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Foissner (1996b) has evidence that it is mixokinetal , involving 
elements from the parental oral region. B Subclass Hypotrichia . In Diophrys , the oral primordium begins develop-
ment in a subsurface pouch while five ventral streaks appear at the cell equator ( a ). The ventral streaks divide into 
an anterior or proter and posterior or opisthe group ( b , c ). Cirral differentiation and migration occur as the oral cili-
ature develops ( c , d ). (from Hill, 1981.) C Subclass Stichotrichia . In Parakahliella , the oral primordium develops 
by kinetosomal proliferation on the ventral surface ( a , b ). Two sets of ventral streaks - an anterior proter set and a 
posterior opisthe set develop and cirri differentiate and migrate as the oral primordium continues to develop ( c , d ). 
(from Berger et al., 1985.)
Fig. 7.8. Division morphogenesis of representatives from each of the subclasses of the Class SPIROTRICHEA . 
A Subclass Stichotrichia . In Halteria , formerly an oligotrich , the oral primordium (arrowhead) develops on the cell 
surface ( a ). New sets of bristle kinetosomes appear anterior and posterior (arrows) to parental bristle kinetosomes ,
which eventually dedifferentiate as development proceeds ( b\u2013d ). (from Song, 1993.) B Subclass Choreotrichia . In 
Strombidinopsis , the oral primordium begins development in a subsurface pouch (arrow) ( a ). Oral development pro-
ceeds to a \u201cbarrel stave-like\u201d formation ( b, c ), and then the opisthe\u2019s oral structures expand out onto the cell surface 
(d ). Kinetosomal replication of somatic kinetids occurs within the kineties. (from Dale & Lynn, 1998.) C Subclass 
 Oligotrichia . In Strombidium , the oral primordium (arrow) begins development on the cell surface in the region of 
junction between the ventral kinety and the girdle kinety ( a ). As development of the oral primordium proceeds, there 
is kinetosomal replication in the girdle and ventral kineties and a complex series of morphogenetic movements ( b,
c ). (from Petz, 1994.)
7.5 Division and Morphogenesis 165
166 7. Subphylum 2. INTRAMACRONUCLEATA: Class 1. SPIROTRICHEA
the actual cellular mechanisms remain to be deter-
mined (Frankel, 1989). Martin (1982), for exam-
ple, assumes homology between hypotrichs and 
 stichotrichs using a Wallengren -like numbering 
system. We believe it premature to assume that these 
patterns are homologous until we have a firmer 
understanding of the underlying cellular mecha-
nisms determining pattern development. Thus, we 
present only a general description of stichotrich 
 division morphogenesis , touching on some major 
differences in the development of pattern (Fig. 
7.7). It may be that the application of molecular 
approaches will not only provide refutation of 
competing schemes derived by morphologists, but 
application of molecular phylogenetics may inform 
the evolution of division morphogenesis in stichot-
richs. A general assumption is made that the ances-
tral stichotrich was a ciliate with many files of small 
 cirri (e.g., Phacodinium , Fig. 7.2; Plagiotoma , 
Fig. 7.4), and that as evolution proceeded this 
number was reduced to a few scattered cirri (e.g., 
Stylonychia , Fig. 7.4), although it now seems that 
Plagiotoma is a derived form (Foissner et al., 2004; 
Schmidt et al., 2007). Foissner (1996b) tentatively 
characterizes stomatogenesis in Plagiotoma as par-
akinetal. Somatic kineties are completely renewed 
during division morphogenesis by proliferation 
of streaks within the parental kineties in both the 
proter and opisthe (Albaret, 1973; Fleury, 1983). 
These features, along with macronuclear repli-
cation bands (Dworakowska, 1966), support its 
placement within the Subclass Stichotrichia . 
 Among stichotrichs , there is a bewildering array 
of patterns, placed into parakinetal and epiapoki-
netal types by Foissner (1996b), who admits that 
all stichotrichs may be epiapokinetal since electron
microscopy does not clearly implicate parental 
structures in kinetosomal replication (Grimes, 
1972, 1973). Whether or not the oral primordium 
proliferates in relation to the parental infracili-
ature, the ventral cirral primordia may arise in at 
least two ways in the opisthe. The proter ventral 
cirral primordia almost always arise separately 
from those of the opisthe, so two sets of somatic 
cirral streak primordia are present in stichotrichs
at the outset, rather than one set that divides as in 
the hypotrichs (Fig. 7.7). To simplify the diversity 
of patterns considerably, in the vast majority of 
genera, a series of streaks , from 3 to more than 
20, arise separately from the oral primoridium 
often in association with the dedifferentiation 
of parental cirri (Fig. 7.7) (e.g., Amphisiellides , 
Eigner & Foissner, 1994; Bakuella , Eigner & 
Foissner, 1992; Coniculostomum , Kamra & Sapra, 
1990; Deviata , Eigner, 1995; Gastrostyla , Hu & 
Song, 2000; Hemigastrostyla , Song & Hu, 1999; 
Holosticha , Hu & Song, 2001a; Histriculus , Berger, 
Foissner, & Adam, 1985; Kahliella , Berger & 
Foissner, 1988; Lamtostyla , Petz & Foissner, 1996; 
Laurentiella , Martin, Fedriani, & Perez-Silva, 
1983; Parakahliella , Berger & Foissner, 1989b; 
Paraurostyla , Wirnsberger, Foissner, & Adam, 
1985; Steinia , Voss & Foissner, 1996; Stylonychia
(= Tetmemena ), Wirnsberger, Foissner, & Adam, 
1986; Thigmokeronopsis , Hu, Song, & Warren, 
2004; Wicklow, 1981; Urosomoida , Ganner, 
Foissner, & Adam, 1986/1987). The other way is 
for a series of streaks , from five to more than ten, 
to appear to derive from the opisthe oral primor-
dium (e.g., Amphisiella , Voss, 1992; Circinella , 
Foissner, 1994a; Gonostomum , Song, 1990a; 
Metaurostylopsis , Song, Petz, & Warren, 2001; 
Pseudokeronopsis , Hu & Song, 2001b; Urosoma , 
Foissner, 1983a). In both cases, the relation of cir-
ral structures to the oral primordium may be more 
a function of the density of ciliation on the ventral 
surface. Where cirri are dense, cirral primordia 
appear to arise separately from the oral primor-
dium; and where cirri are sparse, cirral primordia 
appear to emerge by kinetosomal proliferation 
from the oral primordium. Until we have more 
concrete understanding of the mechanisms under-
lying primordium formation, we should not put too 
much weight on subtle differences in these spatial 
patterns.
 Primordia for marginal cirri and for dorsal kine-
ties typically develop within the parental files and 
as proliferation proceeds, the parental kinetosomes 
are resorbed. However, the primordia may also 
appear beside the parental files and subsequent 
migration may make it appear that proliferation 
has occurred within the parental cirral file (see 
Wirnsberger et al., 1985). Finally, Eigner (1995, 
1997, 2001) has defined neokinetal proliferation , 
especially in forms with longitudinal cirral files, in 
which additional new primordia or anlagen derive 
from the primary anlagen and migrate anteriorly or 
posteriorly from it to provide new structures. 
 Two unusual groups bear special mention. First, 
Paraholosticha divides within a cyst , dedifferen-
tiating all parental structures first and then devel-
oping new structures in an epiapokinetal fashion 
(Dieckmann, 1988). Foissner (1996b) speculated 
that this may have evolved as an adaptation to the 
highly variable terrestrial and semiterrestrial habi-
tats in which Paraholosticha is found, demonstrat-
ing a parallel evolution with division morphogenesis 
in some colpodeans (see Chapter 12 ). Second, the 
 halteriids , such as Halteria and Meseres , are now 
placed by molecular sequences within the Subclass 
 Stichotrichia (Bernhard et al., 2001), so the plank-
tonic \u201c oligotrich \u201d body form has evolved conver-
gently in stichotrichs . Stomatogenesis in halteriids 
is typed as epiapokinetal like that of other stichot-
richs (Foissner, 1996b). The somatic infraciliature is 
replaced