Who runs the (decomposition) world? Microbes influencing decomposition and attraction of the blow fly, Cochliomyia macellaria

Carrion decomposition typically consists of five stages: fresh, bloated, active decay, advanced decay, and dry. Stages are usually described and guided by microbial and insect activity within and around the remains. Microbes within, and on, a deceased vertebrate produce volatile organic compounds (VOCs) as a by-product of metabolism. These VOCs are key mechanism regulating blow fly (Diptera: Calliphoridae) (i.e., key invertebrate decomposer of carrion) attraction and colonization. In the current study, we determined the answer to these questions. Axenic and xenic mice were allowed to decompose in a controlled environment to assess the stages of decomposition. Secondly, using a dual-choice cube olfactometer, attraction of adult secondary screwworm, Cochliomyia macellaria, (Diptera: Calliphoridae) to the carcasses was determined as they decomposed. Oviposition preference was determined in a dual choice experiment as well. This study determined that the bloat stage of decomposition is absent in axenic mice, as well as later fluid purge. Xenic fluid purge occurred on day 6 while axenic fluid purge did not occur until day 13. Olfactometer results indicate that the presence of microbes associated with carrion is a key factor driving attraction of blow flies to carrion at different stages throughout decomposition. In addition, microbial absence reduces C. macellaria oviposition by almost 90%. Such data serve as a foundation for exploring microbial variation across decomposing resources and its role in regulating foraging behavior of blow flies, and other carrion-frequenting arthropods, in natural settings.