Integumental glands of the tick Rhipicephalus appendiculatus (Acari: Ixodidae) as potential producers of semiochemicals

The opisthosomal integument and associated secretory organs of Rhipicephalus appendiculatus Neumann larvae, nymphs, females and males, both unfed and fed were examined by light and electron microscopy. Type 1 dermal glands were found on the alloscutum and scutum of all ticks. They were undeveloped in unfed ticks and reached full development in engorging ticks. They produced secretory granules from 2 glandular cells but without accumulation of a reservoir of secreted material. Type 2 dermal glands were found in all ticks, with pores on the alloscutum, edge of scutum, and on anal plates. These glands produced secretion during feeding and accumulated large reservoirs of secreted material that were present in engorging, recently detached and questing ticks. Spiracular glands were found in all ticks below the spiracle plate. They produced small amounts of secretion and had pores to the exterior by way of spiracle goblets. No obvious cycle of secretory activity was recorded. Foveal glands were present and produced secretions in nymphs, females, and males. They were largest in females with an accumulation of secretory vesicles in feeding ticks. The potential function of these glands is discussed in the context of the chemical ecology of this tick.