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enabling the organism to continuously probe the 
environment for food while it moves forwards or 
backwards or remains stationary on it somatic cirri 
(Deitmer et al., 1984). The oral polykinetids and 
 paroral of spirotrichs can be underlain by microtu-
bules and/or a nodal filamentous reticulum , which 
may confer on the region a highly contractile nature 
(see references above). For example, tintinnids and 
other choreotrichs are able to not only contract the 
body but also the oral region, possibly due to these 
filamentous elements (Grim, 1987; Laval-Peuto, 
1994). The microtubular elements likely provide 
structural support for the oral region (Grain, 1984; 
Tuffrau & Fleury, 1994). Large accumulations of 
 pharyngeal disks in the oral region may enable 
spirotrichs, like Euplotes , to rapidly form as food 
vacuole membranes the rough equivalent of the 
entire surface area of the cell and so exploit a peri-
odically abundant food source (Kloetzel, 1974). 
 7.5 Division and Morphogenesis 
 Spirotrichs typically divide while free-swimming 
with few notable exceptions, such as the stichot-
rich Paraholosticha (Dieckmann, 1988; Tuffrau 
& Fryd-Versavel, 1977). Foissner (1996b) presents 
a comprehensive review of the types of stomato-
genesis and division morphogenesis in the ciliates. 
The literature on stomatogenesis of stichotrichs is 
particularly rich as the features of division morpho-
genesis have been instrumental in establishing phy-
logenetic hypotheses about relationships among 
families and genera (e.g., see Berger & Foissner, 
1997; Eigner, 1997, 1999, 2001; Foissner, 1996b; 
Petz & Foissner, 1992). These, in turn, are now 
being tested by molecular phylogenetics (Bernhard 
et al., 2001; Foissner et al., 2004; Schmidt et al., 
2007). Our review below will briefly characterize 
the nature of division morphogenesis in the vari-
ous spirotrich subclasses. Because of Foissner’s 
comprehensive review, few references are made to 
earlier literature. 
 Stomatogenesis of the Subclass Protocruziidia 
(i.e., Protocruzia ) has been characterized as mix-
okinetal since elements of both somatic and paren-
tal infraciliature are involved in oral primordium 
formation (Foissner, 1996b). However, Grolière 
et al. (1980a) have provided the only published 
description, which does not demonstrate involve-
ment of parental oral structures, typing it as 
 parakinetal . The oral polykinetids assemble from 
anterior to posterior and from right to left in the 
primordial field while the paroral differentiates 
as a file of dikinetids along the right side of the 
primordial field (Fig. 7.7). 
 Division morphogenesis has not been described 
for Phacodinium or Licnophora (Foissner, 1996b). 
This presents an opportunity for future research. 
 Deroux (1974) provided the first detailed 
description of stomatogenesis in a choreotrich , 
Strobilidium . Foissner (1996b) classifies chore-
otrich stomatogenesis as hypoapokinetal since 
it occurs for most of the process in a subsurface 
cortical pouch . Initial kinetosomal proliferation 
appears to occur on the cell surface, and the region 
invaginates as oral development proceeds (Dale & 
Lynn, 1998) (Fig. 7.8). The developing oral polyki-
netids form a particularly characteristic “barrel 
stave-like” formation across the outer or surface 
end of which the developing paroral extends (Fig. 
7.8). Kinetosomal proliferation occurs within the 
somatic kineties, which lengthen and are sub-
divided at cytokinesis . This has been observed 
in Strombidinopsis , Strobilidium , and tintinnids 
(Agatha, 2003a; Dale & Lynn, 1988; Deroux; Petz 
& Foissner, 1992, 1993). 
 Hypotrichs also share the feature of oral pri-
mordium development within a subsurface pouch , 
and have been characterized as hypoapokinetal 
(Foissner, 1996b) (Fig. 7.7). In hypotrichs , the 
earliest kinetosomes of the oral primordium appear 
in a subsurface pouch (e.g., Aspidisca , Song, 2003; 
Certesia , Wicklow, 1983; Diophrys , Hill, 1981; 
Song & Wilbert, 1994; Euplotes , Wise, 1965; 
Uronychia , Hill, 1990). However, the primordium 
develops on the cell surface of the related disco-
cephalines (Wicklow, 1982). The somatic ciliature 
may be renewed differently on dorsal and ventral 
surfaces. On the ventral surface to the posterior right 
of the proter’s oral region, typically five, but up to 
ten, primordial streaks form by kinetosomal replica-
tion (Fig. 7.7). These kinetosomes appear not to be 
associated with parental somatic kinetids, but may 
acquire kinetosomes from parental structures as the 
parental structures dedifferentiate. These ventral 
streaks elongate and eventually split into two sets, 
one giving rise to the proter’s and the other to the 
opisthe’s ventral ciliature (e.g., Certesia , Wicklow, 
1983; Diophrys , Hill, 1981; Song & Wilbert, 1994; 
Euplotes , Wise, 1965; Uronychia , Hill, 1990; dis-
cocephalines , Wicklow, 1982). Movements of cirral 
primordia both posteriorly and anteriorly are driven 
by the assembly of microtubular structures associ-
ated with them (Fleury, 1991a; Ruffolo, 1976b). 
 Wallengren (1900) devised a method of numbering 
these ciliary streaks and the subsequently differen-
tiating cirri in Euplotes and this has served as an 
important means of comparing the development of 
 hypotrichs and stichotrichs (see also Martin, 1982; 
Wise, 1965). Dorsal kinety streaks may appear in 
both proter and opisthe alongside parental kineties, 
and with kinetosomal replication ultimately replac-
ing the parental structures (e.g., Diophrys , Song 
& Wilbert, 1994). In contrast, dorsal kinetosomal 
replication in euplotids occurs within each dorsal 
kinety (Frankel, 1975; Song, 2003). The pattern of 
intensity of replication is guided by global posi-
tional systems (Frankel, 1989). 
 Oligotrich stomatogenesis appears to fall into 
two types, possibly related to the extent of develop-
ment of the cortical polysaccharide plates. Foissner 
(1996b) typed it as epiapokinetal because the oral 
primordium forms on the cell surface independ-
ent of parental infraciliature in some Strombidium
species (Agatha, 2003b; Agatha, Strüder-Kypke, 
& Beran, 2004; Song & Wang, 1996). However, 
Fauré-Fremiet (1953) described it to occur in a long
inpocketing beneath the polysaccharide plates of 
Strombidium oculatum , and this neoformation 
organelle was confirmed in Pelagostrombidium 
fallax by Petz and Foissner (1992). In the early 
stages of oral primordium formation, prolifera-
tion may begin on the cell surface, followed by 
invagination as development of the oral structures 
proceeds (Petz, 1994) (Fig. 7.8). This is similar to 
the process in the choreotrichs , and later dividers 
in both groups may be characterized as showing an 
enantiotropic kind of cell division (Fauré-Fremiet, 
1953; Petz & Foissner, 1993). 
 There is a rich literature on the patterns of division
morphogenesis in stichotrichs with the perspectives 
of different investigators leading to very different 
sets of relationships (e.g., see Berger & Foissner, 
1997; Eigner, 1997, 1999; Martin, 1982; Wicklow, 
1981). The pattern of development has been inter-
preted using the system of Wallengren (1900), 
which has been modified to accommodate a larger 
diversity of patterns (e.g., Martin, 1982). Pattern 
development in ciliates is controlled at both global
and local levels, and although we have some ideas 
of the properties of the developmental processes, 
7.5 Division and Morphogenesis 163
Fig. 7.7. Division morphogenesis of representatives from each of the subclasses of the Class SPIROTRICHEA . A
Subclass Protocruziidia . In Protocruzia , stomatogenesis appears to be parakinetal here, involving kinetosomal pro-
liferation adjacent to the equatorial region of Kinety 1 ( a , b ) and then differentiation of the adoral polykinetids and 
 paroral ( c-e ) (from Grolière et al., 1980a). However,