Parasites are highly specialized creatures. Their living is frequently confined to one certain host.
Commonly there is a great dependence from the parasite to his host or its hosts.
Parasitism could refer to various factors of the host (matter of the body, food supply, oxygen demand, osmotic reasons, pH-value or temperature regulation).
The stress and debilitation of the host depends on the extensity of the parasite infestation.
It is not invariably the case that the parasite infestation causes life-threatened injuries of the host, but it affects to its growth, well-being, the body’s defences, propagation, and life expectancy.
Toxic metabolic products of the parasite, remained internal or external injuries, or the extraction of food may cause the hosts reduction of life expectancy. Especially in further adverse conditions of live.
Normally the environment of the parasite is a creature. For being able to live in that environment, the parasites have accommodated themselves to their living environment in many ways.
Caused by the different kinds of acclimatization, size, way-of-life, and interaction between parasite and host, parasites are differenced based on certain criteria. Some of them are:

macroparasites and microparasites
endoparasites or ectoparasites
epiparasitism
kleptoparasitism
parasitoids
social parasites
brood parasitism
opportunism
parasitic plants
parasitic bacteria

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