Search

Sponges play a key role in Antarctic marine benthic community structure and dynamics and are often a dominant component of many Southern Ocean benthic communities. Understanding the drivers of sponge distribution in Antarctica enables us to understand many of general benthic biodiversity patterns in the region. The sponges of the Antarctic and neighbouring oceanographic regions were assessed for species richness and biogeographic patterns using over 8,800 distribution records. Species-rich regions include the Antarctic Peninsula, South Shetland Islands, South Georgia, Eastern Weddell Sea, Kerguelen Plateau, Falkland Islands and north New Zealand. Sampling intensity varied greatly within the study area, with sampling hotspots found at the Antarctic Peninsula, South Georgia, north New Zealand and Tierra del Fuego, with limited sampling in the Bellingshausen and Amundsen seas in the Southern Ocean. In contrast to previous studies we found that eurybathy and circumpolar distributions are important but not dominant characteristics in Antarctic sponges. Overall Antarctic sponge species endemism is ∼43%, with a higher level for the class Hexactinellida (68%). Endemism levels are lower than previous estimates, but still indicate the importance of the Polar Front in isolating the Southern Ocean fauna. Nineteen distinct sponge distribution patterns were found, ranging from regional endemics to cosmopolitan species. A single, distinct Antarctic demosponge fauna is found to encompass all areas within the Polar Front, and the sub-Antarctic regions of the Kerguelen Plateau and Macquarie Island. Biogeographical analyses indicate stronger faunal links between Antarctica and South America, with little evidence of links between Antarctica and South Africa, Southern Australia or New Zealand. We conclude that the biogeographic and species distribution patterns observed are largely driven by the Antarctic Circumpolar Current and the timing of past continent connectivity.

The Antarctic Peninsula has experienced a rapid increase in atmospheric temperature over the last 50 years. Whether or not marine organisms thriving in this cold stenothermal environment are able to cope with warming is of concern. Here, we present changes to the growth and shell characteristics of the ecologically important, small and short lived brooding bivalve Lissarca miliaris from Signy Island, Antarctica. Using material collected from the 1970's to the present day, we show an increase in growth rate and adult shell deterioration accompanied by a decrease in offspring size, associated with an increase in annual average temperatures. Critical changes to the bivalve's ecology seen today evidence the problem of a shift in baseline since the onset of warming recorded in Antarctica. These small bivalves are demonstrating ecophysiological responses to subtle warming that, provided warming continues, could soon surpass a physiological tipping point, adding to warming associated threats such as increased predatory pressure and ocean acidification.

Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR) in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp.), stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae), bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more complex than previously recognised., Competing Interests: The authors have declared that no competing interests exist.

Although studies of population genetic structure are commonplace, a strong bias exists toward species from low latitudes and with relatively poor dispersal capabilities. Consequently, we used 280 amplified fragment length polymorphism bands to explore patterns of genetic differentiation among 8 populations of a high latitude broadcast-spawning marine mollusc, the Antarctic limpet Nacella concinna. Over 300 individuals were sampled along a latitudinal gradient spanning the Antarctic Peninsula from Adelaide Island to King George Island (67°-62°S), then to Signy Island (60°S) and South Georgia (54°S). Populations from the Antarctic Peninsula exhibited little genetic structure but were themselves strongly differentiated from both Signy and South Georgia. This finding was analytically highly robust and implies the presence of significant oceanographic barriers to gene flow in a species long regarded as a classic example of a widely dispersing broadcast spawner.

The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two sub-species and at least five "forma". However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (+/-0.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems.

The Edman Sequence Research Group (ESRG) of the Association of Biomolecular Resource designs and executes interlaboratory studies investigating the use of automated Edman degradation for protein and peptide analysis. In 2008, the ESRG enlisted the help of core sequencing facilities to investigate the effects of a repeating amino acid tag at the N-terminus of a protein. Commonly, to facilitate protein purification, an affinity tag containing a polyhistidine sequence is conjugated to the N-terminus of the protein. After expression, polyhistidine-tagged protein is readily purified via chelation with an immobilized metal affinity resin. The addition of the polyhistidine tag presents unique challenges for the determination of protein identity using Edman degradation chemistry. Participating laboratories were asked to sequence one protein engineered in three configurations: with an N-terminal polyhistidine tag; with an N-terminal polyalanine tag; or with no tag. Study participants were asked to return a data file containing the uncorrected amino acid picomole yields for the first 17 cycles. Initial and repetitive yield (R.Y.) information and the amount of lag were evaluated. Information about instrumentation and sample treatment was also collected as part of the study. For this study, the majority of participating laboratories successfully called the amino acid sequence for 17 cycles for all three test proteins. In general, laboratories found it more difficult to call the sequence containing the polyhistidine tag. Lag was observed earlier and more consistently with the polyhistidine-tagged protein than the polyalanine-tagged protein. Histidine yields were significantly less than the alanine yields in the tag portion of each analysis. The polyhistidine and polyalanine protein-R.Y. calculations were found to be equivalent. These calculations showed that the nontagged portion from each protein was equivalent. The terminal histidines from the tagged portion of the protein were demonstrated to be responsible for the high lag during N-terminal sequence analysis.

The current review outlines the distribution of flavonoids and phenolic acids in eleven species of Silphium (Asteraceae). The chemosystematic significance of these findings is discussed and compared with DNA and morphological-based assignments for eleven species. Special attention is given to the five flavonol triglycosides that were previously isolated and characterized from Silphium species: isorhamnetin 3-O-alpha-L-rhamnosyl (1""-->6")-O-beta-D-galactopyranoside 7-O-beta-L-apiofuranoside (1), quercetin 3-O-alpha-L-rhamnosyl (1"'-->6")-O-beta-D-galactopyranoside 7-O-beta-L-apiofuranoside (2), quercetin 3-O-beta-L-galactosyl (1"'-->6")-O-beta-D-rhamnopyranoside 7-O-alpha-L-apiofuranoside (3), kaempferol 3-O-beta-D-apiofuranoside 7-O-alpha-L-rhamnosyl (1""-6"')-O-beta-D-galactopyranoside (4) and kaempferol 3-O-beta-D-apiofuranoside 7-O-alpha-L-rhamnosyl (1""-->6"')-O-beta-D (2"'-O-E-caffeoylgalactopyranoside) (5). In addition, several other known mono and diglycosidic flavonoids, along with 18 phenolic acids, were also identified and the structures of all of the compounds were established by LC/MS and NMR spectral investigations.

Phylum Tardigrada consists of ∼1000 tiny, hardy metazoan species distributed throughout terrestrial, limno-terrestrial and oceanic habitats. Their phylogenetic status has been debated, with current evidence placing them in the Ecdysozoa. Although there have been efforts to explore tardigrade phylogeny using both morphological and molecular data, limitations such as their few morphological characters and low genomic DNA concentrations have resulted in restricted taxonomic coverage. Using a protocol that allows us to identify and extract DNA from individuals, we have sequenced 18S rDNA from 343 tardigrades from across the globe. Using maximum parsimony and Bayesian analyses we have found support for dividing Order Parachela into three super-families and further evidence that indicates the traditional taxonomic perspective of families in the class Eutardigrada are nonmonophyletic and require re-working. It appears that conserved morphology within Tardigrada has resulted in conservative taxonomy as we have found cases of several discrete lineages grouped into single genera. Although this work substantially adds to the understanding of the evolution and taxonomy of the phylum, we highlight that inferences gained from this work are likely to be refined with the inclusion of further taxa-specifically representatives of the nine families yet to be sampled. © The Willi Hennig Society 2008., (© The Willi Hennig Society 2008.)

Background: Meiofauna - multicellular animals captured between sieve size 45 mum and 1000 mum - are a fundamental component of terrestrial, and marine benthic ecosystems, forming an integral element of food webs, and playing a critical roll in nutrient recycling. Most phyla have meiofaunal representatives and studies of these taxa impact on a wide variety of sub-disciplines as well as having social and economic implications. However, studies of variation in meiofauna are presented with several important challenges. Isolating individuals from a sample substrate is a time consuming process, and identification requires increasingly scarce taxonomic expertise. Finding suitable morphological characters in many of these organisms is often difficult even for experts. Molecular markers are extremely useful for identifying variation in morphologically conserved organisms. However, for many species markers need to be developed de novo, while DNA can often only be extracted from pooled samples in order to obtain sufficient quantity and quality. Importantly, multiple independent markers are required to reconcile gene evolution with species evolution. In this primarily methodological paper we provide a proof of principle of a novel and effective protocol for the isolation of meiofauna from an environmental sample. We also go on to illustrate examples of the implications arising from subsequent screening for genetic variation at the level of the individual using ribosomal, mitochondrial and single copy nuclear markers., Results: To isolate individual tardigrades from their habitat substrate we used a non-toxic density gradient media that did not interfere with downstream biochemical processes. Using a simple DNA release technique and nested polymerase chain reaction with universal primers we were able amplify multi-copy and, to some extent, single copy genes from individual tardigrades. Maximum likelihood trees from ribosomal 18S, mitochondrial cytochrome oxidase subunit 1, and the single copy nuclear gene Wingless support a recent study indicating that the family Hypsibiidae is a non-monophyletic group. From these sequences we were able to detect variation between individuals at each locus that allowed us to identify the presence of cryptic taxa that would otherwise have been overlooked., Conclusion: Molecular results obtained from individuals, rather than pooled samples, are a prerequisite to enable levels of variation to be placed into context. In this study we have provided a proof of principle of this approach for meiofaunal tardigrades, an important group of soil biota previously not considered amenable to such studies, thereby paving the way for more comprehensive phylogenetic studies using multiple nuclear markers, and population genetic studies.

The Edman Sequencing Research Group (ESRG) designs studies on the use of Edman degradation for protein and peptide analysis. These studies provide a means for participating laboratories to compare their analyses against a benchmark of those from other laboratories that provide this valuable service. The main purpose of the 2006 study was to determine how accurate Edman sequencing is for quantitative analysis of polypeptides. Secondarily, participants were asked to identify a modified amino acid residue, N-epsilon-acetyl lysine [Lys(Ac)], present within one of the peptides. The ESRG 2006 peptide mixture consisted of three synthetic peptides. The Peptide Standards Research Group (PSRG) provided two peptides, with the following sequences: KAQYARSVLLEKDAEPDILELATGYR (peptide B), and RQAKVLLYSGR (peptide C). The third peptide, peptide C*, synthesized and characterized by ESRG, was identical to peptide C but with acetyl lysine in position 4. The mixture consisted of 20% peptide B and 40% each of peptide C and its acetylated form, peptide C*. Participating laboratories were provided with two tubes, each containing 100 picomoles of the peptide mixture (as determined by quantitative amino acid analysis) and were asked to provide amino acid assignments, peak areas, retention times at each cycle, as well as initial and repetitive yield estimates for each peptide in the mixture. Details about instruments and parameters used in the analysis were also collected. Participants in the study with access to a mass spectrometer (MALDI-TOF or ESI) were asked to provide information about the relative peak areas of the peptides in the mixture as a comparison with the peptide quantitation results from Edman sequencing. Positive amino acid assignments were 88% correct for peptide C and 93% correct for peptide B. The absolute initial sequencing yields were an average of 67% for peptide (C+C*) and 65.6 % for peptide B. The relative molar ratios determined by Edman sequencing were an average of 4.27 (expected ratio of 4) for peptides (C+C*)/B, and 1.49 for peptide C*/C (expected ratio of 1); the seemingly high 49% error in quantification of Lys(Ac) in peptide C* can be attributed to commercial unavailability of its PTH standard. These values compare very favorably with the values obtained by mass spectrometry.

Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa. The deeper parts of the Southern Ocean exhibit some unique environmental features, including a very deep continental shelf and a weakly stratified water column, and are the source for much of the deep water in the world ocean. These features suggest that deep-sea faunas around the Antarctic may be related both to adjacent shelf communities and to those in other oceans. Unlike shallow-water Antarctic benthic communities, however, little is known about life in this vast deep-sea region. Here, we report new data from recent sampling expeditions in the deep Weddell Sea and adjacent areas (748-6,348 m water depth) that reveal high levels of new biodiversity; for example, 674 isopods species, of which 585 were new to science. Bathymetric and biogeographic trends varied between taxa. In groups such as the isopods and polychaetes, slope assemblages included species that have invaded from the shelf. In other taxa, the shelf and slope assemblages were more distinct. Abyssal faunas tended to have stronger links to other oceans, particularly the Atlantic, but mainly in taxa with good dispersal capabilities, such as the Foraminifera. The isopods, ostracods and nematodes, which are poor dispersers, include many species currently known only from the Southern Ocean. Our findings challenge suggestions that deep-sea diversity is depressed in the Southern Ocean and provide a basis for exploring the evolutionary significance of the varied biogeographic patterns observed in this remote environment.

Diaphana haini n.sp. is described from Antarctica. With a depth range from about 400 to 2100 m, D. haini is the second Antarctic species of this genus to extend into the deep sea, the other being D. inflata (Strebel, 1908). Phylogenetic analysis has allowed D. haini to be incorporated within Schiøtte's (1998) cladogram for this genus and, thereby clarify its historical zoogeography. A record of D. inflata from the Weddell Sea extends its known distribution range. The recorded geographic distribution now ranges from South Georgia to the Antarctic continent, and the depth range is extended considerably, from 252-310 m to 1645 m.

A neuropeptide hormone isolated from corpora cardiaca of Melanoplus sanguinipes was purified by HPLC. The HPLC fractions were examined for adipokinetic activity with an in vivo bioassay. A single large UV absorbent peak was active in the mobilization of lipid while the other HPLC fractions showed no detectable activity. This large peak had a retention time and amino acid composition identical to synthetic Lom-AKH-I which was analyzed in a parallel manner. The primary sequence structure, pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-Thr-NH2, was determined by automated gas-phase Edman degradation. The peptide was deblocked prior to sequencing using pyroglutamate aminopeptidase and the sequence was confirmed with mass spectrometry. The C-terminus of the peptide was determined to be blocked, as indicated by the lack of digestion with carboxypeptidase A. The knowledge of the primary sequence of Mes-AKH allows the use of a commercially available synthetic peptide and its antibodies for use in future research with Melanoplus sanguinipes.

Nebulin, a giant actin binding protein, coextends with actin and is thought to form a composite thin filament in the skeletal muscle sarcomere. To understand the molecular interactions between nebulin and actin, we have applied chemical cross-linking techniques to define molecular contacts between actin and ND8, a two-module nebulin fragment that promotes actin polymerization and inhibits depolymerization by binding to both G- and F-actin. The formation of a 1:1 complex with a dissociation constant of 4.9 microM between ND8 and G-actin was demonstrated by fluorescence titration of dansyl-ND8 with G-actin. Treatment with a zero-length cross-linker, l-ethyl-3-[3-(dimethylamino) propyl]carbodiimide (EDC), cross-linked the ND8-G-actin complex covalently without impairing actin's ability to polymerize. End-labeling Western blot and sequence and mass analyses of purified conjugated peptides revealed the cross-linking between lysine 5 of ND8 and the two N-terminal acidic residues of G-actin. Similarly, we have shown by end-labeling that cross-linking of ND8 to F-actin occurred at the N-terminus of actin protomer. The binding of nebulin to the N-terminus of actin is likely to be significant in its ability to affect actin polymerization. Furthermore, the association of nebulin modules with the actin N-terminus in subdomain 1 supports the hypothesis that nebulin wraps around the outer edges of actin filaments where Sl, tropomyosin, and several actin binding proteins are known to interact.

While studying the delivery of cytoplasmic proteins to the presynaptic terminals of CNS neurons, we discovered unique characteristics of one protein (p118) conveyed in slow component b (SCb) of axonal transport, the large group of proteins representing the cytoplasmic matrix. Alone among the SCb group, p118 coisolated with the synaptic junctional complex on biochemical fractionation of the radiolabeled synaptic regions. Purification and amino acid sequencing of this protein revealed it is most likely the guinea pig form of type I (brain) hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1). Further biochemical treatments were consistent with this identity. The majority of type I brain hexokinase has been thought to be associated primarily with membranes, in particular the mitochondrial outer membrane. We found that the majority of type I hexokinase is transported toward the terminals at a rate at least 10 times slower than that exhibited by the maximal or average rate of mitochondria. This suggests that, in the axon, the enzyme exhibits transient or dynamic interactions with mitochondria that are moving more rapidly. It is not clear whether hexokinase binds exclusively to mitochondria, or also exhibits association with nonmitochondrial membranes. The unexpected enrichment of hexokinase during synaptic junctional complex purification may result from its strong association with the presynaptic membrane portion of the synapse.

New cationic 99Tc/99Tc complexes formed with various symmetrical and asymmetrical vicinal dioximes of different carbon chain length (C5-C8) were synthesized by reduction of pertechnetate with BH4-, separated by HPLC and characterized by i.r./u.v./vis. spectroscopy, FAB mass spectrometry and electrophoresis. All complexes studied are trisdioximes containing boron as a constituent. Their lipophilicity, as assessed by the octanol/saline partition coefficient, ranges over almost four orders of magnitude. The myocardial uptake of the 99mTc complexes in mice proves to be lower than expected. The organ distributions are distinctly affected by the lipophilicity, the position of the dioxime group and the introduction of a terminal methoxy group.

[99Tc(phen)3]Cl2 was synthesized by reduction of pertechnetate with sodium borohydride in the presence of an excess of 1,10-phenanthroline and characterized by FAB mass spectrometry, magnetic susceptibility measurements, and i.r./vis/u.v. spectrophotometry. For biodistribution evaluation in mice [99mTc(phen)3]Cl2 could be obtained in a radiochemical purity of 92.5% using a similar procedure. The rather hydrophilic chelate was predominantly excreted by the kidneys. Its low blood retention resulted in a heart/blood activity ratio of 4.2 at 100 min post-injection.

The synthesis and purification of two new ligands, 15-[bis(3,4-dimethyl arsino)phenyl] pentadecanoic acid (FA-DIARS) and [bis(16,17-dimethyl phosphino)] heptadecanoic acid (FA-DMPE) and the preparation of their corresponding 99Tc/99mTc complexes of the general formula [Tc(III)L2Cl2]+, wherein L is FA-DIARS or FA-DMPE are reported. After careful purification by preparative HPLC, the 99Tc complexes were characterized by spectroscopy, while the 99mTc complexes were used to determine the biodistribution in mice. The results of the organ distribution studies indicated a relatively high uptake in heart (5-7% dose/g). The complexes were, however, found to be very slowly cleared from the blood, probably due to strong binding to serum proteins. Further, the heart to liver and heart to lung ratios were unfavourable. Attempts to improve the efficacy by synthesizing complexes containing one fatty acid per molecule are also described.