The histochemistry of Stellantchasmus falcatus Onji and Nishio, 1915 (Trematoda: Heterophyidae) metacercarial cyst in the mullet Mugil cephalus L. and histopathological alterations in the host†

The metacercarial cyst of the heterophyid trematode Stellantchasmus falcatus in the striated muscles of the mullet Mugil cephalus consists of three layers. Histochemical studies have indicated that these layers are chemically distinct. The acellular inner layer is comprised of complex carbohydrate polyanions rich in acidic groups while the medial cellular layer is comprised of a neutral mucopolysaccharide including a moeity of carbohydrate poiyanions. These two layers are believed to be of parasite origin. The outer layer is cellular and is of host origin. It is the most chemically complex and is believed to include one or more of the following: mucopolysaccharides, glycolipids and phospholipids. In addition, the carbohydrate moeity associated with the mucopolysaccharides and/or glycolipids is in the form of sulphated carbohydrate polyanions with undissociated carboxyls as well as acidic groups. The presence of the parasite results in the necrotic degeneration of the host's myofibers situated in the proximity of the parasite. Large fat cells fill the spaces vacated by necrotic muscle cells and many blood cells occur along the periphery of the parasite.