Influence of dung volatiles on the process of resource selection by coprophagous beetles

Summary. Most dung beetles colonize the faeces of several vertebrate species without much discrimination, and are thus often considered as polyphagous. Recent studies have provided evidence for clear feeding preferences in scarab beetles colonizing dung of herbivore species, but little is known about these insects’ abilities to discriminate among odours from faeces of various herbivores. In this study, trophic preferences were examined using blocks of pitfall traps baited with dung from four different herbivore species, i.e., sheep, cattle, horse, and red deer, in a mountainous area of south-central France. 4941 coprophagous scarabs, belonging to 27 species, were captured. Beetles were more attracted to dung of sheep (2257 individuals) than that of cattle (1294 individuals), followed by deer dung (768 individuals) and horse dung (622 individuals). Eleven of the 27 beetle species collected had significant feeding preferences for one of the four dung types. For each insect species, trophic habits did not vary between the two different sites of trapping, an open pasture and a wooded habitat. In laboratory olfactometer bioassays, scarab beetles orientated preferentially towards the dung volatiles from the dung type they preferred in the field. Trypocopris pyrenaeus, Anoplotrupes stercorosus, and Aphodius rufipes were more attracted to volatile compounds from sheep dung, Onthophagus fracticornis significantly preferred horse dung volatiles, and Aphodius haemorrhoidalis responded positively to deer dung odours. The role of dung olfactory cues in the process of resource selection by dung beetles is discussed.     

Effects of chronic exposure to radiofrequency electromagnetic fields on energy balance in developing rats

The effects of radiofrequency electromagnetic fields (RF-EMF) on the control of body energy balance in developing organisms have not been studied, despite the involvement of energy status in vital physiological functions. We examined the effects of chronic RF-EMF exposure (900 MHz, 1 V?m^?1) on the main functions involved in body energy homeostasis (feeding behaviour, sleep and thermoregulatory processes). Thirteen juvenile male Wistar rats were exposed to continuous RF-EMF for 5 weeks at 24 °C of air temperature (T _a) and compared with 11 non-exposed animals. Hence, at the beginning of the 6th week of exposure, the functions were recorded at T _a of 24 °C and then at 31 °C. We showed that the frequency of rapid eye movement sleep episodes was greater in the RF-EMF-exposed group, independently of T _a (+42.1 % at 24 °C and +31.6 % at 31 °C). The other effects of RF-EMF exposure on several sleep parameters were dependent on T _a. At 31 °C, RF-EMF-exposed animals had a significantly lower subcutaneous tail temperature (?1.21 °C) than controls at all sleep stages; this suggested peripheral vasoconstriction, which was confirmed in an experiment with the vasodilatator prazosin. Exposure to RF-EMF also increased daytime food intake (+0.22 g?h^?1). Most of the observed effects of RF-EMF exposure were dependent on T _a. Exposure to RF-EMF appears to modify the functioning of vasomotor tone by acting peripherally through α-adrenoceptors. The elicited vasoconstriction may restrict body cooling, whereas energy intake increases. Our results show that RF-EMF exposure can induce energy-saving processes without strongly disturbing the overall sleep pattern.     

Characterisation of the physico-mechanical parameters of MSW

Following the basics of soil mechanics, the physico-mechanical behaviour of municipal solid waste (MSW) can be defined through constitutive relationships which are expressed with respect to three physical parameters: the dry density, the porosity and the gravimetric liquid content. In order to take into account the complexity of MSW (grain size distribution and heterogeneity larger than for conventional soils), a special oedometer was designed to carry out laboratory experiments. This apparatus allowed a coupled measurement of physical parameters for MSW settlement under stress. The studied material was a typical sample of fresh MSW from a French landfill. The relevant physical parameters were measured using a gas pycnometer. Moreover, the compressibility of MSW was studied with respect to the initial gravimetric liquid content. Proposed methods to assess the set of three physical parameters allow a relevant understanding of the physico-mechanical behaviour of MSW under compression, specifically, the evolution of the limit liquid content. The present method can be extended to any type of MSW.     

Towards the Prediction of Heat and Mass Transfer in an Air-Conditioned Environment for a Life Support System in Space

Long-term flights or the establishment of permanent bases in space provide serious challenges for life support systems. Plants are essential companion life forms for such space missions, where human habitats must mimic the cycles of life on earth to generate and recycle food, oxygen and water. Nowadays, the chemical–mechanical recycling systems used in the international space station are much more compact, less labour intensive and more reliable than plant-based systems, but these systems would be too expensive for the long-term human exploration. In order to improve living conditions for humans and plants, we need an accurate characterisation of the mass transfer phenomena related to condensation of humid air. We are interested in developing an experimental protocol, which would help us to establish a theoretical model describing the heterogeneous transfers along a wall or a plant in an air-conditioned environment. Initially, we started in dry conditions by measuring the velocity profiles within the boundary layer that develop on a horizontal or a vertical flat plate in a wind tunnel. The velocity ranged from 0.5 to 2.5 m s^?1. Existing coupled heat and mass transfer measurement results relevant to our applications are discussed.     

高盐工业废水人工湿地处理中植物的筛选

通过人工湿地中试实验,考察了芦苇、睡莲、水葱、狭叶香蒲和宽叶香蒲水生植物单元对经生化处理的石油和精细化工工业区的工业废水中盐含量较高、氮磷营养盐含量较低和化学需氧量(COD)含量较高的废水中污染物的去除情况,研究了在植物不同生长阶段系统中COD的去除同盐度之间的关系,探讨了盐度差异对植物生长状况的影响,为确定人工湿地适合的进水盐度,达到有效去除高含盐量工业废水中有机污染物提供依据。结果表明,芦苇、睡莲和狭叶香蒲3种植物单元内高含盐量工业废水中污染物的净化效果较水葱和宽叶香蒲单元的净化效果好:前3种植物单元内COD、生化需氧量(BOD)和总磷(TP)的去除率大约在38%、55%和62%左右,而水葱和宽叶香蒲2种植物单元内COD、BOD和TP的去除率大约在30%、36%和52%左右;系统中各个单元内总氮(TN)去除率都在85%以上。在植物的不同生长阶段,人工湿地系统中氯离子浓度与COD浓度之间的相关性存在差异:植物生长初期,系统中氯离子浓度与系统中COD浓度之间无显著相关性,而在植物生长旺期和末期,两者则成正相关关系。因此,需根据植物的生长阶段调整人工湿地的进水盐度。     

Biomonitoring of traffic-related nitrogen oxides in the Maurienne valley (Savoie, France), using purple moor grass growth parameters and leaf N/N ratio

Effects of traffic-related nitrogenous emissions on purple moor grass (Molinia caerulea (L.) Moench) transplants, used here as a new biomonitoring species, were assessed along 500 m long transects orthogonal to roads located in two open areas in the Maurienne valley (French Alps). Leaves were sampled during summer 2004 and 2005 for total N-content and ¹⁵N-abundance determination while nitrogen oxides (NO and NO₂) concentrations were determined using passive diffusion samplers. A significant and negative correlation was observed between plant total N-content, and ¹⁵N-abundance and the logarithm of the distance to the road axis. The strongest decreases in plant N parameters were observed between 15 and 100 m from road axis. They were equivalent to background levels at a distance of about 800 m from the roads. In addition, motor vehicle pollution significantly affected vegetation at road edge, as was established from the relationship between leaf ¹⁵N-abundance, total N-content and road traffic densities.     

Effects of the mixture of diquat and a nonylphenol polyethoxylate adjuvant on fecundity and progeny early performances of the pond snail Lymnaea stagnalis in laboratory bioassays and microcosms

Effects of the bipyridylium herbicide diquat and tank-mix adjuvant Agral((R))90 were investigated on various life history traits of the freshwater pulmonate snail Lymnaea stagnalis. Trait expression was measured in simple laboratory bioassays on small size groups of snails, and under more complex, indoor microcosm conditions, on larger groups of snails. Microcosms were provided with sediment, plants, and fish, thus allowing a more complex level of intra and inter-specific interactions to develop. Treatments were performed with substances alone or in mixture, at concentrations ranging from 4.4 to 222.2mugl(-1) for diquat, and from 10 to 500mugl(-1) for Agral 90, under a fixed ratio design. Adult growth was negatively affected by diquat and its mixture with Agral 90 both at the highest concentrations (222.2 and 500mugl(-1), respectively). Fecundity expressed differently in bioassays and microcosms, but no effect of the chemicals could be observed on this trait. Progeny development was impaired by 222.2mugl(-1) diquat and its mixture with 500mugl(-1) Agral 90, as reflected by longer development time and reduced hatching rate of clutches laid by the exposed animals, as compared to the controls. Hatching data suggested that diquat bioavailability was lower in microcosms than under bioassay conditions. Consistently, chemical analysis showed that diquat disappeared more rapidly from the water in microcosms than in bioassays. Moreover, the differential expression of several life history traits under bioassays and microcosms conditions was probably also influenced by the level of intraspecific interaction, which differed among the systems. When significant, the effect of diquat was attenuated by the presence of Agral 90, indicating antagonistic interaction between the two substances. Such a deviation from additivity was partly validated statistically.     

Fate of a stilbene-type fluorescent whitening agent (DSBP) in the presence of Fe(III) aquacomplexes: from the redox process to the photodegradation

The behaviour of 4,4′-bis(2-sulfostyryl)biphenyl (DSBP), a fluorescent whitening agent, was investigated in the presence of Fe(III) aquacomplexes at room temperature. In the dark, a two-step reaction was observed when adding Fe(III) to a solution of DSBP: an initial fast redox reaction between DSBP and the monomeric species Fe(OH)²⁺ and a slower reaction leading to the coagulation of oxidised DSBP and iron. This phenomenon is due to the formation of a complex or an ion-pair between Fe(II) and/or Fe(III) with oxidised DSBP and it probably occurs by charge neutralisation in our experimental conditions. The precipitation of DSBP depends on the initial concentration in Fe(OH)²⁺ and is achieved for a ratio [Fe(OH) ²⁺]/[DSBP] of 5 approximately. Under irradiation at 365 nm, a complicated behaviour was observed: a complexation of iron by oxidised DSBP favoured by irradiation and a degradation of DSBP induced by an intramolecular electron transfer in the complex or by a photoredox of Fe(OH)²⁺ species generating OH radicals in the supernatant. The complete degradation of DSBP is reached four times faster in the presence of Fe(III) with respect to the direct photolysis of DSBP alone. Moreover, the total mineralization of DSBP obtained in less than 120 h upon irradiation at 365 nm is only observed in the presence of the ferric ions, enlightening the efficiency of the method involving Fe(III) and UV irradiation.