Lizard Malaria Parasites

Life cycle of Plasmodium mexicanum

Above are a series of photographs that illustrate the life cycle of P. mexicanum (and in general, can stand for the life cycle of Plasmodium parasites). The vertebrate host is the western fence lizard, Sceloporus occidentalis, which occurs in woodland habitats in California. The insect vector is the sandfly, Luzomyia vexator. When a vector takes a blood meal, both asexual stages and gametocytes are included. The asexual stages die, but the gametocytes emerge from the blood cells. A picture of a female (darker blue above) and male (pink below) is shown in one photograph. A midgut full of fresh blood is shown. Within the midgut, the male gametocytes produce several mobile gametes; the flagella are shown emerging from the male gametocyte. After the male and female cells combine, the parasite is briefly diploid, but quickly undergoes meiosis. Eventually, mature oocysts appear on the midgut wall (a complete midgut with oocysts is shown, and a close-up of the oocysts). The sporozoites emerge from the oocysts and travel to the vector's oral glands to be injected into the next lizard during the vector's second blood meal. Details of this process, and the effect of the parasite on the behavior of the insect vector are given in Fialho and Schall (1995, Journal of Animal Ecology). Rob Fialho was a highly skilled and creative experimental parasitologist whose career ended far too soon when he died of cancer after a tough nine-year fight.