Abstract
A microbiological survey was carried out to clarify the causative organism of spotting disease of sea urchin Strogylocentrotus intermedius, which occurred at Shakotan-Cho Fisheries Breeding Center, Hokkaido at the end of August in 1993. A filiform bacterium which formed brightly yellowish colonies on solid media was isolated from coelomic fluid of diseased animals. Gliding movement on seawater agar plate and 40.5 of DNA GC mol% confirmed that the isolate belongs to the family Cytophagaceae.
Experimental infection of sea urchin with the isolate was perfomed by the immersion method using 106, 105 and 104 CFU/m/ at 20°C, 23°C and 25°C. All the animals challenged with 106 CFU/ml at 23°C and 104 CFU/ml at 25°C died, some of which showing spotting lesions, at one and three days after the challenge, respectively. No mortality was observed at 20°C. The bacterium was reisolated from coelomic fluids and surfaces of dead sea urchins. These results suggested that the bacterium was the pathogen of spotting disease of Strongylocentrotus intermedius.
