Ultrastructural review of Choleoeimeria spp., a coccidium infecting the gall-bladder epithelium of reptiles.

Choleoeimeria Paperna and Landsberg, 1989 is a reptile coccidium with unique features. Its endogenous development occurs in the cells of the bile epithelium. Its host cell while becoming hypertrophic emerges above the epithelial surface. The following species studied by electron microscopy: C. alloagamae Paperna, 2007 from Agama sp. West Africa; C. allogehyrae Paperna, 2007 from Gehyra australis and C. heteronotis Paperna, 2007 from Heteronotia binoei, from Australia, and C. pachydactyli Paperna and Landsberg, 1989 from Pachydactylus capensis from South Africa. The fine structure of the respective endogenous stages is fairly uniform. The host-cell hypertrophy coincides with a drastic depletion of the microvilli, their junction zone with the underlying cell extends into numerous long and fine membranal out-folds. The PV of all infected cells is filled with typical round granular particles. Young meronts undergo binary fission. The differentiating microgamont develops an expanded multilobed body. Macrogamont's organelles include type 1 and type 2 wall forming bodies, canaliculi and granular bodies, suspected to be the precursors of the sporozoites refractile bodies. The oocyst wall forms from 4 wall-membranes consolidating over the zygote plasmalemma.