A new species of Isospora Schneider, 1881 (Apicomplexa: Eimeriidae) from the Bali (Rothschild's) mynah Leucopsar rothschildi (Passeriformes: Sturnidae), and comments concerning the genera Atoxoplasma Garnham, 1950 and Isospora.

A new species of isosporan (Apicomplexa: Eimeriidae) is reported from the Bali mynah Leucopsar rothschildi (Passeriformes: Sturnidae). Oöcysts of Isospora rothschildi n. sp. are spherical to subspherical, 22.3 x 21.6 (20-26 x 19-23) microm, with a shape index (length/width) of 1.03 (1.00-1.15). A micropyle and oöcyst residuum are absent, but one to many polar granules are present. Sporocysts are ovoidal, 15.9 x 10.6 (15-18 x 9.5-11) microm, with Stieda and substieda bodies and a shape index of 1.50 (1.39-1.65). Each sporocyst contains an ellipsoidal sporocyst residuum, 8.0 x 5.8 (6-11 x 5-8), and each sporozoite contains two refractile bodies. No correlation was found between the presence of coccidian oöcysts in the faeces of some of the birds and Atoxoplasma in blood smears.