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& Katz, 2001) while trees based on large subunit 
rRNA gene sequences place the colpodeans near to 
 nassophoreans and oligohymenophoreans (Baroin-
Tourancheau, Villalobo, Tsao, Torres, & Pearlman, 
1998). Histone gene sequences (Bernhard & 
Schlegel, 1998) and α-tubulin nucleotide sequences 
(Baroin-Tourancheau et al., 1998) support this latter 
 Foissner (1993a, 1994b) recognized two sub-
classes, the Subclass Colpodia and Subclass 
 Bryometopia , based primarily on features of the 
reticulate silverline system . There are three gen-
eral types of silverline systems in the colpodeans : 
the colpodid , platyophryid , and kreyellid patterns. 
Foissner (1978) demonstrated the usefulness of the 
 silverline system in identifying relationships among 
 colpodeans . However, as shown many years ago by 
Taylor and Garnjobst (1939) and confirmed by 
Foissner (1993a, 1994b), the silverline system is a 
dynamic element of the cortex, even changing from 
one type to another within the same species! Thus, 
we are reluctant at this time to support the subclass 
taxa based only on this feature and will await gene 
sequence data to confirm this fundamental divi-
son within the class. We currently recognize six 
orders in the class: Bryometopida , Bryophryida , 
 Bursariomorphida , Colpodida , Cyrtolophosidida , 
and Sorogenida , based mainly on the monographic 
work of Foissner (1993a). 
 The Order Bryometopida is characterized as hav-
ing an argyrome with a very highly reticulated and 
subdivided dense network (i.e., “kreyellid type” , 
Foissner, 1993a). Oral structures include typi-
cally a paroral of dikinetids, sometimes modified, 
and several left oral polykinetids. There are four 
families in the order: Bryometopidae , Jaroschiidae , 
 Kreyellidae , and Trihymenidae . 
 The Order Bryophryida , monotypic for the 
Family Bryophryidae , is characterized by right 
oral kineties that at least include a series of radially 
oriented kinetosomal rows, except for the genus 
Notoxoma , in which these are interpreted to have 
been reduced to dikinetids. There can be a single 
or multiple left adoral polykinetids composed of 
square-packed kinetosomes (Foissner, 1993a). 
 The Order Bursariomorphida , which includes the 
Families Bursariidae and Bursaridiidae , is charac-
terized by an expansive oral cavity whose left side 
is lined by many, long and equidistantly spaced oral 
polykinetids (Fernández-Galiano, 1979; Foissner, 
1993a). These oral polykinetids are typically of 
two to three rows of kinetosomes, arranged in a 
square-packed arrangement. The right oral ciliature 
is composed of many regularly or slightly irregu-
larly and obliquely arranged “paroral” kineties. 
 The Order Colpodida includes colpodeans that 
undergo merotelokinetal stomatogenesis , developing
a left oral polykinetid that is composed of several
to many rows of regularly-spaced monokinetids. 
Foissner (1993a) recognized the monotypic Order 
 Grossglockneriida as distinct from the Order 
 Colpodida . However, the similarities in stoma-
togenesis and general morphology strongly 
suggest affinities between the two, whose genera 
are not greatly different based on SSUrRNA gene 
sequences (Lynn et al., 1999). In addition to 
the Family Grossglockneriidae , we also include the 
following families: Colpididae, Hausmanniellidae , 
 Marynidae , Bardeliellidae , and Grandoriidae . 
 Of the remaining orders recognized by Foissner 
(1993a, 1994b), this leaves the Cyrtolophosidida 
and Sorogenida . Lasek-Nesselquist and Katz 
(2001) have noted the strong genetic similarities in 
SSUrRNA gene sequences between Sorogena , the 
only representative for the Order Sorogenida , and 
those of the cyrtolophosidid Platyophrya . They 
recommended suppression of the Order Sorogenida , 
which is considered distinct primarily on the basis of 
the unusual sorocarp development in the life cycle 
of its type genus (Foissner, 1993a). Furthermore, the 
stomatogenesis of Sorogena appears to be similar 
to that of Platyophrya and other cyrtolophosidids 
(Bardele et al., 1991). However, we have maintained 
this order, monotypic for the Family Sorogenidae , 
until a more complete analysis of molecular genetic 
diversity compels us to suppress it. 
 Finally, taxa in the Order Cyrtolophosidida show 
strong similarities in stomatogenesis to bryome-
topids , like Bryometopus (cf., Dragesco, Fryd-
Versavel, Iftode, & Didier, 1977; McCoy, 1977; de 
Puytorac, Perez-Paniagua, & Perez-Silva, 1979b; 
Wirnsberger, Foissner, & Adam, 1985b). However, 
we have maintained the Order Cyrtolophosidida , 
which likely includes representatives similar to the 
common ancestor of the class. The order, character-
ized by a simple paroral of dikinetids and several to 
many left oral polykinetids , includes ciliates with 
the basic features of the class and is comprised 
of the following families: Cyrtolophosididae , 
 Platyophryidae , Woodruffiidae , and Sagittariidae . 
 There is clearly a need for gene sequences 
from more representatives of this class to test 
the competing classifications (e.g., the one pro-
posed here, Foissner, 1993a; de Puytorac et al., 
1979b). Molecular studies would also resolve the 
placement of the Families Tectohymenidae and 
 Pseudochlamydonellidae , which we consider incertae
sedis in this class. 
12.1 Taxonomic Structure 245
246 12. Subphylum 2. INTRAMACRONUCLEATA: Class 6. COLPODEA
 12.2 Life History and Ecology 
 Encystment is the life history feature that typifies 
the colpodeans . To our knowledge, all colpodeans 
can develop resistant resting cysts in response to 
desiccation. This has meant that more than any 
other class, their global distribution has been 
assured. Species of the genus Colpoda are notori-
ous for this ability. Several studies have demon-
strated the high vagility of Colpoda species by 
 aerial dispersal (Maguire, 1963a, 1963b; Rivera 
et al., 1992). This high vagility is supported by 
studies that have not demonstrated any global 
 biogeography in the genetic variation in ribosomal 
DNA within Colpoda species (Bowers & Pratt, 
1995; Bowers, Kroll, & Pratt, 1998) nor in vari-
ations in physiological responses, such as growth 
rate and sensitivity to toxicants (Xu, Bowers, 
& Pratt, 1997). Nevertheless, Foissner (1994b) 
noted some restrictions in biogeography of other 
genera: Orthokreyella and Tectohymena have only 
been reported from Laurasia while Puytoraciella , 
Apocolpoda , and Jaroschia have only been reported 
from Gondwanaland . 
 Colpodeans are typically found in water associ-
ated with mosses, forest litters, and soils where the 
water may range from fresh to brackish and salty. 
These so-called “terrestrial” ciliates have been found 
in these habitats in Europe and Asia (Detcheva, 
1973; Foissner, 1980d, 1993a, 1994b; Griffiths, 
2002; Grolière, 1977; Hattori & Hattori, 1993; 
Tirjaková & Matis, 1985; Vargas & Hattori, 1990), 
the Americas (Bamforth, 1973, 1980; Foissner, 
1997c; Rivera et al., 1992), Africa (Buitkamp, 
1977; Foissner, 1988c), Australia (Foissner, 1988c, 
1990, 1997c), Antarctica (Ryan et al., 1989), and 
 Hawaii (Foissner, 1993b, 1994c). Several unusual 
habitats include pitcher plants (Addicott, 1974; 
Rojo-Herguedas & Olmo, 1999) and tree holes 
(Novotny, Lynn, & Evans, 1977). 
 Colpodeans have also been reported from streams, 
temporary ponds, and lakes in Europe (Foissner, 
1979e, 1997b; Skogstad, Granskog, & Klaveness, 1987), 
the Americas (López-Ochoterena, 1966), and Africa 
(Dragesco, 1972; Njiné, 1979). However, relatively 
few species are truly limnetic, typically including 
species in the genera Bursaridium , Cyrtolophosis , 
and Pseudochlamydonella (Foissner, 1994b). 
 Colpodeans are not typically marine although several 
species of Platyophrya and Woodruffia have been 
reported from marine environments (Kahl, 1930–