Cryptosporidium, sometimes called crypto, is an apicomplexan genus of alveolates which are parasites that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves watery diarrhea, sometimes with a persistent cough.
Cryptosporidium
Image: lossy page 1 Cryptosporidium outbreak in S Devon 1995.tif
The Apicomplexa are organisms of a large phylum of mainly parasitic alveolates. Most possess a unique form of organelle structure that comprises a type of (non-photosynthetic) plastid called an apicoplast—with an apical complex membrane. The organelle's apical shape is an adaptation that the apicomplexan applies in penetrating a host cell.
Trophozoite of a gregarine
Dividing Toxoplasma gondii (Coccidia) parasites
Trophozoites of the Plasmodium vivax (Haemosporidia) parasite among human red blood cells
Two tachyzoites of Toxoplasma gondii, transmission electron microscopy