Microbial effects on the development of forensically important blow fly species

Abstract

Colonisation times and development rates of specific blow fly species are used to estimate the minimum Post Mortem Interval (mPMI). The presence or absence of bacteria on a corpse can potentially affect the development and survival of blow fly larvae. Therefore an understanding of microbial-insect interactions is important for improving the interpretation of mPMI estimations. In this study, the effect of two bacteria (Escherichia coli and Staphylococcus aureus) on the growth rate and survival of three forensically important blow fly species (Lucilia sericata, Calliphora vicina and Calliphora vomitoria) was investigated.Sterile larvae were raised in a controlled environment (16:8h day: night light cycle, 23:21˚C day: night temperature cycle and a constant 35% relative humidity) on four artificial diets prepared with 100µl of 10 5 CFU bacterial solutions as follows: 1) E. coli 2) S. aureus 3) a 50:50 E. coli: S. aureus mix and 4) a sterile bacteria-free control diet. Daily measurements (length, width and weight) were taken from first instar larvae through to the emergence of adult flies. Survival rates were also determined at pupation and adult emergence. Results indicate that bacteria were not essential for the development of any of the blow fly species.However, larval growth rates were affected by bacterial diet, with effects differing between blow fly species. Peak larval weights also varied according to species-diet combination; C.vomitoria had the largest weight on E. coli and mixed diets, C. vicina had the largest weight on S. aureus diets, and treatment had no significant effect on the peak larval weight of L.sericata. These results indicate the potential for the bacteria that larvae are exposed to during development on a corpse to alter both developmental rates and larval weight in some blow fly species.

New Insights Into Culturable and Unculturable Bacteria Across the Life History of Medicinal Maggots Lucilia sericata (Meigen) (Diptera: Calliphoridae)

“…Diets and breeding environments will also have a great influence on the blowfly gut bacterial profile. Flies are reciprocally dependent on specific bacteria and their metabolic pathways for the growth and development (Zurek et al, 2000;Crooks et al, 2016). Most studies have shown that the best survival rates of flies occur in the unsterilized or mixed bacterial environments (Tomberlin et al, 2017).…”

Microbial management as a driver of parental care and family aggregations in carrion feeding insects

“…Similar external immunity mechanisms are also known to occur in other carrion breeders and feeders, such as blowfly maggots (Kerridge et al, 2005;Pöppel et al, 2015) which can facilitate the growth of a parentally derived, beneficial microbiome around them in absence of parental attendance (Crooks et al, 2016;Junkins et al, 2019). In burying beetles, however, externalized immune defense protects both parents and larvae due to extensive parental care, larval contributions, and overlapping generations, thus facilitating a form of social immunity unusual for subsocial insects (Cotter and Kilner, 2010a;Cotter and Kilner, 2010b;Meunier, 2015;Van Meyel et al, 2018).…”

Recent advances in forensic anthropology: decomposition research

“…The volatile organic compounds (VOCs) produced as bacteria degrade carrion are responsible for attracting blow flies to colonize. Additionally, the presence of bacteria species may be necessary for proper development of many fly species [65, 66]. Therefore, knowledge of bacteria succession and function during decomposition through metagenomics research is important to understand the downstream effects on decomposition rates and patterns.…”

“…Arthropods : Much of the research on decomposition outside of anthropology has focused on necrophagous insects, especially flies and beetles, which are a major contributor to biomass reduction. Factors affecting colonization and the lifecycle of these species have been the primary emphasis of research and are discussed in detail in numerous publications [16, 66–81]. Tomberlin et al.…”