Q.Describe the life cycle of Plasmodium vivax in mosquito with diagram.

In the female Anopheles mosquito, Plasmodium vivax carries out its sexual cycle (sporogony): gametocytes form gametes that fuse to a zygote/ookinete, which forms an oocyst producing sporozoites that reach the salivary glands.

(Diagram: draw and label the stages in the mosquito gut in sequence - male gametocyte (forming microgametes by exflagellation), female gametocyte (macrogamete), fertilisation forming a zygote, the motile ookinete penetrating the stomach wall, the OOCYST full of sporozoites on the outer stomach wall, and the SPOROZOITES migrating to the salivary glands.)

Life cycle of Plasmodium vivax in the mosquito (the SEXUAL cycle - SPOROGONY):

• Plasmodium vivax is DIGENETIC: it completes its life cycle in two hosts - man (the intermediate host, where the asexual cycle occurs) and the FEMALE ANOPHELES mosquito (the definitive host, where the SEXUAL cycle occurs). The female Anopheles is also the vector that transmits malaria.

Stages in the mosquito:

1. Ingestion of gametocytes:

• When a female Anopheles bites and sucks blood from a malaria patient, it takes in the sexual forms - the male (micro-) and female (macro-) GAMETOCYTES - along with other blood stages.

2. Gametogony (formation of gametes) in the mosquito gut:

• In the stomach of the mosquito, the male gametocyte undergoes EXFLAGELLATION to form several thin, motile MICROGAMETES.

• The female gametocyte matures into a single, rounded MACROGAMETE.

3. Fertilisation:

• A microgamete fuses with a macrogamete to form a ZYGOTE (synkaryon).

4. Ookinete formation:

• The zygote becomes elongated and motile, and is now called the OOKINETE (vermicule). It penetrates the wall of the mosquito's stomach and comes to lie on its outer surface.

5. Oocyst and sporogony:

• On the outer stomach wall the ookinete rounds up and secretes a cyst wall, forming an OOCYST.
• Inside the oocyst, repeated nuclear and cytoplasmic divisions produce a large number of tiny, sickle-shaped SPOROZOITES (this multiplication is called sporogony). …