Interkingdom cues by bacteria associated with conspecific and heterospecific eggs of Cochliomyia macellaria and Chrysomya rufifacies (Diptera: Calliphoridae) potentially govern succession on carrion

Authors: BRUNDAGE, ADRIENNE - Texas A&M University; Crippen, Tawni - Tc; SINGH, BANESHWAR - Virginia Commonwealth University; BENBOW, ERIC - Michigan State University; LIU, WENQI - Texas A&M University; TARONE, AARON - Texas A&M University; WOOD, THOMAS - Pennsylvania State University; TOMBERLIN, JEFFERY - Texas A&M University

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2016
Publication Date: 1/12/2017
Citation: Brundage, A.L., Crippen, T.L., Singh, B., Benbow, E., Liu, W., Tarone, A.M., Wood, T.K., Tomberlin, J.K. 2017. Interkingdom cues by bacteria associated with conspecific and heterospecific eggs of Cochliomyia macellaria and Chrysomya rufifacies (Diptera: Calliphoridae) potentially govern succession on carrion. Annals of the Entomological Society of America. 110(1):73-82. doi:10.1093/aesa/saw090.

Interpretive Summary: We investigated the mechanisms that regulate the sequence of insect utilization (i.e. succession) of food and egg laying resources that are short lived in the environment (i.e. carrion). The blow fly utilization of vertebrate carrion serves as a model for the studies. In most instances, initial colonization by blow flies causes increased attraction to and colonization by competing insects, thereby controlling associated insect succession patterns. We examined the response of the secondary screwworm (native to North America) and the hairy maggot blow fly (invasive to North America). Because the hairy maggot blow fly will eat other species’ larvae, we hypothesized that there would be selection for adults that recognize the presence of the eggs of other species to avoid potential predation. Using an apparatus for measuring fly sensitivity to an odor (olfactometer), we measured the residence time response of the blow flies to eggs from the same species and from the competitor species of three different age classes ranging from fresh to 9-h-old (close to hatching). We theorize that many of the odors come from microbial sources, so we then examined the response of these flies to eggs that were or were not surface sterilized to remove egg-associated microbes. Metagenomic sequencing was used to survey the bacteria associated with different ages of eggs from these two species. We report that blow flies exhibit differential responses to eggs from their species and from competing species, which appears to be a result of microbial produced odors. These behaviors are likely tied into the predator-prey interactions between the two species. Preliminary metagenomic analysis revealed the two blow fly species have similar egg-associated microbes, which may serve as a form of camouflage allowing the predator blow fly to colonize, and thereby attract the prey for its larvae.

Technical Abstract: Deciphering the mechanisms that regulate animal behavior related to succession on ephemeral resources is critical for elucidating food web dynamics and nutrient recycling. Blow fly (Diptera: Calliphoridae) colonization and utilization of vertebrate carrion serve as a model for such studies, as they are the primary invertebrates that recycle this ephemeral resource. In most instances, initial colonization by blow flies results in heightened attraction and colonization by competing conspecifics and heterospecifics, thereby regulating associated arthropod succession patterns. We examined the response of Cochliomyia macellaria (native to North America) and Chrysomya rufifacies (invasive) to conspecific and heterospecific eggs. Because Ch. rufifacies is cannibalistic as well as predaceous on heterospecific larvae, we hypothesized that there would be selection for adults to recognize the presence of conspecific and heterospecific eggs and thus avoid potential predation and competition. Using a Y-tube olfactometer, we measured the residence time response of C. macellaria and Ch. rufifacies to conspecific and heterospecific eggs of three different age classes ranging from fresh to 9-h-old (close to hatching). We then examined the response of these flies to eggs that were surface sterilized and to an aqueous solution containing egg-associated microbes. High throughput sequencing was used to survey the bacteria associated with different ages of eggs from these two species. We report that C. macellaria and Ch. rufifacies exhibit differential responses to eggs of conspecifics and heterospecifics, which appears to be a result of microbial volatile-related odors. These behaviors are likely tied into the predator-prey interactions between the two species. Preliminary high throughput metagenomic analysis revealed Ch. rufifacies has a similar egg-associated fauna as C. macellaria, which may serve as a form of camouflage allowing it to colonize and thereby attract C. macellaria, a common prey for its larvae.