Morphological and molecular characterization of Eimeria paludosa coccidian parasite (Apicomplexa:Eimeriidae) in a dusky moorhen (Gallinula tenebrosa, Gould, 1846) in Australia.

An Eimeria species is described from a dusky moorhen (Gallinula tenebrosa). Sporulated oocysts (n = 40) are ovoid, with a pitted single-layered oocyst wall in young oocysts and a relatively smooth wall in the mature oocysts. Oocyst wall was 1.0 µm thick, oocysts measured 17.3 × 13.3 (16.3-17.9 × 12.7-13.9) µm, oocyst length/width (L/W) ratio, 1.3. Oocyst residuum was absent. A large polar granule was always observed in the centre of the micropyle and many small polar granules were observed when the focus was on the wall. Sporocysts are elongate-ovoid, 8.4 × 5.1 (8.0-8.9 × 4.9-5.5) µm, sporocyst L/W ratio, 1.6 (1.5-1.8), sporocyst residuum was present, composed of numerous granules in a spherical or ovoid mass. Each sporocyst contained 2 elongate sporozoites, 7.7 × 2.6 (7-10 × 2.2-3) µm. A spherical-ellipsoid posterior refractile body was found in the sporozoites. A nucleus is located immediately anterior to the posterior refractile body. When the oocyst measurements and features were compared with valid Eimeria species from hosts in the Rallidae family, this Eimeria species was identified as E. paludosa. This is the first report of E. paludosa in Australia and the dusky moorhen (Gallinula tenebrosa) in a new host for this species. Molecular analysis was conducted at three loci; the 18S and 28S ribosomal RNA genes and the mitochondrial cytochrome oxidase gene (COI). At the 18 S locus, E. paludosa shared 97.3% genetic similarity with Eimeria gruis (GenBank accession number: AB544336). It also shared 99.2% genetic similarity with Eimeria crecis (GenBank accession numbers: HE653904 and HE653905) and 98.5% similarity with Eimeria nenei (GenBank accession numbers: HE653906), both of which were identified from a corncrake (Crex crex) in the United Kingdom. At the 28S locus, E. paludosa shared 91.4% similarity with E. papillata from a chicken (Gallus gallus) in the USA. At COI locus, E. paludosa was in a clade by itself and shared 87.2% similarity with E. irresidua, from a European rabbit (Oryctolagus cuniculus) from the Czech Republic. This is the first molecular characterization of E. paludosa.