Recognition of conspecific immunological status in a neotropical paper wasp

Body odor can reflect aspects of individual health. In a social wasp, activation of the immune system by wounding causes changes in the chemical compounds of the body surface. During experimentally induced social interactions, using lures, wasps perceived these chemical cues, minimizing physical contact with wounded (therefore chemically altered) lures. Because many parasites are transmitted by body contact, the wasps' reaction suggests they can minimize the risk of parasite intake into the colony. Host immune activation is common under a pathogen invasion. This physiological response can promote changes in the body surface compounds, thus providing chemical cues related to health that might be useful to conspecifics. By recognizing the current immunological status of social partners, individuals can modulate their behavior to minimize the risk of infection. Tegument wounding, an immune elicitor, is a required step for many parasites to become established in a host. By using the neotropical eusocial paper wasp Mischocyttarus metathoracicus as a model organism, we first performed a lure presentation experiment in the field to test if wasps discriminate conspecific immunological status (experimentally manipulated by wounding) during on nest social interactions. Then, we performed gas chromatography-mass spectrometry analyses to test if immunostimulation by wounding alters the wasps' cuticular hydrocarbon profile. We found that wasps reduce the duration of aggressive physical contact when interacting with wounded lures, despite displaying a similar frequency of inspective and aggressive behaviors toward both the wounded and the control lures. Besides, we found a subtle increase in a single cuticular hydrocarbon in the wounded wasps. Thus, wasps recognize conspecific immunological status, likely by chemical cues, and modulate their behavior in order to defend the colony against intruders while minimizing the personal risk of infection.

Automated summary

Social wasps can recognize the immunological status of conspecifics through chemical cues and adjust their behavior to minimize infection risk. Activation of the immune system leads to changes in body surface compounds, which allow wasps to identify wounded individuals and avoid physical contact with them, reducing the risk of parasite transmission.