Browsing by Author "Kula, Canan"
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Item Open Access Cuticular hydrocarbon analysis for the identification, ageing and geographical variations of forensically important blowflies(2022-02) Kula, Canan; Moore, H E; Drijfhout, F P; Shortland, A.Calliphoridae (blowflies) are important for forensic entomology as they are often the first group of insects to inhabit decomposing remains. To estimate the minimum post-mortem interval (PMImin), blowfly samples are collected from the crime scene and identified, and then the age needs to be determined for each species. Accurate species identification is crucial, as varied species have different life-stage timings. Previous studies on Diptera have shown the possibility of using cuticular hydrocarbon (CHC) analysis to aid species identification, ageing and ultimately calculating PMImin. However, since prior research was conducted at constant temperatures, the effect of fluctuating temperature on chemical profiles and the stability of CHCs in the field remains unclear. This thesis aims to examine the CHC profiles of Lucilia sericata and Calliphora vicina reared outdoors in the United Kingdom, Germany and Turkey in terms of species, age and inter-population differences. The first study investigates whether the stability of the CHC profiles of two colonies reared outdoors can be used to identify species-specific characteristics. The second examines the effects of fluctuating and constant temperatures on the CHC profiles of the life cycle stages and the use of their chemical profiles for age estimations. The final study aims to determine the differences in CHC profiles of the same species living in different habitats and whether they can be used to distinguish populations. The CHC profiles of the samples were extracted and analysed using Gas Chromatography-Mass Spectrometry (GC-MS). The statistical interpretation was carried out using Principal Component Analysis (PCA). The results showed that CHC profiles differed significantly between developmental stages by species, age, rearing temperature and geographical location. This study highlights that despite environmental factors affecting the stability of CHC compositions, the CHC analysis can be used as a complementary tool for identifying and ageing the species. Furthermore, the effects of ambient temperature and geographical variation on CHC profiles may be useful for determining inter-population variations.Item Open Access Geographical variation of cuticular hydrocarbon profiles of adult flies and empty puparia amongst three populations of Calliphora vicina (Diptera: Calliphoridae)(Oxford University Press, 2022-11-14) Kula, Canan; Amendt, Jens; Drijfhout, Falko P.; Moore, Hannah E.Blowflies (Diptera: Calliphoridae) are of great importance in forensic entomology and in determining the minimum post-mortem interval, as they may be the first group of insects to colonise decomposing remains. Reliable species identification is an essential prerequisite. Classically, morphological characters or DNA sequences are used for this purpose. However, depending on the species and the condition of the specimen, this can be difficult, e.g. in the case of empty fly puparia. Recent studies have shown that cuticular hydrocarbon (CHC) profiles are species-specific in necrophagous taxa and represent another promising tool for identification. However, the population-specific variability of these substances as a function of e.g. local climatic parameters has not yet been sufficiently investigated. The aim of this study was to determine the geographical variation of CHC profiles of the blowfly Calliphora vicina depending on different countries of origin. Flies were reared in the UK, Germany and Turkey in common garden experiments under ambient conditions. CHC profiles of the resulting adult flies and their empty puparia were analysed using gas chromatography-mass spectrometry. Data were visualised by principal component analysis and clustered by population. The populations of the UK and Germany, both having similar climates and being geographically close to each other, showed greater similarities in CHC profiles. However, the CHC profile of the Turkish population, whose climate is significantly different from the other two populations, was very different. Our study confirms the high potential of CHC analysis in forensic entomology but highlights the need to investigate geographical variability in chemical profiles.Item Open Access The temperature effect on the cuticular chemical profile of Lucilia sericata blowfly larvae(Cranfield University, 2020-01-14 14:47) Kula, CananForensic entomology has become increasingly important in the last decade. In cases of homicide, suicide or suspicious death, insect specimens are taken into consideration as acceptable evidence like blood, fingerprint or any other biological materials. When solving criminal cases, it is essential to determine the time since death or post-mortem interval (PMI). Entomological evidence can provide valuable information about the prediction of the post-mortem interval and where the death occurred.Forensic entomology, like many other fields in forensic sciences, has been developing using new technologies. Cuticular hydrocarbon (CHC) analysis has become a useful tool for identifying and ageing forensically important blowfly species. Variation in hydrocarbon profiles is significant for climatic adaptation, protection against dehydration and desiccation. The effect of other variables, such as environmental climate and geographic region, and how this may change the CHC structure is not known. In the literature, there are some studies showing differences in the hydrocarbon structure of beetles, fruit flies and house flies when reared at different temperatures. Although there are many studies on the relationship between temperature effect and development time of blowfly species using classical entomology methods, no studies have been conducted using cuticular hydrocarbon analysis. In this regard, this study has been a first in the field of forensic entomology. In this study, L. sericata collected from the wild were used for oviposition. Once eggs were laid on the oviposition medium, the Petri dish containing the meat was transferred to incubators at 14 ºC, 25 ºC and 34ºC. The cuticular hydrocarbons were chemically extracted and analysed for post-feeding larvae. The effect of temperature changes on the cuticular structure was investigated by using Gas Chromatography-Mass Spectrometry.