Temperature increase impairs recognition among nestmates in the social wasp Polybia paulista H. von Ihering, 1896 (Vespidae: Polistinae: Epiponini)

Cuticular hydrocarbons (CHCs) of most terrestrial arthropods primarily serve as a protective barrier against desiccation and infection. Throughout evolution, these compounds have acquired another fundamental function: the exchange of signals during interactions between nestmates. However, even though cuticular hydrocarbons perform a dual function in social insects, little is known about the effect(s) of one function on the other in social insects, and no study has evaluated this relationship in social wasps. Therefore, the present study tests the hypothesis that the level of aggressiveness presented during induced encounters between nestmates of Polybia paulista who were subjected to different conditions temperature is different than between nestmates who remained under the same temperature conditions. If the hypothesis is confirmed, it is likely because the cuticle of the wasps that had been exposed to temperature variation adjusted to these conditions leading them not to recognize the cuticular chemical signature of their colony. To test this hypothesis, workers were exposed to temperature variation in a BOD chamber and then subjected to encounters with workers who were maintained at a constant temperature of 24℃. We also used control groups to evaluate the effect of isolation alone among the groups. According to our results, our hypothesis was confirmed, the level of aggressiveness presented between nestmates who were exposed to temperature variation and those who remained at 24℃ was significantly higher than the levels of aggressiveness presented between nestmates who remained isolated but under constant temperature during the same period, in some cases, it was similar to the aggressiveness presented in encounters between wasps from different colonies. During these encounters, wasps performed alarm behavior, bites, and stings not seen during encounters between wasps that remained under the same temperature, but in isolated groups. The lack of aggressive behavior under isolated conditions indicates that isolation had no effect on chemical recognition signature. These results suggest that temperature variation may have caused some change in the cues that allow recognition between nestmates. On the other hand, these results were not caused by isolation or stress generated by the study design and difference in the CHC profile of workers, as described in the literature, is consistent with our results.(AU)

Anthropic action affects the cuticular chemical profile of social wasps

As a result of environmental change by anthropic action, animal species that inhabit these areas may suffer the effects of it on their phenotypes as a consequence of adapting to these conditions. In the case of social wasps, cuticular chemical compounds may be influenced, since these vary depending on genetic and environmental factors. However, few studies have investigated the synanthropic effects over the cuticular surface of social wasps. Therefore, the aim of this study was to investigate how cuticular compounds vary according to the different degrees of human activity and test the hypothesis that cuticular compounds of social wasps are affected by the level of anthropic activity in which their nests are found. Data on the cuticular chemical compounds composition of colonies of 3 species of social wasps were used along with the level of anthropization of their nesting sites in four municipalities in the state of Mato Grosso do Sul, Brazil. From the geographical coordinates of the sampling sites, the percentages of urban construction areas, agriculture, water body, vegetation and exposed land were calculated, and the nesting sites of the colonies were classified as more or less anthropized areas. The chemical profile was determined by extraction of cuticular compounds and analyzed by Gas Chromatography coupled to Mass Spectrometer (GC-MS). The results show that the cuticular chemical composition of the individuals of these species is affected by the level of anthropization in their nesting sites, with a qualitative and quantitative variation that must be tied not only to genetic differences, but, above all, to the local environmental conditions to which their colonies are subjected.(AU)