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absent or reduced to a few pericytostomal kineto-
somes; macronucleus, homomerous, band-like ; 
17.3 The Ciliate Taxa to Genus 387
micronucleus, present; contractile vacuole, present; 
cytoproct (?); predators of peritrichs and sucto-
rians or on tissues (?) of host; in marine habitats 
as endosymbionts in wide range of hosts, such as 
 ascidians , barnacles , brittle stars , and tunicates ; 
one family. 
 Family HYPOCOMIDAE Bütschli, 1889 
 (syn. Crateristomatidae ) 
 With characteristics of order; five genera. 
 – Crateristoma Jankowski, 1967 
 – Harmocoma Jankowski, 1980 
 – Hypocoma Gruber, 1884 
 – Parahypocoma Chatton & Lwoff, 1939 
 – Rhynchocoma Jankowski, 1975 
 Order Rhynchodida Chatton & Lwoff, 1939 
 (syns. Ancistrocomina , Rhynchodina , Sphe-
nophryina ) 
 Size, small to medium; shape, variable; free-
swimming, but typically attached to the host by 
the oral region; somatic kineties, sometimes with 
non-ciliated kinetosomes, typically organized in 
a thigmotactic field, which may extend to cover 
the entire body or which may be divided in two, 
leaving a large part of the cell surface bare ; no
posterior adhesive region ; macronucleus, vari-
ably shaped, typically not in a band-form; parasites 
of the gills of invertebrates, commonly bivalve 
 molluscs ; two families. 
 Family ANCISTROCOMIDAE Chatton & Lwoff, 
 (syns. Ancistrocominae , Cepedellidae , Hypo-
comellinae , Hypocomidinae ) 
 Size, small to medium; shape, typically pear- or 
banana-like with a pointed anterior end; free-
swimming, but typically attached to host; somatic
kineties, with thigmotactic cilia more or less 
developed, at least near the anterior end, tend-
ing to reduction to a small anterior thigmotactic 
ventral field; with apical sucker ; oral ciliation, 
absent; macronucleus, globular to ellipsoid; micro-
nucleus, present; contractile vacuole, may be 
present; cytoproct (?); feeding on cell contents of 
host tissues; in marine and freshwater habitats as 
parasites of invertebrates, such as polychaetes , a 
 phoronid , and others, but found principally in the 
mantle cavity of molluscs ; 21 genera and one genus 
incertae sedis . 
 – Ancistrocoma Chatton & Lwoff, 1926 
 – Anisocomides Chatton & Lwoff, 1950 
 – Colligocineta Kozloff, 1965 
 – Crebricoma Kozloff, 1946 
 – Enerthecoma Jarocki, 1935 
 – Goniocoma Chatton & Lwoff, 1950 
 – Heterocinetopsis Jarocki, 1935 
 – Holocoma Chatton & Lwoff, 1950 
 – Hypocomagalma Jarocki & Raabe, 1932 
 – Hypocomatidium Jarocki & Raabe, 1932 
 – Hypocomella Chatton & Lwoff, 1924 
 – Hypocomides Chatton & Lwoff, 1922 
 – Hypocomidium Raabe, 1938 
 – Hypocomina Chatton & Lwoff, 1924 
 – Ignotocoma Kozloff, 1961 
 – Insignicoma Kozloff, 1946 
 – Isocomides Chatton & Lwoff, 1950 
 – Kozloffiella Raabe, 1970 
 – Raabella Chatton & Lwoff, 1950 
 – Stegotricha Bower & Meyer, 1993 
 – Syringopharynx Collin, 1915 
Incertae sedis in Family Ancistrocomidae 
 – Cepedella Poyarkoff, 1909 
 Family SPHENOPHRYIDAE Chatton & Lwoff, 
 (syns. Gargariidae , Lwoffidae , Pelecyophyridae ) 
 Size, small to medium; shape, ovoid to elongate, 
flattened; except in one species, adult form or 
trophont unciliated, but with an infraciliature 
in two fields that may diverge from a central (= 
posterior) apex towards the ends of the body; 
attached to host by adhesive “sole” and short 
tentacle ; reproduction, isotomic fission or by bud-
ding; larval form, typically ciliated with kinetal pat-
tern reminiscent of ancistrocomids; macronucleus, 
globular to elongate band-form; micronucleus, 
present; conjugation, often occurring epidemically; 
contractile vacuole, present; cytoproct (?); feed-
ing on cell contents of host tissues; in marine and 
freshwater habitats as parasites in the mantle cavi-
ties of bivalve molluscs ; three genera. 
 – Gargarius Chatton & Lwoff, 1934 
 – Pelecyophrya Chatton & Lwoff, 1922 
388 17. The Ciliate Taxa Including Families and Genera
 – Sphenophrya Chatton & Lwoff, 1921 
Incertae sedis in Order Rhynchodida 
 – Lwoffia Kozloff, 1955 
 Subclass Suctoria Claparède & Lachmann, 1858 
 (syns. Acinet[e] , Acinetaria , Acinetina , 
 Acinet[o]idea , Actinifera , Actinosuctorifera , 
 Atricha , Dystricha , Suctorasina , Suctorea , Suctoriae , 
 Suctorifera , Suctoriorida , Tentaculifer[id]a , Ten-
taculiferiae , Toxistomia p.p .) 
 Size, small to large; shape, variable, from simple 
spheroid to flattened discs to complex branching 
forms; polymorphic, with free-swimming, typi-
cally ciliated larval form and typically sessile, adult 
form, usually non-ciliated, although with an infra-
ciliature; alveoli, well-developed, underlain by a 
thick epiplasm; extrusomes as toxic “oral” hapto-
cysts in tips of suctorial tentacles or arrayed along 
the length of prehensile tentacles; oral structures 
as one to many multiple, rarely none, ingestatory 
suctorial tentacles, short (e.g., Cyathodinium , 
Phalacrocleptes ) or long and extensible (e.g., 
Rhyncheta , Rhynchophrya ), usually supported 
by an outer ring of microtubules and an inner 
set of microtubular ribbons (= the presumed 
phyllae) with extrusomes as haptocysts at the 
tips ; stalk, often present, always non-contractile, 
of varying length and produced by the scopuloid; 
migratory motile ciliated larval form or swarmer, 
produced by some mode of budding, but typically 
bearing neither tentacles nor stalk; macronucleus, 
homomerous; conjugation of different kinds, but 
frequently total with unequal conjugants; con-
tractile vacuole, present; cytoproct, absent; cyst, 
often present; feeding primarily on other ciliates, 
but some species parasites of other eukaryotes; in 
marine, freshwater, and rarely terrestrial habitats, 
widespread, predominantly as ectosymbionts on 
diverse invertebrates, but some as endocommensals 
in hosts ranging from other ciliates to vertebrates; 
three orders. 
NOTE : There is as yet no strong consensus on 
the evolutionary diversification of the suctorians. 
We have remained conservative, and tried to assign 
taxa to the included orders based on the modes of 
budding proposed by Collin (1912). Kormos and 
Kormos (1957a) have proposed a more complex 
classification of budding, which Batisse (1994) 
has partly followed. Revisionary monographs have 
also been published by Jankowski (1981), Curds 
(1985a, 1985b, 1985c, 1986, 1987), and Matthes 
(1988). Dovgal (2002) has undertaken an exten-
sive cladistic analysis and discussed the status of 
taxa at the generic level and above. In the main, 
we have followed Dovgal for taxonomy within the 
group, and strongly recommend this monograph 
as a starting point for future taxonomic investiga-
tions. However, we do not agree with Dovgal on 
two major points. First, we do not recognize the 
class status of the suctorians . Second, we have not 
recognized the vermigenids as a separate group, 
and instead placed these families within the Order 
 Exogenida , especially considering that Dovgal 
suggested that vermigenids may have been derived 
from exogenid ancestors. While a comprehensive 
analysis using gene sequences may prove one of 
these schemes most appropriate, the first small 
subunit rRNA gene sequences suggest that Collin’s 
(1912) system may have validity (Snoeyenbos-
West et al., 2004). 
 Order Exogenida Collin, 1912 
 (syns. Allantosomatida p.p ., Asteriferina , 
 Dendrosomidida p.p ., Ephelophagina , Ephelotida , 
 Ephelotina , Exogenea , Exotropida , Metacinetida 
p.p ., Nemertodendrina p.p ., Oligostomatida 
p.p ., Ophryocephalida p.p ., Ophryodendrida , 
 Ophryodendrina , Paracinetida , Paracinetina , 
 Phalacrocleptida p.p ., Podophryida , Podophryina , 
 Spelaeophryida , Spelaeophryina , Stylostomatina 
p.p ., Thecacinetina , Tomogenea , Urnulida p.p ., 
 Vermigemmida , Vermigenea , Vermigenia ) 
 Size, small to large; shape, diverse; often stalked