Histochemistry and ultrastructure of the metacercarial cyst of Bolbogonotylus corkumi (Trematoda: Cryptogonimidae).

Histochemical and ultrastructural studies were conducted on the metacercarial cyst of the cryptogonimid trematode Bolbogonotylus corkumi from the muscle tissue of fantail darters Etheostoma flabellare. The metacercarial cyst consisted of an outer host capsule and an inner parasite cyst. The host capsule was composed of an outer region of fibroblasts, collagen, macrophages, and unidentified cells, and an inner region containing degenerating cells. The parasite cyst was thin, homogenous, and noncellular in nature. The host capsule stained strongly for connective tissue and proteins and moderately for lipids, nucleic acids, nonspecific esterase activity, and acid and alkaline phosphatase activities. The parasite cyst stained intensely for acid mucopolysaccharides and moderately for acid phosphatase activity. A thick glycocalyx occurred between the parasite cyst and metacercarial tegument.