The sense of smell is an incredibly complex and important sense across the animal kingdom. Insects rely heavily on olfaction for everything from finding mates, shelter, and food to locating oviposition sites.
While a lot of research has been done to understand how insects use chemical cues from plants and other insects to guide their behavior, recent research suggests that microorganisms may also be providing important olfactory information for insects. Microbes all throughout insects and their environments may be providing important chemical information, impacting insect behavior.
In a recent study, researchers investigated the behavioral responses of insect to a range of bacterial odors. The results indicated that volatile mixes of chemicals produced by the bacteria can significantly impact insect behavior.
They studied looked at two types of aphids, Aphidus colemani and Dendrocerus aphidum. In the lab, they isolated 36 strains of microorganisms that are typically associated with aphids and their environment. To test the aphid response to chemical cues only, they eliminated visual cues and exposed the aphids only to the smell. Past work has shown that insects “smell” mixtures of volatile organic compounds. Previous worth with microorganisms has suggested that they produce mixtures of microbial volatile organic compounds (mVOCs), similar to those produced by plants and insects. They analyzed these chemicals produced by each strain to determine whether chemical composition of odors had an effect on the type of behavioral response.
They found that the various microbes were either significantly attractive, neutral, or significantly deterrent to the aphids. The behavioral response depended on the chemical composition of the mVOCs, and also on the species of aphid. The significant impact on aphid behavior indicates that microbial chemical cues may be an important and understudied part of insect behavior.
Analysis of the mVOCs produced by the microbial strains in the study showed that they can be very similar in composition to plant and insect chemical cues. While more work needs to be done to understand the role of microbes in creating these various volatile organic compounds, this study suggests that previously studied plant and insect olfactory cues may actually be derived from microorganisms associated with the plant or insect.
This study provides exciting insight into a new aspect of insect behavior that has previously been unexplored. Organisms like insects rely heavily on sensory information from their environment to mediate their behaviors, and olfaction is one of the most central but least studied modalities.
Goelen, T., Sobhy, I.S., Vanderaa, C., de Boer, J.G., Delvigne, F., Francis, F., Wäckers, F., Rediers, H., Verstrepen, K.J., Wenseleers, T., Jacquemyn, H. and Lievens, B. (2019), Volatiles of bacteria associated with parasitoid habitats elicit distinct olfactory responses in an aphid parasitoid and its hyperparasitoid. Functional Ecology. Accepted Author Manuscript. doi:10.1111/1365-2435.13503