Analyzing cuticular hydrocarbons and stable isotope variation over the life cycle of key forensic insects

• Grant number: 23/11054-6
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Effective date (Start): January 01, 2024
• Effective date (End): June 30, 2024
• Field of knowledge: Biological Sciences - Zoology - Applied Zoology
• Principal Investigator: Luiz Antonio Martinelli
• Grantee: Fernanda Gaudio Augusto
• Supervisor: Jens Amendt
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Research place: Goethe University Frankfurt, Germany
• Associated to the scholarship: 22/01413-6 - Forensic evidence in the decomposition of animal carcasses: use of entomology and stable isotopes, BP.PD

Abstract

Forensic entomology is an important tool in criminal investigations. During the decomposition process, carcasses undergo physical and chemical changes. Necrophagous organisms that feed on those decomposed tissues could reflect such chemical changes. In forensic applications, insect cuticular hydrocarbons (CHCs) have been used in chemotaxonomic identification, age estimation, and geographical assignment. Carbon and nitrogen stable isotope signatures (´13C and ´15N) are usually used to estimate diet and trophic levels but some natural processes can degrade these compounds (e.g., decomposition process). In this way, analyzing the CHCs profiles and stable isotope signatures of insects could reflect the decomposition processes and biochemistry of the carcass as it progresses. The project aims to investigate the CHCs composition and ´13C and ´15N variation during the life cycle (from immatures to adults) of the most important taxa in forensic entomology, the blow flies (Diptera: Calliphoridae). Established fly stocks of relevant taxa will be kept in rearing cages, fed (minced meat)), and the offspring will grow in a controlled environment chamber (temperature and humidity) until adult flies. Gas chromatography-mass spectrometry will be used to analyze the CHCs after the hexane extraction. ´13C and ´15N compositions of insects and diet will be measured by Elemental Analyzer-mass spectrometry from dry samples. We expect to detect the changes in CHCs profiles and ´13C and ´15N signatures over the life cycle and metamorphosis of the species. Finally, we hope to understand the application of these techniques and their correlations in pursuit of new insights for forensic investigations and quantitative methods for future use in postmortem estimations. (AU)