OBSERVATIONS ON AN INTRANUCLEAR MICROSPORIDIAN IN LYMPHOBLASTS FROM FARMED ATLANTIC HALIBUT LARVAE (HIPPOGLOSSUS-HIPPOGLOSSUS L)

An intranuclear microsporidian was observed in lymphoblasts from the kidney of farmed Atlantic halibut larvae (Hippoglossus hippoglossus). In addition to spores, intranuclear pre-spore stages were observed. Uninucleated stages with a slight thickening of the cell membrane were the most simple developmental stages observed. Multinucleated developmental stages contain electron-lucent vesicles and electron-dense discs. The spores are ovoid and measure 2.9 x 1.2 mu m (mean). Sporophorous vesicles, diplokarya and mitochondria were not observed in any of the developmental stages. The developmental stages observed are similar to those of the family Enterocytozoonidae, genus Enterocytozoon. However, there are several differences between the present species and E. bieneusi from enterocytes in man. The relationship to the other species in the genus, E. salmonis can only be determined when all the developmental stages of the species from Atlantic halibut are identified.