Date of Thesis

Spring 2022

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Description

Studying signal evolution at a gene level will help us understand the world, as it provides insight of how diversity arises. Fireflies are a good system to study signal evolution because they rely on relatively simple mating signals and have repeatedly gained and lost adult bioluminescence throughout time. While nocturnal lighted species use bioluminescence for mating, unlighted species likely use pheromones/odorants to find their counterparts. If so, unlighted species are expected to have more functional odorant receptor (OR) genes that facilitate mate finding. However, the OR gene repertoires of most unlighted species are unknown. Therefore, to investigate this hypothesis, I took a transcriptomic approach in one unlighted-adult species, Lucidota atra, for which there is behavioral evidence of pheromone use. I assembled and compared transcriptomes derived from the antenna and the back legs of wild-caught males and females. Using bioinformatic techniques, I identified a total of 64 ORs and an ORco coreceptor gene in L. atra. Phylogenetic analysis revealed that a specific group of ORs diversified in L. atra as compared to other beetles. A differential expression analysis showed that ORs are more functional/expressed in the antenna. While some ORs showed sex-biased expression, only LatrOR45 was significantly upregulated in females, a potential indication that it is a candidate mating or oviposition OR. This study gives foundation for future mechanistic studies in firefly olfaction, as it provides ORs sequences that can be isolated to study OR specificity and sensitivity to certain novel pheromones in fireflies. In the future, comparing L. atra OR repertoire to that of a closely related lighted species could revolutionize our understanding of signal evolution at a gene level.

Keywords

odorant, receptors, olfaction, firefly, smell, genomics

Access Type

Honors Thesis (Bucknell Access Only)

Degree Type

Bachelor of Science

Major

Biology

First Advisor

Sarah Lower

Second Advisor

Moria Chambers

Third Advisor

Ken Field

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