Sarcocystis mucosa (Blanchard 1885) Labbé 1889 in unadorned rock wallabies (Petrogale assimilis) and Bennett's wallabies (Macropus rufogriseus).

Abstract

Macroscopic cysts of a protozoan parasite were detected in the gastro-intestinal walls of two unadorned rock wallabies (Petrogale assimilis) and 20 Bennett's wallabies (Macropus rufogriseus). The cysts were located predominantly in the muscularis externa and the submucosa of the forestomach, small intestine and colon and sometimes in the muscularis externa of the oesophagus and caecum. All cysts exhibited similar morphological and ultrastructural characteristics. They were bounded by thick primary cyst walls (containing distinctive bulbous-like protrusions) and were surrounded by collagen fibres and host connective tissue cells (mainly fibrocytes). The cysts were divided by septae into internal compartments containing metrocytes and cystozoites. The cystozoites contained numerous organelles typical of apicomplexan protozoan parasites (including an apical complex, a micropore, rhoptries, micronemes, polysaccharide granules and 22 subpellicular microtubules) and they were observed to divide by the process of endodyogeny. Despite the unusual location of the cysts, they were classified on the basis of their ultrastructural characteristics as Sarcocystis mucosa (Blanchard 1885) Labbé 1889.