Isospora schoenobaeni sp. n. (Protozoa: Eimeriidae) from the Sedge Warbler (Acrocephalus schoenobaenus)

Abstract. Faeces from Acrocephalus schoenobaenus caught on the Courish spit (Baltic Sea) were examined for coccidia. 9 of 15 birds (60%) had undescribed isosporan oocysts in their faeces. Sporulation took 72 hours at 20 °C. Sporulated oocysts of Isospora schoenobaeni sp. n. are spherial, 27.0 (24.3-29.0) μm, with oocyst wall ca. 1.5 μm thick; a polar granule is present, but no oocyst residuum or micropile occurred. Sporocysts are ovoid, 20.7 (18.2-22.4) x 12.8 (12.0-13.8) μm, with a nipple-like Stieda body and a medium substieda body. A sporocyst residuum was present in the from of numerous minute globules, and 4 sporozoites 6.7 x 4.6 μm in average were lying in the sporocysts. This is the first description of Isospora from the genus Acrocephalus.