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Methods of researching pupal history involving CT-scanning: A novel approach to death time estimations

Final Report Summary - MORPHIC (Methods of researching pupal history involving CT-scanning: A novel approach to death time estimations)

Forensic entomology is today an increasingly robust science which has its main application in the estimation of the minimum post-mortem interval based on the age of necrophagous insects (mainly blow flies) collected from cadavers. However, whilst accurate death time estimations can be inferred from the larval stage of these insects, estimates based on the intra-puparial period are severely limited due to the lack of reliable aging methods. The intra-puparial period is the period during which the larva metamorphoses into an adult fly; it takes place inside an opaque puparium formed by hardening and darkening of the larval cuticle and it accounts for approximately half of the developmental duration. It is, therefore, a crucial time-span for estimating a minimum post-mortem interval.

In recent years, the use of innovative imaging techniques such as micro-computed tomography (micro-CT) and computer-based 3D reconstructions have significantly enhanced research on insect anatomy and development. A recent study demonstrated that micro-CT provides the resolution necessary for describing internal and external morphological changes during metamorphosis.

The scientific objectives of MORPHIC are:
1. To document and analyse the morphological changes during metamorphosis at a temporal resolution more than twice the best current estimate.
2. To develop a novel and reliable methodology for aging puparia for forensic purposes by establishing a solid time-frame for the developmental changes which occur during metamorphosis of forensically important blow flies.
3. To exploit micro-CT research in combination with 3D computer models to create images for teaching and public outreach, providing impressive and interactive reconstructions.

Using micro-CT, we have identified and described the morphological changes taking place during blow fly metamorphosis at a greater temporal resolution than anything hitherto published. Moreover, we have provided, for the first time, quantitative data on the development of particular organ systems during the development of the adult fly. Our results show that the chronology of development remains constant under different experimental temperatures and among different blow fly species, making the current method suitable for aging puparial specimens in a forensic context. An aging method for blow fly puparia has been developed, including both a qualitative and quantitative approach. The qualitative measure of age based on the observation of key morphological characters is complemented with classifiers based on quantitative measures of the volume of different organ systems through development.

Through MORPHIC the fellow acquired solid practical skills on forensic entomology methods and applications, diversifying his expertise with skills on novel imaging techniques of broad application in different areas of research and practice, and developing strategic networks, increasing his opportunities of reaching a permanent position as scientific researcher in Europe. The results of the project are being made available in peer-reviewed publications and through web-based tools to benefit the global community.