Chapter 24, Problem 15STP

Summary Introduction

To write:

The different stages of the sporozoan that occur in mosquitoes and assess the importance of the stages of life cycle that occur in mosquitoes.

Introduction:

Animal-like protists belong to the Apicomplexa phylum. These are often called sporozoans because at some stage in their life cycle these develop spores. Spores are reproductive cells that shape and create a new organism without fertilization. Sporozoans lack locomotive methods and contractile vacuoles.

Explanation of Solution

The life cycle of sporozoans is both asexual and sexual. Sometimes two or more hosts are required to complete the life cycle of the organism. Plasmodium life cycle requires two hosts, human and mosquito. Plasmodium enters the human body as sporozoitis (infectious form) through the bite of infected female Anopheles mosquito. Initially, the parasites propagate inside the liver cells and then attack the red blood cells resulting in their breakup. RBC rupture is associated with release of a poisonous material, haemozoin that is responsible for chilling and high fever occurring every 3 to 4 days. When an Anopheles female mosquito bites an infected individual, these parasites enter into the body of the mosquito and undergo further development. Parasites grow inside them to form sporozoites which are deposited in their salivary glands. Once these mosquitoes bite an individual, the sporozoites are absorbed into his or her body.

Conclusion

Thus, the Plasmodium's life cycle involves two hosts- human and mosquito. When a female mosquito takes up gametocytes with blood meal, fertilization and development take place in the gut of the mosquito. Mature infective stages escape from gut and moves to the mosquito salivary glands.