915 resultados para Species Numbers and Identity


Relevância:

100.00% 100.00%

Publicador:

Resumo:

Within the monitoring programme of the Helsinki Commission (HELCOM) the mesozooplankton of the Bornholm Basin (ICES subdivision 25, station BMP-K2) was sampled by the WP-2 net (lOOfJm) 5-8 times a year in 1988-1992. Abundance, biomass, secondary production and productivity (P/B) were given for mesozooplankton groups and copepod species. Environmental factors recorded were temperature, chlorophyll a and primary production. Within copepods, the dominant species were Temora longicornis and Pseudocalanus minutus with yearly peak values of 40-50% of the monthly copepod numbers and biomasses. The annual production of Temora longicornis was highest (6.5g C/m**2/y). The biomass of all copepods was at its maximum in June (mean = 2.25g C/m**2), especially in 1992 (3.65g C/m**2). The differences between results from two methods used to calculate the production of copepods were greatest in June and July. The cladocerans were only important in summer and the appendicularians only in spring. The productivity (P/B) of the appendicularians was highest of all mesozooplankton groups. Numbers and the biomass of the meroplankton were one or two orders of magnitude below the holoplanktic groups.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The responses of larger (>50 µm in diameter) protozooplankton groups to a phytoplankton bloom induced by in situ iron fertilization (EisenEx) in the Polar Frontal Zone (PFZ) of the Southern Ocean in austral spring are presented. During the 21 days of the experiment, samples were collected from seven discrete depths in the upper 150 m inside and outside the fertilized patch for the enumeration of acantharia, foraminifera, radiolaria, heliozoa, tintinnid ciliates and aplastidic thecate dinoflagellates. Inside the patch, acantharian numbers increased twofold, but only negligibly in surrounding waters. This finding is of major interest, since acantharia are suggested to be involved in the formation of barite (BaSO_4 ) found in sediments and which is a palaeoindicator of both ancient and modern high productivity regimes. Foraminifera increased significantly in abundance inside and outside the fertilized patch. However the marked increase of juveniles after a full moon event suggests a lunar periodicity in the reproduction cycle of some foraminiferan species rather than a reproductive response to enhanced food availability. In contrast, adult radiolaria showed no clear trend during the experiment, but juveniles increased threefold indicating elevated reproduction. Aplastidic thecate dinoflagellates almost doubled in numbers and biomass, but also increased outside the patch. Tintinnid numbers decreased twofold, although biomass remained constant due to a shift in the size spectrum. Empty tintinnid loricae, however, increased by a factor of two indicating that grazing pressure on this group mainly by copepods intensified during EisenEx. The results show that iron-fertilization experiments can shed light on the biology and the role of these larger protists in pelagic ecosystem which will improve their use as proxies in palaeoceanography.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Ecological work carried out on the Antarctic and Magellan shelves since the first IBMANT conference held at the UMAG, Punta Arenas in 1997 is summarized to identify areas where progress has been made and others, where impor- tant gaps have remained in understanding past and present interaction between the Antarctic and the southern tip of South America. This information is complementary to a review on shallow-water work along the Scotia Arc (Barnes, 2005) and recent work done in the deep sea (Brandt and Hilbig, 2004). While principally referring to shipboard work in deeper water, above all during the recent international EASIZ and LAMPOS campaigns, relevant work from shore stations is also included. Six years after the first IBMANT symposium, significant progress has been made along the latitudinal gradient from the Magellan region to the high Antarctic in the fields of biodiversity, biogeography and community structure, life strategies and adaptations, the role of disturbance and its significance for biodiversity, and trophic coupling of the benthic realm with the water column and sea ice. A better understanding has developed of the role of evolutionary and ecological factors in shaping past and present-day environmental conditions, species composition and distribution, and ecosystem functioning. Furthermore, the science community engaged in unravelling Antarctic-Magellan interactions has advanced in methodological aspects such as new analytical approaches for comparing biodiversity derived from visual methods, growth and age determination, trophic modelling using stable isotope ratios, and molecular approaches for taxonomic and phylogenetic purposes. At the same time, much effort has been invested to complement the species inventory of the two adjacent regions. However, much work remains to be done to fill the numerous gaps. Some perspectives are outlined in this review, and sug- gestions are made where particular emphasis should be placed in future work, much of which will be developed in the frame of SCAR's EBA (Evolution and Biodiversity in the Antarctic) programme.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

A relevant subject in our globalized world concerns the relationship between language and identity, specifically amongst migrant youngsters’ experience of group belonging. This study therefore focused on how adolescents born to foreign parents in Sweden, perceived their multilingualism as part of their identity formation. I also aimed to include how socio-economic aspects could affect the process of identity construction. Thus, the investigation was performed with seventh grade students at a primary school located in the Stockholm suburb Bredäng. The methods consisted of a questionnaire, which was completed by the entire class and a group interview where six students participated. The results revealed that students adapted their language use based on the context, but Swedish was used most habitually. The informants viewed their multilingualism as beneficial but yet fully aware of the linguistic ideologies functioning in society. By combining their minority and majority language, the students were left with different ethnic identities and had diverse interpretations of what it meant to be Swedish. Even though all of them perceived themselves to have multiple ethnic identities, this was not solely seen positively. The issue of belonging was raised and the students claimed to be outcasts everywhere. However, the results differed depending on whether the students were born in Sweden or not. Also, most of them struggled with the process of assumed and ascribed identities, since they perceived themselves to be Swedish but experienced that society valued them as immigrants. Lastly, the study revealed that there were connections between their multilingualism and social mobility as the relationship towards the motherland was highly prioritized even with low levels of economic capital. 

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Thesis (Ph.D.)--University of Washington, 2016-06

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The biology of Paryphanta busbyi watti, an endangered carnivorous land snail, was studied mostly by following large juvenile and adult snails with harmonic radar. The snails are nocturnally active and most (79%) hide during the day under leaf litter or in dense vegetation. Fecal analysis showed that the diet is primarily earthworms, but some cannibalism of smaller snails occurs. Empty shells appear to be an additional source of dietary calcium. Mating occurred most frequently between April and July. Mating snails stayed together for 4-7 days, and each pair reversed their positions at least twice. Four snails were first found mating 151-1240 d after they acquired adult shells, and 7 snails were observed mating a second time after 66-298 d. We found 8 nests and observed 6 snails ovipositing; 5 snails laid eggs in holes they dug and one laid eggs in a crevice between rocks. In 2 instances, oviposition was recorded 52 and 140 d after mating. Snails were estimated to lay on average similar to17.5 eggs per year in 3-5 clutches. Most oviposition was observed in August/September, but some occurred between November and February. Of the snails that died, pigs killed 13.6% and humans inadvertently killed another 13.6%. Other snails died from unknown causes mostly during the drier and warmer months, from November to April. This large land snail survives in the presence of introduced predators, but some life history traits could predispose it to a rapid decline in numbers if new predators arrive.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Birds show striking interspecific variation in their use of carotenoid-based coloration. Theory predicts that the use of carotenoids for coloration is closely associated with the availability of carotenoids in the diet but, although this prediction has been supported in single-species studies and those using small numbers of closely related species, there have been no broad-scale quantitative tests of the link between carotenoid coloration and diet. Here we test for such a link using modern comparative methods, a database on 140 families of birds and two alternative avian phylogenies. We show that carotenoid pigmentation is more common in the bare parts (legs, bill and skin) than in plumage, and that yellow coloration is more common than red. We also show that there is no simple, general association between the availability of carotenoids in the diet and the overall use of carotenoid-based coloration. However, when we look at plumage coloration separately from bare part coloration, we find there is a robust and significant association between diet and plumage coloration, but not between diet and bare part coloration. Similarly, when we look at yellow and red plumage colours separately, we find that the association between diet and coloration is typically stronger for red coloration than it is for yellow coloration. Finally, when we build multivariate models to explain variation in each type of carotenoid-based coloration we find that a variety of life history and ecological factors are associated with different aspects of coloration, with dietary carotenoids only being a consistent significant factor in the case of variation in plumage. All of these results remain qualitatively unchanged irrespective of the phylogeny used in the analyses, although in some cases the precise life history and ecological variables included in the multivariate models do vary. Taken together, these results indicate that the predicted link between carotenoid coloration and diet is idiosyncratic rather than general, being strongest with respect to plumage colours and weakest for bare part coloration. We therefore suggest that, although the carotenoid-based bird plumage may a good model for diet-mediated signalling, the use of carotenoids in bare part pigmentation may have a very different functional basis and may be more strongly influenced by genetic and physiological mechanisms, which currently remain relatively understudied.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The response of generalist egg parasitoids to alternative natural hosts that are present simultaneously is not well known. We investigated the behavior of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) in relation to two field hosts Helicoverpa armigera Hubner and Spodoptera litura Fabricius, in choice and no choice tests. We quantified the effects of natal host species and post-emergence adult age on the oviposition preference of the parasitoids. H. armigera eggs were consistently preferred over S. litura eggs, regardless of the natal host and adult age. When only S. litura eggs were available as hosts, they were parasitized at statistically similar rates to H. armigera eggs (average of 17 +/- 2.7 vs. 13 +/- 3.0, H. armigera to S. litura). The adult lifespan and lifetime fecundity of T. pretiosum were variable but were affected by natal host species and/or host species to which they were exposed. Mean lifespan and fecundity of parasitoids that had developed in H. armigera eggs and were exposed to H. armigera eggs for oviposition were 13.9 +/- 1.8 days and 98.7 +/- 11.0 adult offspring. By contrast, those that developed in S. litura eggs and were exposed to S. litura eggs for oviposition lived for 7 +/- 0.9 days and produced 53.8 +/- 8.0 adult offspring. The ovigeny index (OI) was significantly lower in the parasitoids exposed to H. armigera eggs than in those exposed to S. litura eggs, regardless of the natal host, indicating that H. armigera eggs sustain the adult parasitoids better than S. litura eggs. These results are used to predict parasitoid behavior in the field when both hosts are available. (c) 2006 Elsevier Inc. All rights reserved.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Parasite infracommunities of the wrasse Coris batuensis (Bleeker, 1857) were analysed, and the relationship between endoparasites, diet, and host body weight inferred. Thirty-two fish were collected from Lizard Island, Australia. Percentage frequency of occurrence of prey categories in the gut was determined and abundance, prevalence and species richness of parasites were calculated. Fish mainly ate snails, bivalves and crustaceans and this did not vary with body weight. Thirty-one fish were parasitised with at least one of 21 taxa of parasites (4 ectoparasite and 17 endoparasite species), with an average of 4 species and 47 individuals per host. Tetraphyllidean cestode larvae were the most common and abundant group. Parasite life cycles are not known in detail, but small crustaceans, such as copepods and amphipods, are likely to be intermediate hosts for the cestodes, nematodes and digeneans found in C. batuensis. Molluscs, although frequent in the diet, may not be transmitting any parasite species. Numbers of prey and parasite species richness were not correlated. Composition, abundance and species richness of the parasite fauna were similar in hosts with different body weight, corresponding with C. batuensis having a similar diet throughout life. © Queensland Museum.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Language has been seen as a central pillar to ethnic identity. When the possibility of heritage language loss becomes imminent, therefore, concern turns towards the consequences for feelings of ethnic group membership. Heritage language researchers have indicated that the heritage language is so strongly associated with the individual’s cultural background that heritage language loss could have negative implications for the sense of identity to the ethnic group. This study investigates the relationship between language and ethnic identity over time among Gaelic learners in Nova Scotia. In order to identify the specific processes of heritage language use, the Gaelic learners are compared to French (second language), learners living in the same English-speaking milieu. Path analyses reveal that, only among Gaelic learners, there is an initial separation of language and ethnic identity, but that, over time, ethnic identity is a direct outcome of language use. The results support Edwards’ (1985), contention, at least in the case of heritage languages, that language and identity are not always strongly linked. It is suggested that this may be especially true in contexts where there is little opportunity for contact with members of the heritage language group.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Redox-sensitive cell signalling Thiol groups and the regulation of gene expression Redox-sensitive signal transduction pathways Protein kinases Protein phosphatases Lipids and phospholipases Antioxidant (electrophile) response element Intracellular calcium signalling Transcription factors NF-?B AP-1 p53 Cellular responses to oxidative stress Cellular responses to change in redox state Proliferation Cell death Immune cell function Reactive oxygen and nitrogen species – good or bad? Reactive oxygen species and cell death Reactive oxygen species and inflammation Are specific reactive oxygen species and antioxidants involved in modulating cellular responses? Specific effects of dietary antioxidants in cell regulation Carotenoids Vitamin E Flavonoids Inducers of phase II enzymes Disease states affected Oxidants, antioxidants and mitochondria Introduction Mitochondrial generation of reactive oxygen and nitrogen species Mitochondria and apoptosis Mitochondria and antioxidant defences Key role of mitochondrial GSH in the defence against oxidative damage Mitochondrial oxidative damage Direct oxidative damage to the mitochondrial electron transport chain Nitric oxide and damage to mitochondria Effects of nutrients on mitochondria Caloric restriction and antioxidants Lipids Antioxidants Techniques and approaches Mitochondrial techniques cDNA microarray approaches Proteomics approaches Transgenic mice as tools in antioxidant research Gene knockout and over expression Transgenic reporter mice Conclusions Future research needs

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Since independence in 1991, issues of nation and identity have become highly debated topics in Ukraine. This monograph explores not only how national identity is being (re)constructed by the Ukrainian state, but also the processes by which it is negotiated through society. The central argument of this work is that too much attention, concerning identity in Ukraine, has focused on markers of ethnicity and language. Instead, the author advocates a regional approach, engaging with the issue of how Ukraine's regional differences affect nation-building processes. Following the tumultuous events of the 'Orange Revolution', the view of Ukraine as a country inherently 'divided' between 'East' and 'West' has (re)emerged to become a popular explanation for political events. The study outlines the necessity for academics, policymakers and indeed politicians to veer away from this simplistic 'West versus East' divide. The book advocates an analysis of Ukraine's unique brand of regionalism not in terms of divisions, but in terms of regional differences and diversity. The author deconstructs the concept of 'Eastern Ukraine' by focusing on three Ukrainian localities, all adjacent to the Ukrainian-Russian border. The study examines how individuals provide 'their' own understanding of the place of their region within the wider processes of nation building across Ukraine. In doing so, the book develops a 'regional' approach to the study of identity politics in Ukraine.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Wet woodlands have been recognised as a priority habitat and have featured in the UK BAP since 1994. Although this has been acknowledged in a number of UK policies and guidelines, there is little information relating to their detailed ecology and management. This research, focusing on lowland Alnus glutinosa woodlands, aimed to address this data paucity through the analysis of species requirements and to develop a methodology to guide appropriate management for this habitat for the benefit of wildlife. To achieve these aims data were collected from 64 lowland Alnus glutinosa woodlands and a review of the literature was undertaken to identify species associated with the target habitat. The groundflora species found to be associated with lowland Alnus glutinosa woodland were assessed in relation to their optimal environmental conditions (Ellenberg indicator values) and survival strategies (Grime CSR-Strategy) to determine the characteristics (Characters of a Habitat; CoaHs) and range of intra-site conditions (Niches of a Habitat; NoaH). The methodologies, using CSR and Ellenberg indicator values in combination, were developed to determine NoaHs and were tested both quantitatively and qualitatively at different lowland Alnus glutinosa sites. The existence of CoaHs and NoaHs in actual sites was verified by detailed quadrat data gathered at three Alnus glutinosa woodlands at Stonebridge Meadows, Warwickshire, UK and analysed using TWINSPAN and DCA ordination. The CoaHs and NoaHs and their component species were confirmed to have the potential to occur in a particular woodland. Following a literature search relating to the management of small wet woodlands within the UK, in conjunction with the current research, broad principles and strategies were identified for the management of lowland Alnus glutinosa woodland. Using the groundflora composition, an innovative procedure is developed and described for identifying the potential variation within a particular site and determining its appropriate management. Case studies were undertaken on distinct woodlands and the methodology proved effective.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Reactive oxygen species (ROS) and the sphingolipid ceramide are each partly responsible for the intracellular signal transduction of a variety of physiological, pharmacological or environmental agents. Furthermore, the enhanced production of many of these agents, that utilise ROS and ceramide as signalling intermediates, is associated with the aetiologies of several vascular diseases (e.g. atherosclerosis) or disorders of inflammatory origin (e.g. rheumatoid arthritis; RA). Excessive monocyte recruitment and uncontrolled T cell activation are both strongly implicated in the chronic inflammatory responses that are associated with these pathologies. Therefore the aims of this thesis are (1) to further elucidate the cellular responses to modulations in intracellular ceramide/ROS levels in monocytes and T cells, in order to help resolve the mechanisms of progression of these diseases and (2) to examine both existing agents (methotrexate) and novel targets for possible therapeutic manipulation. Utilising synthetic, short chain ceramide to mimic the cellular responses to fluctuations in natural endogenous ceramide or, stimulation of CD95 to induce ceramide formation, it is described here that ceramide targets and manipulates two discrete sites responsible for ROS generation, preceding the cellular responses of growth arrest in U937 monocytes and apoptosis in Jurkat T-cells. In both cell types, transient elevations in mitochondrial ROS generation were observed. However, the prominent redox altering effects appear to be the ceramide-mediated reduction in cytosolic peroxide, the magnitude of which dictates in part the cellular response in U937 monocytes, Jurkat T-cells and primary human peripheral blood resting or PHA-activated T-cells in vitro. The application of synthetic ceramides to U937 monocytes for short (2 hours) or long (16 hours) treatment periods reduced the membrane expression of proteins associated with cell-cell interaction. Furthermore, ceramide treated U937 monocytes demonstrated reduced adhesion to 5 or 24 hour LPS activated human umbilical vein endothelial cells (HUVEC) but not resting HUVEC. Consequently it is hypothesised that the targeted treatment of monocytes from patients with cardiovascular diseases with short chain synthetic ceramide may reduce disease progression. Herein, the anti-inflammatory and immunosuppressant drug, methotrexate, is described to require ROS production for the induction of cytostasis or cytotoxicity in U937 monocytes and Jurkat T-cells respectively. Further, ROS are critical for methotrexate to abrogate monocyte interaction with activated HUVEC in vitro. The histological feature of RA of enhanced infiltration, survivability and hyporesponsiveness of T-cells within the diseased synovium has been suggested to arise from aberrant signalling. No difference in the concentrations of endogenous T-cell ceramide, the related lipid diacylglycerol (DAG) and cytosolic peroxide ex vivo was observed. TCR activation following PHA exposure in vitro for 72 hours did not induced maintained perturbations in DAG or ceramide in T-cells from RA patients or healthy individuals. However, T-cells from RA patients failed to upregulate cytosolic peroxide in response to PHA, unlike those from normals, despite expressing identical levels of the activation marker CD25. This inability to upregulate cytosolic peroxide may contribute to the T-cell pathology associated with RA by affecting the signalling capacity of redox sensitive biomolecules. These data highlight the importance of two distinctive cellular pools of ROS in mediating complex biological events associated with inflammatory disease and suggest that modulation of cellular ceramides represents a novel therapeutic strategy to minimise monocyte recruitment.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

This paper estimates the implicit model, especially the roles of size asymmetries and firm numbers, used by the European Commission to identify mergers with coordinated effects. This subset of cases offers an opportunity to shed empirical light on the conditions where a Competition Authority believes tacit collusion is most likely to arise. We find that, for the Commission, tacit collusion is a rare phenomenon, largely confined to markets of two, more or less symmetric, players. This is consistent with recent experimental literature, but contrasts with the facts on ‘hard-core’ collusion in which firm numbers and asymmetries are often much larger.