Apicoplast

This term describes an ovoid organelle that is found just prior to the anterior end of the nucleus of motile stages of Apicomplexa (Sporozoa) such as merozoites, sporozoites, tachyzoites, bradyzoites, cystozoites, etc. In early times of electron microscopy, it was described as thick walled vesicle with an unknown function in stages of e.g., Toxoplasma gondii , Sarcocystis species, Eimeria species, Isospora species, Plasmodium species, etc. Today, high-resolution electron microscopy shows that this organelle possesses four membranes, which apparently originate from a penetrated red algal (prokaryotic) organism being “parasitized” by a chloroplast which formerly had also been a separate organism (Fig. 1). Finally, this red algae was engulfed by an autotrophic protist, the progeny of which later developed by coevolution into the parasite species of our days.

Fig. 1

The diagrammatic representation shows in section (a) an autotrophic protist (yellow, AU), which engulfes an organism, which...