Effect of 20-hydroxyecdysone on vitellogenesis in the ixodid tick Haemaphysalis longicornis

Abstract

ABSTRACT 20-hydroxyecdysone (20E), a naturally occurring ecdysteroid hormone in arthropods, was administered by injection to female Haemaphysalis longicornis ticks that were partially fed virgin ticks or replete and mated to assess its effect on vitellogenesis. Injection of 20E into the partially fed virgin ticks stimulated vitellogenesis, as determined by significant increases in ovary development, increased amount of vitellogenin (Vg) in fat body, haemolymph Vg accumulation, and ovarian vitellin (Vn) accumulation. Replete mated ticks injected with 20E showed no differences from untreated ticks in the ovary weights or concentrations of fat body Vg, haemolymph Vg, and ovarian Vn. These results demonstrated that 20E administration stimulated vitellogenesis in partially fed virgin ticks but had no effect on replete mated ticks. The implications of these findings on the regulation of vitellogenesis in H. longicornis are discussed.