Fig. 6

Ultrastructure of x-cell plasmodia from rainbow trout. a, b Vacuolate x-cells (X) with marked (electron-dense) adjoining pellicles (P), lipid droplets (L), nucleus (N) with marked nucleolus (Nu) and vacuoles (V). In b, a multivesicular body (MVB) and a region in the cytoplasm with an aggregate of electron-dense membranes (EDM) are visible. c Part of intravascular parasite (X) close to the endocard endothelium (E). MyC myocardial cell. d Deep pellicle-covered invagination into the x-cell, interpreted as a cleft (C). Some invaginations appeared to be branched. e Multivesicular body (MVB) inside a vacuole, apparently confluent with that of another MVB. f Detailed view of pellicle (P) normally composed of three membranes. Ou Outside. g Contact point between two x-cells, where eight membranes can be counted. h Mitochondria with no visible cristae. i Vacuoles with vacuoplast (VP)-like electron-dense inclusions. Scale bars: 1 µm (a–e, h; 0.1 µm (f–g; 0.5 µm (i)