Isospora pichororei n. sp. (Chromista: Apicomplexa: Eimeriidae) from rufous-capped spinetails Synallaxis ruficapilla Vieillot, 1819 (Passeriformes: Furnariidae: Synallaxiinae) in South America.

Spinetails are a suboscine passerines of the genus Synallaxis Vieillot, 1818 which have great interest for ornithology, given the wide diversity of 37 species that are distributed throughout the Neotropical region. Despite this wide diversity and distribution, Synallaxis spp. have never been recorded as hosts of coccidian parasites. In this context, the current study describes a new species of Isospora Schneider, 1881 from rufous-capped spinetails Synallaxis ruficapilla Vieillot, 1819 captured in the Itatiaia National Park, which is a federal conservation unit in Southeastern Brazil. The oocysts of Isospora pichororei Genovez-Oliveira & Berto n. sp. are subspheroidal to ovoidal, measuring on average 25 by 21 μm. Micropyle is present, but discrete. Oocyst residuum absent, but one or two polar granules are present. Sporocysts are ellipsoidal with slightly pointed posterior end, measuring on average 17 by 10 μm. Stieda and sub-Stieda bodies are present. Sporocyst residuum is clustered among the vermiform sporozoites, which have striations, refractile bodies and nucleus. This morphology was different from the other Isospora spp. recorded in the host family Furnariidae. Molecular identification was targeted by the amplification and sequencing of a locus of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. This sequence had the highest similarity of 99.5% with a sequence deposited for Isospora oliveirai Ortúzar-Ferreira & Berto, 2020, which is a coccidian species that parasitizes suboscine tityrids Schiffornis virescens (Lafresnaye, 1838), also in the Itatiaia National Park. Phylogenetic analysis grouped some species in subclades, including I. pichororei with I. oliveirai; however, it was inconclusive in an expectation of parasite-host coevolution. Finally, I. pichororei is established as new to science, being the first description from Synallaxinae and the third description from Furnariidae. Furthermore, this is the first Isospora sp. from the host family Furnariidae to have a molecular supplementation by sequencing a locus of the cox1 gene of the mitochondrial genome.