Question

Motile zygote of Plasmodium occurs in the

• A. midgut of female Anopheles
  
• B. salivary glands of Anopheles
  
• C. human RBCs
  
• D. human liver
  

Answer 1

The correct option is A midgut of female Anopheles


When erythrocytes containing macro and microgametocytes are ingested by female Anopheles mosquitoes, these develop into female and male gametes. Gametes fuse to form a diploid zygote that becomes motile and elongates called ookinete. Ookinete migrates to the mosquito gut wall and penetrates and forms an oocyst. Oocyst undergoes meiosis and forms sporozoites which migrate to the salivary gland of mosquitoes. When an infected female Anopheles mosquito feeds on another host it transfers sporozoites along with saliva.

Sporozoites travel to the hepatic cells through the bloodstream. In the liver cells (hepatic cells) sporozoites undergo asexual division (exo-erythrocytic schizogony) to produce merozoites. Merozoite released from the liver cells penetrates erythrocytes. Inside the erythrocytes, these merozoites enlarge and are termed trophozoites. The trophozoites undergo asexual reproduction to produce schizont, which eventually divides to producing more merozoites which are released upon erythrocytes lysis. The released merozoites infect other erythrocytes and this cycle repeats after every 48 to 72 hours depending upon the species of Plasmodium involved. Occasionally merozoites differentiate into microgametocytes and macrogametocytes.