Margolisiella kabatai gen. et sp.n. (Apicomplexa: Eimeriidae), a parasite of native littleneck clams, Protothaca staminea, from British Columbia, Canada, with a taxonomic revision of the coccidian parasites of bivalves (Mollusca: Bivalvia).
Two of 98 native littleneck clams, Protothaca staminea, from Cooper's Cove, Sooke Basin, British Columbia, Canada, were found to be infected with an eimeriid parasite. Merogonic, gamontogonic and sporogonic development were observed in renal tubular epithelial cells. Sporulation of the oocysts occurred within the host. Mature oocysts were spherical (mean diameter 41 µm, range 30-44), and contained about 32 subspherical sporocysts (9 × 10 µm), each of which contained 4 sporozoites. Spherical (19 µm in diameter, range 18-20), cyst-like structures and smaller multinucleate bodies, some of which resembled sporocysts, were also seen. A review of the coccidian parasites of bivalves led to the erection of the new genus, Margolisiella (family Eimeriidae) to accommodate M. kabatai sp. nov. Four previously described monoxenous species (Pseudoklossia patellae, P. chitonis, P. tellinovum and P. haliotis) are transferred to the new genus. The 2 remaining possibly heteroxenous species (P. pelseneeri and P. glomerata) are retained in the genus Pseudoklossia (family Aggregatidae).