Functional Morphology of the Feeding Apparatus of the Cattle Tick, Haemaphysalis longicornis

From the viewpoint of the functional morphology, this report presents scanning electron and light microscopic observations on the feeding apparatus of the adult cattle tick, Haemaphysalis longicornis. The digits of the chelicerae act as a cutting organ for host skin and tissues. Protrusion of the whole chelicerae may be effected by an increase in internal body pressure and regulated by the cheliceral retractor muscles. The cheliceral sheath and hypostome bear many denticles which stabilized attachment of ticks to a host. Pulsations of the hypostomal membrane appear to be associated with a flowing of host blood and tick saliva. The labrum seems to close the pharyngeal orifice so that an inflow of saliva into the pharynx is prevented. The function of the salivarium is thought to be a salivary valve, because its floor undergoes a vertical motion by antagonistic actions of the constrictor muscles of the ala. Thus, a mixture of host blood and tick saliva would be precluded by the regulation among the labrum, the salivarium and the constrictor muscles of the ala. The pharynx functions as a sucking pump for host blood by contraction and relaxation of its dilator and constrictor muscles.