Members of this family have 2 flagella which originate anteriorly; one is directed anteriorly and the other posteriorly. The anterior end is more or less drawn out. There are 1 to several contractile vacuoles. There are several genera of free-living and parasitic forms in this family.
These are small, more or less ovoid, plastic forms with an anterior cytostome and a central or anterior nucleus. Cysts are formed.
Bodo caudatus (Dujardin, 1841) Stein, 1878 is a common coprophilic form and also occurs in stale urine and stagnant water. It is 8 to 18 u long and 2.5 to 6 u wide, with a polymorphic body ranging in shape from spherical to elongate ovoid. It has a tiny contractile vacuole, a single vesicular nucleus with a large endosome and a rounded parabasal body. This species and also B. foetus and B. glissans have been found in material from bulls submitted for Tritrichomonas foetus diagnosis.
These are small forms with a plastic body, one flagellum directed anteriorly and the other running backward over the body to become a trailing flagellum. The nucleus is piriform and is connected with the basal granule of the flagella. The cysts are spherical and uninucleate. A number of freshwater and coprophilic species have been described, but it is not clear whether all the species are valid.
Cercomonas longicauda Dujardin, 1841 is a common coprophilic flagellate. Its trophozoites are amoeboid, 2 to 15 u long, have 2 contractile vacuoles, and ingest food by means of pseudopods. Its cysts are 4 to 7 u in diameter.
Cercomonas heimi (Hollande) is similar to C. longicauda but is piriform and has longer flagella.
Cercomonas equi (Sabrazes and Muratet, 1908) (syn., C. asini) was described from the large intestine of the horse and donkey and also occurs in their feces.
Cercomonas faecicola (Woodcock and Lapage, 1915) (syn., Helkesimastix faecicola) was found in the feces of the goat. It is ovoid, with a rigid, pointed anterior end. The anterior flagellum is very short and easily overlooked. The trophozoites are 4 to 6 u long and the cysts 3 to 3.5 u in diameter.
Cercomonas crassicauda Dujardin, 1841 occurs in fresh water and is also coprophilic. It has been found in material from bulls submitted for examination for Tritrichomonas foetus (Morgan and Hawkins, 1952). Its trophozoites measure 10 to 16 by 7 to 10 u.
Noble (1956) found Cercomonas sp. in fresh bovine and porcine feces, and cultivated them in feces in the refrigerator at 4° C for 5 months. Noble (1958) found that Cercomonas sp. appeared in fecal specimens from Wyoming elk, bison, cattle, horses and sheep after storage at 4°C for 6 to 7 days. They persisted for several weeks and then died out. They failed to survive in soil alone or in soil mixed with boiled feces, nor could they be found in soil samples taken from areas where elk, sheep or horses were present. Noble concluded that this and other coprophilic protozoa may require certain essential metabolites produced by bacteria.
The Cercomonas sp. trophozoites observed by Noble (1958) were 5.4 by 2.5 u, somewhat tadpole-shaped, with a broad anterior end tapering to a highly flexible tail-like posterior end. An extremely short anterior flagellum, visible only with phase contrast, extended from a minute subterminal cytostome. Another flagellum arose from the anterior region, passed thru the cytoplasm ventral to the nucleus, emerged about 2/3 of the body length from the anterior end, and continued as a long trailing whip. Eight to 10 large, dark cytoplasmic granules were arranged along this flagellum. The cytoplasm contained a large contractile vacuole and many food vacuoles. The nucleus was vesicular.
The body is somewhat amoeboid. The 2 flagella often appear to emerge separately from the body. The anterior flagellum is very short and often rolled up into a ring. The posterior flagellum is very thick and more than 2 to 3 times the length of the body. There is a single vesicular nucleus. The cyst is spherical, and 4 to 8 young individuals apparently emerge from it.
There is a single species in this genus, Pleuromonas jaculans Perty, 1852, which occurs in stagnant water. It is 6 to 10 u long and about 5 u wide. Uribe (1921) found large numbers of this protozoon in the ceca of young chickens which he had fed Heterakis material, and believed that it could become adapted to parasitism.
The body is spindle-shaped. An anterior and a free trailing flagellum arise from 2 blepharoplasts at the anterior end. The nucleus is anterior to the middle of the body and contains scattered chromatin granules but no endosome. A rhizoplast runs from the blepharoplast to a centrosome on the nuclear membrane. A perirhizoplastic ring surrounds the rhizoplast a short distance behind the blepharoplast; this is considered a parabasal body. A paranuclear body the same size as the nucleus lies beside the nucleus; it divides when the nucleus divides, and stains with hematoxylin but not with protargol. All the species are parasitic. They are common in the intestines of reptiles and amphibia. Synonyms of this genus are Prowazekella Alexeieff, 1912 and Schizobodo Chatton, 1917. Proteromonas brevifilia Alexeieff, 1946 occurs in the cecum of the guinea pig.