Changes in Isotopic Signature during the aging process of black-legged ticks

Tick borne diseases are a growing problem, so it is important to understand all we can about tick ecology and host use. The LoGiudice lab has been investigating whether stable isotope analysis (SIA) can be used to identify the prior host that a flat questing tick fed on. SIA is commonly used to study food web relationships as the heavier isotopes of some elements bioaccumulate in the tissues of consumers. Ticks consume host blood, and it has been demonstrated by our lab and others that tick tissues are enriched in ¹⁵N over their hosts by a relatively constant amount. I am investigating whether isotopic signature of adult blacklegged tick, Ixodes scapularis, changes after their molt as they continue to metabolize their blood meal. To this end, molted ticks fed on chipmunks, Tamias striatus, during the summer of 2017 were maintained in an environment that simulated natural conditions. They were frozen at monthly intervals and submitted for stable isotope analysis. Spacing out the freeze dates enabled me to track whether isotopic signatures changed during the aging process. I will compare isotopic signatures from ticks that were frozen immediately after molting to those aged at roughly 30 day intervals between 128 and 232 days (n=78). Based on data from the literature, I predict that a slight, but significant increase in δ¹⁵N and in δ¹³C. Understanding the degree and variability of change in isotopic signature as ticks age will allow us to calibrate our host identification technique to account for the time of year that the tick was collected.