Role of Chrysomya albiceps (Diptera: Calliphoridae) and Musca domestica (Diptera: Muscidae) Maggot Crop Contents in Identifying Unknown Cadavers.

Forensic entomology focuses on the analysis of insect larvae present at crime scenes to help identify unknown cadavers. Carrion-feeding maggots store food in a crop located at the anterior end of the gut. DNA recovered from the crop can be amplified, sequenced, and identified to determine the origin of the food. This information could help investigators to identify a missing victim if maggots are discovered at a crime scene in the absence of a corpse. Chrysomya albiceps (Wiedemann) and Musca domestica (Linnaeus) are primary forensic species. Little or no information on the identification of unknown cadavers using C. albiceps and M. domestica larvae is available, and we aimed to compare the effectiveness of using the crop contents of instars of C. albiceps and M. domestica larvae to identify corpses at different time intervals. Two hundred and forty larvae of both species were reared on rat and/or mouse liver, and DNA from crop contents was extracted after different time intervals from different instar larvae. DNA was amplified using specific primers that match the mitochondrial cytochrome oxidase subunit I (mt COI) gene of the food source. Results showed that food provided to larvae affected life span and the ability to be used to identify unknown cadavers. Chrysomya albiceps larvae proved more useful than M. domestica larvae. Moreover, crop contents of third instar larvae of both species fed for 24 h are more useful than contents from other time intervals in identifying unknown tissues. Results are promising and may help investigators to identify unknown/missing victims.

Gene expression as age estimation marker in the larval stages of the forensic blowfly, Chrysomya albiceps, at different temperatures.

The blowfly Chrysomya albiceps (Diptera: Calliphoridae) has been known to breed in both animal and human carcasses in different geographical regions and is considered an important post-mortem indicator in forensic entomology. Determining the age of its larvae is an essential tool for the accurate determination of post-mortem intervals (PMI). This study adopted a molecular-based approach for age determination of the immature stages of the blowfly, C. albiceps, by evaluating the genes 15_2, 2014192, EcdR, AR, hsp90, and Actin, during larval development at different temperatures. Targeted genes were amplified by real-time PCR (RT-PCR), and the resulting amplicons were normalized against the two housekeeping genes, rp49 and 19_2. Data showed that the expression profile of AR was constant throughout all larval developmental stages at all tested temperatures. 2014192 showed low expression levels throughout the 1st, 2nd, and 3rd larval stages. Hsp90 and EcdR showed different expression profiles. The expression of 15_2 was low at the tested temperatures and was undetectable on most days. Collectively, the results of this study indicate that larvae exhibit temperature-dependent and age-specific up- and down-regulation in the expression profile of the targeted genes. This may indicate a possibility to be utilized as age estimation markers for C. albiceps.