Kleptoparasites: a twofold cost of group living for the colonial spider, Metepeira incrassata (Araneae, Araneidae)

Several species of kleptoparasitic and araneophagic spiders (Araneae: Family Theridiidae, Subfamily Argyrodinae) are found in colonial webs of the orb-weaving spider Metepeira incrassata (Araneae, Araneidae) from Mexico, where they steal food and/or prey upon their spider hosts. Census data from natural M. incrassata colonies reveal that the incidence of these species increases with colony size. This pattern may reflect the presence of several other orb-weaving spiders, each with their own kleptoparasitic species, invading larger M. incrassata colonies. As the number of these associated spiders increases, so does the density and number of Argyrodinae species in M. incrassata colonies, suggesting that associated spiders might reduce their own kleptoparasite load by building their webs within M. incrassata colonies. This represents a twofold cost to M. incrassata, as a field enclosure experiment revealed that a primarily kleptoparasitic species (Argyrodes elevatus) may reduce prey available to their hosts, but a kleptoparasitic/araneophagic species (Neospintharus concisus) inflicts high mortality upon M. incrassata. However, the cost of kleptoparasitism and predation by these species may be offset in part for M. incrassata individuals in large colonies by certain defensive mechanisms inherent in groups, i.e., “attack-abatement” and “selfish herd” effects. We conclude that increased occurrence of kleptoparasitic and/or predatory Argyrodinae spiders is a consequence of colonial web building and is an important potential cost of group living for colonial web-building spiders.     

Effects of Neutral Posture on Muscle Tension During Computer Use

This study focused on developing a new approach to seated work positions as conducted on 67 office workers who use a Visual Display Terminal (VDT) as a major function of their working day. Muscle tension was measured by surface electromyography (sEMG) while participants were asked to adopt 4 selected working postures. Pain was measured before and after ergonomic intervention on the Nordic scale, which was modified for this study. Adjustable workstations were used to place participants in desired positions during the clinical testing sessions and the extended intervention period. Results indicate the effects of this ergonomic intervention may have positive effects on muscle tension and pain, significant enough to encourage employers to implement training and workstation modifications following these guidelines.     

Size and spatial structure in deep versus shallow populations of the Mediterranean gorgonian <Emphasis Type="Italic">Eunicella singularis</Emphasis> (Cap de Creus,northwestern Mediterranean Sea)

In the Western Mediterranean Sea, the gorgonian Eunicella singularis (Esper, 1794) is found at high densities on sublittoral bottoms at depths from 10 to 70 m. Shallow colonies have symbiotic zooxanthellae that deeper colonies lack. While knowledge of the ecology of the shallow populations has increased during the last decades, there is almost no information on the ecology of the deep sublittoral populations. In October and November 2004 at Cap de Creus (42°19′12″ N; 03°19′34″ E), an analysis of video transects made by a remotely operated vehicle showed that shallow populations (10–25 m depth) were dominated by small, non-reproductive colonies, while deep sublittoral populations (50–67 m depth) were dominated by medium-sized colonies. Average and maximum colony heights were greater in the deeper populations, with these deeper populations also forming larger patch sizes and more extensive regions of continuous substrate coverage. These results suggest that shallow habitats are suitable for E. singularis, as shown by the high recruitment rate, but perturbations may limit or delay the development of these populations into a mature stage. This contrasts with the deep sublittoral habitats where higher environmental stability may allow the development of mature populations dominated by larger, sexually mature colonies.     

Rapid analysis of neonicotinoid insecticides in guttation drops of corn seedlings obtained from coated seeds

Regarding the hypothesis that neonicotinoid insecticides used for seed coating of agricultural crops - mainly corn, sunflower and seed rape - are related to the extensive death of honey bees, the phenomenon of corn seedling guttation has been recently considered as a possible route of exposure of bees to these systemic insecticides. In the present study, guttation drops of corn plants obtained from commercial seeds coated with thiamethoxam, clothianidin, imidacloprid and fipronil have been analyzed by an optimized fast UHPLC-DAD procedure showing excellent detection limits and accuracy, both adequate for the purpose. The young plants grown both in pots - in greenhouse - and in open field from coated seeds, produced guttation solutions containing high levels of the neonicotinoid insecticides (up to 346 mg L(-1) for imidacloprid, 102 mg L(-1) for clothianidin and 146 mg L(-1) for thiamethoxam). These concentration levels may represent lethal doses for bees that use guttation drops as a source of water. The neonicotinoid concentrations in guttation drops progressively decrease during the first 10-15 days after the emergence of the plant from the soil. Otherwise fipronil, which is a non-systemic phenylpyrazole insecticide, was never detected into guttation drops. Current results confirm that the physiological fluids of the corn plant can effectively transfer neonicotinoid insecticides from the seed onto the surface of the leaves, where guttation drops may expose bees and other insects to elevated doses of neurotoxic insecticides.     

Modelling spatial distribution of hard bottom benthic communities and their functional response to environmental parameters

In this study we analyzed and modelled spatial distribution of hard bottom benthic communities in the Lagoon of Venice, and used the model to derive functional response of these communities to changing environmental conditions.     

Analysis of energy recovery potential using innovative technologies of waste gasification

In this paper, two alternative thermo-chemical processes for waste treatment were analysed: high temperature gasification and gasification associated to plasma process. The two processes were analysed from the thermodynamic point of view, trying to reconstruct two simplified models, using appropriate simulation tools and some support data from existing/planned plants, able to predict the energy recovery performances by process application. In order to carry out a comparative analysis, the same waste stream input was considered as input to the two models and the generated results were compared. The performances were compared with those that can be obtained from conventional combustion with energy recovery process by means of steam turbine cycle. Results are reported in terms of energy recovery performance indicators as overall energy efficiency, specific energy production per unit of mass of entering waste, primary energy source savings, specific carbon dioxide production.     

Is the participatory formulation of policy strategies worth the effort? The case of climate change adaptation in Austria

Participation is usually regarded as a good practice in environmental policymaking, but its effects on policy strategies are unclear. Based on literature research, surveys, and interviews with participants, the present paper assesses whether decisional participation in formulating Austria’s National Adaptation Strategy (NAS) was worth the effort. Assessed against the goals of the participation process, we find that it raised awareness for adaptation and facilitated an exchange among the participants and that it improved the content of the NAS. However, regarding the goal of enhancing the acceptance of and commitment to the NAS, we find that this has been achieved among those who participated but not among high-level policymakers who are responsible for implementing the NAS. We conclude that (decisional) participation has its benefits in formulating comprehensive policy strategies but that it is most likely not able to overhaul their well-documented weaknesses, among them weak political commitment and implementation failures.

     

Stakeholder engagement in social learning to resolve controversies over land-use change to plantation forestry

Rapid land-use change arising from incentives for afforestation has created tensions in rural communities previously dominated by agricultural enterprises. This paper reports on an innovative experiment with social learning that incorporated participatory modelling to resolve community concerns in a case study of plantation forestry in the Upper Clarence catchment of north-eastern NSW Australia. The development of a diagnostic framework helped identify socioeconomic and environmental issues within the community for investigation by a self-selected participatory advisory committee (PAC) representing a diversity of views. Implementation of a social learning exercise offered empathetic and intellectual engagement among PAC members that maintained interest, built confidence, and improved problem-solving capacity while fostering group ownership over decision making. A shared understanding of dynamic landscape problems helped empower participants to collaboratively develop solutions for improved management and operational practices, and cooperate to explore further options for plantation industry development under existing policy guidelines which are presented in this paper. As a result of frank discussions between diverse stakeholders in a mutually respectful learning environment that combined local, scientific and expert knowledge, concerns dissipated and participants developed a more favourable view of plantation forestry activity.     

Degradation of Poly(Ethylene Glycol)-Based Nonionic Surfactants by Different Bacterial Isolates from River Water

Different bacterial strains able to attack polyoxyethylene-type nonionic surfactants were isolated by enrichment procedure from the surface waters of the Arno River. Alkylphenol polyethoxylates and alkyl polyethoxylates, as well as polyethylene glycols, were degraded and assimilated by bacterial strains in axenic cultures. Degradative routes of polyethyleneoxide chains were investigated by matching each bacterial isolate with several types of nonionic surfactants and polyethers and by the identification of their degradation products isolated during aerobic digestion experiments. In accordance with previous reports, the first attack led to the shortening of the poly(oxyethylene) chains of the nonionic surfactants. It was found that the strains able to degrade PEG segments of nonionic surfactants possess enzymatic systems unable to degrade free PEGs, whereas those degrading the latter substrates cannot degrade PEG segments coupled to hydrophobic moieties.     

Development of Layered Sediment Structure and its Effects on Pore Water Transport and Hyporheic Exchange

Hyporheic exchange is known to provide an important control on nutrient and contaminant fluxes across the stream-subsurface interface. Similar processes also mediate interfacial transport in other permeable sediments. Recent research has focused on understanding the mechanics of these exchange processes and improving estimation of exchange rates in natural systems. While the structure of sediment beds obviously influences pore water flow rates and patterns, little is known about the interplay of typical sedimentary structures, hyporheic exchange, and other transport processes in fluvial/alluvial sediments. Here we discuss several processes that contribute to local-scale sediment heterogeneity and present results that illustrate the interaction of overlying flow conditions, the development of sediment structure, pore water transport, and stream-subsurface exchange. Layered structures are shown to develop at several scales within sediment beds. Surface sampling is used to analyze the development of an armor layer in a sand-and-gravel bed, while innovative synchrotron-based X-ray microtomography is used to observe patterns of grain sorting within sand bedforms. We show that layered bed structures involving coarsening of the bed surface increase interfacial solute flux but produce an effective anisotropy that favors horizontal pore water transport while limiting vertical penetration.