Cuckoo wasps manipulate foraging and resting activities in their hosts

Parasite-induced alterations in host behaviour have been reported in a large number of taxa. However, some parasites are better than others to exploit the resources offered by their hosts. To date, our understanding of the extent to which some obligate parasites exploit social insect colonies is still limited. In this study, we examined parasite-mediated behavioural alterations of Polistes biglumis wasps parasitized by the obligate social parasite Polistes atrimandibularis by comparing host female-activity in parasitized and non-parasitized colonies. Host foundresses foraged more and rested less in parasitized than in non-parasitized colonies (controlling for the number of larvae in the nest, the time of day, and the day in the season). Next, we used short-term parasite removal experiments to investigate how social parasites manipulate their hosts. We found that parasitized hosts foraged more and rested less when social parasites were on the nest rather than after their removal, and we tested which kind of interactions occurred between parasites and hosts. P. atrimandibularis parasites may use mainly non-aggressive interactions (such as antennation and trophallaxis) to manipulate host activities, rather than visual, acoustic or chemical signals as other parasites do.     

Chlorination in a wastewater treatment plant: acute toxicity effects of the effluent and of the recipient water body

This study investigates the impact of wastewater treatment plant (WWTP) effluent on the toxicity of the recipient water body and the effectiveness of the disinfection treatment applied (sodium hypochloride) to assure the compliance of both microbiological and toxicological emission limits. No toxicity was found in the majority of samples collected from the recipient river, upstream and downstream of the WWTP, using three different toxicity tests (Vibrio fischeri, Daphnia magna, and Pseudokirchneriella subcapitata). Only three samples presented toxic unit (TU) values with V. fischeri, and one presented TU with P. subcapitata. The influent toxicity ranged from slightly toxic to toxic (TU = 0.68–4.47) with V. fischeri, while only three samples presented TU values with the other tests. No toxicity was found in the absence of chlorination, while the mean toxicity was 3.42 ± 4.12 TU with chlorination in the effluent. Although no toxicity or very slight toxicity was found in the receiving water, its residual toxicity was higher than the US EPA Quality Standard in two samples. Escherichia coli concentration had a lower mean value in the chlorinated effluent: 13,993 ± 12,037 CFU/100 mL vs. 62,857 ± 80,526 CFU/100 mL for the not chlorinated effluent. This difference was shown to be significant (p < 0.05). E. coli in ten chlorinated samples was higher than the limit established by European and Italian Legislation. The mean highest trihalomethanes (THMs) value was found in the influent samples (2.79 ± 1.40 μg/L), while the mean highest disinfection by-products (DBPs) was found in the effluent samples (1.85 ± 2.25 μg/L). Significant correlations were found between toxicity, sodium hypochlorite, THMs, DBPs, E. coli, and residual chlorine. In conclusion, this study highlighted that the disinfection of wastewater effluents with sodium hypochlorite determines the increase of the toxicity, and sometimes is not enough to control the E. coli contamination.     

Sex adjustments are not functionally costly in simultaneous hermaphrodites

Because of their double sex functions, hermaphrodites are selected to optimize their investment in the two sex functions. Sex allocation (SA) theory predicts that, in promiscuous mating conditions, simultaneous hermaphrodites should adjust their reproductive investment so as to invest an amount of resources into the male relatively larger than that invested into the female function. In contrast, in monogamy, individuals should invest relatively larger amount of resources into the female function at the expenses of the male function. In the study of SA patterns of simultaneous hermaphrodites little attention has been paid to allocate adjustments costs, which may play an important role in determining variations in SA pattern among species. Indeed, the costs paid for such adjustments may constrain sex investment resulting in suboptimal allocation. We evaluated the costs of SA adjustments on individual fitness in each sexual function in the simultaneous, outcrossing hermaphrodite Ophryotrocha diadema. Following a crossover design, we compared the reproductive success in paternal and maternal offspring of focal hermaphrodites, which were put in replicated monogamous and promiscuous regimes. We document that those hermaphrodites that switched mating regimes and altered their sex investment accordingly did not entail large short-term fitness costs in any sexual function compared to those that were in stable mating regimes. Indeed, individuals changed their sex investment quickly and appropriately to current mating conditions. Hermaphrodites, which had to adjust their SA, did not decrease their maternal or paternal reproductive output with respect to those which did not change their SA. Time needed to shift resources from one to the other sex function is 5 days (the time interval between successive egg layings is of 3 days) indicating that selective pressures for SA adjustments may favour great plasticity and quick adjustments of sex investments in simultaneous hermaphrodites.     

Opportunistic discrimination of alien eggs by social wasps (Polistes biglumis, Hymenoptera Vespidae): a defense against social parasitism?

Foundresses of the social wasp Polistes biglumis were tested to see whether they were able to recognize alien eggs experimentally introduced into their own nests. Foundresses removed alien conspecific reproductive-destined eggs while they accepted worker-destined eggs. The results indicate that social wasps discriminate among eggs and that they discriminate against alien eggs destined to produce unrelated reproductives. P. biglumis is a strictly solitary founding species, with no reproductive competition within colonies; thus, brood discrimination abilities could have evolved as a counteradaptation against intra- and inter-specific brood parasitism. Received: 12 May 2000 / Revised: 15 July 2000 / Accepted 20 July 2000     

Biostimulation of the autochthonous microbial community for the depletion of polychlorinated biphenyls (PCBs) in contaminated sediments

In this study, the effect of the biostimulation of the autochthonous microbial community on the depletion of polychlorinated biphenyls (PCBs) in historically contaminated sediments (6.260?±?9.3 10^?3?μg PCB/ g dry weight) has been observed. Biostimulation consisted of (1) the amendment of an electron donor to favor the dehalogenation of the high-chlorinated PCBs and (2) the vegetation of sediments with Sparganium sp. plants to promote the oxidation of the low-chlorinated PCBs by rhizodegradation. The effects of the treatments have been analyzed in terms of both PCB depletion and changes of the autochthonous bacterial community structure. The relative abundance of selected bacterial groups with reference to untreated sediments has been evaluated by quantitative real-time PCR. The amendment of acetate determined the enrichment of anaerobic dechlorinators like Dehalococcoides sp. Vegetation with Sparganium sp. plants determined the enrichment of either (3) the dechlorinators, Dehalococcoides and the Chloroflexi o-17/DF-1 strains or (4) the Acidobacteria, β-Proteobacteria, Actinobacteria, α-Proteobacteria, Bacteroidetes, and Firmicutes. The combination of the two biostimulation strategy determined the 91.5 % of abatement of the initial PCB content.     

Determination of polycyclic aromatic hydrocarbons in urban street dust: implications for human health

The determination of sixteen polycyclic aromatic hydrocarbons in urban street dust has been done. Samples were collected from 12 sampling locations in a city centre location (Newcastle upon Tyne, north east England) and extracted using in situ pressurised fluid extraction followed by gas chromatography mass spectrometry. From the results it was possible to identify three groups, with respect to PAH concentration, with PAH contents ranging between 0.6-2.3 mg kg⁻¹, 15.6-22.5 mg kg⁻¹ and 36.1-46.0 mg kg⁻¹. The total PAH content of samples from these sampling sites has been compared to 22 urban locations around the world; comparable levels were found in these samples compared to the other cities around the world.The potential source of PAHs has been investigated by investigating the proportion of pyrogenic and petrogenic material in urban street dust using specific individual PAH ratios. The results indicate that the PAH content of urban street dust from the chosen sites are more likely to be due to pyrogenic sources i.e. vehicle exhaust emissions. The particle size fractions (<63 μm; 63-125 μm; 125-250 μm; 250-500 μm; 500-1000 μm; and 1000-2000 μm) of individual PAHs in three selected sampling sites was investigated. In two of the selected sites the PAH content was independent of particle size whereas in sampling site 10 elevated PAH levels are noted in the <63 μm size fraction. Sampling site 10 is located at the junction of three road tributaries which are used as major access points to the east of the city centre. Finally, the potential health risk for unintentional consumption of PAHs was assessed in terms of a mean daily intake (based on an ingestion rate of 100 mg d⁻¹). It was found that all 4-6 membered ring PAHs had concentrations in excess of the mean daily intake thereby reflecting a potential health risk, particularly in the smallest size particle fractions.