engleski

Type and ultrastructure of Didymocystis wedli and Koellikerioides intestinalis (Digenea, Didymozoidae) cysts in captive Atlantic bluefin tuna (Thunnus thynnus L.)

The tissue reaction to fish trematodes usually displays encapsulation of parasites, followed by different degree of the inflammatory response, dependent on the site, size and abundance of parasites. Didymozoa (Didymozoidae, Trematoda) are highly abundant and diverse digeneans of pelagic fish, encysted in gonochoristic or hermaphroditic formations in gills, cartilaginous, mucous and connective tissue in nose, mouth and gill cavity, digestive organs, kidneys, gonads, skin and fins. In order to evaluate the type and ultrastructure of the Atlantic bluefin tuna (Thunnus thynnus) tissue reaction to didymozoids, TEM microscopy of two tissue-embedded didymozoid species was assessed, along with the monoclonal antibodies labeling (anti-fish collagen type I, anti-human cytokeratin, anti-vimentin antibodies). Ultrastructure of Didymocystis wedli (prevalence=61.75%, abundance=28.91) encapsulated in gill filaments and Koellikerioides intestinalis (prevalence=54.65%, abundance=10.96) in the intestinal submucosa, showed that thin parasitic hindbody tegumentum was directly embedded in layers of connective tissue bands. Only scarce cellular elements (lymphocytes, fibroblasts and fibrocytes) infiltrated the connective tissue capsule, differing by its thickness, not the type of filaments expressed. Cysts showed positive reaction to extracellular collagen and both appeared positive for cytoskeletal intermediate filaments vimentin and cytokeratin.

Didymocystis wedli ; Koellikerioides intestinalis ; Atlantic bluefin tuna ; Thunnus thynnus

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