Cryptocaryon irrttans (Ciliophora): photoperiod and transmission in marine fish

Abstract

The ciliate Cryptocaryon irritans Brown, 1951 is a parasite of tropical marine fishes, being recorded chiefly from coral reef species (Laird, 1956; Burgess, 1978; Colorni, 1985). The disease, cryptocaryosis, accounts for fish mortalities in aquaria (De Graaf, 1973) and mariculture systems (Huff & Burns, 1981; Colorni, 1985; Kaige & Miyazaki, 1985; Rasheed, 1989); however, relatively few studies have been undertaken on the biology of C. irritans, as highlighted by Lorn & Dykova (1992). Sikama (1937) described the major features of the life cycle, infection of the fish epidermis alternating with a free-living phase of reproduction within a protective cyst. Most other investigations of C. irritans have been concerned with morphology (Sikama, 1937, 1938; Brown, 1951, 1963; Nigrelli & Ruggieri, 1966; Cheung et al., 1981; Colorni, 1988) with a recent work on the ultrastructure of the pellicle (Matthews et al., 1993). Little is known regarding the behaviour of free-living stages and the possible influence of environmental factors on transmission. Nigrelli & Ruggieri (1966) noted photopositive responses in theronts. The establishment and maintenance of C. irritans in mullet under controlled conditions (Burgess & Matthews, 1994) provided an opportunity further to investigate light in the survival strategy of this fish pathogen.