Neural Involvement in the Control of Salivary Gland Degeneration in the Ixodid Tick Amblyomma Hebraeum

Abstract

We have developed a simple, quantitative assay to monitor salivary gland function in ixodid ticks. Salivary glands of engorged (l·0–3·0 g), or partially engorged (0·40–1·0 g), Amblyomma hebraeum Koch lose virtually all secretory function within 4 days after engorgement. Salivary glands from partially-fed ticks (0·20–0·30 g) lose 75 % of their secretory ability by 4 days post-removal, but retain this level of function for at least another 11 days. Partially-fed ticks (0·20–0·30 g) removed from the host for 4 days and then allowed to re-attach and resume feeding for a further 2 days, recover much of their lost function. Cutting the opisthosomal nerves of partially-fed ticks (0·40–1·0 g) inhibits salivary gland degeneration. Excising the seminal receptacle from partially-fed ticks (0·40–1·0 g) inhibits salivary gland degeneration. Replacement of the seminal receptacle permits salivary gland degeneration to proceed normally. The factor from the seminal receptacle appears to be distinct from tick salivary gland degeneration factor (TSGDF; Harris & Kaufman, 1981). Injecting a crude extract of male genital tracts into large, partially-fed ticks (0·40–1·0 g), which had had their seminal receptacles removed, caused virtually complete salivary gland degeneration. Such ticks, when injected with an extract of male salivary glands, showed no such degeneration. This suggests that the factor associated with mating originates in the male and is transferred to the female during copulation.