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These proteins are Ca 2+ -binding 
proteins , which show antigenic similarity to those 
of the ecto-endoplasmic layer of Polyplastron
(Vigues & Grolière, 1985). The filaments of the 
 ecto-endoplasmic layer can be specialized to ena-
ble the contraction of the neck of Lacrymaria olor
(Tatchell, 1980), retract the ciliophore , which bears 
the somatic cilia in entodiniomorphids (Grain, 
1994), and can “carry” the nuclear apparatus in 
some trichostomes (Grain, 1966a). 
 Williams et al. (1981) were the first to observe 
that the somatic monokinetids of Spathidium had 
two transverse ribbons. The litostome kinetid can 
now be characterized as a monokinetid bearing a 
slightly convergent postciliary ribbon at triplet 9, 
a laterally directed kinetodesmal fibril at triplets 6 
and 7, and two transverse ribbons of which a tan-
gential one, T1, is associated with triplets 3 and 4 
and a somewhat radial one, T2, is associated with 
triplet 5 at some time during kinetid development 
(Fig. 9.4) (Lynn, 1991 and references therein). 
More recent descriptions have confirmed this for 
additional genera of haptorians (Foissner & Leipe, 
1995; Grim, 1993a; Johnson et al., 1995; Lipscomb 
& Riordan, 1991, 1992). Lipscomb and Riordan 
(1991) demonstrated that the tangential transverse 
microtubules might have their origin in the lamina 
corticalis of Helicoprorodon , a feature that might 
be shared by other haptorians . Furness and Butler 
(1986) observed the transient appearance of a single 
microtubule during somatic kinetid replication in the 
 entodiniomorphid Eudiplodinium (Fig. 9.4). They 
concluded this to be homologous to T2 and used this 
to explain why other entodiniomorphids only exhib-
ited the T1 (see also Lynn, 1991). The postciliary 
ribbons of haptorians may form a two-layered struc-
ture of “n + 1-over-n” microtubules as they reach 
the cortex; typically, this is a “4-over-3” assemblage 
(Fig. 9.5). Postciliary ribbons of trichostomes are 
also “bundled” near their origin and may be reduced 
in number (Fig. 9.4). Nematodesmal microtubules 
may extend from the somatic kinetosomes into the 
cytoplasm, and these may be responsible for deter-
mining asymmetries in cell shape, such as the tail 
and proboscis of Dileptus (Golińska, 1991). 
 The girdle of somatic ciliature of the cyclot-
richiid Myrionecta (= Mesodinium ) is very unusual 
and unlike that of Didinium (Figs. 9.1, 9.2). The two 
ciliary elements of the girdle are a posterior file of 
kinetosomes in zig-zag arrangement but showing 
none of the typical litostome fibrillar associates, 
and a polykinetid of loosely arranged kinetosomes 
Fig. 9.4. Schematics of the somatic kinetids of the Class 
 LITOSTOMATEA . ( a ) Monokinetid of Homalozoon . 
(b ) Monokinetid of Spathidium . ( c ) Monokinetid 
of Balantidium . ( d ) Monokinetid of Dasytricha . ( e ) 
Monokinetid of Eudiplodinium showing transient appear-
ance of T2 (arrowhead). ( f ) Monokinetid of Entodinium , 
showing interrelation of kinetodesmal fibrils between 
kinetids. Note how the postciliary microtubules appear 
to segregate into two rows (see Fig. 9.5) (from Lynn, 
1981, 1991)
9.3 Somatic Structures 201
is situated anterior to each of these files (Grain 
et al., 1982). This unusual kinetid structure is cor-
related with the great genetic divergence observed 
in the SSUrRNA genes of cyclotrichiids and other 
 haptorians (Johnson et al., 2004; Strüder-Kypke 
et al., 2006). 
 Haptorians and some trichostomes have clavate 
cilia , typically localized as a longitudinal differen-
tiation of two to four somatic kineties, depending 
upon the genus. These cilia tend to be shorter and 
swollen compared to other somatic cilia, primarily 
because the axonemal structure is aberrant. They 
are typically arranged in pairs (e.g., Enchelydium – 
Foissner & Foissner, 1985; Fuscheria – Foissner & 
Foissner, 1988; Homalozoon – Liepe & Hausmann, 
1989; Spathidium – Bohatier, Iftode, Didier, & 
Fryd-Versavel, 1978), posterior to the oral region 
on what might be defined as the dorsal surface. 
However, in Dileptus , these clavate pairs are on 
the dorsal surface of the proboscis anterior to the 
cytostome (Grain & Golińska, 1969), while they 
may be distributed adjacent to each tentacle base in 
Actinobolina (Holt et al., 1974). Clavate cilia have 
been observed around the oral region in Balantidium
(Paulin & Krascheninnikow, 1973), possibly mak-
ing up the Villeneuve-Brachon field of kineties (see 
Guinea, Anadón, & Fernández-Galiano, 1992). 
 Clavate cilia occur above the region of the concre-
ment “vacuoles” of other trichostomes (see below), 
and on the paralabial organelle of entodiniomor-
phids (see Oral Structure below). Although there 
is no direct experimental evidence, clavate cilia 
are considered to be sensory structures, probably 
functioning like the dorsal bristles of some hypot-
richs and stichotrichs (Görtz, 1982a). Locomotory 
cilia can differentiate to clavate cilia and the con-
Fig. 9.5. Somatic cortex of a typical litostome whose postciliary ribbons , composed of two rows, extend alongside 
each other into the cortical ridges. Note that the tangential transverse ribbons extend anteriorly into the cortical ridge 
while the radial transverse ribbons extend somewhat posteriorly. (Modified after Leipe & Hausmann, 1989.)
verse can occur during regeneration of Dileptus
(Golińska, 1982a, 1982b), while high temperatures 
can increase the number of microtubules in the 
axonemes of clavate cilia (Golińska, 1987). 
 Mucocysts are a common feature of the cortex of 
the litostomes . In the trichostomes , if the cortex 
has a thickened epiplasm , mucocysts are not usu-
ally present. Loxophyllum is an unusual haptorian , 
which has “warts” along its body that bear clusters 
of extrusomes. An unusual small extrusome, called 
a conocyst , may also be found in these (Hausmann, 
1977, 1978). 
 Mitochondria are common in free-living forms. 
 Hydrogenosomes , typical of commensal lito-
stomes , have been reported in vestibuliferids 
(Müller, 1993; Yarlett, Hann, Lloyd, & Williams, 
1981; Williams, 1986) and entodiniomorphids 
(Grain, 1994; Müller; Paul, Williams, & Butler, 
1990; Snyers, Hellings, Bovy-Kesler, & Thines-
Sempoux, 1982; Yarlett, Coleman, Williams, & 
Lloyd, 1984). Balantidium may have both mito-
chondria and hydrogenosomes (Grain, 1994). 
Much remains to be learned about the enzymatic 
functioning of the hydrogenosomes of litostomes . 
However, it is clear that the hydrogenosomes 
from Isotricha and Dasytricha respond reversibly 
to oxygen tension levels in the rumen , producing 
 hydrogen only when oxygen tensions are lower. 
This, in turn, influences production of methane by 
 rumen methanogens (Lloyd, Hillman, Yarlett, & 
Williams, 1989). 
 Litostomes have a variety of different “storage”
products in the cytoplasm. The buetschliid con-
crement “vacuoles” contain calcium carbonate 
and are surrounded by hydrogenosomes (Grain, 
1994). Concrement “vacuoles” of paraisotrichids 
also contain calcium carbonate (Grain, 1994). 
 Blepharocorythids have a “vacuole” that is con-
sidered homologous to the concrement “vacuoles” 
of other litostomes , although it does not contain 
 calcium carbonate (Grain, 1994). Zinc granules 
have been reported in the cytoplasm of some ento-
diniomorphids (Bonhomme, Quintana, & Durand, 
1980).The parapharyngeal mass of Homalozoon
has granules containing high levels of magnesium , 
 potassium , calcium , and phosphorus (Kuhlmann, 
Walz, & Hausmann, 1983). 
 Haptorians may store paraglycogen in large 
granules (e.g., Homalozoon – Kuhlmann et al., 
1983). However, trichostomes apparently do not 
store glycogen . These endosymbionts store amylo-
pectin , a starch-like polysaccharide ,