Family Isotrichidae

In this holotrichasin trichostomorid family, the mouth is terminal or subterminal, and the pharynx is ciliated, with longitudinal striations in its wall. Somatic ciliation is complete and practically uniform. This family contains the 2 most important holotrich genera of ruminants.

Genus Isotricha

The body is oval and flattened, with dense, longitudinal rows of cilia. The cytostome is at or near the anterior end. Several contractile vacuoles are present. The macronucleus is kidney-shaped; it and the micronucleus are connected to each other and suspended by fibrils which constitute the karyophore. Locomotion is toward the rear.

Isotricha prostoma Stein, 1859 is the most widely distributed of all the ruminant ciliates. It occurs in the rumen and reticulum of cattle, sheep and goats. Becker and Talbott (1927) found it in 58% of 26 cattle in Iowa. It measures 80 to 195 by 53 to 85 u, and its cytostome is subterminal.

I. intestinalis Stein, 1859 also occurs in the rumen and reticulum of cattle, sheep and goats. Becker and Talbott (1927) found it in 19% of 26 cattle in Iowa. It measures 97 to 130 by 68 to 88 u, and differs from I. prostoma in that its cytostome and nucleus are more posterior.

Genus Dasytricha

The body is oval and flattened. The cilia are in spiral, longitudinal rows. There is no karyophore.

Dasytricha ruminantium Schuberg, 1888 occurs in the rumen and reticulum of cattle, sheep and goats. Becker and Talbott (1927) found it in 38% of 26 cattle in Iowa. It measures 50 to 75 by 30 to 40 u.