan localities and Antarctica were used for this study. The general information indices defined here are: absolute radiolarian abundance, nassellarian/spumellarian ratio, percentage of sponge spicules, morphological diversity and degree of recrystallization and fragmentation. Indices like radiolarian, nassellarian and sponge spicule abundance are suitable for a simple characterization of samples and sections even in poorly preserved material. The spicule abundance in basinal sediments indicates turbiditic influences and provides a proxy for shelf distance and water depth. The relative nassellarian content is useful for a bathymetrical interpretation in Tethyan sediments. Although there is a great loss of information in using only general information indices, the method has the advantage of being appropriate for sedimentologists unfamilar with radiolarian taxonomy, thus providing a fast and powerful tool for paleoecological analysis, which is applicable to different geological periods.     

西南极乔治王岛早第三纪遗迹化石

南极乔治王岛始新统化石山组含多种类型遗迹化石,常与鸟类足迹相伴产出。记述的１新遗迹属及所属的５新遗迹种,从遗迹化石形态两侧对称,纵向延伸,缺乏疣足及其它附肢构造等特征看,推测造迹者为软体蠕虫类,很可能属于寡毛纲的动物。这些化石反映了浅水河湖的沉积环境。     

Are tree trunks habitats or highways? A comparison of oribatid mite assemblages from hoop-pine bark and litter

Abstract Oribatid mites (Acari: Oribatida) are among the most diverse and abundant inhabitants of forest soil and litter, but also have species-rich assemblages on bark and in the canopies of trees. It is unclear whether the trunk of a tree acts simply as a 'highway' for movement of mites into and out of the canopy, or whether the trunk has a distinctive acarofauna. We compare oribatid assemblages from the trunk bark of hoop pine ( Araucaria cunninghamii ) with those from litter collected beneath the same trees. A 1.0 by 0.5 m area of bark was sampled from three trees at each of five sites using a knockdown insecticide. A 1-L sample of leaf litter was collected as close as possible to the base of each sampled tree. Mites were extracted using Tullgren funnels, identified to genus and morphospecies, and counted. Assemblages were almost 100% distinct, with only one oribatid morphospecies ( Pseudotocepheus sp.) collected from both litter and bark. Litter had a higher taxon richness than bark in total and per sample, but oribatids made up a greater percentage of the acarofauna in the bark samples. We had expected that the more consistent physical substrate of bark would be reflected in greater similarity of oribatid faunas on trunks than in litter; however, the opposite proved to be the case. We conclude that hoop-pine trunks are habitats rather than highways for oribatid mites. Based on the observed higher turnover among bark faunas, tree trunks may represent habitat islands whose colonisation by particular oribatid species is more stochastic than that of the more continuous 'sea' of litter.     

Diversity and spatial distribution of amoA-encoding archaea in the deep-sea sediments of the tropical West Pacific Continental Margin

Aims:  The ecological characteristics of the deep-sea amoA -encoding archaea (AEA) are largely unsolved. Our aim was to study the diversity, structure and distribution of the AEA community in the sediments of the tropical West Pacific Continental Margin, to develop a general view of the AEA biogeography in the deep-sea extreme environment.
Methods and Results:  Archaeal amoA clone libraries were constructed. Diverse and novel amoA sequences were identified, with the Bohol Sea, Bashi Strait and Sibuyan Sea harbouring the highest and the Bicol Shelf the lowest AEA diversity. Phylogenetic and statistical analyses illustrate a heterogeneous distribution of the AEA community, probably caused by the differential distribution of the terrestrial or estuarine AEA in the various sampling sites.
Conclusions:  The deep-sea sedimentary environments potentially harbour diverse and novel AEA in the tropical West Pacific Continental Margin. The stations in the Philippine inland seas (including station 3043) may represent AEA assemblages with various terrestrial influences and the stations connected directly to the open Philippine Sea may represent marine environment-dominant AEA assemblages.
Significance and Impact of Study:  Our study indicates the potential importance of geological and climatic events in the transport of terrestrial micro-organisms to the deep-sea sedimentary environments, almost totally neglected previously.