Sexual Stages in the Life History of the Hemogregarine Hepatozoon rarefaciens (Sambon and Seligmann, 1907)*

SYNOPSIS. Sexual stages of a reptilian hemogregarine Hepatozoon rarefaciens are described from the hemocoele of a mosquito vector Culex tarsalis. The gametocytes associate within 0.5 hr after biting. Most of the gametocytes then pair off and begin to differentiate. After about 26 hr at 22–23 C, the macrogametocyte usually becomes crescent‐shaped with the microgametocyte lying in the concavity. The nucleus of the macrogametocyte enlarges considerably, while the microgametocyte divides into 2 and eventually into 4 spindle‐shaped microgametes which are biflagellated. The macrogametocyte increases in size and rounds up to form a macrogamete. Gamete formation is usually completed by 60 hr and fertilization begins soon thereafter. The zygotes develop into the uninucleate oocysts described previously. In some other species of Hepatozoon, gametogenesis has been described as taking place in the stomach of the arthropod vector, with the microgametocytes transforming without cytoplasmic division into non‐flagellated microgametes. The occurrence of 2 distinct types of gametogenesis may possibly be a basis for separating Hepatozoon into 2 genera.