A new Isospora species (Apicomplexa: Eimeriidae) from Taiwan Blue Magpie (Urocissa caerulea) (Passeriformes: Corvidae) with the first complete corvid coccidian mitogenome

Passerine birds are highly susceptible to Isospora infections, yet the coccidian fauna of endemic Taiwanese avifauna remains largely unexplored. Here, we describe Isospora kwongchungi n. sp. (Apicomplexa: Eimeriidae) from the Taiwan Blue Magpie ( Urocissa caerulea , Corvidae), utilizing an integrative taxonomic approach. Morphological characterization was complemented by Sanger sequencing of the nuclear 18S ribosomal RNA (rRNA) gene (1,679 bp) and Oxford Nanopore Technologies (ONT) long-read sequencing of the complete mitochondrial genome (6,251 bp). Sporulated oocysts are subspherical to spherical (28.9 × 26.4 μm) with a smooth, single-layered wall, possessing both a polar granule and a distinct oocyst residuum. Sporocysts are ovoid (22.3 × 13.6 μm) and feature a knob-like to bubble-shaped Stieda body, a rounded substieda body, and a compact ellipsoidal sporocyst residuum. While the 18S rRNA gene phylogeny exhibited limited intrageneric resolution, the concatenated tree of three mitochondrial protein-coding genes robustly placed I. kwongchungi n. sp. in a clade with Isospora spp. from the invasive Javan myna ( Acridotheres javanicus , Sturnidae) and the American robin ( Turdus migratorius , Turdidae). This study establishes a molecular anchor for corvid-associated Isospora and highlights the efficacy of combining traditional and next-generation sequencing in resolving the evolutionary dynamics of wildlife parasites.