Impact of feeding, molting and relative humidity on cuticular wax deposition and water loss in the lone star tick, Amblyomma americanum.
To determine whether there is a correlation between the amount of lipids on the surface of ticks and their permeability to water, we quantified cuticular surface wax and measured water-loss rates in the ixodid tick Amblyomma americanum from nonfed nymph to egg-laying female. Ticks deposited no extra cuticular lipids during feeding, permitting maximum transpiratory water loss that presumably helps to concentrate the bloodmeal; and ticks deposited additional cuticular wax after apolysis that reduced integumental water loss, which likely prepares ticks for off-host existence. A remarkable three-fold boost in surface wax deposition and extreme water retention were noted after host drop-off following feeding. This wax is likely host-derived. Fed nymphs could discriminate between low and high relative humidity, enabling pharate adults to conserve lipid that would otherwise be lost with the exuvia and feces. This conservation strategy likely adds to the lipid pool needed by the tick to survive in a dry environment and complements the tick's behavioral abilities for seeking out optimum conditions for water conservation and host location.