Honors Theses

Date of Award

5-2024

Document Type

Undergraduate Thesis

Degree Name

BS

Department

Biology

Faculty Mentor

Jason L. Strickland

Advisor(s)

Jonathan H. Perez, Laura A. Frost

Abstract

Venomous species, particularly snakes, have captured human interest for decades. Over the last few decades, scientists have studied front-fanged venomous snakes to develop drugs, treat human disease, better manage snakebites, and answer ecological and evolutionary questions. However, these studies have largely ignored rear-fanged snakes which account for two-thirds of total snake species, despite only accounting for 23 % of published venom gland transcriptomes. To address the lack of knowledge about rear-fanged snake (RFS) venom, we sequenced the messenger RNA from the Duvernoy’s gland in 9 male and 10 female Common Garter Snakes, Thamnophis sirtalis. I produced the first Duvernoy’s venom gland transcriptome for Thamnophis sirtalis and found four toxin families that dominate the Thamnophis sirtalis transcriptome: Snake Venom Metalloproteinases (SVMPs), Three-finger toxins (3FTxs), Cysteine-Rich Secretory Proteins (CRISPs), and C-type lectins (CTLs). Thamnophis sirtalis displayed an even percent expression (i.e., aproxamilty 30 % each) of neurotoxic (3FTx-dominated) and enzymatic (SVMP-dominated) components which is unique among RFS. Additionally, we found that both sex and size influenced intraspecific venom expression variation. Specifically, males and females di↵ered in how toxin gene expression changed as they grow. We identified 8 genes that were di↵erentially expressed between males and females, half of which belong to the CTL toxin family. This research highlights just how little we know about RFS venom, and the continuation of RFS studies is crucial to understanding venom evolution fully.

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