HORMONAL-CONTROL OF OVARIAN DEVELOPMENT IN THE TICK AMBLYOMMA-HEBRAEUM KOCH (ACARI, IXODIDAE)

Hormonal control of egg development in the ixodid tick Amblyomma hebraeum Koch was investigated as follows: ovaries from small partially fed or fully engorged females were transplanted into the haemocoel of engorged females that were undergoing vitellogenesis; the transplants responded to this milieu by completing oocyte maturation. The following treatments all failed to stimulate egg development within eight days in small partially fed ticks: (a) slow fusion of 20-hydroxyecdysone (up to 7.2 mug) over 24 h; (b) topical application or injection of up to 50 mug juvenile hormone III; (c) topical application of 10 mug of methylfarnesoate and juvenile hormone III bisepoxide; (d) a combination of 20-hydroxyecdysone and juvenile hormone III. Also, none of the latter treatments accelerated oocyte maturation in engorged females. Injections (up to 100 mug per tick) or topical application (1 mg per tick) of precocene II did not inhibit egg development in engorged females which survived this treatment. Thus, although egg development in A. hebraeum is under hormonal control, the data fail to suggest a specific role for an ecdysteroid or juvenile hormone.