Stable and quantitative small-scale laboratory propagation of Cryptocaryon irritans

We established a laboratory propagation method of Cryptocaryon irritans, a parasitic ciliate of marine fishes, with black molly Poecilia sp. as host fish, using small plastic aquaria. One cycle of the propagation usually takes one week. With this method, 1500-3000 protomonts are obtained from five challenged mollies every week, from which more than 100,000-200,000 theronts are obtained. Using this method, an isolate of C. irritans has been successfully maintained more than three years. This propagation method reduces labor for maintaining and propagating the parasite and will much contribute to researches on cryptocaryoniasis.•The method is a laboratory propagation technique of Cryptocaryon irritans.•Using small plastic aquaria and black molly as a host, the parasites can be stably propagated and maintained.•An isolate of C. irritans has been successfully maintained more than three years.