Ultrastructural aspects of feeding and secretion-excretion by the equine parasite Strongylus vulgaris

Light, scanning, and transmission electron microscopy were employed to prov ide further data on the putative origins of the immunogenic secretory-excre tory product (ESP) of Strongylus vulgaris (Looss 1900). The sharply delinea ted but superficial attachment to the equine caecum by the mouth leaves beh ind an oval area devoid of epithelial cells. Attachment does not extend dee ply enough to reach the muscularis mucosa layer of the equine intestine. Th e progressive digestion of the ingested plug of tissue (epithelial cells, b lood tells and mucous) was visualized. The coelomocytes, floating cells and membranous structures located in the pseudocoelom and intimately associate d with the digestive, excretory and reproductive systems, and with the soma tic muscles are described. The secretory-excretory system comprises two, ve ntrally-located, secretory-excretory glands connected to tubular elements. These glands synthesize granules of various sizes and densities that are de lineated.