ELECTRONIC MICROSCOPY AND HISTOCHEMICAL STUDY OF THE BLOOD FLUKE SANGUINICOLA PLEHNAE (DIGENEA, SANGUINICOLIDAE), A PARASITE OF FRESHWATER FISHES

Morphology of pike parasite Sanguinicola plehnae was studied by histochemical staining, confocal laser scanning microscopy, transmission electron microscopy, and scanning electron microscopy. The staining with fluorescently labeled phalloidin showed muscle layers running in circular and longitudinal directions. Diagonal muscle fibers are located between layers of circulars and longitudinal fibers. The anterior end of the fluke has a miniature ventral mouth and a ventral pharynx; suckers are absent. Longitudinal muscle fibers extend along the esophagus. The short X-shaped caecum of S. plehnae is surrounded by intensely stained muscle fibers. The musculature is found around the lobular testis and around the cirrus surrounded by a large zone of modified lamellar sarcoplasmic appendages with muscle fibers in their expanded portions that are revealed by electron microscopy. Along the lateral edges of S. plehnae a number of deeply rooted spines are found that are visible both by electron microscopy and phalloidin staining. These data indicate that the origin of the spines involves actin muscle filaments. The results confirm the important role the muscular system of digeneans play in the functioning of the digestive and reproductive organs.