The influence of a factor from the male genital tract on salivary gland degeneration in the female ixodid tick, Amblyomma hebraeum

Abstract

In the adult female tick, Amblyomma hebraeum Koch (Acari: Ixodidae), salivary gland degeneration is triggered by an ecdysteroid, provided the female is above a critical weight (about 300–400 mg). In mated females, salivary gland degeneration is complete within 4 days of detachment from the host. In virgin females, salivary gland degeneration is delayed by 4 days. This delay in salivary gland degeneration could be prevented in virgin females by injecting a homogenate of male gonad into the haemocoel. All “male factor” activity associated with the male gonad resides exclusively within the testis/vas deferens/ejaculatory duct; no male factor activity was associated with the spermatozoa or the accessory gland portion of the male gonad. Male factor activity within the gonad increases markedly after males have fed for 5 days. Male factor can be destroyed by either heat treatment or by proteinase K digestion, suggesting that it is a protein. Some male factor activity was also found in the synganglia of either fed, mated males or females, and the ovary from fed mated females, but not in male salivary glands.