“Male factors” in ticks: their role in feeding and egg development

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Abstract
Female ticks of the family Ixodidae utilize their salivary glands as the major organs for fluid balance, secreting back into the host a dilute saliva. Feeding is composed of three phases: a preparatory phase (1–2 days) during which the tick establishes the feeding lesion, a slow phase (~7 days) during which body weight increases 10-fold, and a rapid phase (~1 day) in which body weight increases a further 10-fold. Following engorgement, the salivary glands are resorbed by an autolytic process triggered by an ecdysteroid hormone. If a female is removed from the host prior to repletion, her subsequent behaviour depends mostly on two factors: the degree of engorgement achieved and whether or not she has mated. If removed during the preparatory or slow phase of engorgement, the salivary glands are not resorbed, the tick will lay virtually no eggs and she will reattach to a host if given the opportunity, all of this irrespective of whether she is virgin or mated. If removed during the rapid phase of engorgement, however, mated females will not reattach to a host even if given the opportunity. Instead, they will resorb the salivary glands within 4 days post-removal and lay a batch of eggs. Virgin females removed after exceeding 10-fold the unfed weight likewise refuse to resume feeding if given the opportunity, but salivary gland reabsorption is delayed (to 8 days post-removal); if any eggs are laid, they are infertile. A number of chemical “factors” entering the female during copulation influence her feeding behaviour and egg development. Here we discuss the complexities of these interactions and suggest how they might be adaptive to ticks in nature.