Saccules

Saccules are terminal structures of ciliate protozoa, best known for their function in cyst formation. They are composed of sac-like vesicles whose external walls are formed from a single layer of ciliary membranes, containing numerous secretory granules and various proteins. Saccules are responsible for the storage and release of secretory and excretory products, including mucous and reproductive materials, and can be used to store energy reserves. They are important for the survival of the organism and play a role in the formation of cysts, aiding in the dispersal of ciliate species. This is especially important for the spread of pathogens and parasites.