Reference no: EM132761334

Thanatochemistry, also referred to as, ''chemistry of death,'' is a poorly studied branch of science, and limited information is available regarding the cadaveric volatile organic compounds (VOCs). During carrion decomposition, emitted VOCs are suspected to be responsible for the attraction of forensically important insects (Statheropoulos et al., 2007). However, little information is available on the VOCs emitted by necrophagous Diptera throughout their life cycle (Frederickx et al., 2012a). To explore the potential use of VOCs for determining the age of blow fly immatures, Gas chromatography-mass spectrometry (GC-MS) was used to investigate the developmental changes of VOC composition in the larvae and pupae of Chrysomya rufifacies, (Macquart) (Diptera: Calliphoridae). The aim of this study was to investigate whether VOCs released by the Chrysomya rufifacies immatures can be used for identification and age estimation of immatures. GC-MS was used to identify the profile of 58 volatile organic compounds (VOCs) emitted by the immature stages (larvae and pupae) of Chrysomya rufifacies from all the samples as shown in Table R3. These 58 compounds include 14 hydrocarbons (24%), nine carboxylic acids (16%), seven ketones (12%), six amides (10%), four aldehydes (7%), four esters (7%), four nitrogen-containing compounds (7%), four carbolic acids (7%), three alcohols (5%), two acetates (3%) and one sulphur-containing compound (2%) (Figure R5). Eight of these volatile compounds (benzaldehyde, tridecane, triacetin, tetradecane, pentadecane, eicosane, butylated hydroxytoluene, and hexadecane) were found to be constitutively expressed throughout the development of the investigated immature stages (larvae and pupae). On the contrary, compounds like propanoic acid, 2-methyl- butanoic acid, 2-methyl phenylethyl alcohol, acetamide, n-(2-methyl propyl), and indole were emitted only by larval stages. The rest of the compounds showed more dynamic patterns of expression throughout development. Based on the abundances, 37 compounds were selected for quantitative analysis of both the treatment and control samples.

During this research work, attempts have been made to determine the age of immature stages of forensically important insect species (Chrysomya megacephala and Chrysomya rufifacies) with the help of some recent age estimation techniques. Cuticular hydrocarbon compounds (CHC's) have also been utilized in the field of entomology for ageing, gender identification and species identification. (Tregenza et al., 2000; Savarit and Freveur, 2002; Brown et al., 2000; Desena et al., 1999; Hugo et al., 2006; Brown et al., 1992; Chen et al., 1990; Mpuru et al., 2001; Jackson and Bartelt 1986; Steiner et al., 2006 and Marican et al., 2004). Cuticular hydrocarbons (CHC) may give the same accuracy as DNA techniques for ageing the insects. Composition of cuticular hydrocarbon changes with age in some of the insect's species. These compounds are very useful to age the postfeeding larvae, which is quite long and difficult to differentiate morphologically. Analysis of Volatile Organic Compounds (VOCs) released by insects' stages (immature and mature) can enables the entomologist to distinguish the feeding third instar from post feeding and young pupae from the older one. According to Frederickx and Co-workers, the volatile profile has shown a variation in both composition and quantity in larvae and pupa of Calliphora vicina (Robineau-Desvoidy) (Diptera: Calliphoridae)

Question: Why Volatile Organic Compounds need to determine the identification and age of immature stage to estimate Post mortem interval?