title: The distribution, prevalence, and morphological features of the cystic stage of an apicomplexan parasite of native littleneck clams (Protothaca staminea) in British Columbia.
abstract: Sixty-nine of 98 native littleneck clams (Protothaca staminea) collected from Cooper's Cove, Sooke Basin, British Columbia during November 1995 contained apicomplexan cysts. The cysts, which measured 20-150 microns in diameter occurred in several tissues, particularly in the kidney and in connective tissue surrounding the intestine and contained closely packed, banana-shaped zoites that measured about 25 x 4 microns. A pronounced fibrillar layer underlain by labyrinthine structures separated the host tissues from the cyst wall. The apical region of the zoites was reinforced and appeared as an electron-dense, caplike structure. The cysts probably represent a stage of a heteroxenous coccidian life cycle, with a predator of clams serving as the definitive host in which gamogony and sporogony occur.
authors.affiliation: Department of Zoology, University of Toronto, Ontario, Canada.
authors.forename: S S
authors.initials: SS
authors.lastname: Desser
authors.forename: S M
authors.initials: SM
authors.lastname: Bower
mesh_terms: D000818:Animals; D016782:Apicomplexa / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D049872:Bivalvia / Q000469:parasitology*; D001955:British Columbia; D008854:Microscopy, Electron