This document discusses various parasitic adaptations that allow parasites to survive within host organisms. It provides examples of parasites that have different body shapes and sizes depending on the available space in the host, including intracellular parasites that are very small and intestinal parasites that are larger. It also describes how parasites have structures like hooks or suckers to attach to host tissues, protective coverings to avoid digestive enzymes, and can utilize aerobic or anaerobic respiration depending on oxygen levels. Parasites also exhibit high reproductive rates and complex life cycles involving multiple larval stages. Overall, the document outlines morphological, anatomical and physiological changes parasites undergo to adapt to the host environment.

1. • Topic
• Submitted to
• Presented by
• Roll no.
• Semester
• Department of Zoology
• Parasitic adaptation
• Prof. Saeed Ahmad
• Noor Ullah.
• Z-30
• 8th

2. PARASITIC ADAPTATIONS
 The survival of a parasite in the body of the host depends
upon its abiity to adapt to the surrounding environment at
the site of its infection, this is called microenvironment. To
adapt to this microenvironment, certain morphological,
anatomical and physiological changes occur and because
of which the parasite survives in the host. Such changes
which facilitate a parasite to adapt to parasitic mode of life
in the host itself are called parasitic adaptations.

3. TAENIA SOLIUM
Different types of parasitic adaptations are as follows:
1.Body shape and size
Body shape and size of he parasite
depends upon the space available at the
site of infection.
e.g., Intracellular parasites are very small
in size – Plasmodium.
Enerozoic parasites are usually large in
size – Taenia solium, Ascaris
lumbricoides.
Hepatophagic parasites are moderately
large and flat – Fasciola.
Parasites dwelling in the blood vessels are
slender and elongated – Schistosomes.

4.  2. Locomotory struturres almost absent in the parasitic forms , as they
need not move in search of food.
3.A parasite in the body, if occurs, without attaching to
the surrounding tissues , it gets carried away to a
nonspecific site or to the exterior of the body , in which
case, is survival is not possible. Thererfore , to remain at
the specific site of infection , they attach to the
surrounding tissues. For this purpose , all the parasites
are provided with adhesive structures like hooks.
e.g., Echinostomes , Monogenetic trematodes are
equipped with suckers.
Trematodes and Cestodes are equipped with rostellum.
Taenia solium (a cestode) is equipped with rostellum ,
hooks and suckers.
taenia scolex with
hooks and suckers

5. 4.In the case of intestinal parasites , there is
every possibility, that they are either harmed
, injured or digested by the gastrointestinal
secetions of the host.
To protect from the harmful effects of
digestive enzymes , the parasite’s body
surface is covered with
cuticle( Nematodes – Ascaris
or
Tegument ( Flatworms – Taenia soium).
Intestinal worms may also secrete
some antienzymes that neutralize the
digestive enzymes of the host.
e.g., Taenia soium.
Teguent in Taenia
cuticle in ascaris

6. 5. In the bodyof a host where parasites live , the amount of oxygen
may very high( lungs) or relatively less (intestine and liver ).
The catabolic activity of parasites living in oxygen rich
environment are predominantly of aerobic type.
e.g., Human lung fluke – Paragonimus vestermoni.
The parasites live in less or no oxygen content are facultative
anaerobes. They can carry on aerobic respiration if oxygen is
available and anaerobic respiration in the absence of oxygen.
e.g., Ascaris lumbricoides.
Some parasites live as obligatory anaerobes as the availability of
oxygen is very rare for them.
e.g ., Taenia solium , Entamoeba histolytica.

7.  6.The reproductive potential of parasites is veery high.
 e.g., Taenia soium lays about 35,000 eggs/day.
 Fasciola hepatica lays about 10,000 eggs/day,
 Ascaris lumbricoides lays about 2,00,000 of eggs/day.
 Inspite of numerous risks during development, such high reproductive
potential ensures the continuation of parasitic race.

8. Redia of liver fluke
7.In addition to the production of enormous
number of eggs , there will be multiplication of
larval stages resulting in the production of several
infecting agents. This process called as
polyembryony occurs in trematodes.
e.g., The life cycle of trematode includes
five larvalstages viz.,
miracidium , sporocyst, redia ,cercaria and
metacercaria. Of these , sporocyst exhibits
polyembryony producing a number of rediae and
redia exhibits polyembryony producing a number of
cercariae. Thus the life cycles of endoparasites are
very complex as they exhibit high host-paarasite
specificity.
Larval stages of liver fluke

9. 8. Infective stages of the monogenetic parasites like Entamoeba
histolytica need to survive outside the body of host in the open
environment. Hence, they are exposed to harsh environmental conditions ,
they are to tide over the unfavorable conditions , they are enclosed in a
protective envelope forming cyst.
9. Due to the presence of the parasites , host’s
immunological system gets activated producing specific
antibodies to eliminate parasites. However , parasites elude
the action of antibodies generally by a process of molecular
mimicry , in which the parasites covered by molecules that
are similar to that of the host. These are considered by
host’s antibodies as self molecules and fail to counteract.

10. 9. Some parasites e.g., Plasmodium and HIV
constantly change the antigenic polypeptides.
The parasitic antigens change in different stages of
development. Hence , it is not easy for the host to
switch on the required defense mechanisms or to
produce suitable vaccines against these diseases.

11. THANKS