Ha Thi Nguyen

Thesis

The use of published microsatellite primers on Calliphora species (Diptera: Calliphoridae) for the purpose of species and sub-population differentiation.

Summary

An important aspect of forensic entomology is the determination of the post-mortem interval (PMI). The PMI can be calculated using insects collected from the crime scene, primarily by determining the age of calliphorids taken from a corpse. However, identification of larvae by the use of morphological features can be difficult as there is a lack of larval keys for the Calliphoridae, lack of distinguishable features in immature stages and specimens may be damaged during collection or transportation. Therefore, a new approach is needed in the identification of calliphorids to overcome any problems associated with morphology.

DNA- based techniques have been developed to identify calliphorids of forensic significance. Several studies have utilised DNA in calliphorids as DNA can be easily obtained from specimens in any lifestage and even from poorly preserved samples.

My research looks at the use of microsatellites which are polymorphic loci within an organism’s DNA. Their variability allows good discrimination in population level studies which may aid in the correct identification of cryptic species, thus, characterising insects as originating from specific geographical localities. In particular, my thesis considers forensically significant species Calliphora dubia and Chrysomya rufifacies and looks at the possibility of intraspecies variation.

Why my research is important

Critical to PMI estimation is the correct identification of insects. Incorrect identification of insects may result in the application of inappropriate developmental data in estimation of insect cycle which may potentially result in a difference of several days in the PMI estimate. My research is important as it may aid in a better and faster identification system for blowflies on carrion. DNA based techniques are able to provide fast identification between all forensically important species and are accurate and form robust confirmation of the species. It is also applicable to all life stages of calliphorid and provide identification from damaged, poorly preserved and dead specimens. My research may also be a stepping block for further studies in this area.