A Genetically Marked Maggot to Better Understand Corpse Decomposition Ecology

Authors

Amber E. MacInnis, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Biology

First Advisor's Name

Jeffrey Wells

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Matthew DeGennaro

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Laura Serbus

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Jamie Theobald

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Bruce McCord

Fifth Advisor's Committee Title

Committee member

Keywords

blow fly, forensic entomology, transgenic, fluorescent, postmortem interval

Date of Defense

4-3-2023

Abstract

The age of a blow fly larva is commonly used in forensic investigations to estimate the minimum postmortem interval (PMImin). In forensic entomology, a maggot of unknown age is compared to experimental reference data to predict its age adjusted for temperature. However, typical reference data illustrate development rate under artificial conditions. Current practices do not satisfy an important criterion for expert testimony: that a technique has a known error rate under realistic conditions. This would require empirical validation, but such experiments have not been performed in forensic entomology. Under realistic conditions, it is difficult to know the true age of a maggot. If a larva could be persistently marked, eggs of known age could be added to the wild population and would develop under casework conditions to be recovered later and form the validation set. We aimed to create a heritable marking through the insertion of a fluorescent protein in the germline. piggyBac transformation was successful, but with a lower success rate than anticipated based on previous work. However, larvae exhibited uniform fluorescence throughout the generations. Short read Illumina sequencing and genome assembly showed all founding fluorescent parents contained the same single insertion. And transcriptome of wild type (non-fluorescent) adults shows no transcripts within the insertion region suggesting this may be intergenic. Development studies were produced for wild type, heterozygous, and homozygous lines. Age predictions of individuals of both transgenic genotypes included the true age >99% of the time. This suggests development rate of the flies was not altered due to insertion of the transgene and is the first step in creating a suitable marked line for use in field studies. This marks a step forward in the field as they will facilitate the validation of growth rate models used for insect age estimation.

Identifier

FIDC011099

Recommended Citation

MacInnis, Amber E., "A Genetically Marked Maggot to Better Understand Corpse Decomposition Ecology" (2023). FIU Electronic Theses and Dissertations. 5330.
https://digitalcommons.fiu.edu/etd/5330