Question

List out the parasitic adaptations of Ascaris lumbricoides?

Answer 1

Sol:
Ascaris lumbricoides is a nematode worm which leads a parasitic life in the intestine of man. Hence it is an endoparasite. 

*Body is long and round so that it can easily fit in the lumen of the intestine.
*Cuticle covering the body protect the worm from digestive juices secreted in the host's intestine.
*Ascaris also secretes some antienzymes against digestive enzymes of the host. 
*Papillae present on the lips of the worm help in anchoring to the villi in the intestine.
*Worm can ingest tissue of the host and suck the blood from the host.
*Digested food of host is absorbed by the surface of the body directly from the host's intestine.
*Worm respires anaerobically in the host's intestine which is devoid of oxygen.
*Millions of eggs are produced ata time for the benefit of survival.
*Eggs hatch into juveniles which are present in the environment. Eggs can also be present in the environment.
*Infection is direct through contaminated food and water.

Answer 2

The parasitic adaptations of Ascaris lumbricoides:-

(a) Morphological adaptations:

i. The body is long and cylindrical, pointed at both ends.

ii. The mouth is bounded by three lips which help the parasite to attach with mucous membrane of the host’s intestine.

iii. The parasite is devoid of locomotory organs as the parasite lives in the intestine where protection from enemies and food supply are ensured.

iv. The body wall of Ascaris is covered with cuticle, resistant to the digestive enzymes of the host.

(b) Anatomical adaptations:

i. The pharynx is muscular that facilitates ingestion of food by sucking action. There are no digestive glands.

ii. Sense organs are ill-developed, being found only on lips in the form of papillae.

iii. The digestive tract is simple without pro­vision for storage, as there is constant sup­ply of food.

(c) Physiological adaptations:

i. The body wall is covered with tough, thick and resistant cuticle, shields against the digestive enzymes of the host and anti­toxins.

ii. Ingested food of this parasite is pre- digested, so that there are no elaborate digestive glands.

iii. The respiration is almost entirely anae­robic. Extremely low metabolic rate and anaerobic respiration enable the worm to live inside the host’s intestine, where the free oxygen is negligible.

iv. Reproductive system of Ascaris is well- developed and numerous eggs are pro­duced to make up for the poor chances of the right host being reached.

v. The eggs are covered with resistant cove­ring or chitinous shell which provide safety to the zygote and embryonated eggs from unfavourable environmental factors.

vi. The minute size and resistant nature of eggs make them to withstand prolonged dryness and cold. The minute size eggs afford far and wide dispersal of the parasite.

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