Human Footprint Variation while Performing Load Bearing Tasks

Human footprint fossils have provided essential evidence about the evolution of human bipedalism as well as the social dynamics of the footprint makers, including estimates of speed, sex and group composition. Generally such estimates are made by comparing footprint evidence with modern controls; however, previous studies have not accounted for the variation in footprint dimensions coming from load bearing activities. It is likely that a portion of the hominins who created these fossil footprints were carrying a significant load, such as offspring or foraging loads, which caused variation in the footprint which could extend to variation in any estimations concerning the footprint’s maker. To identify significant variation in footprints due to load-bearing tasks, we had participants (N = 30, 15 males and 15 females) walk at a series of speeds carrying a 20kg pack on their back, side and front. Paint was applied to the bare feet of each participant to create footprints that were compared in terms of foot length, foot width and foot area. Female foot length and width increased during multiple loaded conditions. An appreciation of footprint variability associated with carrying loads adds an additional layer to our understanding of the behavior and morphology of extinct hominin populations.     

Furrows and firmgrounds: evidence for predation and implications for Palaeozoic substrate evolution in Rusophycus burrows from the Silurian of New York

Tarhan, L.G., Jensen, S. & Droser, M.L. 2011: Furrows and firmgrounds: evidence for predation and implications for Palaeozoic substrate evolution in Rusophycus burrows from the Silurian of New York. Lethaia, Vol. 45, pp. 329–341. The Silurian Herkimer Formation of east‐central New York contains abundant, exceptionally preserved composite Rusophycus‐Teichichnus burrows. We suggest that the most likely interpretation of these composite trace fossils is as structures formed by trilobites entering the sediment in search of prey. Parallel alignment of the paired traces, asymmetrical configuration of the Teichichnus along the longitudinal axis of the associated Rusophycus, depth correlation and deformation of the Teichichnus all suggest that this relationship was predatory. In addition, sectioned material indicates that these Rusophycus may have been open at the sediment‐water interface, while the crisp preservation of both Rusophycus and Teichichnus, along with the preservation of such delicate morphological details as scratch marks, suggests that the sediment must have been relatively firm at the time the traces were formed. The formation and preservation of Rusophycus in cohesive sediments located very close to the sediment‐water interface hold important implications for the manner in which we consider Palaeozoic substrates and their temporal and spatial evolution. Moreover, these findings demonstrate that the morphology and taphonomy of ichnological associations may, in the context of sedimentological relationships, prove a powerful proxy for tracking substrate conditions through both space and time. □firmgrounds, New York, predation, Rusophycus, substrate, taphonomy.     

Close and delayed benthic–pelagic coupling in coastal ecosystems: the role of physical constraints

We aimed to analyse the temporal scales of the variability of benthic ammonium flux using data from an estuarine bay (Alfacs Bay, N. W. Mediterranean). Several nitrogen (N) pools in the sediment, their reactivities and their associated fluxes were estimated. Decomposition of labile buried N (4.5 mol N m^-2) was found to cause an ammonium flux of 0.1 mmol N m^-2 d ^-1, referred to as background flux. The fluxes measured from bell-jar incubations were usually higher, between 2 and 6 mmol N m^-2 d ^-1, which reflects mineralization of recent sedimentation. A typical sedimentation event was found to account for 25 – 75 mmol m^-2 of freshly settled N, which should bring on an ammonium flux of about 1.7–5.0 mmol N m^-2 d ^-1, referred to as fast flux. The concordance between measured and computed benthic fluxes is associated with the coupling of benthic fluxes to production and sedimentation. Close benthic–pelagic coupling was observed in winter and early spring, while a delayed flux response to sedimentation, with transient variations of pore water ammonium profiles, showing surface peaks and decreasing concentrations with depth, was found in autumn. Structures, such as viscous layers, which develop over the sediment–water interface, were found to be essential to the regulation of benthic processes and to lead to transient variations of pore water nutrient concentrations and associated fluxes. The temporal scales of the benthic flux response to sedimentation were discussed in terms of the physical structures involved in decomposition (the bulk sediment, the viscous layers or the fresh settled layer), the processes controlling kinetics and diffusion laws. Several scenarios for the benthic- pelagic coupling in Alfacs Bay, in which local (estuarine circulation) and climatic components combine to yield the variability observed, were examined.     

Temporal and spatial variations in the behavior of shrubsteppe birds

Summary We documented patterns of activity and microhabitat use by breeding male Sage Sparrows (Amphispiza belli) and Brewer's Sparrows (Spizella breweri) in the semiarid shrubsteppe of northwestern U.S.A. to determine how their behavior varies in space and time and how these variations relate to environmental features. In analyses of several sites with multiple plots that were studied for 2–4 yr, the frequencies of activities and substrate use varied significantly with year, plot, and location. The major activities, foraging and singing, varied inversely with one another. Thus, although the general structure of the activity budgets of these species was stable (i.e. foraging and singing were always the most frequent activities), there was considerable variation in the quantitative details of their behavior in space and time. Using stepwise regression, we related these variations in behavior to variations in environmental features such as the densities of the same or other species, the number of species in the community, and coverages of the different substrate types. Few patterns emerged, and those that did were generally not in accord with our expectations. In particular, patterns of substrate use were not related to variations in coverages of those substrates. Sage Sparrows, for example, increased their use of sagebrush and grass with increasing grass coverage and with increasing densities of Sage Sparrows. Responses to both variables suggested nonlinear threshold patterns.We interpret the variations in behavior as indicating a loose coupling between behavior and proximate environmental conditions for these species. In such situations, the variability of behavior complicates attempts to test ecological hypotheses (e.g. behavioral niche partitioning) with data from a limited number of locations or years.     

The importance of sediment in the grazing ecology and size class interactions of an armored catfish,Ancistrus spinosus

Synopsis Armored catfish, Ancistrus spinosus, graze substrates in a central Panamanian stream. They ingest both attached algae and sediment that settles onto substrates. During the dry season, this sediment is organic-rich (18–24% ash-free dry weight), and is derived from decomposing periphyton and vegetation from the surrounding, largely deciduous forest. This sediment, however, is not a food for Ancistrus, and in fact imposes energetic costs. These costs were estimated to be 15–22% of the daily energy budgets of 10 g individuals held under experimental conditions. In the stream, the presence of thick sediment on substrates increases the tendency for small Ancistrus to seek out larger individuals or areas cleared by them. Clearing of substrates by larger individuals may be particularly important to smaller Ancistrus during the dry season, when sediment-free substrate in stream pools is in short supply.     

Identification of the different intermediates in the interaction of (A)BC excinuclease with its substrates by DNase I footprinting on two uniquely modified oligonucleotides

(A)BC excinuclease is the enzymatic activity resulting from the joint actions of UvrA, UvrB and UvrC proteins of Escherichia coli. The enzyme removes from DNA many types of adducts of dissimilar structures with different efficiencies. To understand the mechanism of substrate recognition and the basis of enzyme specificity, we investigated the interactions of the three subunits with two synthetic substrates, one containing a psoralen-thymine monoadduct and the other a thymine dimer. Using DNase I as a probe, we found that UvrA makes a 33 base-pair footprint around the psoralen-thymine adduct and that UvrA-UvrB make a 45 base-pair asymmetric footprint characterized by a hypersensitive site 11 nucleotides 5' to the adduct and protection mostly on the 3' side of the damage. Conditions that favor dissociation of UvrA from the UvrA-UvrB-DNA complex, such as addition of excess undamaged DNA to the reaction mixture, resulted in the formation of a 19 base-pair UvrB footprint. In contrast, a thymine dimer in a similar sequence context failed to elicit a UvrA, a UvrA-UvrB or UvrB footprint and gave rise to a relatively weak DNase I hypersensitive site typical of a UvrA-UvrB complex. Dissociation of UvrA from the UvrA-UvrB-DNA complex stimulated the rate of incision of both substrates upon addition of UvrC, leading us to conclude that UvrA is not a part of the incision complex and that it actually interferes with incision. The extent of incision of the two substrates upon addition of UvrC (70% for the psoralen adduct and 20% for the thymine dimer) was proportional to the extent of formation of the UvrA-UvrB-DNA (i.e. UvrB-DNA) complex, indicating that substrate discrimination occurs at the preincision step.     

Bacterial diversity and their metabolic profiles in the sedimentary environments of Ny-Ålesund,Arctic

Sedimentary environments in the Arctic are known to harbor diverse microbial communities playing a crucial role in the remineralization of organic matter and associated biogeochemical cycles. In this study, we used a combination of culture-dependent and culture-independent approaches to understanding the bacterial community composition associated with the sediments of a terrestrial versus fjord system in the Svalbard Arctic. Community-level metabolic profiling and growth response of retrieved bacterial isolates towards different carbon substrates at varying temperatures were also studied to assess the metabolic response of communities and isolates in the system. Bacterial species belonging to Cryobacterium and Psychrobacter dominated the terrestrial and fjord sediment retrievable fraction. Amplicon sequencing analysis revealed higher bacterial diversity in the terrestrial sediments (Shannon index; 8.135 and 7.935) as compared to the fjord sediments (4.5–5.37). Phylum Proteobacteria and Bacteroidetes dominated both terrestrial and fjord sediments. Phylum Verrucomicrobia and Cyanobacteria were abundant in terrestrial sediments while Epsilonbacteraeota and Fusobacteriia dominated the fjord sediments. Significant differences were observed in the carbon substrate utilization profiles between the terrestrial and fjord sediments at both 4 °C and 20 °C incubations (p?<?0.005). Utilization of N-acetyl-D-glucosamine, D-mannitol and Tween-80 by the sediment communities and bacterial isolates from both systems, irrespective of their temperature incubations implies the affinity of bacteria for such substrates as energy sources and for their survival in cold environments. Our results suggest the ability of sediment bacterial communities to adjust their substrate utilization profiles according to condition changes in the ecosystems and are found to be less influenced by their phylogenetic relatedness.

     

Effects of water depth and substrate type on growth dynamics and biomass allocation of Oryza rufipogon

Oryzarufipogon is known as the ancestor of Asian cultivated rice (Oryzasativa) and the most important germplasm for rice improvement. In this study, we investigated its growth and biomass allocation in response to water depth and substrate type. The results demonstrated that individual plant had an average weight of 18.98 g, 9.36 g, and 10.59 g and produced 77.7 seeds, 35.5 seeds, and 41.6 seeds in deep-, fluctuated-, and shallow water, respectively. Root-to-shoot ratios were 0.37 in deep water, 0.61 in fluctuated water level, and 0.56 in shallow water, reflecting larger investment in roots under water-level fluctuation and shallow water conditions. However, biomass allocation for sexual reproduction was no significant different among the three water levels. In substrates experiment, total biomass and seed production were significantly different between sediment types, and the averages were 10.59 g, 3.56 g, and 0.76 g in biomass and 41.6 seeds, 13.8 seeds, and 0.5 seeds per plant in lake sediment, river sand and clay, respectively. The number of tillers was significantly fewer in sandy and clay substrates than in lake sediments. Individual plant in clay substrates was significantly shorter than those in sandy and in lake sediment substrates. Our study suggests that the plasticity in morphology and biomass allocation of O.rufipogon appears to be an adaptation to the variability in water level and substrate conditions.     

Effects of water depth and substrate type on growth dynamics and biomass allocation of Oryza rufipogon

Oryzarufipogon is known as the ancestor of Asian cultivated rice (Oryzasativa) and the most important germplasm for rice improvement. In this study, we investigated its growth and biomass allocation in response to water depth and substrate type. The results demonstrated that individual plant had an average weight of 18.98 g, 9.36 g, and 10.59 g and produced 77.7 seeds, 35.5 seeds, and 41.6 seeds in deep-, fluctuated-, and shallow water, respectively. Root-to-shoot ratios were 0.37 in deep water, 0.61 in fluctuated water level, and 0.56 in shallow water, reflecting larger investment in roots under water-level fluctuation and shallow water conditions. However, biomass allocation for sexual reproduction was no significant different among the three water levels. In substrates experiment, total biomass and seed production were significantly different between sediment types, and the averages were 10.59 g, 3.56 g, and 0.76 g in biomass and 41.6 seeds, 13.8 seeds, and 0.5 seeds per plant in lake sediment, river sand and clay, respectively. The number of tillers was significantly fewer in sandy and clay substrates than in lake sediments. Individual plant in clay substrates was significantly shorter than those in sandy and in lake sediment substrates. Our study suggests that the plasticity in morphology and biomass allocation of O.rufipogon appears to be an adaptation to the variability in water level and substrate conditions.     

Macrophytes and diatoms – major results and conclusions from the STAR project

The interactions between sensitivity and variability of macrophyte and diatom communities were evaluated as a research support of methodologies required by the Water Framework Directive. Slope and shading were identified as additional typological parameters improving links between unimpacted macrophyte communities and running water types. Two other studies demonstrated indication value of macrophytes for assessment of nutrient enrichment and hydromorphological degradation. The special exercises were realized within the STAR project to evaluate sources of variability/uncertainty in assessment methods based on macrophytes and diatoms. Sampling period and shading of the site were found as major factors affecting variability in macrophyte assessment results. Uncertainty of diatom assessment is predominantly associated with selection of site, substrate type and taxonomic identification. Further extension of indication systems and definition of macrophyte/diatom-specific typology of running waters are considered as the main aims of subsequent investigations.     

Nanomechanics controls neuronal precursors adhesion and differentiation

The ability to control the differentiation of stem cells into specific neuronal types has a tremendous potential for the treatment of neurodegenerative diseases. In vitro neuronal differentiation can be guided by the interplay of biochemical and biophysical cues. Different strategies to increase the differentiation yield have been proposed, focusing everything on substrate topography, or, alternatively on substrate stiffness. Both strategies demonstrated an improvement of the cellular response. However it was often impossible to separate the topographical and the mechanical contributions. Here we investigate the role of the mechanical properties of nanostructured substrates, aiming at understanding the ultimate parameters which govern the stem cell differentiation. To this purpose a set of different substrates with controlled stiffness and with or without nanopatterning are used for stem cell differentiation. Our results show that the neuronal differentiation yield depends mainly on the substrate mechanical properties while the geometry plays a minor role. In particular nanostructured and flat polydimethylsiloxane (PDMS) substrates with comparable stiffness show the same neuronal yield. The improvement in the differentiation yield obtained through surface nanopatterning in the submicrometer scale could be explained as a consequence of a substrate softening effect. Finally we investigate by single cell force spectroscopy the neuronal precursor adhesion on the substrate immediately after seeding, as a possible critical step governing the neuronal differentiation efficiency. We observed that neuronal precursor adhesion depends on substrate stiffness but not on surface structure, and in particular it is higher on softer substrates. Our results suggest that cell–substrate adhesion forces and mechanical response are the key parameters to be considered for substrate design in neuronal regenerative medicine. Biotechnol. Bioeng. 2013; 110: 2301–2310. © 2013 Wiley Periodicals, Inc.     

Substrate selection by saprophagous wood‐borer larvae within highly variable hosts

In insects completing their larval development within a single host, oviposition site is seen as a major determinant of offspring performance. However, in previous studies, the saprophagous wood‐borer Anthophylax attenuatus (Haldeman) (Coleoptera: Cerambycidae) showed no strong response to between‐host variations in nutritional factors influencing larval growth and survival. To explain such weak selection in adults, we hypothesized that substrate selection occurs at a smaller scale by larvae within hosts showing high variability in substrate quality. In this study, we described within‐host variability in wood density and determined whether wood‐boring larvae were found more often than expected in specific decay types. We characterized the variability of decay in 24 snags by producing wood density profiles for each. We then collected larvae from the same snags through wood dissection, and associated a wood density value to each by taking a wood sample around each larva found. We then compared ratios of available and used substrate types defined by wood density. We observed substantial within‐snag variation in wood density. Middle decay class (0.275–0.375 g cm^?3) was significantly overused by larvae, whereas more decayed wood was clearly avoided. High within‐host variability in substrate quality and active or passive selection by larvae of specific substrate types suggest that selection pressures on adult behaviour could be lower than expected for a parasitic species, and might be linked with the weak selection observed at a larger scale by ovipositing adults.     

Fungal Diversity Is Not Determined by Mineral and Chemical Differences in Serpentine Substrates

The physico-chemical properties of serpentine soils lead to strong selection of plant species. Whereas many studies have described the serpentine flora, little information is available on the fungal communities dwelling in these sites. Asbestos minerals, often associated with serpentine rocks, can be weathered by serpentine-isolated fungi, suggesting an adaptation to this substrate. In this study, we have investigated whether serpentine substrates characterized by the presence of rocks with distinct mineral composition could select for different fungal communities. Both fungal isolation and 454 pyrosequencing of amplicons obtained from serpentine samples following direct DNA extraction revealed some fungal taxa shared by the four ophiolitic substrates, but also highlighted several substrate-specific taxa. Bootstrap analysis of 454 OTU abundances indicated weak clustering of fungal assemblages from the different substrates, which did not match substrate classification based on exchangeable macronutrients and metals. Intra-substrate variability, as assessed by DGGE profiles, was similar across the four serpentine substrates, and comparable to inter-substrate variability. These findings indicate the absence of a correlation between the substrate (mineral composition and available cations) and the diversity of the fungal community. Comparison of culture-based and culture-independent methods supports the higher taxonomic precision of the former, as complementation of the better performance of the latter.     

A histochemical principle bearing on correctness of diagnosis in storage diseases

A principle is proposed which may help pathologists avoid errors in diagnosis of storage diseases. Tissues from patients in whom a tentative diagnosis of a metabolic disorder has been made often store a number of metabolites in the cells. The presence of these metabolites can occur in single-enzyme or activator defects as a result of the following causes: (a) deposition of metabolites situated near the main substrate of the defective enzyme in the catabolic path, and compounds which were changed after they were deposited; (b) presence of multiple substrates for this enzyme; (c) co-deposition of molecules bound to the main substrates; (d) existence of multiple substrates for a single defective activator molecule. In contrast to these causes, variability in processes not associated with a single-enzyme or activator deficiency may be due to the following: (e) inhibition of multiple hydrolases by drugs or metabolites; (f) localization of substrates and hydrolases in different compartments; (g) multiple enzyme deficiencies; (h) concentration of metabolites beyond the catabolic capacity of cells. According to the proposed principle, diagnosis of storage disease resulting from a single enzyme deficiency can be negated if a wide-range histochemical test shows that the main substrate of a deficient enzyme is not present in some primary storage cells. The validity of the principle and possible pitfalls are discussed.     

The influence of catchment characteristics on suspended sediment properties

In order to investigate the influence of catchment characteristics on suspended sediment properties, suspended sediment samples were collected from the outlets of 60 small catchments located throughout Southwest England over a 14-month period. The catchments were selected to provide a representative range of topographic, land use, soil and geological characteristics. The suspended sediment samples were collected using time-integrating trap samplers, emptied at monthly intervals. Laboratory analysis focused on a selection of suspended sediment properties, including particle size composition, cation exchange capacity, and organic carbon, nitrogen, metal, radionuclide and phosphorus content. The results presented show that despite the substantial variability of catchment characteristics associated with the 60 sampling sites, the suspended sediment properties generally fell within a relatively limited range. However, statistical analysis identified significant spatial variability of suspended sediment within Southwest England, which in turn can be linked to catchment characteristics.     

基于遥感的煤炭型矿业城市土地利用与生态承载力时空变化分析

运用遥感和社会经济系统发展指数修正生态足迹模型,开展淮南市土地利用与生态承载力时空演化分析。结果表明:1987—2012年,淮南市人均生态承载力总体呈现缓慢降低后略微升高的趋势,2009年是人均生态承载力提升的拐点,表明经济科技因子的提升作用;淮南市生态承载力时空差异显著,总体呈现东南和北部高、西部低的格局,而且区域破碎化加剧的趋势。矿区占用大量耕地以及积水塌陷区的形成,是生态承载力的下降和空间格局分异的主要原因;土地利用转移以耕地、建筑用地为主,水域对土地利用格局的影响日益增强,开展塌陷区整治,将塌陷区形成的水域转换成耕地或建设用地,将是提高淮南市生态承载力的最有效途径之一。     

Brief Communication: Beyond the South African cave paradigm—Australopithecus africanus from Plio–Pleistocene paleosol deposits at Taung

Following the discovery of the “Taung Child” (Australopithecus africanus) in 1924 in the Buxton‐Norlim Limeworks near Taung, the fossil‐bearing deposits associated with the Dart and Hrdli?ka pinnacles have been interpreted as the mined remnants of cave sediments that formed within the Plio–Pleistocene Thabaseek Tufa: either as a younger cave‐fill or as contemporaneous carapace caves. When combined with the Plio–Pleistocene dolomitic cave deposits from the “Cradle of Humankind,” a rather restricted view emerges that South African early hominins derived from cave deposits, whereas those of east and central Africa are derived from fluvio‐lacustrine and paleosol deposits. We undertook a sedimentological and paleomagnetic analysis of the pink‐colored deposit (PCS) from which the “Taung Child” is purported to have derived and demonstrate that it is a calcrete, a carbonate‐rich pedogenic sediment, which formed on the paleo‐land surface. The deposit extends 100 s of meters laterally beyond the Dart and Hrdli?ka Pinnacles where it is interbedded with the Thabaseek Tufa, indicating multiple episodes of calcrete development and tufa growth. The presence of in situ rhizoconcretions and insect trace fossils (Celliforma sp. and Coprinisphaera sp.) and the distinctive carbonate microfabric confirm that the pink deposit is a pedogenic calcrete, not a calcified cave sediment. Paleomagnetic and stratigraphic evidence indicates that a second, reversed polarity, fossil‐bearing deposit (YRSS) is a younger fissure‐fill formed within a solutional cavity of the normal polarity tufa and pink calcrete (PCS). These observations have implications for the dating, environment, and taphonomy of the site, and increase the likelihood of future fossil discoveries within the Buxton‐Norlim Limeworks. Am J Phys Anthropol 151:316–324, 2013. © 2013 Wiley Periodicals, Inc.     

Substrate and structure of ground nests have fitness consequences for an alpine songbird

Songbird nests are an important life‐history component with multiple functions, including the creation of a suitable microclimate for offspring development. Thus, functional nest characteristics may influence fitness correlates, such as nestling size traits, and may co‐vary with prevailing environmental conditions. We investigated among‐ and within‐female variation in nest substrate, lining and decoration structures with associated fitness consequences (hatching success, nestling size traits, nest survival) across two breeding seasons for an alpine population of Horned Lark Eremophila alpestris. We combined these observations with explicit measures of nest temperature to address the influence of nest characteristics on microclimate. Nests in heather substrate had the coldest microclimates compared with grass and bare‐ground substrate, but also the greatest nest survival rates (68% versus 37–44% in other substrates), indicating the potential for substrate use decisions to reflect a trade‐off between microclimate and nest survival in response to prevailing weather and predation risk conditions. Furthermore, nest lining and nest decoration patterns indicated some support for a thermoregulatory function. Nests that were lined with willow (Salix sp.) seed‐down were associated with larger, heavier nestlings and the use of down lining decreased in frequency as the season warmed up. Nest decoration placed in front of the nest (e.g. stones or dirt clumps varying in mass from 5.3 to 186.6 g) was positively associated with warmer nest microclimates. Females demonstrated high phenotypic flexibility, as 61–94% of the observed variance in nest characteristics was explained by within‐female rather than among‐female differences. Such flexible nesting behaviour suggests the capacity to adjust to changing environmental conditions to maintain vital fitness correlates such as nest survival and nestling size development.