Graded recruitment and hunting strategies linked to prey weight and size in the ponerine ant Ectatomma ruidum

According to the weight and size of their prey, Ectatomma ruidum workers can employ different recruitment systems (solitary hunting, cooperative hunting and group hunting with recruitment) when mastering and retrieving prey items from short distances from the nest. Prey size determined the backwards entry typically adopted by this species, while prey weight determined the predatory strategy selected. After a common initial sequence (search for prey, detection, localization), predatory sequences varied in terms of the type of approach, the site of seizure, the reaction after stinging and the type of transport. Nevertheless, irrespective of prey weight and size, seizure was preferentially oriented towards the head and prey were always stung. Short-range recruitment and mass recruitment without trail laying were elicited by a large range of heavy prey (> 2.5 times the weight of an individual worker). According to the mortality risk associated with each prey, hunters exhibited a “prudent” stinging posture associated with an increase in the duration of the subsequent phase of waiting for prey immobilization. The overall time of capture was positively correlated with the weight of the prey. When collective hunting strategies were involved, E. ruidum colonies matched the number of recruited hunters to the size and weight of the prey. Compared to solitary hunting strategies, for short food–nest distances, this graded recruitment appeared to enhance the energetic benefits derived by this species from the use of recruitment systems: the higher the number of workers involved in the recruitment process, the greater the energetic benefits obtained. The exhibition or absence of trail laying behavior in the recruitment responses displayed by E. ruidum workers is discussed in relation to their involvement in scavenging or predatory behavior. Received: 27 June 1996 / Accepted after revision: 3 March 1997     

Cooperative prey capture by young subsocial spiders

Matriphagous young of a subsocial spider Amaurobius ferox exhibit collective predation during their post-maternal social period. In this paper, we examine functional mechanisms of collective predation by sibling groups. Predation efficiency increased with increasing number of individuals within each group. Solitary or paired individuals were generally unable to capture a 20 mg cricket. In larger groups, more individuals participated and captured the prey more quickly. Some siblings did not take part in paralyzing prey, but later consumed it. The proportion of these profiteers within a group increased with the group size. Presented with prey of different sizes (1, 5, or 40 mg), siblings were most aggressive towards each other when predating on 5 mg prey. Prey of this size could be captured by a single individual and yet were sufficiently large for more than one individual to eat. Siblings were much less aggressive towards one another during the capture of 40 mg prey, which require the assistance of other individuals to capture. By providing the same mass of prey in different numbers of individuals (a single cricket of 40 or 40 mg of first-instar crickets), we tested the influence of cooperation on the post-maternal social period. We found no difference in the development of young during the social period nor the timing of dispersal and the body mass of dispersing individuals. We conclude that the young of this subsocial animal increased predation efficiency by cooperative hunting after the mother's death.     

The Effect of Heat on the Physicochemical Properties of Bacteriophage MS2

The differences in physicochemical characteristics between infectious and non-infectious viral particles are poorly known. Even for heat, which is known as one of the most efficient treatments to inactivate enteric viruses, the global inactivation mechanisms have not been described yet. Such knowledge would help distinguish between both types of particles and therefore clarify the interpretation of the presence of viral genomes in food after heat treatment. In this study, we examined in particular the differences in electrostatic charge and hydrophobicity between the two particle types. MS2 phage, a common surrogate for enteric viruses, was used as a model virus. The heat-induced inactivation process of the infectious phages caused hydrophobic domains to be transiently exposed and their charge to become less negative. The particles also became progressively permeable to small molecules such as SYPRO Orange dye. The presence of non-infectious phage particles in which the genome was not accessible to RNases has been clearly demonstrated. These observations were done for MS2 phages exposed to a temperature of 60 °C. When exposed to a temperature higher than their critical temperature (72 °C), the particles were disrupted and the genome became available for RNases. At lower temperatures, 60 °C in this study, the transient expression of hydrophobic domains of remaining infectious phages appeared as an interesting parameter for improving their specific detection.     

Priming effect: bridging the gap between terrestrial and aquatic ecology

Understanding how ecosystems store or release carbon is one of ecology's greatest challenges in the 21st century. Organic matter covers a large range of chemical structures and qualities, and it is classically represented by pools of different recalcitrance to degradation. The interaction effects of these pools on carbon cycling are still poorly understood and are most often ignored in global-change models. Soil scientists have shown that inputs of labile organic matter frequently tend to increase, and often double, the mineralization of the more recalcitrant organic matter. The recent revival of interest for this phenomenon, named the priming effect, did not cross the frontiers of the disciplines. In particular, the priming effect phenomenon has been almost totally ignored by the scientific communities studying marine and continental aquatic ecosystems. Here we gather several arguments, experimental results, and field observations that strongly support the hypothesis that the priming effect is a general phenomenon that occurs in various terrestrial, freshwater, and marine ecosystems. For example, the increase in recalcitrant organic matter mineralization rate in the presence of labile organic matter ranged from 10% to 500% in six studies on organic matter degradation in aquatid ecosystems. Consequently, the recalcitrant organic matter mineralization rate may largely depend on labile organic matter availability, influencing the CO2 emissions of both aquatic and terrestrial ecosystems. We suggest that (1) recalcitrant organic matter may largely contribute to the CO2 emissions of aquatic ecosystems through the priming effect, and (2) priming effect intensity may be modified by global changes, interacting with eutrophication processes and atmospheric CO2 increases. Finally, we argue that the priming effect acts substantially in the carbon and nutrient cycles in all ecosystems. We outline exciting avenues for research, which could provide new insights on the responses of ecosystems to anthropogenic perturbations and their feedbacks to climatic changes.     

An economic analysis of China’s domestic crude oil supply policies

ABSTRACT

China’s domestic oil production has lagged the growth in domestic oil consumption since the beginning of the 21st century, leading to a growing reliance on imports. In response, the Chinese government has introduced a number of policies, including import license constraints, to support domestic suppliers. In an effort to measure the economic impact of these policies we develop a short-run equilibrium model of China’s wholesale oil and gas market at the provincial scale. We construct counterfactual scenarios that suggest that relaxing policies that prioritize domestic production in 2016, when the average price of Chinese oil imports was US$42 per barrel (bbl), could have increased China’s import demand by 0.29 million barrels per day (MMbbl/d). This results in a substitution of 9% of China’s domestic production in 2016, and a reduction of US $2.8 billion in crude supply costs including transportation as the imported oil has more direct access to the country’s pipeline network, compared to the displaced domestic production. In addition, rising import prices since mid-2017 may provide a window of opportunity for Chinese policymakers to proceed with further deregulation of the domestic oil sector, as the short-term impact on domestic producers is reduced.     

Influence of fly ash aided phytostabilisation of Pb, Cd and Zn highly contaminated soils on Lolium perenne and Trifolium repens metal transfer and physiological stress

Due to anthropogenic activities, large extends of soils are highly contaminated by Metal Trace Element (MTE). Aided phytostabilisation aims to establish a vegetation cover in order to promote in situ immobilisation of trace elements by combining the use of metal-tolerant plants and inexpensive mineral or organic soil amendments. Eight years after Coal Fly Ash (CFA) soil amendment, MTE bioavailability and uptake by two plants, Lolium perenne and Trifolium repens, were evaluated, as some biological markers reflecting physiological stress. Results showed that the two plant species under study were suitable to reduce the mobility and the availability of these elements. Moreover, the plant growth was better on CFA amended MTE-contaminated soils, and the plant sensitivity to MTE-induced physiological stress, as studied through photosynthetic pigment contents and oxidative damage was lower or similar. In conclusion, these results supported the usefulness of aided phytostabilisation of MTE-highly contaminated soils.     

Favourable interaction between photooxidation and bacterial degradation of anthracene in sea water

A mixed bacterial community isolated from a marine biotope highly polluted with hydrocarbons proved to be able to use anthraquinone, a product of anthracene photooxidation considered as a relatively stable molecule in a marine medium.     

Quality control for sampling of PCDD/PCDF emissions from open combustion sources

Both long duration (>6 h) and high temperature (up to 139 °C) sampling efforts were conducted using ambient air sampling methods to determine if either high volume throughput or higher than ambient air sampling temperatures resulted in loss of target polychlorinated dibenzodioxins/dibenzofurans (PCDDs/PCDFs) from a polyurethane foam (PUF) sorbent. Emissions from open burning of simulated military forward operating base waste were sampled using EPA Method TO-9A for 185 min duration using a filter/PUF/PUF in series combination. After a 54 m³ sample was collected, the sampler was removed from the combustion source and the second PUF was replaced with a fresh, clean PUF. An additional 6 h of ambient air sampling (171 m³) was conducted and the second PUF was analyzed to determine if the PCDD/PCDF transferred from the filter and the first PUF. Less than 4.4% of the initial PCDD/PCDF was lost to the second PUF. To assess the potential for blow off of PCDD/PCDF analytes during open air sampling, the mobility of spiked mono- to hepta-PCDD/PCDF standards across a PUF sorbent was evaluated from ambient air temperatures to 145 °C with total volumes between 600 L and 2400 L. Lower molecular weight compounds and higher flow amounts increased release of the spiked standards consistent with vapor pressure values. At 600 L total sampled volume, the release temperature for 1% of the tetra-CDD (the lowest chlorinated homologue with a toxic compound) was 87 °C; increasing the volume fourfold reduced this temperature to 73 °C.     

Responses of soil nitrification activities to copper after a moisture stress

Environmental Science and Pollution Research - Some steps of the soil nitrogen (N) cycle are sensitive to environmental pressures like soil moisture or contamination, which are expected to evolve...