The sexual mode of reproduction in the life cycle of a malarial parasite (Plasmodium spp.) involves several steps, beginning with the initiation of the process in the mosquito vector and ending with the formation of sporozoites ready to infect a new host. Here are the different steps in the sexual mode of reproduction:
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Mosquito Infection: The sexual phase of the malarial parasite's life cycle begins when a female Anopheles mosquito ingests blood containing mature gametocytes of the malaria parasite during a blood meal from an infected human host.
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Gametogenesis: Within the mosquito's midgut, male and female gametocytes undergo gametogenesis, a process where they differentiate into gametes. Male gametocytes produce multiple motile male gametes (microgametes), while female gametocytes develop into non-motile female gametes (macrogametes).
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Fertilization: Upon maturation, male gametes (microgametes) seek out and fertilize female gametes (macrogametes) within the mosquito's midgut, forming zygotes.
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Zygote Development: The zygotes undergo rapid development, forming motile ookinetes. Ookinetes penetrate the midgut epithelium of the mosquito and develop into oocysts.
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Oocyst Maturation: Inside the mosquito's midgut wall, the oocysts grow and undergo a series of divisions (sporogony) to produce numerous sporozoites.
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Sporozoite Release: Eventually, the mature oocysts rupture, releasing thousands of sporozoites into the mosquito's hemolymph.
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Migration to Salivary Glands: The released sporozoites travel through the mosquito's body and eventually reach its salivary glands, where they become concentrated and stored.
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Transmission to Host: When the infected mosquito takes a blood meal from a human host, it injects sporozoites along with its saliva into the host's bloodstream.
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Infection of Host: The injected sporozoites rapidly enter hepatocytes (liver cells) and begin the asexual phase of the malarial life cycle, initiating the development of liver-stage parasites.
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Formation of Merozoites: Inside the liver cells, sporozoites mature and undergo multiple divisions to produce thousands of merozoites.
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Release of Merozoites: The mature liver-stage parasites rupture the hepatocytes, releasing merozoites into the bloodstream.
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Bloodstream Infection: Merozoites invade red blood cells (RBCs) and initiate the erythrocytic cycle, leading to the production of more merozoites and the onset of clinical symptoms of malaria in the host.
This completes the sexual mode of reproduction in the life cycle of the malarial parasite, with the cycle repeating when infected mosquitoes bite humans and transmit sporozoites, restarting the process.
