Scanning electron microscopy of the oocyst and sporocyst of Toxoplasma gondii.

Oocysts and sporocysts of T. gondii were examined with the scanning electron microscope. The oocysts were slightly ellipsoidal in shape with a smooth outline. The sporocysts were also ellipsoidal with a smooth surface on which there were a number of raised ridges. The ridges represent the junctions between the four plates comprising the sporocyst wall. From the distribution of the ridges it was concluded that the wall consisted of two upper and two lower plates which were at an angle to each other and which interlocked along the mid-line suture. The specific orientation of the plates would provide a structure extremely resistant to mechanical disruption. During excystation, an infolding of the surface was observed along the suture lines between the plates of the sporocyst wall.