a family of structurally complex parasitic infusorians of the order Entodiniomorpha. The body is covered by a strong cuticular shell. Usually there is an internal skeleton and a contained “endoplasmic sac,” which has the function of food digestion. The ciliary cover is not uniform. The Ophryosco-lecidae reproduce by means of division and conjugation (isoga-mous or, less commonly, anisogamous).

There are 34 genera, with 220 species. The organisms are found in the digestive tract of herbivores, including cattle, camels, deer, antelope, sheep, goats, horses, donkeys, mules, zebras, rhinoceroses, tapirs, anthropoid apes, and elephants. Some species are predators and cannibals.

After penetrating the walls of the stomach and intestines, the Ophryoscolecidae enter the bloodstream and carry pathogenic microbes throughout the entire organism of the host. Frequently the infusorians themselves are infected with bacteria, fungi, or other infusorians. The biomass of Ophryoscolecidae in the digestive tracts of host animals is very great. Some scientists believe that the organisms activate the process of fermentation in the rumen of ruminants. Transmission of the parasite from one animal to another occurs by contact (through saliva) or ingestion of manure-polluted feed.