Cap 10

peritrichs (Padnos & Nigrelli, 1947). Probably 
the most complex life cycle so far worked out for 
a suctorian is that of Tachyblaston , an unusual 
obligate parasite of the larger suctorian Ephelota . 
This parasite shows an alternation of generations 
– a generation parasitic on the trophont of Ephelota
and then a generation epibiotic on the stalk of this 
host suctorian (Grell, 1950, 1973). 
 Most studies of feeding by phyllopharyngeans 
have been descriptive, and so we know very little 
of the quantitative aspects of their feeding ecology. 
Balczon and Pratt (1996) measured ingestion rates 
of the cyrtophorian Trithigmostoma cucullulus on 
the diatom Navicula . This ciliate can consume a 
 diatom every 2 min and may consume almost 10% 
of the daily diatom production. In the marine envi-
ronment, Epstein and Shiaris (1992) estimated that 
a Chlamydodon species consumed more than 125 
 bacteria per hour, which amounted to less than 1% 
of the bacterial standing stock per day. Thus, these 
ciliates have much less of an impact on their prey 
than the planktonic oligotrichs and choreotrichs 
appear to do (see Chapter 7 ). 
10.2 Life History and Ecology 219
Fig. 10.5. Stylized drawings of representatives of the Subclass Suctoria of the Class PHYLLOPHARYNGEA . The 
 exogenid Ephelota . The evaginogenid Discophrya and its bud . The exogenid Podophrya shown as three individuals 
parasitizing the stichotrich Stylonychia . A top view of the evaginogenid Heliophrya , attached to the substrate by 
secreted material
220 10. Subphylum 2. INTRAMACRONUCLEATA: Class 4. PHYLLOPHARYNGEA
 Suctorian species may occur in close proxim-
ity to each other and may be associated based on 
their tolerances of water conditions rather than 
competitive interactions (Bereczky, 1990). Kent 
(1980, 1981) explored the quantitative relationships 
between food levels and fecundity in Tokophrya 
lemnarum . She demonstrated that fecundity was 
directly related to food level while the number of 
non-attaching embryos was higher on a low level 
diet. This suggests that this suctorian tries to escape 
areas of low prey density by dispersing. Laybourn 
(1976) measured respiratory rates of Podophrya
under different growth temperatures and condi-
tions. She noted that this sessile ciliate, as with 
other sessile forms, had over an order of magnitude 
lower respiratory rate than similar-sized free-swim-
ming species, like Paramecium or Tetrahymena . 
With so few studies, there clearly remains much to 
explore about the ecology of suctorians . 
 Given the few reports on the ultrastructure of 
 cyrtophorians , it is not surprising that we know 
 relatively little about the extent of symbioses of 
other organisms with or on them. Epibiotic bac-
teria have been observed in depressions on the 
surface of the cyrtophorian Brooklynella (Lom 
& Corliss, 1971), the chonotrich Spirochona
(Fahrni, 1983), and the suctorian Ephelota (Grell 
& Benwitz, 1984). Matthes and Gräf (1967) iden-
tified Flavobacterium buchneri as the bacterial 
endosymbiont of Discophrya , a suctorian genus 
whose species often have bacterial endosymbionts 
(Matthes, 1973). Treatment with antibiotics reduced 
the bacterial population in Discophrya and led to 
 gigantism , reduced reproduction, and a shortened 
lifespan of the suctorian , suggesting that the sym-
biosis was essential (Curry & Butler, 1975). 
 There are very few reports of predation on phyl-
lopharyngeans , although we can imagine that all 
those predators previously reported to consume 
other ciliates will also consume phyllopharyn-
geans . Addicott (1974) notes that mosquito larvae 
in pitcher plants prey on the ciliate community, 
which included Chilodonella and Dysteria species. 
Batisse (1994b) noted that any predators that con-
sume the hosts of symbiotic forms will indirectly 
be predators of the ciliates. He listed heliozoans , 
 amoebae , and even other suctorians as predators of 
 suctorians . For example, the suctorian Acinetopsis
rara feeds exclusively on the suctorian Ephelota
gemmipara (Grell, 1973). Phyllopharyngeans 
themselves may be parasitized by other organisms. 
Görtz and Maier (1991) described a bacterium 
that invades the macronucleus of the cyrtophorian 
Trithigmostoma , while Canter and Dick (1994) 
reviewed the literature on fungal parasites of suc-
torians and described a new genus of oomycete 
fungus , Eurychasmopsis , parasitizing the parasitic 
suctorian Podophrya . 
 Much of the behavior of phyllopharyngeans 
remains conjectural. Some cyrtophorians , like 
Chlamydodon mnemosyne , have a stigma appara-
tus that enables sensitivity to blue-light, suggesting 
flavins or flavin-like pigments are involved. Mildly 
starved cells are positively phototactic while well-
fed cells are negatively phototactic (Kuhlmann, 
1998; Kuhlmann & Hemmersbach-Krause, 1993a; 
Selbach & Kuhlmann, 1999; Selbach, Hader, 
& Kuhlmann, 1999). The swarmer stages of chono-
trichs and suctorians are undoubtedly sensitive to 
chemical constituents in substrates as they often 
settle preferentially on particular body parts of their 
hosts or near to other members of their species. To 
our knowledge, there has been no experimentation 
to explore these sensitivities. 
 Encystment or resistant stages are common 
among phyllopharyngeans , especially freshwa-
ter and terrestrial cyrtophorians and suctorians 
(e.g., Canter et al., 1990; Fauré-Fremiet, 1945; 
Fernàndez-Leborans, Tato-Porto, & Sorbe, 1996; 
Foissner, 1979b). Encystment has not been reported 
for chonotrichs and rhynchodians . Deroux (1994a) 
reported that Cyrtophoron , a marine cyrtophorian 
that lives in the littoral splash zone, is unusual 
in that it encysts, and even divides in a “division 
cyst.” Jackson and Berger (1985a) observed that 
Tokophrya lemnarum has a relatively long survival 
time even though it can encyst . They reported that 
food deprivation does not induce encystment in 
this species, although in the field study of Canter 
et al. (1990) there was a correlation between 
reducing prey densities and onset of encystment 
in Podophrya . Laybourn (1976) noted that encyst-
ment of Podophrya in culture correlated with 
lower temperature. Thus, it may be inappropri-
ate to generalize on which factors are important 
in stimulating encystment . Kent (1981) reported 
that totally starved individuals had the longest 
mean life span. This is probably due to a reduced 
metabolic rate, recorded by Laybourn (1976) for 
 starved Podophrya , and a reduced accumulation 
of toxic waste products. Rudzinska (1974) noted 
the appearance of autophagic vacuoles in starved 
Tokophrya , enabling survival for a period of time 
prior to encystment . 
 Suctorians are unusual among ciliates in lacking 
a cytoproct . Thus, wastes accumulate in the cyto-
plasm during the lifespan of a cell. Nevertheless, 
Batisse (1994b) noted that some suctorians , 
although lacking the cytoproct , can eliminate waste: 
Thecacineta may sequester wastes in the cell apex 
and sever this periodically, while Dendrosoma and 
Ephelota may eliminate wastes near the base of 
the tentacles . Rudzinska (1962) has demonstrated 
that overfeeding shortens the adult life span of 
Tokophrya , probably due to the accumulation of 
wastes. While lifespans of cells varied consider-
ably, even within a clone, the average lifespan of 
cells decreased as the clonal life cycle progressed 
(see Nuclei, Sexuality and Life Cycle below) 
(Colgin-Bukovsan, 1979; Karakashian, Lanners, & 
Rudzinska, 1984). 
 10.3 Somatic Structures 
 It is difficult to generalize about the body shape 
and size of phyllopharyngeans . Some free-living 
 cyrtophorians and most rhynchodians are very 
small ciliates, less than 50 µm in length, but typi-
cally ovoid in shape (Figs. 10.1, 10.3). Chonotrichs 
have a basic groundplan