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related to fragmentation of 
the micronuclear chromosomes and processing of 
the genomic DNA during macronuclear develop-
ment (see also Riley & Katz, 2001). 
 Class SPIROTRICHEA Bütschli, 1889 
 (syns. Halteriia p.p ., Halteriida p.p ., Membranellata 
p.p ., Membranellophora p.p .; Polytrichidea + 
 Oligotrichidea , Postcilio desmatophora p.p ., Spirotricha 
p.p ., Spirotrichophora p.p.) 
 Size, small to large; shape, variable, from spheroid 
to cone-shape to dorsoventrally flattened; free-swim-
ming or sessile, with some loricate forms that may 
be attached to substrates and/or sedentary attached 
within lorica; somatic ciliation, holotrichous in some 
groups, but nearly devoid of cilia in others; somatic 
dikinetids usually with the anterior or both kineto-
somes ciliated or somatic polykinetids, called cirri; 
extrusomes as mucocysts or trichocyst-like trichites; 
oral ciliature conspicuous, with adoral zone of 
oral polykinetids, typically as paramembranelles, 
especially prominent and often encircling oral 
region clockwise before entering the oral cavity ; 
one or more “parorals” on the right, and if two, as 
paroral (= outer) and endoral (= inner) membranes; 
stomatogenesis, typically parakinetal or apokinetal, 
but mixokinetal in Protocruzia ; fission almost always 
17.3 The Ciliate Taxa to Genus 347
isotomic; macronuclear DNA replication by repli-
cation bands (except in Subclasses Protocruziidia
and probably Phacodiniidia (but latter needs con-
firmation) ); conjugation, typically temporary and 
isogamontic, but at least one case of total conjugation; 
feeding habits, diverse, ranging from microphagous 
bacterivores to predators on other ciliates and even 
small metazoans; widely distributed in marine, fresh-
water, and terrestrial habitats; seven subclasses. 
NOTE : Molecular evolution studies suggest 
that the Subclasses Protocruziidia , Phacodiniidia , 
 Licnophoria , Hypotrichia , Choreotrichia , Oligotrichia , 
and Stichotrichia belong to a monophyletic group here 
called the Class SPIROTRICHEA (see Lynn & Strüder-
Kypke, 2002). Macronuclear replication bands have 
not been demonstrated in protocruziids and phacodini-
ids . Protocruziids demonstrate a form of macronuclear 
division unique within the phylum (Ammermann, 
1968; Ruthmann & Hauser, 1974) and may deserve 
separate status as a monotypic class. Phacodiniids need 
careful restudy to determine whether or not they have 
replication bands or something akin to them. 
 Subclass Protocruziidia de Puytorac, Grain, & 
Mignot, 1987 
 Size, small; shape, ovoid; free-swimming; alveoli 
not well-developed; body with monokinetid or diki-
netid field on right side and dorsal surface; somatid 
dikinetids with short kinetodesmal fibrils and over-
lapping postciliary microtubular ribbon, which do not 
form postciliodesmata; extrusomes, trichocyst-like; 
adoral zone of 6 (5–8) oral polykinetids on left of oral 
region; paroral to posterior and right of oral region, 
composed of dikinetids; stomatogenesis, mixokinetal; 
nuclear apparatus a cluster of similar-sized nuclei 
with paradiploid macronuclei surrounding one or 
more micronuclei; macronuclear division appar-
ently as separation of two composite (?) chromo-
somes per macronucleus ; conjugation, not reported; 
contractile vacuole (?); cytoproct (?); microphagous, 
on bacteria, microalgae, and smaller protists; in 
marine and brackish water habitats; one order. 
 Order Protocruziida Jankowski, 1980 
 With characters of subclass; one family. 
 Family PROTOCRUZIIDAE Jankowski, 1980 
 With characters of order; one genus. 
 – Protocruzia de Faria, da Cunha, & Pinto, 1922 
 Subclass Phacodiniidia Small & Lynn, 1985 
 Size, medium; shape, ovoid, compressed later-
ally; free-swimming; cortex with rigid and ribbed 
pellicle (= cuirass) and well-developed alveoli; 
somatic ciliature, in widely spaced rows, of 
linear polykinetids of 6–8 kinetosomes with 
delicate cilia ; only a few cirrus-like somatic 
polykinetids, composed of two rows of kineto-
somes; oral region, long, with an adoral zone 
of conspicuous oral polykinetids, terminating 
at the cytostome, very near posterior pole of 
organism; paroral, series of obliquely-oriented, 
short files of kinetosomes ; macronucleus horse-
shoe-shaped; micronuclei, multiple; contractile 
vacuole, present; cytoproct, present; feeding on 
bacteria, microalgae, and smaller protists; mainly 
in freshwater and terrestrial habitats (e.g., moss 
on trees); one order. 
 Order Phacodiniida Small & Lynn, 1985 
 (syn. Protohypotrichina p.p .) 
 With characters of the subclass; one family. 
 With characters of the order; one genus. 
 – Phacodinium Prowazek, 1900 
 Subclass Licnophoria Corliss, 1957 
 (syns. Licnophorida , Scaiotricha p.p .) 
 Size, medium; shape, in form of hour-glass, 
with prominent oral disc apically and conspicu-
ous aboral attachment disc at posterior pole ; 
free-swimming, but typically attached to substrate; 
somatic cilia, essentially absent, except for pos-
terior ciliary rings encircling attachment disc ; 
adoral zone of oral polykinetids encircling oral 
region; paroral as single file of kinetosomes; sto-
matogenesis, apokinetal; macronucleus, typically 
moniliform; micronucleus, one to several; con-
jugation, temporary; contractile vacuole, absent; 
cytoproct, absent; microphagous on bacteria, 
microalgae, and perhaps organic detrital particles 
derived from host’s feeding activities; in marine 
habitats as “ectocommensals” on organisms ranging
from an alga (substratum for one species) to a variety 
of invertebrates (e.g., tunicates, coelenterates, 
annelids, molluscs, and the respiratory trees of sea 
cucumbers); one order. 
348 17. The Ciliate Taxa Including Families and Genera
 Order Licnophorida Corliss, 1957 
 With characteristics of subclass; one family. 
 Family LICNOPHORIDAE Bütschli, 1887 
 With characteristics of order; two genera. 
 – Licnophora Claparède, 1867 
 – Prolicnophora Jankowksi, 1978 
 Subclass Hypotrichia Stein, 1859 
 (syns. Euplotia , Hypotricha p.p ., Hypotrichea 
p.p ., Hypotrichida p.p ., Hypotrichina p.p ., 
 Hypotrichorida p.p ., Pseudohypotrichina ) 
 Size, small to medium; shape, dorsoventrally 
flattened, typically rigid, oval to rectangular; free-
swimming; alveoli well-developed and, at least 
in euplotids, filled with a protein, called platein ; 
somatic ciliature commonly represented by rows 
or localized groups of polykinetids, called cirri, 
conspicuous on the ventral surface; dorsally, files 
of widely spaced dikinetids with short cilia 
(“sensory bristles”) and retention of a laterally-
directed kinetodesmal fibril ; files of marginal 
cirri, incomplete or absent; somatic infraciliature 
typically retained during encystment ; prominent 
adoral zone of generally numerous oral polyki-
netids, as paramembranelles, on left-anterior por-
tion of the ventral surface, bordering a broad, 
non-ciliated peristomial field and sometimes con-
tinuing over apical end of body onto the dorsal 
surface; paroral as paroral and/or endoral in diplo- 
or polystichomonad condition; stomatogenesis, 
generally apokinetal, beginning in a cortical pocket 
in some forms, but sometimes parakinetal; macro-
nucleus, ellipsoid to band-shaped or in fragments, 
with replication bands moving from ends to mid-
dle when the nucleus is elongated; micronucleus, 
one to several; conjugation, temporary; contractile 
vacuole, at least present in freshwater forms; cyto-
proct, present; microphagous and macrophagous; in 
marine, freshwater, and terrestrial habitats, widely 
distributed as free-living forms, but a few species 
as ectocommensals on various invertebrates and 
one inquilinic in an echinoid; two orders. 
NOTE : Sequences of small subunit rRNA genes 
of species assigned to this subclass generally show 
rapid sequence evolution. This may explain why 
the representative

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