"Tetrodotoxin (TTX) is a powerful neurotoxin that prevents the propagation of action potentials, leading to paralysis and sometimes death in nearly all animals. However, a diverse group of marine and freshwater animals possess TTX, which they use for offense, defense, and communication. One of most studied TTX-mediated interactions is the predator-prey arms race between the rough-skinned newt (Taricha granulosa) and common garter snake (Thamnophis sirtalis). Variation in toxicity among populations of newts matched by TTX-resistance in predatory snakes has captured the focus of much research centered on the hypothesis that the arms race is the sole driver of variation. Nevertheless, recent studies suggest a more complex dynamic. Explanations of the dramatic variation in TTX among different populations of newts can only be constructed once fundamental questions about the origin, function, and transmission of TTX in newts have been more thoroughly explored. In this study, I took two approaches to address the origin, function, and transmission of TTX: 1) a cohabitation experiment in which I paired toxic and non-toxic newts to test whether toxicity can be acquired through contact, and 2) an experiment to determine the distribution and concentration of TTX in different tissues. The cohabitation experiment revealed no detectable change in the toxicity of non-toxic male newts, suggesting that a physical or physiological impediment prevents non-toxic newts from becoming toxic. The tissue toxicity experiment demonstrated that TTX is present throughout the body in structurally and functionally diverse tissues, which has many implications for the involvement of TTX in communication and reproduction in addition to defense."--Page ii.
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