Small Organisms with a Large Impact: How Microbes Regulate Attraction and Colonization of a Primary Colonizer of Carrion

The time of colonization can be critical in determining circumstances surrounding colonization event(s) in several entomological fields. This colonization event begins the post colonization interval (PostCI) which forensic entomologists attempt to estimate. A vast majority of the research applied in casework focuses on development rates, making PostCI estimates more precise. However, forensic entomologists understand that there is a period of time in which the insect has to detect and locate remains called the pre-colonization interval. The duration of the PreCI can be affected by a variety of factors, but effects of the microbiome have not been explored. Microbes are known to produce volatile organic compounds for various purposes and as by-products of metabolism. Cell autolysis also produces VOCs, but it is unknown which VOCs primary colonizers are utilizing to detect and assess a resource. In the current study, we address this unknown. Axenic and xenic mouse carcasses were obtained and individually placed in sterile treatment containers. Each carcass was swabbed to isolate and identify microbes present prior to use in a dual-choice cue olfactometer. Cochliomyia macellaria adults were allowed to respond for 2- and 8-hour trials throughout decomposition. At the conclusion of the behavior experiments each day, VOC samples were taken from each treatment container followed by an oviposition assay on day 8. Adults significantly preferred the xenic mouse over the axenic mouse and oviposition data showed a ~90% reduction in oviposition without microbes showing that microbes play a great role in attraction to and oviposition on a carrion resource.