The origin, structure, and histochemical characterization of encapsulating cysts in the oyster Crassostrea virginica parasitized by the cestode Tylocephalum sp

摘要: Abstract The formation of fibrous capsules enveloping Tylocephalum metacestodes in the oyster Crassostrea virginica commences when invading parasite compresses surrounding Leydig cells during migration. This is followed by thickening intercellular material between and infiltration leukocytes. innermost layer capsule comprised fibroblastlike which possess a gamma metachromatic acid mucopolysaccharide-rich matrix. remaining fibers represent concentrically deposited thickened originating from peripheral cells. These fibers, as well material, are reticular, rather than collagenous, include glycoproteins and/or mucoproteins neutral polysaccharides. stimulant for this type cellular response may be form parasite-secreted PAS-positive, diastase-resistant substance. difference thickness encapsulating cysts found zone beneath host's alimentary tract digestive gland believed to due greater abundance tissue, hence at first site.