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5 Geschlecht, Ernaehrung und Entwicklungszustand (vittellogene Phase und Paarungszustand). Die Ergebnisse tragen zum Verstaendnis von geruschssinnund physiologisch gesteurtem Verhalten der Insekten sowie der Dekompositionsprozesse bei und ermoeglichen zuverlaessigere Leichenliegezeitbestimmungen. 1 Abstract After death a body undergoes chemical processes, which depend on oxygen, bacteria, temperature, humidity, and more. The longer a body remained undetected, the more important it is to know these parameters to estimate the time of death. During the decay, a dead body emits a series of odour types, depending on the stage of decomposition. As necrophagous insect species are attracted by the characteristical decomposition odour, we use their predictable succession on a corpse and our knowledge about the larval development rates to draw conclusions about the post mortem interval (PMI). These estimations are based on case-studies and locally collected data as insect succession and development can vary due to external circumstances, as well as distribution and local temperature-adaptation of the insects. However, the interactions between external factors and the resulting emission of different odours and therefore on insect settlements is largely unknown. This study gives new insights on decomposition processes according to climate conditions, the production of volatile odour pattern of distinct decay stages and the attraction of necrophagous insects, exemplified on Lucilia caesar Linneus, 1758 (Diptera: Calliphoridae), to these odours and separated volatile compounds. Furthermore it is shown that insects of the same species, settling a dead body, are attracted by different odour pattern, thus by different decomposition stages, depending on their sex, nutrition and development stage (vittellogenous phase and mating status). The results contribute to the understanding of insect behaviour mediated by odour and physiological parameters, decomposition processes and help making reliable estimates of the exact time of death. General Introduction 6 2 General Introduction 2.1 Postmortem chemical changes6 2.1.1 Early corpse changes7 2.1.1.1 Cooling7 2.1.1.2 Rigidity7 2.1.1.3 Lividity8 2.1.2 Late corpse changes8 2.1.2.1 Autolysis (self digestion) 8 2.1.2.2 Decomposition (Heterolysis) 9 A) Protein degradation (proteolysis) 11 B) Fat degradation13 C) Carbohydrate degradation14 2.1.3 Conserving corpse changes16 2.1.3.1 Mummification16 2.1.3.2 Adipocere16 2.2 Calculating the post mortem interval (PMI) 17 2.2.1 PMI by early corpse changes17 2.2.2 PMI by forensic entomology20 2.2.2.1 History of forensic. entomology.. 21 2.2.2.2 Succession... 22 2.2.2.3 Development23 2.2.3 PMI by chemical marker24 A) Proteins24 B) Fat25 C) Carbohydrate25 D) Volatile organic compounds26 2.2.4 PMI by VOCs and Forensic Entomology29 2.3. The fly29 2.3.1 Systematic29 2.3.2 The biology of blowflies30 2.3.3 Medical aspects of blowflies32 2.4 The olfactory sense of flies33 2.5. References36 2.6 Aim and outline49 2.1 Postmortem chemical changes Postmortem transformation is the decay of organic matter by autolysis or by microorganisms such as bacteria, fungi and protozoa (heterolysis) or soft tissue conservation according to the different environmental conditions (Campobasso et al., 2001). In the following the change of chemical compounds and their products and by-products are described in detail. General Introduction 7 Furthermore the methods of estimating the post mortem intervals (PMI), the use of forensic entomology and the biology of the model species Lucilia caesar are explained. 2.1.1 Early corpse changes Several simultaneous processes occur immediately after the death of a body, including cooling, rigidity and lividity caused by the halt of cell processes. These changes are immediately visible and are used for the calculating of short post mortem intervals (PMIs) (see 2.2.1). 2.1.1.1 Cooling The decreasing temperature of a corpse is the first consequence after death (algor mortis) (Vass, 2001). Before reaching the body interior, the temperature gradient has to be overcome by conduction and convection, radiation or evaporation. This can take between minutes to several hours and is highly variable, whereas further temperature decrease occurs at a predictable theoretical rate (Brinkmann and Madea, 2004; Perper, 2006). 2.1.1.2 Rigidity Along with the temperature decrease, within hours after death, the body becomes stiff (rigor mortis), which starts at the eyelids and proceeds at the neck and jaw muscles before spreading throughout the whole body. The stiffness is caused by the telescoping of actin and myosin filaments, which occur after death by a neural impulse via the myoceptor. Ca ions diffuse from the area of higher concentration (in the terminal cisternae and extracellular fluid) to an area of lower concentration (in the sarcomere). ATPase splits adenosine triphosphate (ATP) to adenosine diphosphate (ADP) and phosphate and actin bonds to myosin. In living bodies ATP is synthesised to break these bonds. This is impossible within a dead body depleted of oxygen. Therefore ATP is no longer provided to operate the pumps in the membrane of the sarcoplasmic reticulum, which transports calcium ions back into the terminal cisternae (Schmidt-Nielsen, 1997; Ahern and Laver, 1998). In addition, in living bodies lactic acid, formed through anaerobic muscle activity, can easily be metabolised after oxygen absorption (Maltais et al., 1996; General Introduction 8 Westerblad et al., 2002). Conversely, in a dead body glycogen decomposition leads to an irreversible high lactic acid concentration, resulting in the catenation of actin and myosin and the subsequent stiffness of the body (Vass, 2001). The rigor mortis dissipates after 2-10 days due to proteolysis during the decomposition, which causes muscle relaxation (Perper, 2006). 2.1.1.3 Lividity During the lividity process (also called livor mortis or hypostasis) red discolorations of the skin become visible as the blood sinks through gravitation into the lower parts of the body. The vascular permeability increases causing a decrease of the hemo-concentration and displacement of blood (Vass, 2001; Madea et al., 2007). 2.1.2 Late corpse changes The actual decay of the soft tissue begins four minutes after death although not visible at the beginning. The complete decomposition takes up to several months or even years. 2.1.2.1 Autolysis (self digestion) Anaerobic cell decomposition is the first step of a body’s decomposition, starting from the cell interior without bacteria activity. This process ends with cleavage of peptide chains, which are not further decomposed to amino acids (Forster and Ropohl, 1986). As the O2 supply to the cells ceases after death the blood CO2 content increases together with decreasing pH value, leading to cell poisoning and thus nutrient-rich liquids emanate from the cell. Enzymes like lipase, protease or amylase destroy the cells from the interior, particularly in tissues with high enzyme and water content, such as liver, brain, spleen and adrenal gland (Vass, 2001). The resulting effect is softening of the tissue without gas production (Forster and Ropohl, 1986) and

Examinations of decomposition-processes and the olfactory sense of the necrophagous fly Lucilia caesar (L.) (Diptera: Calliphoridae) in relationship to the fly's physiological state