348 



THE CILIATES 



of membranelles) is usually absent or 

 inconspicuous. This subclass contains 4 

 orders of veterinary interest. In the order 

 Gymnostomorida ("naked mouth"), the cyto- 

 stome opens directly at the surface or else 

 into a slight depression which has no oral 

 ciliature. This order includes 2 families 

 of which members occur in the large in- 

 testine of equids or ruminants or in the 

 rumen and reticulum of ruminants. 



In the order Suctoriorida only the 

 young have cilia, while the adults have 

 tentacles. All members of this order are 

 free-living except for one genus which 

 occurs in the large intestine of equids. 



In the order Trichostomorida ("hair 

 mouth"), the cytostome is usually at the 

 base of a well-defined oral pit or vesti- 

 bulum, which in turn may sometimes be 

 preceded by an oral groove. The vesti- 

 bular wall bears 1 or more dense fields 

 of adoral (vestibular) cilia. The great 

 majority of trichostomes are free-living, 

 but there are 5 families which contain 

 parasites of domestic animals. 



In the order Hymenostomorida ("mem- 

 brane mouth"), the adoral cilia are fused 

 in membranes, the number, size and ar- 

 rangement of which vary in different gen- 

 era. The free-living genera Paramecium 

 and Tetrahymena belong to this order; the 

 latter is occasionally parasitic. The most 

 important parasite in the order is Ichthyo- 

 phthirius, which is often a serious patho- 

 gen of aquarium fish, causing a disease 

 known as "ick. " 



iorida contains a group of remarkably 

 bizarre genera which occur in ruminants 

 and equids. In this order, ciliation may 

 be limited to the adoral zone or there may 

 be 1 or more additional bands or groups of 

 membranelles. The internal anatomy is 

 complex, and unique "skeletal plates" may 

 be present. There are 2 families. The 

 Ophryoscolecidae have not more than 1 

 "dorsal" or "metoral" band of membran- 

 elles in addition to the adoral zone and 

 occur in the rumen and reticulum of rum- 

 inants. The Cycloposthiidae have 2 or 

 more bands of membranelles in addition to 

 the adoral zone, and occur in the large in- 

 testine of equids and also of anthropoid 

 apes. 



A. CILIATES OF RUMINANTS 



A tremendous number and bewildering 

 variety of ciliates swarm in the rumen and 

 reticulum of ruminants, and a few species 

 occur in the large intestine. Many are 

 holotrichs, but the most bizarre ones are 

 ophryoscolecids. No attempt will be made 

 here to differentiate all the species, but 

 the genera will be described and the prin- 

 cipal species mentioned, and the relations 

 of the different groups to their hosts will 

 be discussed. Further taxonomic and 

 morphologic information is given by Becker 

 and Talbot (1927), Dogiel (1927), Kofoid 

 and Mac Lennan (1930, 1932), Chavarria 

 (1933), Polyansky and Strelkov (1938) and 

 Lubinsky (1957). 



In the subclass Spirotrichasina, the 

 buccal ciliature, and especially the multi- 

 partite adoral zone of membranelles, is 

 conspicuously developed. The body cili- 

 ature is typically sparse, and all the sim- 

 ple cilia may even be replaced by cirri; in 

 one order, the Heterotrichorida, however, 

 the body ciliation is usually complete. 



This subclass contains 2 orders of 

 veterinary interest. In the order Hetero- 

 trichorida the somatic ciliation is usually 

 complete. One genus in this order, Nycto- 

 therus, occurs in amphibia and various in- 

 vertebrates, but has also been found in the 

 feces of ruminants. The order Entodin- 



FAMILY BUETSCHLIIDAE 



In this holotrichasin gymnostomorid 

 family, the cytostome is usually at the 

 anterior end, there are ordinarily a poster- 

 ior cytopyge, one or more contractile vac- 

 uoles and an anterior concretion vacuole 

 which some authors think is a statocyst. 

 Cilia are uniformly distributed over the 

 body or are restricted to certain areas. 

 This family includes a number of genera 

 and species, the great majority of which 

 occur in the cecum and colon of equids. 

 One genus, however, is found in the rumen 

 of cattle and camels. 



