- The environment must have a sufficiently humid environment for the ticks to maintain water balance.
- A mix of animal species to act as hosts for each stage of tick development (explained in the life cycle section).
Ticks are also vulnerable to desiccation during periods in between hosting (questing), and the development phase.
During questing and developing, ticks can get their water from ingesting hydroscopic liquid. This enables ticks to maintain a stable water balance as long as humidity in their microclimate doesn’t fall below 80%.
Therefore ticks can only survive in the questing areas where a good cover of vegetation and a matt of decaying matter is available. This is why ticks are commonly found in fields and grassy areas when it has rained recently. Ironically although ticks need an extremely high water percentage to survive, they cannot survive floods.
Life Cycle
Ixodes Canisuga, also known as the dog tick, is the most common tick in Northern Europe.
There are three stages in the development of ticks;
- Lava
- Nymph
- Adult female
The life cycle takes 3 to six years to complete, with each stage taking at least one year. Blood feeding occurs once in each stage.
The diagram to the right shows the life cycle of a tick.
Larvae have six legs, climb the vegetation and wait for a passing host, usually a mouse. There they feed for 2-3 days and they increase their weight 10-20 times. Thy then drop off into the vegetation and continue to grow.
After several months, the lava molts to an 8-legged nymph of around 2mm.
A few months later the nymph molts again into the final stage of tick development; the adult. The adult female can only feed successfully on larger animals such as dogs, deer sheep and cows. When it feeds it can grow to 150 times its original weight. The immature stages of the tick can paratize almost any warm blooded animal.
The picture to the left is of a male and female tick mating.
Whilst mating, the female continues to feed, engorging herself so that she can produce well nourished eggs. The males feed every so often to stay alive. When the female is ready to lay her eggs, she drops of the host lays her eggs and dies.
Anatomy of a tick
The picture to the right is the anchorage part of the tick, scientifically named the hyposome. This organ grips onto the hosts flesh keeping the tick attached.
To the left is the front view of the ixodes canisuga, showing the hyposome, and alos another mouthpart called the chelicerae. The chelicerae are horizontal jaws, they break the skin and help in the feeding process.
Adaptations
As mentioned before, the hyposome anchors the tick to the host, and the chelicerae help to keep the blood flowing, but ticks also have anticoagulant in their saliva glands. This stops the blood clotting making it easy for the blood to flow. The tick also has elasticized skin so that it can expand whilst feeding on blood.
The diseases that ticks carry
Ticks carry the disease Borrelia, also known as lyme disease. This disease causes relapsing fevers. This disease is passed on because the bacterium migrates from the gut to the salivary glands. So when the mite feeds, the saliva containing the bacterium is passed through to the host.
They also carry encephalitis, a viral infection which is less common, but deadly. Encephalitis causes inflammation of the brain.
