A) having a large number of contractile vacuoles
B) having two contractile vacuoles
C) having no contractile vacuole
D) None of the above
Correct Answer: C
Solution :
Entamoeba histolytica is commonly found harbouring the lumen of the upper part of the large intestine. It causes amoebic dysentery or amoebiasis. In E. histolytica, contractile vacuole is absent as it inhabits an isotonic environment. The osmotic concentration of its body protoplasm equals to that of the intestinal fluid of the host and hence, no water enters the parasite by osmosis. Thus, there is no need of osmoregulation. On the other hand, protoplasm of Amoeba proteus is of higher concentration than the freshwater of its environment. The mechanism which effects the water regulation is called osmoregulation. Contractile vacuole helps in osmoregulation.
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