Q.4. What is parasitism? Explain how an animal adapts itself to the parasitic mode of life as evidenced by the structure and life history of Taenia, Ascaris and Fasciola.
Give an account of the parasitic adaptations of Taenia solium.
What is adaptation? Explain with reference to the structure and life-history of Taenia solium.
Parasitism
Parasitism is an association between two organisms when one (the parasite) lives on another (host) receiving nourishment and shelter without any compensation for the host. Hence the parasite lives at the cost of the host, therefore, causing it harm. Sometimes it proves so harmful that it ultimately results in its death.
Parasitic Adaptations of Taenia
Taenia is an intestinal parasite of vertebrates. It has undergone great structural modifications to meet the demands of its specific environment. Several complications have arisen in its life-history to ensure dispersal of race.
The modifications due to parasitic mode of life can be discussed under the following two heads :
I. Structural Modifications
(A) Changes in the External Form
1. Body is dorsoventrally flattened and ribbon-like or tape-like.
2. The anterior end of the body or the head is modified into a holdfast or region of attachment. It has developed suckers and hooks to ensure firm hold of the host tissue.
3. Neck region possesses power of adding new segments to the body so that the animal grows throughout its life.
4. The body consists of large number of segments each containing a complete set of reproductive organs. The posterior segments contain only the fertilised eggs and the developing embryos. These have power of detachment.
(B) Change in the Internal Organisation
1. The surface of epidermis around the body is lost and is replaced by a thick and resistant cuticle formed of insoluble proteins to protect it form the effect of intestinal juice of the host.
2. Complete absence of alimentation since the parasite gets readymade and fully digested food which is absorbed through the general surface.
3. The excretory system has taken over the function of osmoregulation. It controls the amount of water inside the body tissues and removes excess of it.
4. It depends on anaerobic type of respiration.
5. The sense organs are absent except that it possesses tangoreceptors as found in other endoparasitic forms. The nervous system also undergoes degradation in other parts of the body except in the region of attachment.
6. The most remarkable feature is the development of a very complicated reproductive system. Each proglottid acts as a single individual possessing a set of reproductive organs.
7. Germarium (ovary) is highly branched so that it can produce large number of eggs.
II. Complications in the Life-history
1. To cover the risk of finding individuals of different sexes in one host the organism and moreover each segment is hermaphrodite and there occurs self-fertilisation.
2. These possess enormous fertility, the mature proglottid producing about 30 to 40 thousand eggs. The over-production of offsprings is necessary to maximize the chances of reaching the proper host and ensure the perpetuation of race.
3. The complicated life-history is a remarkable feature in the parasite since a secondary host, pig is introduced to ensure its dispersal from one primary host to another.
III. Physiological Adaptations
A few of the physiological adjustment in Taenia are as follows:
1. Taenia is physiologically adapted to take liquid food from the intestine of the host.
2. It maintains equilibrium with the osmotic pressure of the host. The pressure inside the parasite and outside remains the same so that there is no difficulty in exchange of water.
3. The metabolic processes of the parasite are adapted to function under anaerobic condition. The energy is obtained by the fermentation of glycogen.
4. It secretes anti-enzymes in order to protect itself against the effect of the digestive enzymes of the host.
5. Tapeworm stimulates the host gut to secrete mucus which forms a protective envelope around the body.
BSc 1st Year Lower Non-chordates Taenia Solium Sample Model Practice Question Answer Papers
BSc 1st Year Sample Model Practice Mock Test Question Answer Papers