Isospora serinuse n. sp. (Apicomplexa: Eimeriidae) from a domestic canary (Serinus canaria forma domestica) (Passeriformes: Fringillidae) in Western Australia.

A new species, Isospora serinuse n. sp., (Apicomplexa:Eimeriidae) is described from a single domestic canary (Serinus canaria forma domestica) (subspecies S. c. domestica) in Western Australia. Sporulated oocysts of Isospora serinuse n. sp. are spherical or subspherical, 25.5 (24.4-27.0) × 23.5 (22.0-24.8) µm, with a shape index (length/width) of 1.09; and a smooth bilayered oocyst wall, 1.2 µm thick (outer layer 0.9 µm, inner 0.3 µm). A polar granule is present, but a micropyle and oocyst residuum are absent. The sporocysts are lemon-shaped, 18.9 (17.8-20.2) × 11.8 (10.6-13.0) µm, with a shape index of 1.6. Stieda and substieda bodies are present, the Stieda body being a small crescent shape and the substieda being indistinct. Each sporocyst with four vermiform sporozoites arranged head to tail. A sporocyst residuum is present and composed of numerous granules of different sizes that are scattered among the sporozoites. Morphologically, the oocysts of Isospora serinuse n. sp. were different from those of all known valid Isospora spp. Molecular analysis was conducted at 3 loci: the 18S and 28S ribosomal RNA and two separate regions of subunit I of the mitochondrial cytochrome oxidase (COI) gene (designated COIa and COIb). At the 18S locus, Isospora serinuse n. sp. exhibited 97.5% similarity to Isospora sp. Tokyo from a domestic pigeon (Columba livia domestica) in Japan. At the 28S locus, I. serinuse n. sp. exhibited 94.9% similarity to Isospora anthochaerae n. sp. from a red wattlebird (Anthochaera carunculata) in Australia. At the COIa locus, I. serinuse n. sp. exhibited 95.7% similarity to Isospora sospora sp. ex Apodemus flavicollis from a yellow-necked mouse and Isospora gryphoni from an American goldfinch (Carduelis tristis) respectively. At the COIb locus, I. serinuse n. sp. exhibited 96.7% similarity to an Isospora (iSAT4) from a European pied flycatcher (Ficedula hypoleuca). Based on morphological and molecular data, this isolate is a new species of Isospora, which is named Isospora serinuse n. sp. after its host, the domestic canary (S. canaria forma domestica).