Studies on cryptocaryoniasis in marine fish: effect of temperature and salinity on the reproductive cycle of Cryptocaryon irritans Brown, 1951

Abstract

Trophonts of Cryptocaryon irritans Brown from infected three-spot damselfish, Dascyllus trimaculatus Ruppell, were kept at temperatures ranging from 7 to 37°C to observe encystment and development of the tomites. At 30, 25 and 20^C, the percentage of trophonts that had encysted in 16 h were 70, 77 and 64% respectively; at 37^C, 44% encysted and at 7°C only 10% had encysted.The optimum temperature for excystment was 30°C; 50% excysted in 5 days and 100% in 7 days. At 25°C, 60% of the tomites started to excyst on the eighth day, and 70% on the ninth day. At 20°C, 10% started to excyst on the ninth day, reaching 40% on the tenth day. No excystment occurred at 37 and 7°C.Newly encysted tomonts were placed in various dilutions of sea water (31 %o) and kept at temperatures ranging from 7 to 37°C. Low salinities, i.e. 16%o and lower caused tomonts to rupture. At 37, 20 and TC, 35% of the tomonts started to rupture immediately in 50% sea water, while at 30 and 25 C, 30% of the tomonts ruptured in 25% seawater. However, none of the cysts developed normally at these dilutions. The percentage rupturing increased with decreasing salinity.

Characterization of Cryptocaryon irritans, a parasite isolated from marine fishes in Taiwan

“…Cheung et al (1979) likewise noted that lower salinity has an adverse effect on the development of this parasite. Salinity can, however, only be lowered when the water and the cultured fishes can be easily manipulated and controlled.…”

Infections of Cryptocaryon irritans on wild fish from southeast Queensland, Australia

“…Indeed the heaviest infections at Site 1 occurred at 17"C, and infections were still recorded at 15"C, a temperature at which C. irritans infections were found not to occur in previous studies (Wilkie & Gordm 1969). In contrast, Cheung et al (1979) found the optimal temperature for excystment of C, irritans to be 30°C. This indicates the possible existence of strains of C, irritans which can be differentiated by their temperature tolerances, as has been proposed previously for C. irritans by Diamant et al (1991), and for the freshwater ciliate .!cht!…”

Effects of High Temperature and Dissolved Oxygen Concentration on the Development of Cryptocaryon irritans (Ciliophora) with a Comment on the Autumn Outbreaks of Cryptocaryoniasis.

“…Cryptocaryon irritans has a parasitic phase and an encysted free-living stage in its life cycle (Colorni and Diamant, 1993 Cheung et al (1979). Our preliminary data suggest that tomonts can not properly develop in low dissolved oxygen (DO) concentrations, and the effect of low DO on the tomonts seems to be involved in the inconsistency.…”