In vitro recovery and identification of Y-STR DNA from chrysomya albiceps (Diptera, calliphoridae) larvae fed a decomposing mixture of human semen and ground beef

Abstract

Worldwide, several women become victims of rape every day. Many of those women are also murdered, with their bodies sometimes being found in an advanced state of decomposition, resulting in loss of evidence important to criminal investigations. Diptera is one of the main orders associated with human body decomposition. Fly species that belong to the family Calliphoridae are usually scavengers and are frequently found on decomposing bodies, thereby playing an important role in forensic entomology. The recovery and genotyping of human Y-STR DNA from the gastrointestinal contents of the calliphorid Chrysomya albiceps larvae has promising applications in the investigation of sexual crimes, such as rape, and in cases of murder and abandonment of the victim’s body, which may be found in a state of decomposition. We studied this species of fly with the aim of supporting such investigations. After establishment of a colony, larvae were fed with decomposing human semen mixed in ground bovine meat (1 mL per 200 g beef). Larvae (10-15) were collected every 24 h and kept in 70% ethanol, to give a total of 96 larvae obtained after eight days of decomposition. The digestive system of each larva was resected. Molecular typing was conducted, which comprised sample extraction, quantification, amplification, and capillary electrophoresis with 16 STR loci from the Y chromosome. We succeeded in establishing a Y-STR DNA profile, with amplification of up to 11 loci, from individual samples, or up to 15 loci, when a combination of samples corresponding to the time-points 48, 72, 120, 144, and 192 h was used.