The life cycle of Plasmodium mexicanum is complex an includes stages found in both lizards and sand flies. The video below shows an animation of the parasite’s life cycle, and below that are photos showing different stages of the parasite.
When Plasmodium mexicanum first infects a lizard’s red blood cell, it develops into a trophozoite, or feeding stage parasite.
Within the red blood cell, the trophozoite undergoes asexual reproduction, becoming a schizont.
Once mature, the schizont divides and bursts the red blood cell, releasing merozoites into the blood stream, which in turn infect new red blood cells.
Some merozoites become trophozoites again. Others develop into sexual cells called gametocytes. When treated with Giemsa, male gametocytes stain white to slightly pink with a large, diffuse pink nucleus and clumped pigment granules.
Females gametocytes stain blue with a compact pink nucleus and dispersed pigment granules.
Male and female gametocytes are taken up in the blood by the insect vector (the sand fly Lutzomyia spp.) when it feeds. Within the midgut of the sand fly, male gametocytes release multiple flagellated gametes through a process called exflagellation.
When male and female gametes combine, they form an ookinete, which penetrates the midgut wall and forms an oocyst (pictured).
Within the oocyst, the parasite undergoes another cycle of asexual reproduction, forming sporozoites.
The sporozoites (pictured) burst the oocyst and make their way to the sand fly’s salivary glands, where they will be injected into a new host the next time the insect feeds.