Parasite-Host Interaction
Ticks are obligate blood feeders. All active stages require blood as a nutritive source and, in the case of adults, for sperm or egg production.
Because of the mechanical processes and salivary secretions associated with blood feeding, the tick-host parasitic interaction is complex.
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Host Seeking
Hard Ticks
Hard ticks seek hosts by an interesting behavior called "questing." Questing ticks crawl up the stems of grass or perch on the edges of leaves on the ground in a typical posture with the front legs extended, especially in response to a host passing by.
Certain biochemicals such as carbon dioxide as well as heat and movement serve as stimuli for questing behavior. Subsequently, these ticks climb on to a potential host which brushes against their extended front legs.
Soft Ticks
Some soft ticks seek hosts by questing on low-lying vegetation, but the vast majority are nest parasites, residing in sheltered environments such as burrows, caves, or nests.
Certain biochemicals such as carbon dioxide as well as heat and movement serve as stimuli for host seeking behavior.
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Blood Feeding
Hard Ticks
Hard ticks feed for extended periods of time on their hosts, varying from several days to weeks, depending on such factors as life stage, host type, and species of tick.
The outside surface, or cuticle, of hard ticks actually grows to accommodate the large volume of blood ingested, which, in adult ticks, may be anywhere from 200-600 times their unfed body weight.
Soft Ticks
Soft ticks feed for short periods of time on their hosts, varying from several minutes to days, depending on such factors as life stage, host type, and species of tick. The feeding behavior of many soft ticks can be compared to that of fleas or bedbugs, as once established, they reside in the nest of the host, feeding rapidly when the host returns and disturbs the contents. The outside surface, or cuticle, of soft ticks expands, but does not grow to accommodate the large volume of blood ingested, which may be anywhere from 5-10 times their unfed body weight.
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Salivary Secretion
Tick saliva is a complex mixture serving a variety of functions. Soon after attachment, ixodid ticks (except a few species of Ixodes) secrete a milky white material that hardens into a latex-like cone surrounding the hypostome. This is the initial core of the cement cone.
The cement secretions are provided by the A, D and E cells of the types II and III granular acini.
The feeding period is accompanied by copious secretion of salivary fluids. This pattern of salivary gland activity parallels the sequence of attachment, wound site formation, feeding, mating and repletion that characterizes the parasitic period.
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