Isospora speciosae n. sp. (Apicomplexa: Eimeriidae) from the black-polled yellowthroat Geothlypis speciosa Sclater, 1859 (Passeriformes: Parulidae) in Ciénegas del Lerma, Mexico.

A new coccidian species, Isospora speciosae n. sp. (Apicomplexa: Eimeriidae) collected from the black-polled yellowthroat Geothlypis speciosa Sclater, is reported from the marsh Ciénegas del Lerma Natural Protected Area, Mexico. Sporulated oöcysts of the new species are subespherical to ovoidal, 24-26 × 21-23 (25.7 × 22.2) μm, with a length/width (L/W) ratio of 1.1; one or two polar granules are present, but micropyle and oöcyst residuum are absent. Sporocyts are ovoidal, 17-19 × 9-11 (18.7 × 10.2) μm, with a L/W ratio of 1.8; Stieda and sub-Stieda bodies are both present, but para-Stieda body is absent; sporocyst residuum compact. The new species is the sixth species of Isospora recorded in a bird of the family Parulidae in the New World.