Based on the arrangement and shape of the buccal structure, scuticociliates isolated from cultured olive flounder Paralichthys olivaceus belonged to the family Uronematidae and showed many characteristics of Uronema marinum. There was variation in the morphometry of clinical isolates taken from different organs of infected flounder. However, the isolates did not show any significant difference in morphometry under cultured conditions. The ciliates were easily maintained in in vitro medium to which antibiotic agents had been added and which had been enriched with the raw brain tissue of a healthy olive flounder. The ciliates propagated in a wide range of both temperature (6 to 30°C) and salinity (10 to 35 ppt). KEY WORDS: Olive flounder · Paralichthys olivaceus · Scuticociliatosis · Uronema marinum Resale or republication not permitted without written consent of the publisherDis Aquat Org 47: [49][50][51][52][53][54][55] 2001 infected brain were put into 3 ml of normal saline in a tissue culture dish (35 × 10 mm, Corning) at room temperature. One ml of infected culture medium (with 10 ml of saline) was transferred into a 25 cm 2 tissue culture flask (Corning) at 17°C. The saline medium consisted of a 0.85% sterile physiological saline solution containing 0.1% antibiotic (penicillin-streptomycin, Sigma). The whole brain tissue of a healthy flounder (juvenile, avg 15 cm), in a raw state, was washed several times and added to the cultures, as food for ciliates. Ciliates were subpassaged (1 ml of infected culture medium was inoculated into 10 ml of fresh medium prepared as above), every 7 to 10 d. Cultures were maintained at 17 ± 1°C. Each clinical isolate was examined unstained to record vital characteristics. Cultured ciliates were fixed in formalin or Bouin's fluid, washed in distilled water and subsequently stained with Giemsa solution or by silver nitrate impregnation using standard techniques (Klein 1958, Foissner 1991. Stained or unstained ciliates were examined under a light microscope, and their sizes were measured using an ocular micrometer. For scanning electron microscopy, cultured ciliates were fixed in an equal volume of fixative (5% glutaraldehyde, 1 volume + 0.2 M sodium cacodylate, 1 volume) and washed with 0.2 M sodium cacodylate buffer, pH 7.4 at 4°C, followed by a post-fixative in 2% aqueous osmium tetroxide for 20 min. The specimens were placed on a fine mesh (10 µm) made of Nitex nylon netting, dehydrated in a graded ethanol series, criticalpoint-dried, and examined with a Jeol JSM-35 scanning eletron microscope.Biology of ciliates. The effects of temperature and salinity on viability and reproductive ability were investigated to estimate the biological characteristics of the ciliate. 0.1 ml of cultures (<10 3 cell ml -1 ) were inoculated into 10 ml of fresh medium in 25 cm 2 tissue culture plates containing juvenile flounder brain tissue as mentioned above, and then incubated at different temperatures (6 to 36°C) and salinities (5 to 50 ppt). To define whether temperature and salin...

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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

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