Meeting Abstract
Intrinsic factors such as plant toxins and nutrients are well known to influence diet selection in mammalian herbivores, yet extrinsic factors like ambient temperature have received less attention. Growing evidence suggests that dietary plant toxins become more toxic at warmer ambient temperatures. This phenomenon, known as temperature-dependent toxicity (TDT), could have serious implications for mammalian herbivores that must balance homeothermy with xenobiotic metabolism in a warming environment. Here, we explored TDT in two distantly related mammalian herbivores, the desert woodrat (Neotoma lepida) and the common brushtail possum (Trichosurus vulpecula), through investigations of the hepatic response to TDT. We utilized two methods to measure liver function. Hypnotic state assays determined drug clearance times and provided a non-lethal, whole-organism measure of overall liver function, and differential gene expression in the liver was measured with a species-specific microarray. In both herbivores, drug clearance times were significantly longer at warmer temperatures compared to cooler temperatures, indicating a decrease in liver function. In the microarray investigation with N. lepida, a greater number and diversity of genes were differentially expressed at 22°C compared to 27°C, providing further evidence that warmer temperatures impede overall liver function. Taken together, our work has identified reduced liver function as a potential mechanism of TDT as well as called attention to the commonality of TDT across mammalian herbivores, regardless of their body size or the dietary plant toxins they face at every meal. These results have also elucidated new challenges that mammalian herbivores may face as global temperature rise.
