Q.Describe the life cycle of plasmodium vivax in mosquito.

The life cycle of Plasmodium vivax in the mosquito (the sporogonic/sexual cycle) begins with ingested gametocytes and ends with infective sporozoites in the mosquito's salivary glands.

Plasmodium vivax, the malarial parasite, has a two-host life cycle: an asexual (schizogonic) cycle in humans (the intermediate host) and a sexual (sporogonic) cycle in the female Anopheles mosquito (the definitive host, since fertilization/sexual reproduction occurs here). The mosquito-stage life cycle proceeds as follows:

1. Uptake of gametocytes: When a female Anopheles mosquito bites an infected human and takes a blood meal, it ingests red blood cells containing the sexual stages of the parasite — male microgametocytes and female macrogametocytes — along with other blood-stage forms (which do not survive in the mosquito).

2. Gametogenesis: Inside the mosquito's stomach (midgut), the gametocytes mature into gametes.

   • The microgametocyte undergoes exflagellation, throwing out several thread-like, flagellated microgametes.
   • The macrogametocyte matures directly into a single macrogamete.

3. Fertilization: A motile microgamete fuses with the macrogamete to form a diploid zygote.

4. Ookinete formation: The zygote elongates and becomes a motile, worm-like ookinete, which actively penetrates the epithelial wall of the mosquito's midgut.

5. Oocyst formation: On reaching the outer surface of the gut wall, the ookinete rounds up and encysts, forming an oocyst.

6. Sporogony: Inside the oocyst, the nucleus divides repeatedly (sporogony), producing thousands of thread-like sporozoites.

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