The process of gamete formation is called gametogony. The stages of gametogeny are:
(i) Formation of Pungametes: The process of formation of pungametes or spermatozoa is called spermatogenesis. In the process of exflagellation, the nucleus of each microgametocyte divides to produce 4-8 nuclei. At this time 4-8 projections are formed in the cytoplasm. This is called cytoplasmic projection. One nucleus enters each projection. Each projection with a nucleus develops into a pungamete or microgamete. Pungamites swim for fertilization.
(ii) Formation of strygametes: The process of formation of strygametes or ovules is called oogenesis. Each macrogametocyte gives rise to one strigamete or macrogamete. One end of the macrogamete swells to form the fertilization cone. The cone region is called the Fertilization Cone or Reception Cone. The nucleus of the egg is located near the cone.
(iii) Fertilization: The gametes move individually towards the fertilization cone of the ovule. One sperm enters each egg. Later their nuclei fuse to form a zygote. This process is called fertilization. Fertilization is completed within 20-22 hours.
(iv) Wookinet/Vermicule: After 12-14 hours the quiescent spherical zygote becomes elongated and motile. It is called wokkinet or vermicule. Uokinetes are 18-24 microns in length and 3-5 microns in width.
(v) Oocysts: Within 24 hours the ookinetes break through the wall of the mosquito crop and come out and take spherical shape. Then within 40 hours it is covered with a thin film. It is called a oocyst. The nucleus of the oocyst divides first by meiosis and then by mitosis. Meiosis of oocyst is called postzygotic meiosis. A mosquito crop may contain 50-500 oocysts. The resulting oocysts appear spongy and 4-5 times larger in size (50-60 µ).