A new strain of Cryptocaryon irritans from the cultured olive flounder Paralichthys olivaceus

Abstract

An obligate parasite, Cryptocaryon irritans, which is responsible for the white spot disease of marine fish is known to develop in the temperature regime over 19°C. Recently, however, we found white spot disease of olive flounder Paralichthys olivaceus during winter at water temperatures ranging between 12 and 16°C in Korea. In the present study we isolated a C. irritans-like ciliate from the affected fish and investigated its reproductive characters to compare the newly found ciliate with typical C. irritans. The newly found ciliate had an additional process in the reproductive stage, characterized by a budding before palintomic division, and it showed a higher ability to carry out tomitogenesis at a low temperature (16°C) than at a high temperature (24°C). Nevertheless, the present ciliates still had much in common with typical C. irritans with respect to clinical, histopathological, and morphological characters, suggesting that it is a new strain of C. irritans, adapted to lower water temperature. KEY WORDS: Cryptocaryon irritans-like ciliate · White spot disease · Olive flounderResale or republication not permitted without written consent of the publisher

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

“…In the skin of the host grouper fingerling, the trophonts did not penetrate the scale layer and were encapsulated by the outermost single layer of epithelial cells; this increases the development success of the trophonts and the virulence of the parasite, since invasion by theronts and eventual establishment of trophonts can occur with relative ease. Production of daughter tomonts by budding was reported by Jee et al (2000). In the present study, we observed that the presence of tomonts with constrictions and apparent 'budding' did not result in the formation of a new cyst wall and complete separation despite the division of cells inside the cyst.…”

“…These were pathological results of the infection. The parasites settle within narrow epithelial enclaves, in extended tunnels burrowed in the epithelium, or in the basement membrane of the gill filament (Diamant et al 1991, Colorni & Burgess 1997, Jee et al 2000. In the present study, some trophonts were observed to have burrowed at the base of the secondary lamella layer (thereby 'lifting' this) and in the branchial arch.…”

“…Classifying Cryptocaryon irritans as a distinct isolate or strain on the basis of certain development parameters has been suggested (Diamant et al 1991, Diggles & Adlard 1997, Jee et al 2000. For example, Diamant et al (1991) described a seemingly distinct isolate that, when the gills were severely infected, could also infect the skin and eyes that had individual and weakly adherent tomonts and trophonts in extended tunnels burrowed in the epithelium.…”

“…Diamant et al (1991) reported mortality of gilt-head sea bream Sparus aurata broodstock due to infection by a Cryptocaryon-like ciliate (distinct from C. irritans) on the Mediterranean coast at an ambient temperature of 22°C. Variants or strains of C. irritans have also been recognised, based on various parameters (Diggles & Lester 1996a,b,c, Diggles & Adlard 1997, Jee et al 2000.…”

Development of the Macronucleus of <i>Cryptocaryon irritans,</i> a Parasitic Ciliate of Marine Teleosts, and its Ingestion and Digestion of Host Cells

“…The development of the tomont is affected by temperature (Wilkie and Gordin, 1969), dissolved oxygen, and salinity (Yoshinaga, 2001;Coloni, 1985;Cheung et al, 1979). Strain-specific differences in the periods required for the release of theronts have also been reported (Diggles and Adlard, 1997;Jee et al, 2000). To clarify how environmental factors affect the development of tomont and the periods required for the release of theront may allow the prediction and prevention of outbreaks of cryptocaryoniasis in aquaculture facilities, such as marine net cages and land-based tanks.…”