Excystation of Isospora arctopitheci Rodhain, 1933 with notes on a similiar process in Isospora begemina (Stiles, 1891) Lühe, 1906.

The in vitro excystation process of sporozoites of Isospora arctophitheci Rodhain, 1933 from the titi marmoset Saguinus geoffroyi and of Isospora bigemina (Stiles, 1891) Lühe, 1906 from the bobcat, Lynx rufus is presented. Sporocysts of both species lack a Stieda body and when exposed to a trypsin-sodium taurocholate (pH 7.4) excysting fluid the walls of both collapse in a similar fashion, along apparently predetermined lines. Similarities and differences on excystation between. I. arctopitheci, I. bigemina, and other Isospora, Eimeria, and Sarcocytis species are summarized. Such studies show that 2 distinct patterns of sporozoite excystation have been described to date, and both appear to be related to the structure of the sporocyst.