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Carbon-14 calibrated amino acid racemization ( super(14)C/AAR) data and lead-210 ( super(210)Pb) data are used to examine sediment accumulation rates, stratigraphic order, and the extent of time-averaging in sediments collected from the One Tree Reef lagoon (southern Great Barrier Reef, Australia). The top meter of lagoonal sediment preserves a stratigraphically ordered deposit spanning the last 600 yrs. Despite different assumptions, the super(210)Pb and super(14)C/AAR chronologies are remarkably similar indicating consistency in sedimentary processes across sediment grain sizes spanning more than three orders of magnitude (0.1-10 mm). Estimates of long-term sediment accumulation rates range from 2.2 to 1.2 mm yr super(-1). Molluscan time-averaging in the taphonomically active zone is 19 yrs, whereas below the depth of final burial (15 cm), it is 110 yrs/5 cm layer. While not a high-resolution paleontological record, this reef lagoon sediment is suitable for paleoecological studies spanning the period of Western colonization and development. This sedimentary deposit, and others like it, should be useful, albeit not ideal, for quantifying anthropogenic impacts on coral reef systems.

Geomorphic change, water resources development and climate change can alter the timing, frequency, magnitude and duration of replenishment of floodplain wetlands via overbank flows. If we understand the ecological consequences of these hydrological changes, environmental water allocations can be used more effectively to sustain wetland biodiversity and associated ecosystem processes. We analysed longterm monitoring data for 13 wetlands on the floodplain of the Murrumbidgee River in south-eastern Australia to determine how aquatic macroinvertebrate assemblages related to the proportion of time during which a wetland contained water. The more temporary wetlands had significantly different and poorer assemblages than the more permanent ones, with frequency of occurrence significantly negatively related to permanence for eight invertebrate genera and positively related for 17. The invertebrates most strongly associated with more temporary wetlands were mainly crustaceans whose resting stages withstand drying, together with highly mobile insects. Those associated with more permanent wetlands included a prawn, molluscs and less mobile insects. These findings suggest that maintaining a broad spectrum of hydrological regimes at the local scale is necessary if macroinvertebrate diversity on the Murrumbidgee River floodplain is to be sustained.

A specific 1 arrow right 3- beta -D-glucanase with molecular mass 37 kDa was isolated in homogeneous state from crystalline style of the commercial marine mollusk Tapes literata. It exhibits maximal activity within the pH range from 4.5 to 7.5 at 45dgC. The 1 arrow right 3- beta -D-glucanase catalyzes hydrolysis of beta -1 arrow right 3 bonds in glucans as an endoenzyme with retention of bond configuration, and it has transglycosylating activity. The K sub(m) for hydrolysis of laminaran is 0.25 mg/ml. The enzyme is classified as a glucan endo-(1 arrow right 3)- beta -D-glucosidase (EC 3.2.1.39). The cDNA encoding this 1 arrow right 3- beta -D-glucanase from T. literata was sequenced, and the amino acid sequence of the enzyme was determined. The endo-1 arrow right 3- beta -D-glucanase from T. literata was assigned to the 16th structural family (GHF 16) of O-glycoside hydrolases.

One of the most interesting Mesozoic Lagerstaetten, Shar Teg in southwestern Mongolia, is reviewed. The geological structure and oryctocoenoses of Shar Teg are described. Shar Teg is one of the most diverse Jurassic Lagerstaetten in terms of fossils represented. Fossils from Shar Teg include aquatic and terrestrial plants, mollusks, crustaceans, insects, fishes, amphibians, reptiles, and mammals. Insects are the most diverse group. To date, a total of 297 species of 161 families and 22 orders have been described or recorded in Shar Teg, making it possible to reconstruct comprehensively the Jurassic biota of the locality. The oryctocoenosis composition is peculiar; it includes only six species described from other localities. The oryctocoenosis appears to link the faunas of eastern Asia, Central Asia, and Europe. A total of 31 new species are described.

Although the Western Isles have been subject to a number of recent archaeological investigations, there has been limited recent work on molluscan assemblages, despite the very good degree of preservation to be expected in a number of deposits and the significant work in the 1970s and 1980s on a number of sites such as Northton, Baleshare, and Hornish Point. In the meantime, land snail analysis has flourished in southern England and elsewhere in Europe, with the development of new techniques of numerical analysis such as the taxocene framework, the use of land snail assemblages in climate reconstruction, and recent refinements in amino acid dating. This paper provides a brief summary of the work to date on Hebridean snail assemblages, and presents preliminary results from work in progress, exploring aspects of site-formation processes, middening, land use, and relative dating that can be explored using land snails.

The bioaccumulation and biomagnification of mercury (Hg) and selenium (Se) were investigated in sub-tropical freshwater food webs from Burkina Faso, West Africa, a region where very few ecosystem studies on contaminants have been performed. During the 2010 rainy season, samples of water, sediment, fish, zooplankton, and mollusks were collected from three water reservoirs and analysed for total Hg (THg), methylmercury (MeHg), and total Se (TSe). Ratios of delta 13C and delta 15N were measured to determine food web structures and patterns of contaminant accumulation and transfer to fish. Food chain lengths (FCLs) were calculated using mean delta 15N of all primary consumer taxa collected as the site-specific baseline. We report relatively low concentrations of THg and TSe in most fish. We also found in all studied reservoirs short food chain lengths, ranging from 3.3 to 3.7, with most fish relying on a mixture of pelagic and littoral sources for their diet. Mercury was biomagnified in fish food webs with an enrichment factor ranging from 2.9 to 6.5 for THg and from 2.9 to 6.6 for MeHg. However, there was no evidence of selenium biomagnification in these food webs. An inverse relationship was observed between adjusted delta 15N and log-transformed Se:Hg ratios, indicating that Se has a lesser protective effect in top predators, which are also the most contaminated animals with respect to MeHg. Trophic position, carbon source, and fish total length were the factors best explaining Hg concentration in fish. In a broader comparison of our study sites with literature data for other African lakes, the THg biomagnification rate was positively correlated with FCL. We conclude that these reservoir systems from tropical Western Africa have low Hg biomagnification associated with short food chains. This finding may partly explain low concentrations of Hg commonly reported in fish from this area.

Secondary succession is changing the character of many temperate forests and often leads to closed-canopy stands. In such forests set aside for conservation, habitat management alternatives need to be tested experimentally, but this is rarely done. The Swedish Oak Project compares two often debated alternatives: minimal intervention and non-traditional active management (conservation thinning) on plots of each type replicated at 25 sites. We study responses of several taxa, and here report results for land molluscs. They are considered to be sensitive to more open, drier forest and we predicted a negative effect of the thinning (26% reduction of the basal area; mean value for 25 experimental forests). We sampled molluscs in the litter in ten 20 x 25 cm subplots, and by standardised visual search, in each plot. In total, we recorded 53 species of snails and slugs (24 369 individuals) and the mean species richness in plots was 17. Two seasons after thinning, mean ( plus or minus SE) species richness had decreased by 1.4 ( plus or minus 0.9) species in thinning plots, but increased by 0.7 ( plus or minus 1.0) species in minimal intervention plots, a significant but small change with considerable variation among sites. In matched comparisons with minimal intervention, thinning reduced the overall abundance of molluscs. Most species responded negatively to thinning - but only five of the 53 species were significantly affected, and reproduction seemed to be negatively affected in only one species. An ordination analysis did not reveal any particular change in the species community due to thinning. Thus, the negative effect of conservation thinning on land molluscs was apparently mild - one reason was that many trees, shrubs and other forest structures remained after the treatment. Conservation thinning may be recommended, since other taxa are favoured, but minimal intervention is also a useful form of management for molluscs and saproxylic taxa.

Comparative analysis of the genomes of one mollusc ( Lottia gigantea ) and two annelids ( Capitella teleta and Helobdella robusta ) enable a more complete reconstruction of genomic features of the last common ancestors of protostomes, bilaterians and metazoans; against this conserved background they provide the first glimpse into lineage-specific evolution and diversity of the lophotrochozoans. Genomes record emergence of bilaterals This paper presents the draft genome sequences of two annelids — a freshwater leech ( Helobdella robusta ) and a bristly, segmented marine worm ( Capitella teleta ) — and a mollusc, the owl limpet ( Lottia gigantea ). These two phyla account for nearly one-third of known marine species and are of importance both ecologically and as experimental systems, yet they have not been served well by genomics efforts. Comparison of these genomes with those already available reveal some of the genetic changes linked to the origin and diversification of bilateral animals that are thought to have evolved during the 'Cambrian explosion' of multicellular life around 500 million years ago. Current genomic perspectives on animal diversity neglect two prominent phyla, the molluscs and annelids, that together account for nearly one-third of known marine species and are important both ecologically and as experimental systems in classical embryology 1 , 2 , 3 . Here we describe the draft genomes of the owl limpet ( Lottia gigantea ), a marine polychaete ( Capitella teleta ) and a freshwater leech ( Helobdella robusta ), and compare them with other animal genomes to investigate the origin and diversification of bilaterians from a genomic perspective. We find that the genome organization, gene structure and functional content of these species are more similar to those of some invertebrate deuterostome genomes (for example, amphioxus and sea urchin) than those of other protostomes that have been sequenced to date (flies, nematodes and flatworms). The conservation of these genomic features enables us to expand the inventory of genes present in the last common bilaterian ancestor, establish the tripartite diversification of bilaterians using multiple genomic characteristics and identify ancient conserved long- and short-range genetic linkages across metazoans. Superimposed on this broadly conserved pan-bilaterian background we find examples of lineage-specific genome evolution, including varying rates of rearrangement, intron gain and loss, expansions and contractions of gene families, and the evolution of clade-specific genes that produce the unique content of each genome.

Background Histones are the basic packaging units of eukaryotic DNA and are essential for the dynamics of chromatin and the regulation of epigenetics. Canonical histones and their variants exhibit important functional differences in biological processes. However, little is known about the role of histone family members in molluscs, which are known for their ecological and morphological diversity. Results Core histone families of 28 molluscan species (12 bivalves, 8 gastropods, 6 cephalopods, 1 scaphopod and 1 polyplacophora) were systematically identified. The evolutionary conservation and lineage-specific innovations were discovered using phylogenomic and transcriptomic analyses. Cephalopods showed a striking expansion of canonical histone genes with brain-enriched expression patterns. Synteny analyses revealed conserved, collinear histone clusters unique to cephalopods. Histone variants, specially H2A and H3 paralogs, display conserved motifs potentially involved in nucleosome stability and lineage-specific residues involved in functional specialization. Developmental transcriptomics revealed the dynamic expression of histone variants in early embryogenesis and the gonads, suggesting that H2A and H3 variants are involved in chromatin remodeling, pluripotency maintenance and germline regulation. Macro-H2A was highly expressed during larval neurodevelopment and in sensory organs, suggesting important roles in neural plasticity. Conclusion This study represents the first comprehensive inventory and characterization of core histone genes in molluscs, and will facilitate understanding of the evolutionary patterns and functional properties of core histones in relation to neurogenesis of molluscs. These findings advance our understanding of chromatin evolution and its contribution to phenotypic innovation in non-model taxa.

When molluscs got ahead The Mollusca are one of the most successful animal phyla — ubiquitous, varied in body plan and with a long fossil record. Their interrelationships have been a matter of debate, but phylogenomic methods are beginning to resolve the issue. A new study answers some questions about the base of the molluscan tree, showing that, contrary to the traditional view, bivalves and gastropods are members of sister taxa. This finding also raises the possibility that centralization of neural and sensory organs in the head region, and the development of protective shells, may have occurred on several occasions in the evolutionary history of the molluscs. Evolutionary relationships among the eight major lineages of Mollusca have remained unresolved despite their diversity and importance. Previous investigations of molluscan phylogeny, based primarily on nuclear ribosomal gene sequences 1 , 2 , 3 or morphological data 4 , have been unsuccessful at elucidating these relationships. Recently, phylogenomic studies using dozens to hundreds of genes have greatly improved our understanding of deep animal relationships 5 . However, limited genomic resources spanning molluscan diversity has prevented use of a phylogenomic approach. Here we use transcriptome and genome data from all major lineages (except Monoplacophora) and recover a well-supported topology for Mollusca. Our results strongly support the Aculifera hypothesis placing Polyplacophora (chitons) in a clade with a monophyletic Aplacophora (worm-like molluscs). Additionally, within Conchifera, a sister-taxon relationship between Gastropoda and Bivalvia is supported. This grouping has received little consideration and contains most (>95%) molluscan species. Thus we propose the node-based name Pleistomollusca. In light of these results, we examined the evolution of morphological characters and found support for advanced cephalization and shells as possibly having multiple origins within Mollusca.