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vestibulum . There 
are no oral toxicysts and most species have hydrog-
enosomes rather than mitochondria . We prefer 
the name Trichostomatia for the class rather than 
 Vestibuliferia because some entodiniomorphids 
(i.e., Buetschliidae ) do not have a vestibulum . The 
subclass is divided into three orders. The Order 
 Vestibuliferida includes ciliates that are holotri-
chously ciliated and have a vestibulum , defined as 
an oral cavity or depression lined by densely ciliated 
kineties, typically as extensions of somatic kineties. 
Members of the Order Entodiniomorphida have 
somatic ciliation restricted as girdles, bands, and 
tufts, and may or may not have a deep oral cavity. 
A new order, Order Macropodiniida n. ord., form 
what might be called a “ribo-order” as there are 
no strong morphological synapomorphies for this 
group, and only share their habitat as endocom-
mensals in the forestomach of macropodid and 
 vombatid marsupials . Cameron and O’Donoghue 
(2004b) argue that it is premature to take this taxo-
nomic step. 
 The Order Vestibuliferida includes six families:
 Balantidiidae , Isotrichidae , Paraisotrichidae , Proto-
caviellidae (= Hydrochoerellidae ), Proto halliidae , and 
 Pycnotrichidae . Grain (1966a, 1966b) provided
details of the cytology and ultrastructure of ves-
tibuliferids , demonstrating the nature of their oral 
structures as very slightly specialized extensions 
of somatic kineties whose kinetids bear trans-
verse ribbons and nematodesmata that support 
the cytopharynx. Ito and Imai (2000a, 2000b) 
described several new genera and species from the 
 cecum of the South American capybara , following 
the classic work of Da Cunha and Muniz (1925, 
1927). Grim (1988, 1993a) has provided ultrastruc-
tural descriptions of Balantidium species from 
tropical fishes and the pycnotrichid Vestibulongum , 
confirming the haptorian nature of their somatic 
monokinetids. Strüder-Kypke et al. (2006) ques-
tioned the monophyly of the Order Vestibuliferida 
since Balantidium did not group with the other ves-
tibuliferids based on SSUrRNA gene sequences. 
Again, we have remained conservative here until a 
larger sampling of vestibuliferids and Balantidium
species justifies this conclusion. 
 There is a tremendous literature on the Order 
 Entodiniomorphida , from the early work of the 20th 
century by Dogiel (1927, 1946), Noirot-Timothée’s 
(1960) monograph on cytology and ultrastruc-
ture, to the study series of Latteur (1968/1969, 
1970), Lubinsky (1957a, 1957b), and Wolska 
(1971, 1981). The order, which includes three 
suborders, is consistently the sister clade to the 
 vestibuliferids in gene sequence trees (Cameron & 
O’Donoghue, 2003a; Strüder-Kypke et al., 2006). 
The Suborder Archistomatina is monotypic: the 
Family Buetschliidae includes ciliates with a con-
crement vacuole overlain by a clavate field . There 
are typically girdles of somatic kineties at the 
anterior, middle, and posterior ends. The anterior 
“girdle” comprises the oral ciliature. The Suborder 
 Blepharocorythina is also monotypic: members of 
the Family Blepharocorythidae have a vestibulum 
lined by several kinety fields. The concrement 
vacuole is absent. However, we accept Wolska’s 
(1971) argument that the patch of somatic kineties 
remaining is homologous to the patch overlying the 
archistomatine concrement vacuole , an hypothesis 
that needs testing by gene sequence data. 
 The Suborder Entodiniomorphina is the largest of 
the three. We accept Wolska’s (1971) hypothesis for 
the evolution of the entodiniomorphid oral ciliature 
(i.e., ophyroscolecid ) from a blepharocorythine -like 
ancestor, and await gene sequence data that will test it. 
The suborder includes ten families: Cycloposthi idae , 
Gilchristidae, Ophryoscolecidae , Parentodiniidae , 
 Polydiniellidae , Pseudoentodiniidae , Rhinozetidae , 
 Spirodiniidae , Telamodiniidae , and Troglodytellidae . 
The Entodiniomorphina are characterized by somatic 
ciliature that is arranged in bands or tufts. The 
oral cavity of these ciliates is a vestibulum lined 
with densely ciliated, tightly spaced single rows of 
kinetosomes, sometimes termed polybrachykine-
ties , which functionally behave like membranelles 
when they beat. This lead to the earlier placement 
of this group with the heterotrichs and hypot-
richs (Corliss, 1961). Grain (1994) and others have 
recognized subfamilies while Bonhomme, Grain, 
and Collet (1989) have suggested the families 
might be grouped on the basis of the ultrastruc-
ture of the ecto-endoplasmic fibrillar layer . One 
group of families has only transverse strands in 
the ecto-endoplasmic layer (i.e., Cycloposthiidae , 
 Ophryoscolecidae , Troglodytellidae ) while the other 
group (i.e., Spirodiniidae , Tripalmariidae ) has both 
transverse and longitudinal strands. This is yet 
another hypothesis that must await testing by gene 
sequence analysis . Lubinsky (1957a, 1957b) and 
Imai (1998) have presented phylogenetic analyses 
for the evolution of ophryoscolecid genera based 
on morphological features, primarily based on the 
increasing complexity of skeletal and ciliary struc-
tures. Wright and Lynn (1997a) have found some 
consistency between morphological and molecular 
phylogenies, but reserved judgement until a larger 
sampling of entodiniomorphid genera had been 
 The Order Macropodiniida n. ord. is formally 
established here for a clade of entodiniomorophids 
that consistently groups as the sister clade of 
the previous two orders (Cameron, Wright, & 
O’Donoghue, 2003; Strüder-Kypke et al., 2006) 
(see Chapter 17 ). Dehority (1996) first recog-
nized this group as a novel assemblage of ciliates, 
endosymbiotic in macropodid marsupials , and 
established the Family Macropodiniidae to repre-
sent that fact. Since then, Cameron and coworkers 
(Cameron, 2002; Cameron & O’Donoghue, 2002a, 
2002b, 2003a, 2003b, 2004a, 2004b; Cameron, 
Adlard, & O’Donoghue, 2001a, 2001b) have 
established two new families, the Amylovoracidae 
and the Polycostidae , and considerably expanded 
the host range of macropodiniids in Australian 
 marsupials . Except for their shared habit as marsu-
pial endosymbionts, these ciliates are not strongly 
united by one feature, but their oral cavities, like 
some vestibuliferids , are lined by extensions of 
somatic kineties and are supported by oral nema-
todesmata . 
 At the species level, much research remains to 
be done, especially on entodiniomorphids . Species 
in this order have often been established based on 
the possession of novel spines or small shape diffe-
rences. However, Poljansky and Strelkow (1938) 
recognized that alimentary tract conditions may 
stimulate the appearance of certain forms, and 
this has been confirmed by others (Chardez, 1983; 
Dehority, 1994). In vitro cultivation of clones of 
 rumen ciliates has now confirmed this phenotypic 
plasticity (Dehority, 2006; Miltko, Michalowski, 
Pristas, Javorsky, & Hackstein, 2006). The latter 
study suggested that several morphospecies were 
in fact not genetically distinct, but could be derived 
from an Ophryoscolex caudatus progenitor. In the 
only study of genetic variability of populations of 
litostome endosymbionts, Wright (1999) demon-
strated no genetic variability in the internally tran-
scribed spacer regions from isolates of Isotricha 
prostoma derived from cattle on two continents. 
9.1 Taxonomic Structure 191
 9.2 Life History and Ecology 
 Litostomes cannot be discussed as a homogeneous 
assemblage as the life histories of the haptorians , as 
free-living predators, are much different from the 
life histories of trichostomes , which are endosym-
bionts of vertebrates. It is safe to say, as with other 
classes discussed so far, that the distributions of 
members of both subclasses

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