Ultrastructure of erythrocytic stages of avian Plasmodium spp. of the sub-genus Novyella and its 'globule'

A globule frequently refractory, appearing blue, pale blue, or white with Giemsa stain, is characteristic of the intraerythrocytic stages of the type species and of most of the other species included at present in the sub-genus Novyella. This globule is absent from the other Plasmodium sub-genera. An ultrastructural study has been performed on schizogonic stages of Plasmodium merulae from the blood of the blackbird, Turdus merula. In section the globule contains a finely granular substance suggesting a condensed or coagulated substance. It differs distinctly from a classical food vacuole by denser contents, and show in some sections (19, 23) a peripheral opaque rim with a radial arrangement of ribosomes. Except for the presence of the globule, in other details P. merulae do not diverge from the ultrastructure common to the intraerythrocytic stages of avian Plasmodium.