Ecdysteroids in the camel tick, Hyalomma dromedarii (Acare: Ixodidae), and comparison with sex pheromone activity

The ecdysteroid 20-hydroxyecdysone (20-OH ecdysone) and 2 other radioimmunoassay (RIA) positive ecdysteroids were found in unfed and feeding adult H. dromedarii ticks. Increases in total ecdysteroids per tick occurred during female feeding, especially following mating and repletion. Ecdysteroid content in unfed and feeding males remained approximately the same (estimated by RIA) or declined (estimated by HPLC). Changes in concentration of 20-OH ecdysone resembled the changes in total ecdysteroid content in most cases. High-performance liquid chromatography (HPLC) gave substantially higher estimates of total ecdysteroid content in the various tick life stages or physiological states than did RIA. The greatest increases in all ecdysteroids, including 20-OH ecdysone, occurred following mating and during repletion.