ONE-CELLED ANIMALS— PHYLUM PROTOZOA 



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because all persons must die sooner or later, taking all their parasites 

 to the grave with them. We have already mentioned the mosquito 

 as the agent of spread. Just any kind of mosquito, however, cannot 

 serve this purpose — it must be a female Anopheles mosquito. It must be 

 a female because male mosquitoes are vegetarian in their diets and suck 

 the juices of plants. The females also suck such juices, but will take 

 blood when they can get it. It must be an Anopheles mosquito because 

 this is the one in which Plasmodium can continue its life cycle and, as 

 the physiology of other mosquitoes is different, the parasite cannot live 

 in their bodies. 



Cyst producing spores 



■Ameboid zygote 



Sperm and egg uniting to form zygote 

 Egg (from female gametocyte) 



Sperm (from male gametocyte) 

 Spore going to salivary glands 



t- <_0 Female gametocyte 



*~ @ Male gametocyte 



Fig. 7.9. Cycle of the malarial organism in the Anopheles mosquito. As the mosquito 

 sucks blood from an infected person, some male and female gametocytes are taken in. 

 In the mosquito's stomach these form eggs and sperms. An egg and a sperm unite 

 and form a zygote which then becomes amoeboid and makes its way through the 

 stomach wall. It encysts on the outside of this wall and produces many sporozoites. 

 These migrate to the salivary glands and may be injected into another person along 

 with the saliva. The entire cycle requires about twelve days. 



