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& Walkosz, 1975). The transformation of 
the telotroch to a stalked zooid has been studied in 
the colonial Zoothamnium and solitary Vorticella , 
under controlled culture conditions (Suchard & 
Goode, 1982; Vacchiano et al., 1992). Stalk forma-
tion requires microtubules to transport secretory 
vesicles to the sites of exocytosis as the stalk forms 
and elongates (Suchard & Goode, 1982). 
Fig. 15.6. Schematics of the somatic kinetids of the Class OLIGOHYMENOPHOREA . ( a–d ) Kinetids of the 
Subclass Peniculia . ( a–c ) Dikinetids of the Order Peniculida – Paramecium ( a ), Disematostoma ( b ), Frontonia ( c ). 
(d ) Monokinetid of the Subclass Peniculia and Order Urocentrida – Urocentrum . ( e , f ) Monokinetids of the Subclass 
 Apostomatia – Hyalophysa ( e ) and Collinia ( f ) (from Lynn, 1981, 1991)
 The stalk of sessiline peritrichs is composed of 
the secreted outer sheath that surrounds, in some 
species, an extension of the zooid ’s cytoplasm. The 
bulk of this extension is filled with a contractile 
myoneme , called the spasmoneme (Allen, 1973a, 
1973b). The spasmoneme is continuous with the 
filamentous myonemes in the zooid itself, and 
these, in turn, are attached by a linkage complex 
to adjacent cisternae of endoplasmic reticulum, 
which may be the sites for Ca 2+ necessary to induce 
contraction (Allen, 1973a, 1973b). The contractile 
proteins of the spasmoneme are not related to actin 
or myosin , and have therefore been termed spas-
mins (Amos, Routledge, & Yew, 1975; Routledge, 
1978). Spasmins , which are related to centrin and 
 calmodulin , may not be solely responsible for 
contraction (Asai, Ninomiya, Kono, & Moriyama, 
1998). In addition to these filamentous myonemes 
of the zooid , there are other contractile filaments 
that retract the epistomial disk and there is a collar 
 sphincter that closes the apical pole (Lom, 1994). 
 The other major group of peritrichs , the mobilines , 
are distinguished by an aboral adhesive disk (Fig. 
15.3). On its oral side, the adhesive disk is bounded 
by a locomotor fringe , organized in three compo-
nents in trichodinids: an “oral” or superior girdle of 
solitary or paired lateral cilia; a locomotor wreath 
or middle girdle, composed of oblique rows of 3–8 
kinetosomes, reminiscent of the telotroch girdle of 
Opisthonecta ; and an “aboral” or inferior girdle 
of groups, typically pairs of kinetosomes and cilia 
(Hausmann & Hausmann, 1981a; Maslin-Leny 
& Bohatier, 1984). Fibrillar rootlets attach the kine-
tosomes of the inferior and middle girdles respec-
tively to the outer peripheral pin and middle radial 
pin of the skeletal components of the adhesive disk 
(Hausmann & Hausmann, 1981b). The radial pins 
articulate with the innermost skeletal element, the 
Fig. 15.7. Schematics of the somatic kinetids of the Class OLIGOHYMENOPHOREA . ( a–e ) Kinetids of the 
Subclass Hymenostomatia – Monokinetids of Tetrahymena ( a ), Glaucoma ( b ), Colpidium ( d ), and Ichthyophthirius
(e ). Dikinetid of Colpidium ( c ). ( f ) Monokinetid of the Subclass Astomatia – Coelophrya (from Lynn, 1981, 1991)
15.3 Somatic Structures 305
 denticles , which have been traditionally used after 
 silver staining , to discriminate genera and species. 
The denticles have a complex structure whose 
detailed anatomy has only recently been revealed 
by scanning electron microscopy preceded by 
either nitric acid dilution (Kruger, Basson, & Van 
As, 1993) or sonication (Gaze & Wootten, 1999). 
To further complicate the interpretation of these 
 denticles in a taxonomic context, their relative 
morphology can change as the diameter of the 
mobiline body increases (Kazubski, 1967). Given 
these insights, molecular genetic studies are now 
required to test the robustness of a taxonomy that is 
based primarily on denticle morphology. 
 Oligohymenophoreans are rarely found within 
 loricas or other secreted structures. Among the 
free-living forms, the scuticociliate Calyptotricha
is an exception, building a tube-like lorica in which 
it lives (Wilbert & Foissner, 1980). However, the 
 peritrichs include several families characterized by 
the form and diversity of their loricas , which can 
have a smooth or more architectured surface (e.g., 
Couch, 1973; Clamp, 1987, 1990, 1991, 1992; 
Finley & Bacon, 1965; Warren & Carey, 1983). 
The lorica is a structure, primarily proteinaceous, 
which is likely secreted by the scopula in some 
species (González, 1979). The lorica of Platycola
apparently sequesters heavy metals , such as manga-
nese , preferentially concentrating them above their 
environmental concentrations (Warren & Carey, 
1983). Undoubtedly the most conspicuous secreted 
structure among peritrichs , and perhaps ciliates 
as a phylum, is the gelatinous matrix secreted by 
Ophrydium species, which can range from 2 cm 
in diameter up to 30 cm in diameter (Duval & 
Margulis, 1995; Winkler & Corliss, 1965). 
Fig. 15.8. Schematics of the somatic kinetids of the Subclass Scuticociliatia of the Class OLIGOHYMENOPHOREA . 
(a , b ) Monokinetid and dikinetid of Cinetochilum . ( c ) Monokinetid of Dexiotricha . ( d , e ) Monokinetid and dikinetid 
of Cohnilembus . ( f ) Monokinetid of Conchophthirus (from Lynn, 1981, 1991)
Fig. 15.9. A Schematics of the somatic polykinetid of the scuticociliate Schizocaryum of the Class 
 OLIGOHYMENOPHOREA (from Lynn, 1981, 1991). B Somatic cortex of a typical oligohymenophorean based on 
the somatic cortex of Tetrahymena and Colpidium
15.3 Somatic Structures 307
 Contractile vacuoles are a conspicuous organelle 
in many oligohymenophoreans . They are typically 
solitary and restricted to the posterior half of the 
cell. However, peniculines often have two, one in 
each half of the cell while astomes can have doz-
ens, whose distribution patterns have been used to 
characterize species (de Puytorac, 1994g). The con-
tractile vacuole of peritrichs is cryptic as it opens 
into the infundibulum at the anterior end of the cell. 
New contractile vacuoles are positioned at each 
cell division by a global positioning system that is 
able to proportionally “measure” cell size (Frankel, 
1989; Nanney, 1980; Nanney, Nyberg, Chen, & 
Meyer, 1980b). The contractile vacuole complex 
of oligohymenophoreans , such as Paramecium , 
Tetrahymena , and Vorticella , is composed of two 
major membranous compartments, the spongiome 
and the contractile vacuole itself (Patterson, 1980; 
Allen & Naitoh, 2002). Much remains to be learned 
of the details of the mechanism of water sequestra-
tion . It is clear that the spongiome membrane has 
 vacuolar-ATPases that pump ions, probably K + and 
Cl− , into this compartment to create an osmotic 
gradient drawing water and metabolic wastes from 
the cytosol (Allen & Naitoh; Allen, Ueno, Pollard, 
& Fok, 1990; Stock, Gronlien, Allen, & Naitoh, 
2002). Fluid is then moved to the contractile 
vacuole itself, which periodically rounds prior to 
expulsion. The fluid is excreted through the con-
tractile vacuole pore , which is supported by heli-
cally coiled microtubules, and which serves as the 
origin for ribbons of microtubules that radiate out 
from the pore to support the membranous compo-
nents of the spongiome (Chapman & Kern, 1983; 
McKanna, 1973a). Similar to natural populations 
of marine ciliates, Paramecium species continue 
to adapt and maintain contractile vacuole function, 
even in environments with high osmotic strength. 
They do this, in part, by regulating the amounts 
of the free amino acids proline and alanine in the 
cytoplasm (Cronkite & Pierce, 1989). Stock, Allen, 
and Naitoh (2001) argued that the maintenance of 
 contractile vacuole function, even at these high