Cap 8

2005). In contrast, over 
80% of the methane produced by the American 
cockroach can be attributed to ciliates (Gijzen & 
Barugahare, 1992). In other anaerobic habitats, 
stimulation of bacterial production by ciliate graz-
ing can enhance methane production , here not 
by endosymbiotic bacteria , but by the free-living 
 methanogens . Organic acids, such as acetate and 
propionate, excreted by the ciliates may stimulate 
bacterial growth (Biagini, Finlay, & Lloyd, 1998). 
 Research on the endosymbiotic armophoreans , 
the clevelandellids , has primarily focussed on the 
symbionts of frogs and insects . The amphibians
of Cameroon have provided a rich resource to 
probe the biology of the clevelandellids . Frog’s 
eggs are not infected and frog’s with a direct life 
cycle were never found to carry ciliates. The small 
 frog Phrynodon sandersoni provides a “natural 
experiment” to confirm these facts. Its tadpoles
develop without a digestive tract; of course, the 
 tadpoles are uninfected and so are the adults 
(Amiet & Affa’a, 1985). Affa’a and coworkers 
(Affa’a, 1988a; Affa’a & Amiet, 1985, 1994; 
Amiet & Affa’a, 1985) have concluded that there 
are three general life histories of infaunation. First, 
the ciliates may be found only in the juvenile or 
 tadpole stages of the host: this applies to such species 
as Nyctotheroides brachystomus , Neonyctotherus
reticulatus , and Parasicuophora aberrans . Second, 
other species, such as Nyctotheroides heteros-
tomus and Prosicuophora basoglui , infaunate only 
the adult stage. Finally, both tadpole and adult 
stages are infaunated by other species, such as 
Nyctotheroides teochii . 
 We do not know what factors control the dis-
appearance of ciliates from the tadpole or the 
appearance of ciliates in the adults. Affa’a (1986b) 
has shown that gonadotropins induce encystment 
in Prosicuophora and Nyctotheroides . It may be 
that the changes at metamorphosis of the tadpoles 
induce encystment in those forms that occur only in 
the tadpole and induce excystment in those forms 
that occur only in the adult. Ingestion of cysts is 
probably the main mode of transmission, although 
infection by live ciliates may occur since the feces 
of adult frogs have an abundance of ciliates (Amiet 
& Affa’a, 1985). The prevalence of a ciliate species 
in a frog host varies from one locality to another, 
although it is not yet clear what factors determine 
8.2 Life History and Ecology 179
180 8. Subphylum 2. INTRAMACRONUCLEATA: Class 2. ARMOPHOREA
this variability (Affa’a, 1986a, 1988a). Geographic 
variation has also been reported for Nyctotherus
species that infect cockroaches : similar ciliate 
genotypes can occur in different insect genera 
at the same or distant localities (van Hoek et al., 
1998). The ciliates apparently have no effect on 
the amphibian hosts. However, those resident in 
 cockroaches may significantly increase the growth 
rate and body weight of their hosts (Gijzen & 
Barugahare, 1992). 
 Reid and John (1983) characterized the cysts of 
the clevelandellids as flask-shaped, noting similarities
to those of the heterotrichs (see also Esteban et al., 
1995; Takahashi & Imai, 1989). Cysts are crucial 
to the maintenance of the life histories of the endo-
symbiotic clevelandellids and must certainly be 
important for those armophorids , such as Metopus , 
which are found in soils. How widely cyst-forming 
is distributed in other members of the class remains 
to be determined. 
 8.3 Somatic Structures 
 Armophorean ciliates are quite variable in shape 
and size. Clevelandellids are intermediate in size 
at around 100 µm; armophorids can range up to 
300 µm in length. Shapes are also quite variable. 
 Armophorids , especially caenomorphids , have a 
rigid, armor-like pellicle with processes and spines , 
but larger metopids can be quite flexible. The 
 armophorid body is developed into an anterior lobe 
that can become quite twisted, and along which 
travel the perizonal or frontal kineties (Fig. 8.1). 
Smaller forms may have somatic ciliature reduced 
to anterior and posterior cirrus-like tufts. 
 On the other hand, clevelandellids are very 
densely ciliated with closely packed somatic kine-
ties. These somatic kineties converge on each other 
forming what are called sutures or secant systems 
(Fig. 8.1). In clevelandellids , these are typically 
preoral, apical, caudal, and postoral; the length and 
precise positions of these secant systems is used in 
distinguishing genera (e.g., Affa’a, 1983; Albaret 
& Njiné, 1976; Earl, 1991; Grim, 1998). 
 The cell membrane is underlain by an alveolar 
layer that may be conspicuous in some caenomor-
phids (Fenchel et al., 1977), but it is apparently very 
compressed, or perhaps even absent, in metopids 
(Fenchel & Finlay, 1991a) and clevelandellids 
(de Puytorac & Grain, 1969). 
 Somatic kinetids are dikinetids throughout the 
class. However, as with the Class SPIROTRICHEA , 
there is considerable diversity in kinetid structure 
within the Class ARMOPHOREA . Unfortunately, 
much of this research remains to be published, 
appearing only in abstract form or as schematic 
drawings without micrographic support (Tuffrau 
& de Puytorac, 1994). We will rely on these but 
caution that detailed descriptions need to be pub-
lished to corroborate the drawings (Fig. 8.2). The 
armophorid somatic dikinetid is characterized as 
follows: a ciliated anterior kinetosome with a tan-
gential transverse ribbon at triplets 3, 4, 5 and a cili-
ated posterior kinetosome with a well-developed 
 divergent postciliary ribbon and a laterally-directed 
 kinetodesmal fibril at triplets 5, 6, 7 that may not be 
striated (Schrenk & Bardele, 1991). Other micro-
tubules have been reported to accompany the ante-
rior transverse ribbon near triplets 5 or 6 while a 
pair of presumably transverse microtubules is situ-
ated between the two kinetosomes opposite triplet 
4 of the posterior kinetosome (Da Silva Neto in de 
Puytorac & Tuffrau, 1994; Esteban et al., 1995) 
(Fig. 8.2). Foissner and Agatha (1999) observed 
by silver-staining what might be well-developed 
 cathetodesmal fibrils in several Metopus species. 
The postciliary microtubular ribbons extend along-
side each other in the cortical ridges (Fig. 8.3). 
 Paulin (1967) and de Puytorac and Grain (1969) 
provided the first evidence of the clevelandellid 
 somatic dikinetid of Nyctotherus and Sicuophora , 
respectively. Grim (1998) has provided some 
information on the dikinetid of the clevelandellid 
Paracichlidotherus . The clevelandellid dikinetid 
can now be characterized as follows: a ciliated 
anterior kinetosome that bears a tangential trans-
verse ribbon at triplets 4, 5 and a striated cathe-
todesmal fibril extending to the lateral left from 
an origin near triplet 2; and a ciliated posterior 
kinetosome with a divergent postciliary ribbon and 
a kinetodesmal fibril homologue at triplets 5, 6 
(Fig. 8.2). Grim reported two transverse microtu-
bules associated with the posterior kinetosome of 
Paracichlidotherus . The striated cathetodesmal fibrils 
of clevelandellids may be bifurcated (Fernández-
Galiano, 1986; de Puytorac & Grain; de Puytorac
& Oktem, 1967). De Puytorac and Grain (1969) 
illustrated the cathetodesmal fibril of Sicuophora
as having two origins, one as indicated above on 
the anterior kinetosome and the other on the poste-
rior kinetosome near the base of the kinetodesmal 
Fig. 8.2. Schematics of the somatic kinetids of representatives of the Class ARMOPHOREA . ( a ) Dikinetid of 
Metopus . ( b ) Dikinetid of Paracichlidotherus . ( c ) Dikinetid of Nyctotherus . ( d ) Dikinetid of Sicuophora (from Lynn, 
1981, 1991)
8.4 Oral Structures 181
fibril homologue. No micrographic evidence is 
presented for this interpretation so we have revised 
our drawing accordingly (Fig. 8.2). 
 We need to have