Light and electron microscopic observations on the ciliate Cryptocaryon irritans Brown, 1951 throughout the life cycle

Cryptocaryon irritans is a parasitic ciliate of marine fish and is responsible for the fish disease called "white spot disease". This disease can cause extreme fish loss in marine aquaria and mariculture environments. Cryptocaryon has a complex life cycle consisting of trophont, tomont, tomite, and theront stages.; The purpose of this research was to investigate the ultrastructure of the somatic and oral cortex of the parasite throughout the life cycle.; The somatic kineties of C. irritans consists mainly of monokinetids. The somatic dikinetids exist close to the oral area. There are at least 3-4 rows of somatic dikinetids posterior to the oral dikinetids. The kinetid pattern of the somatic mono, dikinetid and oral dikinetids is very similar in both the theront and trophont of Cryptocaryon. The oral ciliature is composed of dikinetid cilia both in the theront and in the trophont. A row of oral dikinetids with associated papillae rings the cytostome. The oral ribs extend from the oral dikinetids toward the oral opening. The cytopharyngeal apparatus consists of the innermost cytopharngeal tube and a basket of nematodesmata which surrounds it. Near the oral apparatus there is a set of three membranelles (adoral organelles) both in the theront and the trophont.; The structure of the kinetid and oral apparatus suggest that Cryptocaryon irritans has closer affinities to Prostome ciliates than the Hymenostome of which Cryptocaryon is a member and it should be included in the ciliate class Prostomatea.