Inhibition of predator attraction to kairomones by non-host plant volatiles for herbivores: a bypass-trophic signal

Background Insect predators and parasitoids exploit attractive chemical signals from lower trophic levels as kairomones to locate their herbivore prey and hosts. We hypothesized that specific chemical cues from prey non-hosts and non-habitats, which are not part of the trophic chain, are also recognized by predators and would inhibit attraction to the host/prey kairomone signals. To test our hypothesis, we studied the olfactory physiology and behavior of a predaceous beetle, Thanasimus formicarius (L.) (Coleoptera: Cleridae), in relation to specific angiosperm plant volatiles, which are non-host volatiles (NHV) for its conifer-feeding bark beetle prey. Methodology/Principal Findings Olfactory detection in the clerid was confirmed by gas chromatography coupled to electroantennographic detection (GC-EAD) for a subset of NHV components. Among NHV, we identified two strongly antennally active molecules, 3-octanol and 1-octen-3-ol. We tested the potential inhibition of the combination of these two NHV on the walking and flight responses of the clerid to known kairomonal attractants such as synthetic mixtures of bark beetle (Ips spp.) aggregation pheromone components (cis-verbenol, ipsdienol, and E-myrcenol) combined with conifer (Picea and Pinus spp.) monoterpenes (α-pinene, terpinolene, and Δ3-carene). There was a strong inhibitory effect, both in the laboratory (effect size d = −3.2, walking bioassay) and in the field (d = −1.0, flight trapping). This is the first report of combining antennal detection (GC-EAD) and behavioral responses to identify semiochemical molecules that bypass the trophic system, signaling habitat information rather than food related information. Conclusions/Significance Our results, along with recent reports on hymenopteran parasitoids and coleopteran predators, suggest that some NHV chemicals for herbivores are part of specific behavioral signals for the higher trophic level and not part of a background noise. Such bypass-trophic signals could be of general importance for third trophic level players in avoiding unsuitable habitats with non-host plants of their prey

Anti-α-gliadin antibodies (AGA) in the serum of coeliac children and controls recognize an identical collection of linear epitopes of α-gliadin

Anti-gliadin antibodies can be found in the serum of patients with overt and subclinical coeliac disease, but also in that of some controls. The aim of the present study was to identify the linear epitopes of the α-gliadin molecule to which the humoral response is directed. Therefore, the IgG and IgA antibody reactivity against an overlapping set of synthetic peptides covering the entire sequence of α-gliadin was measured in the sera from patients with coeliac disease, from controls with elevated titres of anti-gliadin antibodies and from healthy children using an ELISA technique. The antibodies mainly recognize peptides derived from the N-terminal region of α-gliadin, containing the motif QPFXXQXPY. Reactivity was also detected against two other synthetic peptides, which do not contain this motif and represent a sequence encoded further to the C-terminal region of α-gliadin. Anti-gliadin antibodies in sera from patients with coeliac disease and from controls recognize the same linear epitopes. Thus, serological investigation of the specificity of these antibodies using a peptide ELISA does not allow discrimination between patients and controls