title: Sarcocystis speeri N. sp. (Protozoa: Sarcocystidae) from the opossum (Didelphis virginiana).
abstract: The North American opossum (Didelphis virginiana) is host to at least 3 species of Sarcocystis: Sarcocystisfalcatula, Sarcocystis neurona, and a recently recognized Sarcocystis sp. A new name, Sarcocystis speeri, is proposed for the third unnamed Sarcocystis. Immunodeficient mice are an experimental intermediate host for S. speeri. Sarcocystis speeri sporocysts are 12-15 x 8-10 microm in size, and its schizonts are found in many organs of mice. Sarcocysts of S. speeri are found in skeletal muscles and they are up to 5 mm long and filiform. By light microscopy, the sarcocyst wall is thin (<1 microm thick); ultrastructurally, the cyst wall is up to 1.8 microm thick and has characteristic steeple-shaped villar protrusions surmounted by a spire. Sarcocystis speeri schizonts are morphologically and antigenically distinct from schizonts of S. neurona, and S. speeri sporocysts were not infective to budgerigars (Melopsittacus undulatus).
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Livestock and Poultry Sciences Institute, Beltsville Agricultural Research Center, Maryland 20705-2350, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Dubey
authors.forename: D S
authors.initials: DS
authors.lastname: Lindsay
mesh_terms: D000818:Animals; D007150:Immunohistochemistry; D007411:Intestinal Diseases, Parasitic / Q000469:parasitology / Q000662:veterinary*; D007421:Intestine, Small / Q000469:parasitology; D008099:Liver / Q000469:parasitology; D008168:Lung / Q000469:parasitology; D051379:Mice; D018345:Mice, Knockout; D008819:Mice, Nude; D008854:Microscopy, Electron; D018482:Muscle, Skeletal / Q000469:parasitology; D009893:Opossums / Q000469:parasitology*; D010311:Parrots; D011817:Rabbits; D012522:Sarcocystis / Q000145:classification* / Q000276:immunology / Q000648:ultrastructure; D012523:Sarcocystosis / Q000469:parasitology / Q000662:veterinary*; D013154:Spleen / Q000469:parasitology