AN INTRANUCLEAR MICROSPORIDIAN IN LUMPFISH CYCLOPTERUS-LUMPUS

Chronic mortalities in lumpfish Cyclopterus lumpus raised in a saltwater recirculation system were associated with the presence of an intranuclear microsporidian. Morphologic changes were characterized by infiltration of lymphocyte-like cells predominantly in the renal interstitium and also in the spleen, liver, gills, stomach, pyloric caecae, heart, ovary and mesenteric fat. Affected cell nuclei contained 1 to more than 6 spherical to oval eosinophilic bodies which stained poorly with hematoxylin and eosin and Giemsa. Ultrastructurally, spores were ovoid (2.1 x 1.0 mum) with a polar tube with 11 turns. The morphology of these spores place them in the genus Enterocytozoon. These spores resemble E. salmonis in salmonids, and Microsporidia rhabdophilia in the rodlet cells of salmonids.