A standardized method for the in vivo maintenance of Cryptocaryon irritans (Ciliophora) using the grey mullet Chelon labrosus as an experimental host.

Experimental primary infections with Cryptocaryon irritans were successfully established in mullet following exposure to theronts and maintained for up to 34 successive cycles in this host. Fish were exposed to measured numbers of theronts collected within 4 hr of excystment. Free-swimming trophonts and reproductive cysts were maintained in wells of tissue culture plates containing sterilized seawater and subjected to a photoperiod of 12 hr light:12 hr dark. Excystment was found to be asynchronous over a period from 84 hr to 35 days. The procedure provided at least a 10-fold yield of parasite material per cycle of transmission.