Natural isotope signatures of host blood are replicated in moulted ticks.

This proof-of-concept study demonstrates that stable isotope ratios of nitrogen and carbon (expressed as δ(13)C and δ(15)N) of host blood are faithfully reproduced in unfed nymphal Ixodes ricinus that developed from larvae fed on that host. Measured isotopic discrimination (i.e. the tick-blood spacing) was between -0.1 and 0.7‰ for δ(13)C and 3.8 and 3.9‰ for δ(15)N. Both δ(13)C and δ(15)N increased significantly with tick ageing. The isotopic analysis of unfed ticks has potential for determining the physiological age of unfed ticks, for identifying the season in which the previous stage had fed and for identifying the main hosts utilized by ticks.