In this family there is a single nucleus and 4 flagella, 1 or 2 of which may be trailing. Enteromonas is parasitic in domestic and laboratory animals, and Tetramitus is coprophilic.
In this genus the life cycle involves flagellate and amoeboid forms; there are also uninucleate cysts. In the flagellate stage the body is ellipsoidal or piriform, with a large, trough-shaped cytostome at the anterior end, a vesicular nucleus with a large endosome, 4 anterior flagella, and a contractile vacuole. Nutrition is holozoic.
Tetramitus rostratus Perty, 1852 (syn., Copromastix prowazeki Aragao, 1916) is found in stagnant water and is also coprophilic. It has been found in human and rat feces. The flagellate stage is 14 to 18 u long and 7 to 10 u wide. The amoeboid stage is 14 to 48 u long and usually has a single lobose pseudopod. The cysts are spherical, thin-walled, and 6 to 18 u in diameter. The life cycle of this species has been studied by Bunting (1926), Bunting and Wenrich (1929) and Hollande (1942).
The body is spherical or piriform and is plastic. It has 3 short anterior flagella, 1 of which may be difficult to see, and a 4th, long flagellum which runs along the flattened body surface and extends free for a short distance at the posterior end of the body. A strand-like funis arises from the blepharoplast and extends posteriorly along the body surface; it stains faintly with iron hematoxylin and strongly with protargol. The nucleus is anterior, vesicular, with or without an endosome. There is no cytostome. The cysts are ovoid, and are tetranucleate when mature. A synonym of this genus is Tricercomonas Wenyon and O'Connor, 1917. This genus has been reported from a number of mammals.
Enteromonas hominis da Fonseca, 1915 (synonyms, Octomitus hominis, Tricercomonas intestinalis, Diplocercomonas soudanensis, Enteromonas bengalensis) occurs in the cecum of man, macaques (Macaca mulatta, M. sinica, M. nemestrina) the golden hamster and probably other animals thruout the world. Wantland (1955) reported it in l%of 500 golden hamsters in the United States. Saxe (1954) transmitted it from the golden hamster to the laboratory rat. Dobell (1934) was unable to infect himself with a culture of E. hominis from the macaque, M. sinica, but believed that future work would show that the human and macaque forms are the same species. Simitch et al. (1959) reported failure to transmit E. hominis to 2 young pigs.
The trophozoite is oval, 4 to 10 by 3 to 6 u, and has many food vacuoles containing bacteria. The cysts are ovoid or ellipsoidal; they are usually binucleate but have 4 nuclei when mature. E. hominis is readily cultivated on the usual media for enteric protozoa such as LES medium; cysts form in the cultures. It is non-pathogenic.
Enteromonas suis (Knowles and Das Gupta, 1929) Dobell, 1935 (syn., Tricercomonas suis) was described from the cecum of a pig in India. It was cultivated easily in Dobell and Laidlaw’s medium. It is shaped like a broad, ovate leaf with a more or less rounded anterior end and a pointed posterior end, and is 9 to 20 u long and 6 to 14 u wide. It moves sluggishly more or less directly forward and does not rotate like Trichomonas. The three anterior flagella are 8 to 18 u long with a mean of 14 u, and the posterior flagellum is 9 to 26 u long with a mean of 17 u. Simitch et al. (1959) found it in 2% of 1800 pigs in Yugoslavia.