Hymenopteran parasitoids can utilize substrate-borne semiochemicals released by conspecifics or by their hosts, increasing the likelihood of successful mating and host location. According to the literature, two substrate-borne chemo-orientation patterns can occur: (1) biased random searching, a non-directional reaction toward the chemicals (kinesis), and (2) trailfollowing searching, a directional response toward the source emitting the chemical compounds (taxis). These two different strategies can be adopted by parasitoids to locate hosts and mates. In host location, random searching is induced by allelochemicals indirectly associated with the host, whereas trail-following behavior is induced by allelochemicals directly emitted by the target organism. In mate finding, sex pheromones emitted by conspecifics can induce either the random searching or the trail-following behavior, although the spatial distribution of virgin conspecifics could be an important factor driving the evolution of substrate-borne chemo-orientation patterns. The chemical nature of substrate-borne semiochemicals has not yet been fully elucidated. Most studies have shown that crude extracts are biologically active for eliciting parasitoid arrestment response, but few studies have clearly characterized their chemical nature. However, experimental evidence indicates that cuticular lipids located in the external layer of insects’ bodies play a role in parasitoid–parasitoid and host– parasitoid communication. The ecological role of parasitoid chemo-orientation in host and mate location is discussed from a biological control perspective
Chemical footprints left behind by true bugs are perceived as contact kairomones by scelionid egg parasitoids. Female wasps encountering a contaminated artificial substrate display a characteristic arrestment posture, holding the body motionless and antennating the surface. In the system Nezara viridula (L.) and its egg parasitoid Trissolcus basalis (Wollaston), previous studies have shown that the kairomone mediating such behavior is part of N. viridula's cuticular hydrocarbons (CHC) and furthermore that the wasp's ability to discriminate host male and female footprints is mainly based on the presence/absence of nonadecane (nC(19)). In this study, the effect of epicuticular waxes of leaves of broad bean, Vicia faba, on wasp responses to footprints of N. viridula females were investigated. Approximately 20% of T. basalis females displayed an arrestment posture when released on the adaxial leaf surfaces of broad bean plants with intact wax layer and without host chemical contamination; whereas approximately 70% of wasps displayed the arrestment posture when intact leaves were contaminated by host female footprints. Adaxial leaf surfaces of broad bean plants dewaxed with an aqueous solution of gum arabic and afterwards contaminated by N. viridula females induced arrestment responses in about 10% of female wasps; the same percentage of arrestment (10%) was observed when the wasps were released on leaves contaminated by host females and subsequently dewaxed. The side of the polymer film that was appressed to the leaf surface, peeled from the contaminated leaves, induced an arrestment posture in about 95% of observed wasps. Scanning electron microscopy (SEM) revealed that the epicuticular waxes occurred as a film densely crystallized as irregularly shaped platelets with spherical granules randomly distributed. These findings demonstrated that epicuticular waxes of broad bean leaves can mediate the foraging behavior of T. basalis females by absorbing contact kairomones of the host.
International Journal of Occupational Medicine and EnvironmentalThe aim of this survey was to assess the seroprevalence of antibodies against Coxiella burnetii (C. burnetii) in subjects at risk of exposure in Sicily, Southern Italy. Material and Methods: Prevalence of IgG antibodies to C. burnetii phase II antigens was evaluated by ELISA in a group of 140 workers at risk of exposure (38 veterinarians, 38 slaughterhouse workers, 44 livestock handlers, 20 laboratory and technical personnel) included in a medical surveillance program and in 42 control subjects. Positive samples were classified as suggestive of prior exposure to C. burnetii. Results: Antibodies against C. burnetii were detected in 88 out of 140 (62.9%) exposed workers and in 6 out of 42 (14.3%) subjects of the control group. The variables evaluated did not seem to have a significant effect on seropositivity to Coxiella with the exception of symptoms in the last 6 months preceding the survey. Conclusions: Our study demonstrated a high seroprevalence of C. burnetii in the group of exposed workers in comparison to non-exposed subjects of the control group. Clinical illness appears to be rare; nevertheless, physicians should consider Q fever in patients with compatible symptoms and occupational exposure to animals and their products. As aerosols represent the main route of infection in animals and humans, these workers are strongly advised to wear respiratory masks. In addition, occupational physicians should consider routine serologic evaluation and vaccination of occupationally exposed workers.
The number of women at risk of rubella infection fell short of the national target set for elimination of CRS. Increased involvement and collaboration by all healthcare workers are, therefore, required to disseminate the information necessary to prevent CRS.
Egg parasitoids are able to find their hosts by exploiting their chemical footprints as host location cues. In nature, the apolar epicuticular wax layer of plants that consists of several classes of hydrocarbons serves as the substrate that retains these contact kairomones. However, experiments on chemical footprints generally have used filter paper as substrate to study insect behavior. Here, we explored the ability of Trissolcus basalis (Scelionidae) females to discriminate between footprint cues left by male and female Nezara viridula (Pentatomidae) on leaves of their host plant Brassica oleracea (broccoli). Furthermore, we analyzed the chemical composition of the outermost wax layer of broccoli leaves to evaluate the degree of overlap in insect and plant cuticular hydrocarbons that could lead to masking effects in the detection of footprint cues. Our results showed that B. oleracea epicuticular wax retains the chemical footprints of adult bugs and allows T. basalis females to differentiate hosts of different sex. Traces of female bugs elicited more extensive searching behavior in egg parasitoids than traces of males. The application of n-nonadecane, a compound specific to male N. viridula, on the tarsi of female bugs prevented parasitoid females from distinguishing between host male and host female footprints. Analyses of B. oleracea leaves revealed that epicuticular waxes were mainly composed of linear alkanes, ketones, and secondary alcohols. Alkanes were dominated by n-nonacosane (nC29) and n-hentriacontane (nC31), while male-specific n-nonadecane (nC19) was absent. The ecological significance of these results for parasitoid host location behavior is discussed.
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