Molecular identification of forensically important blowfly species (Diptera: Calliphoridae) from Germany

Abstract

Forensic entomology applies knowledge about the behaviour and ecology of insects associated to corpses to homicide investigations. It is possible to calculate a minimum post-mortem interval by determining the age of the oldest blowfly larvae feeding on a corpse. The growth rate of the larvae is highly dependent on temperature and also varies between the different blowfly species infesting a corpse. It is, thus, crucial to correctly identify the species collected from a crime scene. To increase the quality of species identification, molecular methods were applied to 53 individuals of six different species sampled in Bonn, Germany: Calliphora vicina, Calliphora vomitoria, Lucilia caesar, Lucilia sericata, Lucilia illustris, and Protophormia terraenovae. We extracted DNA and checked a 229 bp sequence within the mitochondrial cytochrome oxidase subunit I. The sequences of the local flies were aligned to published data of specimens from other countries. We also studied the practical value of the analysed DNA region for their differentiation. All species were matched correctly by a Basic Local Alignment Search Tool (BLAST) search apart from L. caesar and L. illustris. Although molecular methods are very useful-especially if it is necessary to identify small fragments of insect material or very young larvae-we propose to use it only in addition to the conventional methods.

Temperature requirements for the growth of immature stages of blowflies species, Chrysomya albiceps and Calliphora vicina, (Diptera:Calliphoridae) under laboratory conditions

“…Our findings about the life cycle of C.vicina showed that this species will also have shorter life cycle as the temperature increases such a way that at 15°C, its life cycle, from the egg stage to adult, it took 32 days while at 20°C, it took 21 days. For this species, other researchers obtained similar results: Reibe et al (Reibe et al, 2009) at 13°C and 20°C, 45 and 23 days, respectively; Defilippo et al (Defilippo et al, 2013) at 15°C and 20°C, 30. 5 and 20 days, respectively; Bharti (Bharti, 2009) at 20°C and 25°C, 19 and 15.…”

The use of COI barcodes for molecular identification of forensically important fly species in Germany

“…To date, publications on the molecular identification of forensically relevant flies from Germany is limited to two (Schroeder et al 2003;Reibe et al 2009). The research by Reibe et al (2009) deals with the molecular analysis of six blow fly species frequently found on carrion.…”

“…To date, publications on the molecular identification of forensically relevant flies from Germany is limited to two (Schroeder et al 2003;Reibe et al 2009). The research by Reibe et al (2009) deals with the molecular analysis of six blow fly species frequently found on carrion. We extend this research by including additional Diptera species and by focusing on the larger COI barcoding region that has been shown to differentiate even between recently diverged sister species of forensic importance (Nelson et al 2007).…”

“…A molecular marker that can sufficiently identify closely related sister species is necessary where their distributions overlap. In Germany, for instance, the palearctic sister species Lucilia illustris and Lucilia caesar are both found to breed in carrion, but molecular differentiation was impossible in the past (Reibe et al 2009). Although recently diverged, it may be possible that both species have different growth rates, and thus species misidentification may result in an inaccurate PMI min estimate.…”

“…Although recently diverged, it may be possible that both species have different growth rates, and thus species misidentification may result in an inaccurate PMI min estimate. Reibe et al (2009) analyzed a portion of the COI gene other than the region suggested by Hebert et al (2003). This 229-bp-long region was sufficient to distinguish between several blow fly species but not between the recently separated sister species L. caesar and L. illustris.…”