Distribution and dietary regulation of an associated facultative Rhizobiales-related bacterium in the omnivorous giant tropical ant,Paraponera clavata

We document a facultative Bartonella-like Rhizobiales bacterium in the giant tropical ant, Paraponera clavata. In a lowland tropical rainforest in Costa Rica, 59 colonies were assayed for the prevalence of the Bartonella-like bacterium (BLB), 14 of which were positive. We addressed three questions: First, how does the prevalence of BLB within colonies vary with environmental conditions? Second, how does diet affect the prevalence of BLB in P. clavata? Third, how does the distribution of BLB among colonies reflect ambient differences in food resources and foraging habits? A variety of environmental variables that may be predictive of the presence of BLB were measured, and diet manipulations were conducted to test whether the prevalence of BLB responded to supplemental carbohydrate or prey. The ambient frequency of BLB is much higher in young secondary forests, but is nearly absent from older secondary forests. The prevalence of BLB inside field colonies increased over the duration of a 2-week carbohydrate supplementation; however, water and prey supplementation did not alter the prevalence of BLB. The diets of the colonies located in young secondary forest, compared to other habitats, have a diet richer in carbohydrates and lower in prey. The abundance of carbohydrate, or the relative lack of N, in a colony’s diet influences the occurrence of the BLB microbe in P. clavata. As experimental diet manipulations can affect the facultative presence of an N-cycling microbe, a consistent diet shift in diet may facilitate the emergence of tighter symbioses.     

Sperm-depleted males influence the reproductive behaviour of conspecifics

In many insect species, sperm-depleted males (SDMs, i.e. males that have exhausted their sperm after a given number of matings) remain sexually active and continue to mate females. Here, we investigated the behavioural modifications that occur in both sexes of the parasitoid Asobara tabida Nees (Hymenoptera: Braconidae), after matings by fertile males and sperm-depleted males. We show that (i) virgin females, mated females and females mated to a SDM exhibited different behaviours and that (ii) males responded differently to females depending on whether the females had previously mated with an SDM or not. Our findings demonstrate that SDM influenced the reproductive behaviour of both males and females, especially with regard to male responsiveness and female attractiveness. These findings are discussed in the context of adaptive behaviour and fitness maximization in both males and females.     

Qualitative and Quantitative Assessment of Hepatitis A Virus in Wastewaters in Tunisia

Hepatitis A causes substantial morbidity in both industrialized and non-industrialized countries and represents an important health problem in several southern Mediterranean countries. The objectives of the study were as follows: (a) to assess the occurrence of hepatitis A virus (HAV) in Tunisia through the monitoring of urban wastewaters collected at wastewater treatment plants (WTPs); (b) to characterize environmental strains; and (c) to estimate the viral load in raw and treated sewages, in order to evaluate the potential impact on superficial waters receiving discharges. A total of 150 raw and treated wastewaters were collected from three WTPs and analyzed by both qualitative (RT-PCR/nested) and quantitative (qRT-PCR) methods. Of these, 100 (66 %) were found to be positive for HAV by the qualitative assay: 68.3 % in influents and 64.7 % in effluents. The vast majority of HAV sequences belonged to sub-genotype IA, with 11 different strains detected found to be identical to clinical strains isolated from Tunisian patients with acute hepatitis. Five unique variants were also detected, not previously reported in clinical cases. Only two IB strains were found, confirming the rarity of this sub-genotype in this country. The results of the present study indicate a wide circulation of the pathogen in the population, most probably in the form of asymptomatic infections, a finding consistent with the classification of the country as having intermediate/high endemicity. Quantitative data showed high viral loads in influents (3.5E+05 genome copies/liter, mean value) as well as effluents (2.5E+05 genome copies/liter, mean value), suggesting that contaminated water could be a critical element in transmission.     

Molecular Detection of human Noroviruses in Influent and Effluent Samples From Two Biological Sewage Treatment Plants in the Region of Monastir,Tunisia

Noroviruses (NoVs) are responsible for numerous cases of waterborne and foodborne gastroenteritis every year. They are released in the sewage and their detection in this environment can reflect the epidemiology of the viral strains circulating in the community. A three-year (2007–2010) survey was conducted in order to evaluate the presence of human NoVs using RT-PCR in 518 sewage samples collected at the entrance and exit of two biological sewage treatment plants located in Monastir region, Tunisia. In this study, we aimed to genetically characterize the most prevalent GI and GII NoV strains, in order to obtain a rough estimate of the efficacy of disinfection treatments and to compare the results with clinical data documented in the same area during the same period. This work confirms the wide circulation and the genetic diversity of NoVs in Tunisia and the widespread distribution of NoV variants in both raw and treated wastewater. Indeed, NoV was detected in 192 (37.1 %) sewage samples, among them mixed infections with group A rotavirus were detected in 125 (65.1 %) cases. The genotypes of the GI NoVs were GI.1, GI.2, GI.4, GI.5, and GI of unassigned genotype (GI.UA), and the genotypes of the GII NoVs were all GII.12. This study enhances the currently poor environmental virological data gathered in Tunisia, demonstrates the benefit of environmental surveillance as a tool to determine the epidemiology of NoVs circulating in a given community, and underlines the need for the design and support of similar long-term studies in our country, in order to compensate for the absence of a national surveillance system for gastroenteric viruses.     

Insights into the role of age and social interactions on the sexual attractiveness of queens in an eusocial bee, <Emphasis Type="Italic">Melipona flavolineata</Emphasis> (Apidae,Meliponini)

The attraction of sexual partners is a vital necessity among insects, and it involves conflict of interests and complex communication systems among male and female. In this study, we investigated the developing of sexual attractiveness in virgin queens (i.e., gynes) of Melipona flavolineata, an eusocial stingless bee. We followed the development of sexual attractiveness in 64 gynes, belonging to seven age classes (0, 3, 6, 9, 15, 18 days post-emergence), and we also evaluated the effect of different social interactions (such as competition between queens and interactions with workers) on the development of attractiveness in other 60 gynes. We used the number of males that tried to mate with a focal gyne as a representative variable of its sexual attractiveness. During the essays, each gyne was individually presented to 10 sexually mature males, and during 3 min, we counted the number of males that everted their genitalia in response to the presence of a gyne. Here, we show that M. flavolineata gynes are capable to (i) maintain their sexual attractiveness for long periods through adult life, (ii) they need a minimum social interaction to trigger the development of sexual attractiveness, and (iii) that gynes express this trait only within a social context. We conclude that the effective occurrence of matings is conditional on potential social interactions that gynes experienced before taking the nuptial flight, when they are still in the nest. These findings bring insights into the factors determining reproductive success in social insects.     

Sexual selection on receptor organ traits: younger females attract males with longer antennae

Sexual selection theory predicts that female choice may favour the evolution of elaborate male signals. Darwin also suggested that sexual selection can favour elaborate receiver structures in order to better detect sexual signals, an idea that has been largely ignored. We evaluated this unorthodox perspective by documenting the antennal lengths of male Uraba lugens Walker (Lepidoptera: Nolidae) moths that were attracted to experimentally manipulated emissions of female sex pheromone. Either one or two females were placed in field traps for the duration of their adult lives in order to create differences in the quantity of pheromone emissions from the traps. The mean antennal length of males attracted to field traps baited with a single female was longer than that of males attracted to traps baited with two females, a pattern consistent with Darwin’s prediction assuming the latter emits higher pheromone concentrations. Furthermore, younger females attracted males with longer antennae, which may reflect age-specific changes in pheromone emission. These field experiments provide the first direct evidence of an unappreciated role for sexual selection in the evolution of sexual dimorphism in moth antennae and raise the intriguing possibility that females select males with longer antennae through strategic emission of pheromones.     

Postnatal nutrition influences male attractiveness and promotes plasticity in male mating preferences

Poor early-life nutrition could reduce adult reproductive success by negatively affecting traits linked to sexual attractiveness such as song complexity. If so, this might favor strategic mate choice, allowing males with less complex songs to tailor their mating tactics to maximize the reproductive benefits. However, this possibility has been ignored in theoretical and empirical studies. By manipulating the micronutrient content of the diet (e.g., low or high) during the postnatal period of male zebra finches, we show for the first time (1) that males reared on a poor (low) micronutrient diet had less complex songs as adults; (2) that these males, in contrast to the high micronutrient diet group, were more selective in their mating strategies, discriminating against those females most likely to reduce their clutch size when paired with males having less complex songs; and (3) that by following different mating strategies, males reared on the contrasting diets obtained similar reproductive benefits. These results suggest that early-life dietary conditions can induce multiple and long-lasting effects on male and female reproductive traits. Moreover, the results seem to reflect a previously unreported case of adaptive plasticity in mate choice in response to a nutritionally mediated reduction in sexual attractiveness.     

Differential timing and latitudinal variation in sex ratio of Aquatic Warblers during the autumn migration

Differential migration has been extensively reported in spring, but less so in autumn, particularly in relation to sex in monomorphic bird species. Here, we analysed the autumn passage of a monomorphic, globally threatened passerine, the Aquatic Warbler Acrocephalus paludicola throughout Western Europe, with regard to age and sex. We showed that, overall, adults migrated earlier than first-year birds, and males migrated earlier than females during the autumn migration. This may be caused by an overall social dominance of adults over immatures, and differentiated migration strategy of males and females. In addition, we found male-skewed sex proportions, with a tendency to an equalised ratio in more southern stopover sites. This may indicate a male bias in the global population or different migration strategies of the sexes. Differential migration may cause the age and sex classes to be exposed differently to various threats affecting demographic structure of the species.     

大气作用下膨胀土地基的水分迁移与胀缩变形分析

运用土体渗流和蒸发理论,建立了大气-非饱和土相互作用模型;以现场观测的气象数据作为边界条件,进行了地基土中水分迁移的数值模拟,得到了大气作用下地基土体含水量的动态分布规律.计算结果表明,地基土中含水量变化幅度随深度增加而递减,3.5m深度以下土体的体积含水量基本不变,从而确定了南宁地区膨胀土地基的大气影响层深度为3.5...     

Heavy metals' content of automotive shredder residues (ASR): evaluation of environmental risk

Every year between 8 and 9 millions of vehicles in the European Union arrive to their end of life. Car wastes can have a very high metal content, falling into hazardous waste class. A preliminary evaluation of these wastes could be made by metals' leaching test runs which is the main objective of the present study. Evaluation of the total metal content was carried out by X-ray fluorescence and the mobility of these metals using two simple standardized extractions such as the TCLP (Toxicity Characterisation Leaching Procedure) of the US EPA and the German leaching test DIN 38414-S4. Additionally, an extraction test with acetone was performed in order to recognise metals bounded to organic matter. The results show that the total metal content of the ASR can overpass the established values for inert residues. Lead and zinc contents are fairly well correlated with grain-size, whilst other metals' contents do not exhibit clear grain-size dependence.