Members of this family have a single nucleus and a compact antero-lateral group of flagella which beat as a unit. There are 2 genera, Callimastix and Selenomonas.
The body is ovoid, with a compact central or anterior nucleus. There are 12 to 15 long flagella near the anterior end which beat in unison. One species occurs in the body cavity of copepods and the others in ruminants and equids. They are non-pathogenic.
Callimastix frontalis Braune, 1913 occurs in the rumen of cattle, sheep and goats thruout the world. Becker and Talbot (1927) reported it in Iowa. The body is spherical or ovoid, about 12 to 14 u in diameter. The nucleus has a large central endosome. The 12 flagella are about 30 u, long; they arise from a row of basal granules on the anterior margin of the body and join to form a single unit distally. This species has been found in material submitted for diagnosis of Tritrichomonas foetus infections (Morgan and Hawkins, 1952).
Callimastix equi Hsiung, 1929 occurs in the cecum and colon of the horse. The body is kidney-shaped with the hilus at its anterior third; it is 12 to 18 u long and 7 to 10 u wide with a mean of 14 by 8 u. Just behind the hilus is a clear, granule-free area on the margin of which are 12 to 15 basal granules which give rise to flagella 25 to 30 u long; these unite distally and function as a unit. The rest of the cytoplasm is filled with deeply staining granules. The nucleus is 3 u in diameter has a large endosome and lies near the center of the body.
The body is kidney- to crescent-shaped, with blunt ends. One or more flagella are attached to the middle of the concave side. The flagella are thicker at the base than at the free end and are usually 1 to 1.5 times as long as the body. The nucleus is highly refractile and lies on the concave side near the base of the flagella. Reproduction is by transverse binary fission thru the flagellar region. This genus has been placed by many authors in the Spirillaceae among the bacteria, but Jeynes (1955, 1956) showed that it is actually a protozoon. It is not pathogenic.
Selenomonas ruminantium (Certes, 1889) Wenyon, 1926 (syns., Ancyromonas ruminantium, Selenomastix ruminantium) occurs in the rumen of cattle, sheep, goats and various wild ruminants including the gazelle, giraffe, antelope (Cephalophus maxwelli) in Africa and the pronghorn antelope (Antilocapra americana), deer (Odocoileus hemionus) and elk (Cervus nannodes) in the United States (California). It was also found in the blood of the African antelope by Kerandel (1909), of the pronghorn antelope by Chattin, Herman and Kirby (1944) and of the deer (O. hemionus) by Herman and Sayama (1951) in California. According to Lessel (1957), S. ruminantium is the predominant organism found on microscopic examination of the rumen juices.
The body of S. ruminantium is crescent-shaped, 9.5 to 11 by 2 to 3 u, with a tuft of flagella arising from the center of the concave side. The nucleus is in the center of the concave side. There are no cysts. This species has not been cultivated.
Selenomonas palpitans Simons, 1922 occurs in the cecum and upper part of the colon of the guinea pig.
S. sputigena (Flugge, 1886) Dobell, 1932 occurs in the mouth of man. It grows well in thioglycollate broth.