• Journal of Aquaculture
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• v.19 no.3
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• pp.197-204
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• 2006

The pathogenicity and infection route of the Scuticociliate, Philasterdies dicentrarchi, were investigated with the 3 and 5 cm-group of juvenile flounders, Paralichthys olivaceus. The infection rates of 3 cm-group were 40% four days post infection (D.P.I.) and increased to be 90.1% 24 D.P.I., whereas those of 5 cm-group were 20% 8 D.P.I., 42% 16 D.P.I., and 81% 24 D.P.I. The results showed there were several infection routes to internal organs Olive flounder. The first route was started with the infection at the soft part of caudal fin and later reached at fin ray and muscle tissue; the second one was started from lips and mouth tissue of upper jaw and later the pathogen could be observed at either muscle tissue or eyeball and brain; the third one was begun at caudal fin and later the pathogen reached at brain tissu'e through spiral cord; the fourth one was started with the infections at abdominal cavity and anus. P. dicentrarchi infected to brain tissue was first observed 14 D.P.I in 3 cm-group and 20 D.P.I. in 5 cm-group of the juvenile flounder. This indicated that the brain infection of P. dicentrarchi might occur faster in small-sized flounder than large-sized one.