Plasmodium - the malarial parasite (Rust, fig. 13 a-c; C & V fig. 4.14) - While the Apicomplexa are often referred to as the Sporozoa, the malarial parasite does not form spores. Instead, it has a complex life cycle that involves two different hosts, a mammalian host, such as humans, and an invertebrate host, the mosquito genus Anopheles. The sexual stages of reproduction, and an asexual stage of reproduction known as sporogony, take place in the mosquito host. In the human host, another type of asexual reproduction takes place. This is called schizogony and results in the formation of infective stages that can attack and invade the red blood cells of the mammalian host. These protozoa are responsible for the fevers associated with malarial infections. Also found in the circulating red blood cells of the mammalian host are special malarial parasites known as gametocytes, which produce male and female gametes when ingested by a mosquito. These are the stages of the life cycle that are infective to mosquitoes.

Examine the blood films provided and try to identify gametocytes and stages of the schizogonic cycle. Red blood cells are only 7 µm in diameter, and since Plasmodium is an intracellular parasite, you will have to use oil immersion and good microscopic techniques to identify these.