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 lipi ds on the surface of ticks and their permeability to water, we quantif ied cuticular surface wax and measured water-loss rates in the ixodid tick Amblyomma americanum from nonfed nymph to egg-laying female. Tick s deposited no extra cuticular lipids during feeding, permitting maxim um transpiratory water loss that presumably helps to concentrate the b loodmeal; 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 depos ition and extreme water retention were noted after hose drop-off follo wing feeding. This wax is likely host-derived, Fed nymphs could discri minate between low and high relative humidity, enabling pharate adults to conserve lipid that would otherwise be lost with the exuvia and fe ces, This conservation strategy likely adds to the lipid pool needed b y the tick to survive in a dry environment and complements the tick's behavioral abilities for seeking out optimum conditions for water cons ervation and host location. (C) 1997 Elsevier Science Ltd.