Virtual forensic entomology: Improving estimates of minimum post-mortem interval with 3D micro-computed tomography

Abstract

We demonstrate how micro-computed tomography (micro-CT) can be a powerful tool for describing internal and external morphological changes in Calliphora vicina (Diptera: Calliphoridae) during metamorphosis. Pupae were sampled during the 1st, 2nd, 3rd and 4th quarter of development after the onset of pupariation at 23 °C, and placed directly into 80% ethanol for preservation. In order to find the optimal contrast, four batches of pupae were treated differently: batch one was stained in 0.5M aqueous iodine for 1 day; two for 7 days; three was tagged with a radiopaque dye; four was left unstained (control). Pupae stained for 7d in iodine resulted in the best contrast micro-CT scans. The scans were of sufficiently high spatial resolution (17.2 μm) to visualise the internal morphology of developing pharate adults at all four ages. A combination of external and internal morphological characters was shown to have the potential to estimate the age of blowfly pupae with a higher degree of accuracy and precision than using external morphological characters alone. Age specific developmental characters are described. The technique could be used as a measure to estimate a minimum post-mortem interval in cases of suspicious death where pupae are the oldest stages of insect evidence collected.

De novo transcriptome analysis and highly sensitive digital gene expression profiling of Calliphora vicina (Diptera: Calliphoridae) pupae using MACE (Massive Analysis of cDNA Ends)

“…As pupal development takes place inside the puparium, no developmental or morphological changes can be distinguished without a demanding and time-consuming preparation of the puparia [14]. But even after a possible excavation of the pupae, little work has so far been done on establishing a robust method that uses morphological changes for the age estimation of blow fly pupae [13,15,16]. Hence, pupae are usually reared until the eclosion of the adult flies to determine the whole development time.…”

Family Calliphoridae: An Integral Part of Postmortem Interval Estimation

“…The most reliable method is to examine the mtDNA from a COI gene, but this method can be time consuming and leads to a higher rate of error if performed by an inexperienced individual. Another technique of determining PMI involves the use of a 3D Microcomputed tomography for examining the oldest stage of pupae from the Calliphoridae collected [25]. Both techniques provide the investigator with the identity of the Calliphoridae of interest, however, limitations do exist.…”

“…By only focusing on a single, small fragment of DNA, in this case the single COI gene, it may oversimplify the phylogenic grouping by failing to recognize genetic variability [1]. In the case of the 3D Micro-computed tomography, measurements were only performed on a single species of Calliphoridae, namely, Calliphora vicina [25]. To eliminate the minutest possibilities of identification error, both mtDNA sequencing of COI gene and 3D Micro-computed tomography should be performed on as many species found in the Calliphoridae family as possible.…”

Insects feeding on cadavers as an alternative source of human genetic material

“…It is also worthwhile to note that a number of new subdisciplines are also emerging within the broader field of forensic ento mology, including entomotoxicology, virtual forensic entomology, funeral archeoentomology, etc. [4][5][6].…”

“…Można zauważyć, że w obrębie samej entomologii sądowej wyodrębniają się nowe subdyscypliny, takie jak entomotoksykologia, "wirtualna" entomologia sądowa, archeoentomologia funeralna itp. [4][5][6].…”