FIG 1.

Diagrammatic illustration of the developmental cycle of N. bombycis. The life cycle of N. bombycis is divided into an infective phase, a proliferative phase, and a sporogonic phase. In the infective phase, the mature spore germinates and injects the sporoplasm into the host cell. In the proliferative phase, the meront proliferates by binary fission or multiple fissions in the host cell. In the sporogonic phase, the sporont with four nuclei divides into two sporoblasts, and the sporoblasts further develop into mature spores with thick walls.