Classification of the parasitic organism

 

 

   Organisms in these associations may either be on the outer surface of the host organism, (in which case the prefix Ecto- is used) or inside the host organism, (in which case the prefix Endo- is used). These prefixes may be used with any of the animal associations listed above. For example, the flagellate protozoa in the termite guts are Endosymbionts, while the anemone can act as an Ectocommensal with the crab.

  Parasites may act as both ecto- and endoparasites. Parasites may also be classified according to the closeness of the relationship. For example, Facultative Parasites (such as many bacteria) are those where the parasitic lifestyle is only taken up opportunistically, whereas Obligate Parasites (such as all viruses, and most of the helminth parasites described below) are those in which the organism must parasitize another organism.


   These parasites may often cause diseases, in which case they are referred to as Pathogenic Parasites.
In a somewhat broader interpretation of the term parasitism, some organisms exhibit parasitic behavior only early in their life cycle, these being referred to as Brood Parasites. Examples of these include caterpillars of the Large Blue butterfly, which chemically mimic other caterpillars with mutualistic associations with ants but both fail to produce honeydew as compensation and consume ant grubs, and may, in fact, destroy the nest, (thereby acting as a pathogenic parasite for the ants).


In this case, the parasitic lifestyle probably evolved from the mutualistic lifestyle of the other, related butterflies, again illustrating how one form of association may change into another. Another well-known example of a brood parasite is a bird, the cuckoo.

    Some parasites establish themselves in hosts in which they do not ordinarily live. These are called the Incidental Parasites. A temporary parasite is free-living during part of its existence and seeks its host intermittently to obtain its nourishment whereas Permanent Parasite remains on or in its host’s body from early life until maturity, sometimes for its entire life. A parasite that has passed
through the alimentary tract without infecting the host are called Coprozoic or Spurious Parasite.

   Parasites often lack the necessary organs for assimilation of raw materials and depend upon the host for predigested food. An adequate supply of moisture is assured inside the host but during the free-living existence of the parasite,

Inadequate moisture may either prove fatal or prevent larval development. Temperature is likewise important. Each species has an optimal temperature range for its existence and development. Both high and low temperatures are detrimental and even lethal.

SUMMARY

  Organisms interact with each other at different degrees. While some are solely dependent on each other, however, some are opportunistic and can adopt various means for their survival. One association can evolve into the other. An example is seen in commensalism, which can develop into mutualism or parasitism.

   Some parasites reside within their hosts while others are outsides. Obligate parasites live in living tissues, whereas the facultative parasites are more successful in that they are capable of taking other sources of nutrition. Pathogenic parasites are of great medical concern because they cause diseases. The survival of a parasite in its habitat/microhabitat can be influenced by moisture and temperature.