Morphological and molecular characterisation of Isospora butcherae n. sp. in a silvereye (Zosterops lateralis) (Latham, 1801)

A new Isospora (Apicomplexa:Eimeriidae) species is described from a silvereye (Zosterops lateralis) in Western Australia. Sporulated oocysts of this species are spherical, 24.2 (23.1–25.2) × 23.3 (22.8–23.9) μm, with a shape index (length/width) of 1.02, and with a smooth bi-layered oocyst wall, 1.2 μm thick (outer layer 0.9 μm, inner 0.3 μm). A polar granule is present, but the oocyst residuum and a micropyle are absent. The ovoid-shaped sporocysts are 16.1 (15.7–17.3) × 10.5 (15.7–17.3) μm and have a shape index of 1.53. A hemidome-shaped Stieda and a rectangular-shaped substieda body are present. A sporocyst residuum is present and composed of numerous granules of different sizes scattered among the sporozoites. The oocysts from this isolate are morphologically different from those of all known Isospora spp. This coccidian parasite was molecularly characterised at the 18S, 28S ribosomal RNA and the mitochondrial cytochrome oxidase (COI) gene. At the 18S locus, based on 1210 bp of sequence, this new isolate exhibited 99.9, 99.8, 99.7 and 99.5% similarity to I. sp. MAH-2013a (KF648870) from a superb starling (Lamprotornis superbus) in Canada, I. sp. MS-2003 (AY33157) from a Southern cape sparrow (Plocepasser mahali) in America, I. sp. Tokyo (AB75786) from Japan and I. sp. respectively. Further analysis of a subgroup of 300 bp long 18S sequences (n = 11), including I. anthochaerae and the other three Isospora characterised from birds in Western Australia, revealed that I. butcherae n. sp. exhibited 98.3% similarity to both I. sp. MAH-2013a (KF648870) and I. MS-2003 (AY33171). At the 28S locus, this new isolate exhibited 97.3% similarity with I. sp. MS-2003 from a California towhee (Melozone crissalis). At the COI locus, this new isolate exhibited 99.8% similarity to I. neochmiae from a red-browed finch. Based on morphological and molecular data, this isolate is a new species of Isospora, which is named Isospora butcherae n. sp. after Mrs. June Butcher for her lifelong dedication as a wildlife rehabilitator. Graphical abstract ᅟ