BIOLOGICAL CHARACTERISTICS OF Achlya bisexualis FROM FRESHWATER FISH IN THE MEKONG DELTA

This study determined the biological characteristics of Achlya bisexualis which cause pathogenic on some freshwater fish in the Mekong Delta, South of Vietnam. The experiment was carried out on ten strains of A. bisexualis which were isolated from striped catfish (Pangasianodon hypophthalmus), snakehead fish (Channa striata) and red tilapia (Oreochromis sp.). The results showed that optimal temperature of the strains ranged from 28^oC to 33^oC. All isolates tested grew rapidly at pH 5-8. The strains can grow up to salinity 1%. The strains can be used glucose, maltose, mannose, sucrose, arabinose but do not used galactose. A. bisexualis which were isolated from snakehead reacted with arginine and urea but not reacted with strains infected striped catfish and red tilapia. The strains can be able to react with nitrite (5mM) and lipid hydrolysis but no reacted with lysine and nitrite (43 mM).