Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

The macrogametes of Toxoplasma gondii develop within the epithelial cells of the cat ileum. As they develop the nucleus enlarges and dense patches of chromatin which were present in the nucleoplasm, disappear. Polysaccharide granules and lipid globules appear in the cytoplasm and increase in number during development. The wall-forming bodies of Type I (WFB I) appear before the wall-forming bodies of Type II (WFB II); WFB I are smaller, more osmiophilic and more numerous than the WFB II. The WFB I appear to form from vesicles produced by the smooth endoplasmic reticulum, and the WFB II form within the lacunae of the rough endoplasmic reticulum. Double membraned vacuoles appear to form from the nuclear membranes but the function of these is unknown. Throughout development the macrogamete retains a normal pellicle which possesses numerous micropores. The first evidence of oocyst wall formation is the appearance of participate matter in the parasitophorous vacuole which precipitates to form Layer 1 of the oocyst wall. Layers 2 and 3 are unit membranes which form between Layer 1 and the pellicle. During this development the organism has an organelle complement similar to that of the macrogamete. Layers 4 and 5 form between Layer 3 and the pellicle. Layer 4 is osmiophilic and its formation is accompanied by the disappearance of WFB I. Layer 5 is less osmiophilic than Layer 4 and its formation is accompanied by the disappearance of WFB II. The two innermost layers (Layers 4 & 5) in the oocyst wall of Toxoplasma are similar to those found in Isospora spp. and Eimeria spp. Toxoplasma seems to be unusual in that, firstly, it possesses an additional 3 layers and, secondly, all 5 layers are formed outside the pellicle of the original macrogamete.


Journal article


Acta Pathol Microbiol Scand B

Publication Date





491 - 505


Animals, Cats, Cell Membrane, Cell Nucleolus, Cell Nucleus, Cell Wall, Chromatin, Cytoplasm, Cytoplasmic Granules, Endoplasmic Reticulum, Germ Cells, Golgi Apparatus, Ileum, Mitochondria, Toxoplasma