Figure 1.

Life cycle of Ich. Infective theronts bore through the surface mucus and take up residence within the epithelium of susceptible fish. Theronts differentiate into feeding trophonts that grow and exit the host (as tomonts) within 4 to 7 days. Tomonts swim for a brief period and then adhere to an inert support where they secrete a gelatinous capsule. Tomonts divide within the capsule to form hundreds of tomites that differentiate into infective theronts within 18 to 24 hours at room temperature. Theronts that fail to infect fish die within 1 to 2 days.