Cap 17

; macronu-
cleus, two to many globular to ellipsoid nodules; 
micronucleus, present; contractile vacuole, present; 
cytoproct (?); feeding on bacteria, microalgae, and 
smaller protists; in marine and freshwater habi-
tats, including sand, and one species well-known 
ectocommensal on Hydra ; four genera. 
 – Kerona Müller, 1786 
 – Keronopsis Penard, 1922 
 – Paraholosticha Wenzel, 1953 
 – Parakeronopsis Shi, Song, & Shi, 1999 [nomen 
nudum]
 Family PLAGIOTOMIDAE Bütschli, 1887 
 Size, medium; shape, laterally flattened, elongate-
ovoid, with right side slightly concave; free-
 swimming; somatic ciliation, holotrichous, dense, 
of small polykinetids or cirri with no differentia-
tion into cirral groups on either body surface ; 
oral ciliature of extensive adoral zone on its left 
side, coursing from apical end to subequatorial posi-
tion and then entering a deep oral cavity and with 
paroral and endoral along right wall of oral cavity; 
stomatogenesis, parakinetal; macronucleus, as an 
irregular bunch of nodules; micronuclei, several, 
relatively large; contractile vacuole, present; cyto-
proct (?); feeding on bacteria and organic matter in 
host’s digestive system (?); in terrestrial habitats 
as an endocommensals solely in certain species 
of lumbricid oligochaete annelids ; one genus. 
 – Plagiotoma Dujardin, 1841 
 Family PSILOTRICHIDAE Bütschli, 1889 
 (syn. Psilotrichinae ) 
 Size, small to medium; shape, oval to elliptical 
in outline, with posterior spiny extensions in some 
species, and sometimes with zoochlorellae in cyto-
plasm; free-swimming; somatic ventral ciliature 
as long and sparse cirri in seven slightly curved 
cirral files with the postoral oblique cirral file 
developing from the anlage file IV ; frontal cirri; 
marginal cirri, strongly reduced; transverse cirri, 
present; caudal cirri, present; dorsal somatic cili-
ature as several files of monokinetids (?); peristo-
mial areal limited to anterior third of organism with 
oral ciliature typical of order, including paroral and 
endoral; macronucleus, two globular to ellipsoid 
nodules; micronucleus, present; contractile vacu-
ole, present; cytoproct (?); feeding (?); in freshwa-
ter and terrestrial habitats; one genus. 
 – Psilotricha Stein, 1859 
 – Hemiholosticha von Gelei, 1954 
 Family SPIROFILIDAE von Gelei, 1929 
 (syns. Atractidae , Chaetospiridae , Chaetospirina , 
 Chaetospirinae , Chaetospiroidea , Hypotrichidiidae , 
 Microspirettidae , Spiretellidae , Spirofilopsidae , 
 Stichotrichinae , Strongylidae , Strongylidiidae , 
 Strongylidiinae , Strongylidioidea ) 
 Size, small to medium; shape, varied, with some 
forms tailed and others more elongate at the ante-
rior end; free-swimming, but lorica produced by 
some species; somatic ventral ciliature as incon-
spicuous ventral cirri in files curved or spiralling 
obliquely around body, some ending on dorsal 
surface ; transverse cirri, present or absent; caudal 
cirri, present or absent; somatic dorsal ciliature as 
several dorsal files of bristle dikinetids in “dor-
sal strip” helically winding around the body ; 
adoral zone not highly prominent with oral cili-
ature typical of order and with paroral and endoral; 
macronucleus, globular to ellipsoid, single to sev-
eral nodules; micronucleus, present; contractile 
vacuole, present; cytoproct, likely present; feeding 
on bacteria, algae, and smaller protists; in marine 
and freshwater habitats, both benthic and plank-
tonic; 12 genera and one genus incertae sedis . 
 – Atractos Vörösváry, 1950 
 – Chaetospira Lachmann, 1856 
 – Hypotrichidium Ilowaisky, 1921 
17.3 The Ciliate Taxa to Genus 359
 – Microspiretta Jankowski, 1975 
 – Mucotrichidium Foissner, Oleksiv, & Müller, 1990 
 – Parastrongylidium Fleury & Fryd-Versavel, 1985 
 – Pelagotrichidium Jankowski, 1978 
 – Planitrichidium Jankowski, 1979 [nomen nudum] 
 – Spirofilopsis Corliss, 1960 
 – Stichotricha Perty, 1849 
 – Strongylidium Sterki, 1878 
 – Urostrongylum Kahl, 1932 
Incertae sedis in Family Spirofilidae 
 – Kahliela Tucolesco, 1962 
Incertae sedis in Order Stichotrichida 
 – Balladinopsis Ghosh, 1921 [nomen dubium] 
 – Klonostricha Jankowski, 1979 
 – Psilotrix Gourret & Roeser, 1888 
 – Stylonethes Sterki, 1878 [nomen dubium] 
 Order Sporadotrichida Fauré-Fremiet, 1961 
 (syn. Halteriina p.p ., Oxytrichina p.p ., Pleurotrichina 
p.p ., Sporadotrichorina ) 
 Size, small to large; shape, sometimes elongate, 
even tailed, but often oval to elliptical in outline; 
free-swimming; somatic ventral ciliature as fron-
toventral cirri, typically heavy and conspicuous, 
arranged in specific, localized frontal and ven-
tral groups, except in a few taxa (e.g., Family 
Halteriidae, Laurentiella , Onychodromus , and
 Styxophrya ); marginal cirri, typically present; 
transverse cirri, may or may not be present; caudal 
cirri, may or may not be present; dorsal somatic 
ciliature, typically as files of dikinetids with a 
single bristle cilium; oral ciliature as for subclass; 
stomatogenesis, apokinetal, usually with five or 
six anlagen streaks in two groups for differentia-
tion of ventral somatic ciliature ; in marine, fresh-
water, and terrestrial habitats, widely distributed, 
primarily benthic with some forms planktonic, 
others interstitial, and a few species symbiotic, 
either as ectocommensals on the integument or in 
the branchial cavity of several invertebrates or as 
intestinal inquilines of echinoids; three families. 
NOTE : Gene sequences of both actins and small 
subunit rRNA unambiguously place several genera 
of the Family Halteriidae (e.g., Halteria , Meseres ) 
close to the oxytrichid clade (Croft et al., 2003; 
Foissner et al., 2004; Hewitt et al., 2003). We have 
therefore transferred this family to this order from 
the Subclass Oligotrichia . We consider halteriids 
as planktonic descendants of this primarily benthic 
lineage.
 Family HALTERIIDAE Claparède & Lachmann, 
1858
 (syn. Meseridae [for Lieberkuehnidae ]) 
 Size, small; shape, spheroid to subovoid and 
conical; free-swimming, often darting through 
the water; somatic ciliature as somatic kinetids 
with long cilia (i.e., >10 µm long), often as 
cirrus-like “bristles” or stiff cilia ; oral cili-
ature, with the “collar” as an “open” circle 
of apical oral polykinetids, the “lapel” on the 
left side of the oral cavity, and only with the 
paroral (or endoral?) on the right side of the 
oral cavity; macronucleus, single, ellipsoid ; 
micronucleus, present; contractile vacuole, 
present; cytoproct (?); feeding on bacteria and 
microalgae; predominantly in freshwater habitats, 
typically planktonic but some in terrestrial habi-
tats; six genera and two incertae sedis . 
 – Cephalotrichium Meunier, 1910 (subj. syn. 
Strobilidium ) 
 – Halteria Dujardin, 1841 
 – Halterioforma Horváth, 1956 [ nomen oblitum ] 
 – Meseres Schewiakoff, 1893 
 – Pelagohalteria Foissner, Skogstad, & Pratt, 1988 
Incertae sedis in Family Halteriidae 
 – Jeannellia Tucolesco, 1962 (subj. syn. Halter-
ioforma ) 
 – Octocirrus Madhava Rao, 1929 [ nomen dubium ] 
 Family OXYTRICHIDAE Ehrenberg, 1830 
 (syns. Ancystropodiinae , Gastrostylidae p.p ., 
 Gastrostylina p.p ., Onychodromusidae , Oxytri-
chinae , Oxytrichoidea , Pattersoniellidae , Pleuro-
trichidae , Rigidotrichidae (?), Stylonychinae ) 
 Size, small to large; shape, relatively elongate; 
free-swimming; somatic ventral ciliature as fron-
toventral and transverse cirri, typically 18 in 
number, large and distinctive, scattered over 
mid-area of ventral surface, between right and 
left marginal cirral files, usually with three fron-
toventral cirri posterior to posterior vertex of the 
oral region, but several genera with conspicuous 
files of cirri (e.g., Laurentiella , Onychodromus ) ; 
360 17. The Ciliate Taxa Including Families and Genera
right and left marginal files of cirri, obvious;