A New Isospora (Apicomplexa: Eimeriidae) from the Dark-Eyed Junco, Junco hyemalis (L.) (Passeriformes: Passerellidae), in West-Central Arkansas, USA

Purpose

Many passeriform birds are excellent hosts of coccidian parasites but little is known of the coccidians infecting members of the family Passerellidae, particularly from the dark-eyed junco, Junco hyemalis (Linnaeus, 1758). Here, we report from morphometric and mensural data a new species of Isospora from J. hyemalis in Arkansas, USA.

Methods

During November 2020, seven adult J. hyemalis were taken with a mist net from Polk County, Arkansas, USA, and their faecal samples examined for coccidian parasites. Samples were placed in individual vials containing aqueous potassium dichromate. They were examined for coccidia after flotation in Sheather’s sugar solution, measured, and photographed.

Results

A single J. hyemalis (14%) was found to be passing a new species of Isospora. Oöcysts of Isospora pittmani n. sp. were spheroidal to subspheroidal with a smooth bi-layered wall, measured (L × W) 24.8 × 23.8 µm, and had a length/width (L/W) ratio of 1.04; a micropyle and oöcyst residuum was absent but typically one to up to four polar granule(s) was present. Sporocysts are ovoidal to ellipsoidal and measured 15.0 × 10.0 µm, L/W 1.5; a flattened Stieda body was present as well as a barely discernible sub-Stieda body but para-Stieda bodies were absent. The sporocyst residuum was composed of various-sized granules dispersed between and across the sporozoites. A spheroidal to ellipsoidal posterior refractile body and spheroidal anterior refractile body occasionally seen, but a nucleus was not observed. Only two previous isosporans have been reported from passerellid birds and the new species can readily be distinguished from them.

Conclusion

This is the first coccidian reported from J. hyemalis and, more importantly, the first isosporan known from any member of the family Passerellidae in North America.