Description of the oocysts of Eimeria paludosa (Apicomplexa: Eimeriidae) from Fulica americana (Aves: Gruiformes), with comments on synonyms of eimerian species from related birds.

Between November and December 1988, fecal and intestinal contents were collected from 25 northern American coots, Fulica americana americana, in Arkansas and Texas, and examined for coccidial parasites. Seventeen (68%) of the coots were infected with Eimeria paludosa, herein described; for the first time, photomicrographs of the species are presented. Sporulated oocysts are ovoid, 16.5 x 12.6 (15-23 x 11-14) microns, with a lightly to heavily pitted single-layered wall; an oocyst residuum is absent, but a prominent micropyle is present. A large, or several smaller, polar granule(s) is present, usually located beneath the micropyle. Sporocysts are elongate-ovoid, 10.8 x 6.2 (10-12 x 5-7) microns, with Stieda and substieda bodies. A sporocyst residuum is present, normally composed of very fine faint granules scattered among the sporozoites or, rarely, as a spherical mass. Sporozoites are elongate, 8.7 x 2.7 (7-11 x 2-3) microns, in situ. Each sporozoite contains a spherical-ellipsoid posterior refractile body and occasionally a spherical anterior refractile body. A nucleus is located immediately anterior to the posterior refractile body. The occurrence of E. paludosa in F. a. americana is a new host and geographic record for the parasite. In addition, several of the previously described eimerian species from gruiform birds are proposed to be synonyms of E. paludosa.