Browsing by Subject "Forensic entomology"

Now showing 1 - 6 of 6
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    Amplified fragment length polymorphism analysis supports the valid separate species status of Lucilia caesar and L. illustris (Diptera: Calliphoridae)
    (Taylor & Francis:, 2017-12-08) Picard, Christine J.; Wells, Jeffrey D.; Ullyot, Anne; Rognes, Knut; Biology, School of Science
    Common DNA-based species determination methods fail to distinguish some blow flies in the forensically and medically important genus Lucilia Robineau-Desvoidy. This is a practical problem, and it has also been interpreted as casting doubt on the validity of some morphologically defined species. An example is Lucilia illustris and L. caesar, which co-occur in Europe whilst only L. illustris has been collected in North America. Reports that these species shared both mitochondrial and nuclear gene sequences, along with claims that diagnostic morphological characters are difficult to interpret, were used to question their separate species status. We report here that amplified fragment length polymorphism profiles strongly support the validity of both species based on both assignment and phylogenetic analysis, and that traditional identification criteria based on male and female genital morphology are more reliable than has been claimed.
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    Factors Affecting Species Identifications of Blow Fly Pupae Based upon Chemical Profiles and Multivariate Statistics
    (MDPI, 2017-04-11) Kranz, William; Carroll, Clinton; Dixon, Darren A.; Goodpaster, John V.; Picard, Christine J.; Chemistry and Chemical Biology, School of Science
    Alternative methods for the identification of species of blow fly pupae have been developed over the years that consist of the analyses of chemical profiles. However, the effect of biotic and abiotic factors that could influence the predictive manner for the tests have not been evaluated. The lipids of blowfly pupae (Cochliomyia macellaria, Lucilia cuprina, Lucilia sericata, and Phormia regina) were extracted in pentane, derivatized, and analyzed by total-vaporization solid phase microextraction gas chromatography-mass spectrometry (TV-SPME GC-MS). Peak areas for 26 compounds were analyzed. Here we evaluated one biotic factor (colonization) on four species of blow flies to determine how well a model produced from lipid profiles of colonized flies predicted the species of flies of offspring of wild-caught flies and found very good species identification following 10 generations of inbreeding. When we evaluated four abiotic factors in our fly rearing protocols (temperature, humidity, pupation substrate, and diet), we found that the ability to assign the chemical profile to the correct species was greatly reduced.
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    The genomics of development rate variation in Cochliomyia macellaria (Diptera: Calliphoridae)
    (2018-07-16) Lewis, Sarah E.; Picard, Christine J.
    Development rate is a quantitative trait that displays significant variation within many species, including Cochliomyia macellaria Meigen (Diptera: Calliphoridae). Calliphorids are a family of dipterans known as blow flies and are commonly used in forensic entomology to estimate the minimum postmortem interval (PMIMIN), given some assumptions are made. In order to dissect the genetic underpinnings of development rate variation in this species, artificial selection for fast and slow development with population-based resequencing was used. The objective of this study is to isolate and characterize genomic regions that are correlated to development rate variation in blow flies. The first approach used known regulatory development genes from Drosophila melanogaster Meigen (Diptera: Drosophilidae) and isolated variants that were associated with development time changes in artificially selected fast and slow development C. macellaria strains. Three variants located in Ras and Eip74EF were associated with fast or slow development in selection strains with a significant change in allele frequency. The second approach involved the comparison of pooled artificially selected fast and slow C. macellaria genomes to investigate the genetic basis of development rate variation. When comparing the fast and slow genomes, 699 sequences were identified that contained 7290 variants with consistent changes in allele frequency. The variants indicated that the genomic regions that are associated with development rate were associated with developmental processes, including regulation of RNA polymerase II activity, and transporter activity, such as protein dimerization. Of the 699 sequences, 69 sequences were related to Achaete-scute complex and 14 were related to Cyp12A7. The identification of the genomic regions that associated with development rates from this study provides an important resource for future studies in identifying potential genetic markers to increase the effectiveness of PMIMIN estimates. By using significantly associated variants as a priori candidates for future studies, the data increases the understanding of natural development variation in blow flies.
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    Molecular Genetic Methods for Forensic Entomology
    (CRC Press, 2019) Stevens, Jamie R.; Picard, Christine J.; Wells, Jeffrey D.
    A preservative solution containing formaldehyde should not be used if it can be avoided, as formalin can interact with deoxyribonucleic acid (DNA), making subsequent molecular analyses difficult. Some forensic entomologists recommend killing maggots by blanching in hot water; this technique does not appear to hinder any subsequent DNA analysis. Maggots found in the absence of a corpse may still have the victim’s tissue in their gut. Such specimens must be killed and preserved immediately, otherwise the evidence may be digested and lost. There is little doubt about the need for accurate specimen identification in forensic entomology. Intraspecific variation in DNA sequence is commonly observed, so an unknown specimen will often not exactly match the genotype of a reference specimen. Ribonucleic acid analysis can reveal the genes that were active within a tissue sample at the time it was processed.
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    Temporal survey of a carrion beetle (Coleoptera: Silphidae) community in Indiana
    (Indiana Academy of Science, 2015) Owings, Charity G.; Picard, Christine J.
    Carrion beetles (Coleoptera: Silphidae) play an important role in vertebrate decomposition as they utilize carcasses to carry out their life cycles. These beetles represent novel models for behavioral ecology, and can act as important forensic indicators in death investigations. However, population and community dynamics of silphids in Indiana are currently outdated. The aim of this study is to update surveys of a single silphid community with high temporal resolution in order to explore diversity and abundance patterns over time. Beetles were collected from Purdue University multiple times (N = 13) over a period of seven months in order to assess population dynamics at a single site. A total of 1607 specimens constituting seven different species were collected. Species abundance over time and space changed dramatically, and only one species (Nicrophorus tomentosus Weber) was present in nearly all collections (eleven out of thirteen, June–October 2014). It was demonstrated that the community dynamics of silphids at a single site in Indiana aligns with previous studies in the state. Additionally, the community structure of this family appears to change drastically over time in the summer months.
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    Utilizing Phormia Regina as an Environmental Sensor for Resource Identification and Biodiversity Monitoring
    (2024-08) Jensen, Katharine Theresa; Picard, Christine; Manicke, Nicholas; Dembinski, Gina
    Blow flies are a family of carrion insects that are among the first to arrive in the decomposition process. Blow flies are known to ingest carrion, feces, water, and occasionally nectar to meet nutritional requirements. These behaviors make blow flies a unique organism potentially containing genetic material from a variety of sources within one environment. Their global distribution and ease of capture makes them a strong candidate for resource monitoring and identification. While previous studies have evaluated the suitability of blow flies for vertebrate biodiversity estimates, no work has been done looking at their ability to ingest and store genetic material from plants and microbes present in water. It is also not known how long these DNA signals persist in the gut. Through DNA analysis of the blow fly gut, researchers can identify vertebrates that have recently died in an environment, what plant species are present, and what water source the insect utilized. Through lab colony (Phormia regina) feeding experiments, it was determined that at 25 ˚C and 50 % relative humidity, vertebrate and plant DNA persist in the gut for over 120 hours post-ingestion. Wild sample analysis of flies collected from Yellowstone National Park was performed to identify plant species ingested by P. regina in the wild. Following Sanger sequencing, top hits on BLASTn included Brassicales, Juglans cathyensis, and uncultured Candida. This is the first application of environmental DNA analysis techniques to insects for the purpose of plant identification. This work also attempts to characterize microbial profiles of the gut of P. regina for the purpose of water resource identification. Over a two-month collection period, samples were collected from different water resources across Indianapolis. Flies were exposed to these samples in a controlled feeding experiment, followed by sampling at 0- and 72 hours post-exposure. Gut samples were sequenced using Illumina and Operational Taxonomic Unit clustering grouped reads by sequence similarity for identification. Bacteria classes identified included Gammaproteobacteria, Bacteroidia, Flavobacteria, Alphaproteobacteria, Bacilli, Clostridia, Actinobacteria, Betaproteobacteria, and Fusobacteria. Many bacteria classes were common across water samples, although the abundance of each class changed between samples and across time. These unique microbial profiles can be used to identify water resources for potential contamination and chemical dumping. Further work is necessary to generate microbial profiles from the original water sources themselves and for generation of alpha and beta diversities. Overall, this work spans multiple fields. Species identification is important for biodiversity monitoring and environmental surveys. Utilizing blow fly derived DNA allows for detection of living and deceased vertebrates in an environment, plant life, and water quality within one sample. This work also has implications in forensic science, specifically wildlife forensics and chemical detection of clandestine laboratories and chemical weapon compounds.