Studies on Glugea Infection of the Ayu, Plecoglossus altivelis—IV

Abstract

Suspensions of spores of Glugea plecoglossi in distilled water or 0.85% NaCl solution (about 107-108 spores per ml) were injected subcutaneously (0.05 ml) and intraperitoneally (0.1 ml) into Ayu (Plecoglossus altivelis) (9-15 g). Fish injected with distilled water or 0.85% NaCl solution were used for controls. The experimental and control fish were kept at about 19-20°C after injection. After 22 to 35 days all fish were sacrificed and examined by the naked eye for the presence of “Glugea cysts” not only in the site of inoculation but also in the other parts of the body. The results were as follows. In almost all fish inoculated with spores subcutaneously many Glugea cysts had been produced at the site of inoculation. Besides, cysts were observed in internal organs such as pyloric caeca, peritoneum, gonads, adipose tissue and spleen.In the fish received spores intraperitoneally many cysts were observed to be formed on pyloric caeca, peritoneum, gonads, adipose tissue, liver, heart and spleen. In addition, cysts were found in subcutaneous tissue and peripheral muscle tissue in various part of the trunk.This spore injection method seems to be useful for the studies not only on the pathology, and treatment of microsporidioses but also on the life cycle and host range of microsporidia.