An investigation into the factors influencing venom potency in snakes and spiders
Date
2024-03-28Embargo Date
2025-03-27
Author
Lyons, Keith
Metadata
Show full item recordUsage
This item's downloads: 0 (view details)
Abstract
A fundamental question in ecology and toxicology is why some venomous species have more potent
venoms than others. While there is great interest in venomous species from a medical perspective
due to envenomation cases globally, from an ecological perspective, venom is still relatively poorly
understood despite its key role in predator-prey interactions. To address this fundamental question, I
investigate the role of factors associated with diet and prey capture in the evolution of venom potency
in snakes and spiders, two diverse venomous predator groups, using both data collated from the
literature and data collected in the field and lab over the course of my PhD. Additionally, my research
investigates different venom extraction methods as a factor influencing how venom potency is
measured. I investigate the role these factors play in venom potency across four research chapters
that represent stand-alone publications consisting of: “Diet Breadth Mediates the Prey Specificity of
Venom Potency in Snakes.”; “Spider Venom Potency is Prey-specific but does not trade-off with Body
Size or Silk Hunting Strategy.”; “The Relationship between Median Lethal dose (LD50) and Median
Effective Dose (ED50) in Spider Venoms” and “Venom Extraction Method Influences Venom
Composition and Potency in the Giant House Spider Eratigena atrica (C. L. Koch, 1843)”.
In Chapter 2, I use phylogenetic comparative approaches to show that the evolution of preyspecific venom potencies in snakes is contingent on the breadth of a species’ diet, only observing preyspecific patterns in species with taxonomically narrow diets (specialists). In Chapter 3, I extend this
phylogenetic comparative approach to spiders and show that they have evolved prey-specific venom
potencies and that surprisingly the degree of silk use in prey capture does not trade-off with venom
potency. In Chapter 4, I use spider venom bioassay experiments to determine the relationship
between different venom potency measures LD50 and ED50, showing that they have a near isometric
relationship. Finally in Chapter 5, I demonstrate through venom bioassays and Coomassie-stained SDSPAGE gel electrophoresis that using different venom extraction methods, electrical stimulation and
venom gland removal, on the same spider species (Eratigena atrica) can result in venom samples with
significantly different potencies and visibly different protein compositions.
Throughout this thesis I demonstrate the importance of including factors pertaining to diet
and prey capture in the analyses of predator venom evolution along with factors relating to measuring
the toxicity and functionality of venom. By investigating and comparing the multitude of factors
potentially influencing venom evolution in future research, especially those pertaining to the natural
targets of species venoms, we will gain a deeper understanding of the processes surrounding toxin
evolution and why some species venoms are deadlier than others.