Parasitic Adaptations in Helminthes: Morphological and
Physiological Adaption
Helminthes are a group of invertebrate organisms which include animals belonging to two
important phyla namely, platyhelminthes and nemathelminthes. Several species of the
group helminthes have adapted themselves to the parasitic mode of life. A parasite is those
organism which lives at the expense of other organism, and in return it cause injury or harm
to the host. Such an association in which one organism, the parasite, is benefited while the
another one, the host, is harmed is called parasitism. Parasitism has evolved accidently as a
result of contact between different forms of animals, mainly for the purpose of obtaining
nourishment and receiving shelter. In the process the organism from which nourishment is
being obtained gets harmed. Endo-parasites, which live within the body of their host for
major or whole part of the life span show highest degree of adaptation. These adaptations
may be morphological, physiological or reproductive.
Morphological adaptations:
Several morphological adaptations have occurred the body of helminthes parasites in order
to survive well in the body of their host. The adaptions have occurred either in the form of
degeneration of certain organs or attainment of new organs.
(a) Degeneration of organs:
In order to lead a parasitic life complete or partial degeneration or loss of organs have
taken place in the body of helminthes parasites. Such degeneration are found especially in
those organs which are of little or no use to the parasite.
Important organs in which degeneration have occurred are –
1. Organs of locomotion:
(Since the parasite reside in the host body where they live well protected and nourishment
readily available, there is no need to move. Hence, the locomotary organelles are
completely lost. However, in cases where the larval forms are free living, the locomotary
organs in the form of cilia reappears, e.g, Miracidium larva of Fasciola.
2. Tropic organs:
The organs which are concerned with nutrition are called trophic organs. As the parasite
derives fully digested or partially digested nutrition from the host s body, the alimentary
canal has either totally disappeared (e.g. Taenia solium) or exhibit fair degree of
degeneration (e.g. Fasciola, Ascaris).
Physiological Adaption
Helminthes are a group of invertebrate organisms which include animals belonging to two
important phyla namely, platyhelminthes and nemathelminthes. Several species of the
group helminthes have adapted themselves to the parasitic mode of life. A parasite is those
organism which lives at the expense of other organism, and in return it cause injury or harm
to the host. Such an association in which one organism, the parasite, is benefited while the
another one, the host, is harmed is called parasitism. Parasitism has evolved accidently as a
result of contact between different forms of animals, mainly for the purpose of obtaining
nourishment and receiving shelter. In the process the organism from which nourishment is
being obtained gets harmed. Endo-parasites, which live within the body of their host for
major or whole part of the life span show highest degree of adaptation. These adaptations
may be morphological, physiological or reproductive.
Morphological adaptations:
Several morphological adaptations have occurred the body of helminthes parasites in order
to survive well in the body of their host. The adaptions have occurred either in the form of
degeneration of certain organs or attainment of new organs.
(a) Degeneration of organs:
In order to lead a parasitic life complete or partial degeneration or loss of organs have
taken place in the body of helminthes parasites. Such degeneration are found especially in
those organs which are of little or no use to the parasite.
Important organs in which degeneration have occurred are –
1. Organs of locomotion:
(Since the parasite reside in the host body where they live well protected and nourishment
readily available, there is no need to move. Hence, the locomotary organelles are
completely lost. However, in cases where the larval forms are free living, the locomotary
organs in the form of cilia reappears, e.g, Miracidium larva of Fasciola.
2. Tropic organs:
The organs which are concerned with nutrition are called trophic organs. As the parasite
derives fully digested or partially digested nutrition from the host s body, the alimentary
canal has either totally disappeared (e.g. Taenia solium) or exhibit fair degree of
degeneration (e.g. Fasciola, Ascaris).
