Afternoon shedding of a new species of Isospora (Apicomplexa) in the endangered Regent Honeyeater (Xanthomyza phrygia)

Abstract

The Regent Honeyeater (Xanthomyza phyrigia) is an endangered Australian bird species. Breeding populations have been established at Australian zoos in support of re-introduction programs. This species is the host of a new species of Isospora (Apicomplexa). Oocysts are spherical, 25.8 (22.5- 28.75) by 23.8 (20-26.25) µm with a colourless to pale yellow smooth wall undergoing rapid exogenous sporulation, 90% sporulated oocysts in 8 hours at 20 C. Each oocyst contains one polar granule. Sporocysts are ovoid, 18.67 (17-19) by 9.49 (9-10) µm with a flat Stieda body and spherical substieda body devoid of a hyaline body. The asexual stages and sexual phase is within the enterocytes of the duodenum and jejunum. Faeces collected in the morning (AM, n=84) and in the afternoon (PM, n=90) revealed significant diurnal periodicity in oocyst shedding; 21% (18 of 84) of the AM were positive with the mean of 499 oocysts.g-1 compared to the PM with 91% (82 of 90) bird faeces positive with the mean of 129,723 oocysts.g-1. Therefore, parasite checks for these birds should be carried out in the afternoon to obtain an accurate result. In conclusion, it is plausible that captive birds with high parasite burdens could be less likely selected by females for reproduction after release due to their duller plumage than their wild counterparts. Keywords: coccidia, Isospora, Regent Honeyeater, honeyeater, diurnal shedding, oocysts, recovery program.