64 



COLLEGE ZOOLOGY 



of mating type II; and members of mating 

 type II do not conjugate with each other but 

 vill conjugate with members of mating 

 type I, To determine the character of speci- 

 mens of an unknown mating type, it is nec- 

 essary to add them to a culture containing 

 mating type I. If they conjugate with mem- 

 bers of mating type I, they belong to mating 

 type II; if they do not, they belong to mat- 

 ing type I. 



OTHER CILIATA 



Ciliata are widespread in nature. Many 

 species live in fresh water; other species oc- 

 cur in the sea, in the soil, and upon or within 

 the bodies of other animals. 



Most of the ciliates are not parasites and 

 are therefore said to be free-living. Those 

 shown in Fig. 31 are representative of some 

 of the more interesting free-living forms. 



Tetrahymena, a small ciliate (Fig. 31) 

 grows in a culture medium free from all 

 other microscopic organisms and has about 

 the same nutritional requirements as man 

 himself. Studies show it must have a diet of 

 vitamins, amino acids, salts, and sugar. This 

 suggests that even a single-celled animal has 

 physiologic processes nearly as complex as 

 those in man. This tiny organism is playing 

 an increasingly important role in physiologic 

 and genetic research. 



Stentor is trumpet-shaped, bluish in color, 

 has a beaded macronucleus, and cilia spirally 

 arranged around the "mouth"; it may be 

 free-swimming or attached, and at the an- 

 terior end is a complicated disk of cilia. 

 Stylonychia has a flattened body and groups 

 of cilia fused to form cirri, which are used 

 as "legs" in creeping. Vorticella resembles 

 an inverted bell attached to a stalk. 



Parasitic ciliates 



One well-known parasitic species of ciliate 

 lives in man (Fig. 38). Many domesticated 

 and wild animals, both terrestrial and 

 aquatic, are parasitized by ciliates, most of 



which live in the digestive tract. Species be- 

 longing to the genus Opalina are common 

 in the rectum of certain frogs and toads; 

 Opalina (Fig. 31) contains many nuclei of 

 one type. One ciliate lives in the intestine 

 of the earthworm. About 40 species of 

 ciliates live in the first and second chambers 

 of the stomach of cattle, and some are very 

 complex in structure. These may be only 

 mess mates (commensals) without either 

 benefit or harm to cattle. Two common spe- 

 cies of ciliates creep about on the bodies of 

 certain aquatic animals and frequently oc- 

 cur on the fresh-water hydra; these are 

 Kerona (Fig. 32) and Trichodina. Many of 

 the Suctoria are parasitic; one {Podophrya) 

 is of particular interest because it parasitizes 

 other ciliates. 



CLASSIFICATION OF 

 THE CILIATA 



{For reference purposes only) 



Ciliata possess cilia at some stage in their 

 life cycle. In most of them the nuclear mate- 

 rial is separated into a large macronucleus and 

 a smaller micronucleus. Most of them are free- 

 living in fresh water or the sea, but many are 

 parasites of other animals. They may be sepa- 

 rated into two classes and four orders as fol- 

 lows : 



Class 1. Ciliata. Cilia present throughout life; 

 "tentacles" absent. 



Order 1. Holotricha. Cilia typically of 

 equal length all over the body; 

 no adoral cilia. Ex. Paramecium 

 caudatum (Fig. 25) and Chilo- 

 donella (Fig. 31). 



Order 2. Spirotricha. Cilia covering en- 

 tire body, an adoral zone of 

 either large cilia or membranel- 

 les, which are wound to the left 

 along the oral groove. Exs. 

 Stentor coeruleus (Fig. 31) and 

 Balantidium. 



Order 3. Hypotricha. Dorsoventrally flat- 

 tened; with cilia, cirri, and 

 membranelles. Ex. Stylonychia 

 mytilus (Fig. 31). 



