586 research outputs found
The composition and diversity of dinosporin in species of the Apectodinium complex (Dinoflagellata)
No full textOrganic-walled dinoflagellate cysts, produced as a result of sexual reproduction, are important tools for studies on recent and past environments. Additionally, the organic-walled cysts can be used as proxies for understanding the composition and chemical transformations of marine kerogen, the largest global organic carbon pool. However, any usage of dinoflagellate cysts in this manner is predicated on an understanding of the composition and transformations of this potential proxy. Dinoflagellate cyst walls are composed of “dinosporin”, a refractory biomacromolecule that probably represents a suite of chemically distinct biopolymers. In order to investigate both the nature of dinosporin and the extent to which the composition of this biomacromolecule may differ between dinoflagellate cyst taxa, we analyzed cyst species from the genus Apectodinium. The species defined within this genus are visually similar with several seeming to represent end-members along a continuum of morphological variation. Micro-Fourier transform infrared (FTIR) analysis was performed on three of these morphospecies (identified visually as A. paniculatum, A. parvum and A. augustum) from two regionally distinct samples. The analyses showed consistent patterns with clear differences between the species. The dinosporin of A. paniculatum closely resembles cellulose and is rich in ether bonds (Csingle bondO), while the dinosporin of A. augustum contains more carboxyl (COOH) groups. A. parvum appears intermediate in many respects, despite representing an end-member in terms of morphology. These differences are consistent regardless of the regional setting or post-depositional conditions, and strongly suggest that the original cyst wall composition of the species differed when the cysts were formed. These data are the first to clearly show differences in cyst wall composition between species of the same genus and indicate that the chemical diversity of dinosporins is greater than previously thought
Differences in the chemical composition of organic-walled dinoflagellate resting cysts from phototrophic and heterotrophic dinoflagellates
No full textDinoflagellates constitute a large proportion of the planktonic biomass from marine to freshwater environments. Some species produce a preservable organic-walled resting cyst (dinocyst) during the sexual phase of their life cycle that is an important link between the organisms, the environment in which their parent motile theca grew, and the sedimentary record. Despite their abundance and widespread usage as proxy indicators for environmental conditions, there is a lack of knowledge regarding the dinocyst wall chemical composition. It is likely that numerous factors, including phylogeny and life strategy, determine the cyst wall chemistry. However, the extent to which this composition varies based on inherent (phylogenetic) or variable (ecological) factors has not been studied. To address this, we used micro-Fourier transform infrared (FTIR) spectroscopy to analyze nine cyst species produced by either phototrophic or heterotrophic dinoflagellates from the extant orders Gonyaulacales, Gymnodiniales and Peridiniales. Based on the presence of characteristic functional groups, two significantly different cyst wall compositions are observed that correspond to the dinoflagellate's nutritional strategy. The dinocyst wall compositions analyzed appeared carbohydrate-based, but the cyst wall produced by phototrophic dinoflagellates suggested a cellulose-like glucan, while heterotrophic forms produced a nitrogen-rich glycan. This constitutes the first empirical evidence nutritional strategy is related to different dinocyst wall chemistries. Our results indicated phylogeny was less important for predicting composition than the nutritional strategy of the dinoflagellate, suggesting potential for cyst wall chemistry to infer past nutritional strategies of extinct taxa preserved in the sedimentary record
Are the Kimmeridge Clay deposits affected by “burn-down” events? Palynological and geochemical studies on a 1 metre long section from the Upper Kimmeridge Clay Formation (Dorset, UK)
No full textTwo independent analytical approaches, palynology and inorganic geochemistry, were applied to identify potential oxygen “burn-down” events in the Late Jurassic Kimmeridge Clay Formation (KCF). The KCF interval of the rotunda ammonite zone, spanning 121.82–122.72 m depth was sampled from the Swanworth Quarry 1 borehole (Dorset, UK) at 2.5–5.0 cm resolution. Samples were analysed for total organic carbon (TOC), concentrations of elements that are known to be productivity- and/or nutrient-related (e.g. Cu, P), detrital (e.g. Al, Ti, Zr) and redox-sensitive/sulphide-forming (e.g. V, Mo, Fe, Mn, S), and palynofacies components including analysis of organic-walled dinoflagellate cysts (dinocysts) on a species level.The TOC contents generally exceed 2 wt.%, with a maximum of 8.8 wt.% at 122.37 cm depth and elevated values in the central part of the investigated interval. This interval of relatively higher TOC values correlates well with the maximum recovery of marine palynomorphs and low Al values, suggesting that the TOC is primarily of marine organic matter (OM).Changes in V/Al, Mo/Al, Fe/Al, Mn/Al and S patterns at 122.37 m depth mark a shift from anoxic conditions in the lower part of the studied interval to more oxic conditions in its upper part. Such a shift could explain the relatively high TOC and marine palynomorph concentrations in the lower part of the studied interval as a result of better preservation, and the subsequent decrease as an effect of a post-depositional “burn-down”, i.e. OM oxidation. As the amount of marine palynomorphs and TOC content diminishes from the middle part of the section upwards, species-specific changes in dinocyst assemblages can be observed. In particular, concentrations of Circulodinium spp., Cyclonephelium spp., Sirmiodinium grossi, Senoniasphaera jurassica and Systematophora spp. decrease rapidly in comparison to other species, such as Glossodinium dimorphum and Cribroperidinium sp. 1, which may suggest selective degradation of dinocysts due to oxidation.We suggest that post-depositional oxygenation of bottom and pore waters within the sediment was most probably the cause for decreasing TOC values and reduced recovery of marine palynomorphs towards the top of the studied interval in comparison to high TOC and marine palynomorph values in the central part of the studied interval due to anoxic conditions.<br/
Infra red spectroscopy, flash pyrolysis, thermally assisted hydrolysis and methylation (THM) in the presence of tetramethylammonium hydroxide (TMAH) of cultured and sediment-derived Lingulodinium polyedrum (Dinoflagellata) cyst walls
No full textThe macromolecular composition of dinoflagellate cyst walls is poorly understood and is usually referred to as ‘sporopollenin-like’. We have carried out micro-Fourier transform infra red (micro-FTIR) analysis of chemically untreated sediment-derived and enzymatically and chemically purified culture-derived Lingulodiniumpolyedrum cyst walls, which suggests an aliphatic polymer rich in C-O bonds and relatively poor in CH2 and CH3 groups, and which is much closer to cellulose than to sporopollenin or algaenan. This is in agreement with flash pyrolysis–gas chromatography–mass spectrometry (py–GC–MS), with and without tetramethylammonium hydroxide (TMAH) of purified culture derived cyst walls, which indicated an oxygen-rich polymer without normal or isoprenoid carbon chains.The results support a strongly cross-linked carbohydrate-based polymer and as such confirm earlier hypotheses that the cysts were unlike algaenan or sporopollenin, contrasting with the suggestion that the cyst walls were highly aromatic and contained tocopherol as a major monomeric building block
Generalizing Levins metapopulation model in explicit space: Models of intermediate complexity
No full textA recent study [Harding and McNamara, 2002. A unifying framework for metapopulation dynamics. Am. Nat. 160, 173-185] presented a unifying framework for the classic Levins metapopulation model by incorporating several realistic biological processes, such as the Allee effect, the Rescue effect and the Anti-rescue effect, via appropriate modifications of the two basic functions of colonization and extinction rates. Here we embed these model extensions on a spatially explicit framework. We consider population dynamics on a regular grid, each site of which represents a patch that is either Occupied or empty, and with spatial coupling by neighborhood dispersal. While broad qualitative similarities exist between the spatially explicit models and their spatially implicit (mean-field) counterparts, there are also important differences that result from the details of local Processes. Because of localized dispersal, spatial correlation develops among the dynamics of neighboring populations that decays with distance between patches. The extent of this correlation at equilibrium differs among the metapopulation types, depending on which processes prevail in the colonization and extinction dynamics. These differences among dynamical processes become manifest in the spatial pattern and distribution of "clusters" of occupied patches. Moreover, metapopulation dynamics along a smooth gradient of habitat availability show significant differences in the spatial pattern at the range limit. The relevance of these results to the dynamics of disease spread in metapopulations is discussed. (C) 2008 Elsevier Ltd. All rights reserved
The scaling of diving time budgets : insights from an optimality approach
No full textThe authors acknowledge the Natural Environment Research Council for support with this work (grant NER/A/S/2003/00616).Simple scaling arguments suggest that, among air-breathing divers, dive duration should scale approximately with mass to the one-third power. Recent phylogenetic analyses appear to confirm this. The same analyses showed that duration of time spent at the surface between dives has scaling very similar to that of dive duration, with the result that the ratio of dive duration to surface pause duration is approximately mass invariant. This finding runs counter to other arguments found in the diving literature that suggest that surface pause duration should scale more positively with mass, leading to a negative scaling of the dive-pause ratio. We use a published model of optimal time allocation in the dive cycle to show that optimal decisions can predict approximate mass invariance in the dive-pause ratio, especially if metabolism scales approximately with mass to the two-thirds power (as indicated by some recent analyses) and oxygen uptake is assumed to have evolved to supply the body tissues at the required rate. However, emergent scaling rules are sensitive to input parameters, especially to the relationship between the scaling of metabolism and oxygen uptake rate at the surface. Our results illustrate the utility of an optimality approach for developing predictions and identifying key areas for empirical research on the allometry of diving behavior.Peer reviewe
Data: Approaching a population level assessment of body size in pinnipeds using drones, an early warning of environmental degradation.
No full text<p>Data and R sctipts for measuring harbour seal body sizes and estimating mass based on .shp files containing outlines. Associated with the manusctipt currently titled "Approaching a population level assessment of body size in pinnipeds using drones, an early warning of environmental degradation."</p>
<p>1_Seal_Volume_Function.R: A function for the estimation of length, width, and ellipsoid volume of harbour seals from georeferenced polygons representing individual outlines 2_Polygon_Process.R: This script uses the curved_length_vol function (1_Seal_Volume_Function.R) to process a folder full of .shp file subfolders containing georeferenced polygons representing individual outlines and outputs a .csv with estimates of length, width, and ellipsoid volume for each individual. 3_Calibration.R: This script processes and calibrates summarized harbor seal measurements based on reference to known individuals</p>
<p>CSV_Files: Folder containing data files</p>
<p>Known_Seals.csv: True measurments of length and mass for known seals with derived estimates of 'true' width and volume. Drone based estimates of length, width, simple and complex volume for the same individuals, information on pose.</p>
<p>measurments.csv: Drone based estimates of length, width, simple and complex volume for all individuals.</p>
<p>Pup_growth.csv: Data on pup mass by age from Harding et al. 2005 (<a href="https://doi.org/10.1111/j.0269-8463.2005.00945.x" rel="nofollow">https://doi.org/10.1111/j.0269-8463.2005.00945.x</a>).</p>
<p>Slottsskogen_Data.csv: True and drone based measurments for individual captive harbour seals taken on two seperate occasions.</p>
<p>Summarised_Weights.csv: True measurments of length, girth, and mass for harbour seals.</p>
Mythophilia
No full textC. J. Jung and the Humanities: Toward a Hermeneutics of Culture (Routledge, London, £25, 372 pp., 1990) is edited by Karin Barnaby and Pellegrino D'Aciernio. The book is a selection of essays and discussions from a conference in 1986 jointly sponsored by Hofstra University and the C. G. Jung Foundation of New York. Karin Barnaby has taught comparative literature at Hofstra University and is now at New York University, She has published an article on Schiller and Jung and is associate editor of Quadrant. Pellegrino D'Acierno is Associate Professor of Comparative Literature and Director of Italian studies at Hofstra University. He is the author or translator of several books on comparative literature.</jats:p
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