Question

Where will you look for the sporozoites of the malarial parasite?

• A. Salivary glands of freshly molted female Anopheles mosquito
• B. Red blood corpuscles of humans suffering from malaria
• C. Nails of infected humans
• D. Saliva of infected female Anopheles mosquito

Answer 1

The correct option is D Saliva of infected female Anopheles mosquito

Sporozoites of the malarial parasites are present in the saliva of the infected female Anopheles mosquito. These sporozoites enter the bloodstream of humans through the bite of an infected female Anopheles mosquito. 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 produced merozoites which are released upon erythrocytes lysis. The released merozoites infect other erythrocytes and this cycle repeats after every 72 to 48 hours depending upon the species of Plasmodium involved. Occasionally merozoites differentiate into microgametocytes and macrogametocytes.

When erythrocytes containing macro and microgametocytes are ingested by female Anopheles mosquitoes, these are developed into female and male gametes. In the mosquito gut, gametes fuse to form a diploid zygote that gains motility and becomes elongated (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 a female Anopheles mosquito feeds on another host it transfers sporozoites along with saliva.