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et al., 2001; 
Snoeyenbos-West et al., 2002; Strüder-Kypke 
et al., 2002). The possession of macronuclear repli-
cation bands unites the latter five subclasses while 
a dorsoventral differentiation unites phacodiniids 
with hypotrichs and stichotrichs. Since it is likely 
that halteriids have evolved a planktonic life style 
from benthic stichotrich ancestors like Oxytricha , 
it is very likely that oligotrichs and choreotrichs 
are also derived from benthic dorsoventrally-
differentiated ancestors. Perhaps future phylo-
genetic analyses based on genes other than the 
SSUrRNA gene will shed light on these unresolved 
phylogenetic relationships. 
 Applications of molecular methods have enabled 
the identification of a number of spirotrichs spe-
cies. Ammermann, Schlegel, and Hellmer (1989) 
distinguished the sibling species Stylonychia 
mytilus and Stylonychia lemnae using isozymes of 
 isocitrate dehydrogenase . Haentzsch et al. (2006) 
have now used a PCR method based on this gene 
to clearly identify these sibling species , while 
Schmidt, Bernhard, Schlegel, and Fried (2006b) 
have used fluorescence in situ hybridization ( FISH ) 
of SSUrDNA probes for the same purpose. Others 
have employed either random amplified polymor-
phic DNA ( RAPD ) fingerprinting or restriction 
fragment length polymorphisms ( RFLPs ) to distin-
guish species and populations of hypotrichs , such 
as Euplotes (Chen, Song, & Warren, 2001; Kusch 
& Heckmann, 1996; Shang, Chen, & Song, 2002) 
and Uronychia (Chen, Song, & Warren, 2003). 
 Finally, monographic works have recently appeared 
on the spirotrichs . These include monographs on 
the hypotrichs and stichotrichs by Berger (1999, 
2001, 2006a, 2006b) and tintinnids (Alder, 1999). 
 7.2 Life History and Ecology 
 As noted above, spirotrichs are broadly distributed, 
both as symbionts and free-living forms. There is 
not a large number of symbiotic spirotrichs , but 
what species there are colonize a diverse array 
of hosts. For example, Licnophora is found in 
 holothurian echinoderms (Stevens, 1901), on the 
eyes of scallops (Harry, 1980), on cyanobacterial 
filaments (Fauré-Fremiet, 1937), and in the man-
tle cavity of limpets (Van As, Van As, & Basson, 
1999); Kerona polyporum is found on the body of 
Hydra (Hemberger & Wilbert, 1982); Trachelostyla 
tani is found in the mantle cavity of the scallop 
Chlamys (Hu & Song, 2002); Strombidium is found 
associated with echinoid echinoderms (Jankowski, 
1974b; Xu, Song, Sun, & Chen, 2006); Euplotes
tuffraui is also associated with echinoid echi-
noderms (Berger, 1965); Euplotaspis associates 
with the chambers of ascidian tunicates (Chatton 
& Séguéla, 1936); and Plagiotoma is an obligate 
 endosymbiont in the digestive tract of oligochaete 
 annelids (Albaret, 1973; Mandal & Nair, 1975). 
 Free-living hypotrichs and stichotrichs occupy a 
wide range of habitats from freshwater to brackish 
to marine, in sands and soils , and edaphic habitats. 
They are typically substrate-oriented and benthic, 
and are particularly prominent in soil ecosystems 
from Europe to Antarctica (Berger & Foissner, 
1987, 1989a; Blatterer & Foissner, 1988; Foissner, 
1980a, 1982; Petz & Foissner, 1997) where they 
may represent over 30% of the species richness 
and may attain abundances of up to 1,000 g -1 of 
dry soil. Hypotrichs and stichotrichs have also 
been recorded in aquatic habitats from arctic and 
antarctic ice (Agatha, Spindler, & Wilbert, 1993; 
Agatha, Wilbert, Spindler, & Elbrächter, 1990; 
Garrison et al., 2005), in benthic communities in the 
deep Mediterranean Sea (Hausmann, Hülsmann, 
Polianski, Schade, & Weitere, 2002), in freshwater 
ponds in Great Britain (Finlay & Maberly, 2000), 
in streams and rivers in Europe (Cleven, 2004; 
Foissner, 1997b), in tropical littoral habitats (Al-
Rasheid, 1999a; Dragesco & Dragesco-Kernéïs, 
1986), and associated with leaf litter in mangrove 
forests in India (Dorothy, Satyanarayana, Kalavati, 
Raman, & Dehairs, 2003). Isolates from different 
regions have demonstrated adaptations to those 
environments: Antarctic Euplotes species show 
growth rate optima at lower temperatures than tem-
perate and tropical isolates (Lee & Fenchel, 1972) 
as do temperate isolates of the halteriid Meseres
compared to tropical and subtropical isolates 
(Gachter & Weisse, 2006). These cold adapta-
tions arise in some Euplotes species through gene 
mutations in protein-coding genes that increase 
the molecular flexibility of these proteins at low 
temperatures (Pucciarelli, Marziale, Di Giuseppe, 
Barchetta, & Miceli, 2005). 
 Oligotrichs and choreotrichs have been exten-
sively studied in recent years in both freshwa-
ter (e.g., Beaver & Crisman, 1989a; Foissner, 
Berger, & Schaumburg, 1999; Obolkina, 2006; 
Sonntag, Posch, Klammer, Teubner, & Psenner, 
2006; Zingel, Huitu, Makela, & Arvola, 2002) and 
brackish water lakes (Pfister, Auer, & Arndt, 2002) 
and marine (e.g., Lynn & Montagnes, 1991; Pierce 
& Turner, 1992; Sanders & Wickham, 1993) eco-
systems, where they can be found in both neritic 
and eupelagic regions. For marine species, the vast 
majority of studies are not unexpectedly local-
ized near sites of marine laboratories (see Lynn 
& Montagnes, 1991). Tintinnid choreotrichs have 
been quite extensively sampled over all the world’s 
oceans, ranging from the arctic to the antarctic 
(Pierce & Turner, 1993). Some taxa show unusual 
 biogeographic distributions , but these must be 
interpreted with some caution since tintinnids can 
survive in ballast water and be distributed globally 
by humans (Pierce, Carlton, Carlton, & Geller, 
1997). Marine oligotrichs are equally broadly dis-
tributed with recent reports from northern (Dale & 
Dahl, 1987a; Stelfox-Widdicombe, Archer, Burkill, 
& Stefels, 2004) and southern oceans (Pettigrosso, 
Barria de Cao, & Popovich, 1997) to the trop-
ics (Al-Rasheid, 1999; Lynn, Roff, & Hopcroft, 
1991a) and Antarctica (Garrison et al., 2005; 
Leakey, Fenton, & Clarke, 1994; Petz, 1994). 
 Oligotrichs and choreotrichs are now considered 
to play an important role inmicrobial food webs (e.g., 
Beaver & Crisman, 1989b; Pierce & Turner, 1993;
Sanders & Wickham, 1993; Weisse, 2006). Aloricate
 oligotrichs (e.g., Strombidium , Tontonia , Laboea ) 
and choreotrichs (e.g., Strobilidium , Strom bidinopsis ) 
tend to dominate the abundance, ranging from tens to 
thousands per liter. Mean annual abundances are 
typically 1,000 l -1 (Lynn, Roff, & Hopcroft, 1991a; 
Montagnes, Lynn, Roff, & Taylor, 1988; Moritz, 
Montagnes, Carleton, Wilson, & McKinnon, 
2006), but exceptionally high abundances of over 
106 l -1 have been recorded (e.g., Dale & Dahl, 
1987a). Tintinnid choreotrichs typically comprise 
a smaller fraction of the total ciliate abundance, 
ranging up to 25% of the abundance of their 
aloricate relatives (e.g., Abboud-Abi Saab, 1989; 
Gilron, Lynn, & Roff, 1991; Lynn et al., 1991a). 
Because of their loricae, which are easily preserved, 
there is an extensive literature on the ecology of 
 tintinnids . Tintinnid abundances average in the 
10s l -1 in places as geographically distant as the 
 Mediterranean (Abboud-Abi Saab; Cariou, Dolan, 
& Dallot, 1999; Krsinic & Grbec, 2006), Greenland 
Sea (Boltovsky, Vivequin, & Swanberg, 1995), 
 Barents Sea (Boltovsky, Vivequin, & Swanberg, 
1991), and off the cost of Japan (Dohi, 1982). 
7.2 Life History and Ecology 151
However, abundances of 500 l -1 (Cariou et al., 1999)
may occur seasonally, with particularly high abun-
dances, to over 10,000 l -1 , being associated with 
estuarine and near shore locations, for exam-
ples, in North America (Capriulo & Carpenter, 
1983; Verity, 1987), South America (Barría 
de Cao, 1992), and China (Zhang & Wang, 2000). 
Variations have been reported

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