What causes marine “Ich”?
Marine “Ich” is caused by a ciliated protozoan called Cryptocaryon irritans Brown 1951. Ciliates (Phylum Ciliophora) are one of the largest groups of protozoans and all posses cilia or compound ciliary structures for food acquisition or locomotion at some point in their life cycle. Of the some 7200 species that have been described, around one third are ecto- and endo- commensals and parasites (Ruppert and Barnes, 1994). C. irritans is an obligate ectoparasite (Dickerson and Clark, 1996) which means that it is an external parasite that needs the fish host to complete its life cycle. The name ‘Marine “Ich”‘ comes from the fact that it is essentially the marine equivalent on Ichthyophthirius multifiliis Fouquet, 1876, or “Ich” for short. While the two species of ciliates have superficially similar life cycles and signs, they have been found to be only distantly related (Wright and Colorni, 2002) . The life cycle of C. irritans C. irritans has a four stage life cycle, as shown in Figure 1.
