By Lillian Croucher, Biological Sciences
Advisor: Joshua Benoit
Abstract: The state of thanatosis, also known as death-feigning or tonic immobility (TI), is an anti-predatory response. Anti-predatory responses are an important aspect for most organisms to survive and reproduce. Thanatosis is understudied in the case of many blood feeding disease vectors. Ticks and other blood feeding vectors are atypical in the aspect that many of their food sources, such as deer, birds, rabbits, and humans, are potential threats as predators. Thus, ticks may shift between the states of TI and host-seeking depending on their circumstances such as their starvation status. We therefore examined this relationship through analyzing the effects that starvation, body mass, and current life stage had on TI for two tick species. The evidence indicates that TI duration decreases with time since last feeding and varies among life stages and species. RNA-seq studies identified putative genes associated with the process of TI in ticks as starvation increases. Therefore, as ticks continue to starve, these pests prioritize locating a host over avoiding their predators through death-feigning. There are few studies on the direct effects that predators have on ticks, but this is a crucial piece of information for understanding tick-borne pathogen transmission and tick life-history traits.