Author ORCID Identifier
https://orcid.org/0009-0007-6587-1068
Defense Date
2024
Document Type
Directed Research Project
First Advisor
Michelle Peace
Second Advisor
Baneshwar Singh
Third Advisor
Stephen Raso
Fourth Advisor
Christopher Ehrhardt
Abstract
Lucilia sericata (Diptera: Calliphoridae) is a forensically important blow fly species. These flies have been extensively studied as they are one of the earliest colonizers of corpses. Adult females blow flies lay approximately 200-2,300 eggs, which upon hatching will feed off the body as they metamorphosize from first to second, and third instars. The third instar larvae then migrate away from the body in a stage known as pre-pupa, and develop into the puparial stage. The adults emerge from the pupa stage, leaving behind their empty puparium. These developmental stages are used by forensic entomologists to determine a minimum postmortem interval (PMImin). In cases where pupae are the oldest specimen, it can become difficult to determine the age as they are not morphologically distinct to the naked eye past the first day of pupation. Fortunately, cuticular hydrocarbon (CHC) analysis has been a technique developed to determine the age of blow fly specimens, however the majority of studies have focused on the larval and adult stages.
In this study, Direct Analysis in Real Time-Time of Flight-Mass Spectrometry (DART- ToF-MS) was evaluated for its ability to determine the age of L. sericata pupae using the CHC profile as well as the fatty acid (FA) profile based on simple hexane extracts of pupae over the course of seven days. Each day contained six samples of pupae (n = 8) and a hexane extraction blank was run for quality control. Gas Chromatography Mass Spectrometry (GC-MS) was used to support the identification of chemical compounds. eight FAs were identified with DART-ToF- MS, with four confirmed through GC-MS. A minimum of 35 CHCs were identified using DART-ToF-MS, consisting of 14 n-alkanes, 19 Cn:1 species, and 3 Cn:2 species, with only 6 n- alkanes confirmed through GC-MS.
Principal component analysis (PCA) and linear discriminant analysis (LDA) were performed to evaluate whether the DART-ToF-MS profiles can be used to discriminate between the age of the pupae samples. The FA profile was not able to discriminate the ages of the pupae using either statistical method. The CHC profile was able to discriminate the age of the pupae using the LDA, but not the PCA. Stronger discrimination was found when the grouping interval of ages was increased. The results suggest this method to have stronger discrimination over broad ranges of ages rather than small intervals.
Rights
© The Author(s)
Is Part Of
VCU Master of Science in Forensic Science Directed Research Projects
Date of Submission
6-11-2024