Vertebrates respond to being fed upon by ectoparasitic arthropods such as ticks through their immune responses, grooming and mobility. As countermeasures, ticks have developed, among others, a series of chemosensory and behavioural adaptations that are crucial to their resource tracking capabilities on vertebrates. Olfactory receptors in chemosensilla on the first leg-pair of ticks permit them to locate hosts from a distance. These include receptors for respiratory products such as carbon dioxide and other components of breath, and for volatile products common to vertebrates such as branched short-chain fatty acids and aliphatic aldehydes. Ticks can signal their presence on suitable vertebrate hosts through the release of pheromones from exocrine glands. These products serve to increase the apparency of the host to conspecifics and enhance encounter between sexes for mating. For those tick species mating on the ground, encounter between the sexes is mediated by their propensity to aggregate on conspecific faecal products. On the host, constituents of sweat and skin lipids affect the host attachment responses of ticks. Chemoreceptor cells for these products reside in contact chemosensilla on the legs and mouthparts. These appendages are brought regularly into contact with host's surface as the ectoparasite searches for an attachment site from which to feed. The evidence suggests that evolution has forged a chemosensory disposition that is common to ticks.
Species 1: Acari Ixodidae Ixodes ricinus (sheep tick)
Species 2: Acari Ixodidae Amblyomma variegatum (tropical bont tick)
Keywords: semiochemicals, ticks
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA