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121
Abstract The ciliates in this class are thought to 
represent the nature of the ancestral ciliate lineage.
Their non-dividing macronuclei make them “karyo-
logical relicts”. They are a strongly supported clade, 
characterized by postciliodesmata arising from the 
somatic kinetids, their non-dividing macronuclei, 
and by robust phylogenetic support based on small 
subunit rRNA gene sequences. The class is divided 
into three orders, based primarily on oral features. 
These ciliate are conspicuous inhabitants of benthic 
marine habitats. Their elongated worm-like bodies 
can be seen crawling between sand grains and detrital
particles. Thus, they are quite contractile and fl exible, 
and also capable of regeneration. The extrusomes 
of this class are also unique with cnidocysts and 
orthonematocysts being found nowhere else in the 
phylum. Oral structures are quite variable, ranging 
from simple circumoral dikinetids to somewhat 
complex adoral ciliature. Stomatogenesis can be 
either parakinetal or buccokinetal, although much 
remains to be done on this aspect of their biology. 
Their non-dividing macronuclei, which arise at 
each cell division from division of a micronucleus, 
are often numerous and typically clustered around 
a micronucleus. Two unusual features of taxa in the 
group are the harvesting of epibiontic bacteria by 
Kentrophoros and the use of mineral crystals in the 
Müller’s vesicle to sense gravity by Loxodes . 
 Keywords Postciliodesma, paradiploid, interstitial
 The ciliates assigned to this class are considered 
by some to represent the nature of the “dawn” or 
 eociliates that first diverged from the alveolate 
lineage. They have been labeled “ karyological 
relicts ”, a term introduced by Grell (1962) and 
publicized by Raikov (1969, 1982, 1985), because 
they exhibit a simple form of nuclear dualism : the 
 macronucleus is paradiploid but non-dividing. They 
have also been labeled “ cortical relicts ” because 
the cortex in some forms is thought to repre-
sent the ancestral condition: Kentrophoros does 
not have differentiated oral ciliature, but it does 
have somatic dikinetids , which are presumed to 
be the ancestral condition for the phylum (Lynn 
& Small, 1981; Small, 1984). There are over 
130 species of these primarily interstitial ciliates, 
commonly found in the sands and sediments of 
marine littoral environments (Foissner, 1998b). 
Intertidal sands are the habitat for “relict” forms of 
various groups of small invertebrates, leading one 
to believe that the psammophilic karyorelicteans 
are also of ancient vintage (Corliss, 1974b, 1975b; 
Raikov, 1969). Finlay and Fenchel (1986) have 
suggested, based on their research on Loxodes , 
which is the only freshwater representative of the 
class, that these ciliates might also be “biochemical 
relicts” because of the odd mitochondrial potential 
of nitrate respiration under low oxygen conditions, 
which are common in interstitial environments. 
 The karyorelicteans are united by two major 
features: the presence of a non-dividing paradiploid
macronucleus or macronuclei; and by postciliodesmata 
in which the microtubules are arranged as 2 + ribbon 
+ 1 in a repeating fashion (see Somatic Structures ).
The class is supported robustly by small subunit 
rRNA gene sequences (Hammerschmidt et al., 
1996; Hirt et al., 1995). The actin of Loxodes is 
quite divergent from other ciliates (Kim, Yura, Go, 
 Chapter 5 
 Subphylum 1. 
POSTCILIODESMATOPHORA: Class 1. 
KARYORELICTEA – The “Dawn” or 
Eociliates
122 5. Subphylum 1. POSTCILIODESMATOPHORA: Class 1. KARYORELICTEA – The “Dawn” 
& Harumoto, 2004). It is a matter of opinion whether 
this supports the ancestral nature of karyorelicteans
or demonstrates again the unreliability of actin as 
a phylogenetic marker for ciliate evolution (see 
Philippe & Adoutte, 1998). 
 They form a diverse assemblage when one considers 
their oral structures. Some genera are ventrostomous
(e.g., Geleia , Loxodes ); some genera are pros-
tomous (e.g., Trachelocerca , Trachelolophos ); and 
some genera have apparently no differentiated 
oral ciliature (e.g., Kentrophoros ). Bardele and 
Klindworth (1996) have observed that this parallels 
the evolution of oral structures in other groups. 
They argued that Kentrophoros may, in fact, have 
secondarily lost its oral apparatus when it acquired 
the obligatory symbiosis with thiotrophic or sul-
fur bacteria , an interpretation consistent with the 
observations of Foissner (1995a). 
 The distribution of these obligatorily psammobiotic 
species is global, though they are “endemic” with 
respect to their biotope. Means of dispersal remain 
unknown: Corliss and Hartwig (1977) supposed that 
continental drift may have been partially responsible. 
 5.1 Taxonomic Structure 
 We recognize three orders in this class: Order 
 Protostomatida ; Order Loxodida ; and Order 
 Protoheterotrichida . Alternative classifications have 
been proposed: Foissner (1998b) has argued that 
the bristle kinety , which frames the glabrous stripe 
or non-ciliated somatic cortex of protostomatids 
is homologous to that of loxodids , and so he sup-
ports uniting these in the Subclass Trachelocercia 
de Puytorac, Grain, and Mignot, 1987. We remain 
sceptical of this homology until ultrastructural 
investigation has demonstrated clear similarities 
in the kinetid structures or more extensive gene 
sequence data resolves the phylogeny of this class. 
 The Order Protostomatida includes the prostomous
Family Trachelocercidae and the “astomous” 
Family Kentrophoridae (Fig. 5.1). Oral struc-
tures are simple and ingestion may be either at 
the anterior end or along the glabrous stripe (see 
 Oral Structures ). The Order Loxodida includes 
the ventrostomous Families Loxodidae and 
 Cryptopharyngidae . These ciliates typically swim 
on the right surface of their flattened bodies. The 
oral cavity has a simplified ciliature of dikinetids 
(Fig. 5.1). The Order Protoheterotrichida , which 
includes the ventrostomous Family Geleiidae , are 
holotrichously ciliated and contractile, resembling 
their namesakes the heterotrichs (see Chapter 6 ). 
Their non-dividing macronuclei relate them to the 
other karyorelicteans even though their oral struc-
tures are more complex with simple adoral polyki-
netids and unusual paroral polykinetids on the right 
side of the oral region (Fig. 5.1). 
 A number of recent works have provided details 
of the morphology of these taxa: Trachelocercidae 
(Foissner, 1996c, 1997g; Foissner & Dragesco, 1996a, 
1996b), Kentrophoridae (Foissner, 1995a, 1998b), 
Loxodidae (Foissner, 1995/1996, 1996b, 1998b), and 
Geleiidae (Dragesco, 1999), but refer to Chapter 17
for detailed descriptions. 
 5.2 Life History and Ecology 
 These typically elongate and highly contractile 
ciliates are conspicuous consituents of interstitial 
habitats, especially sands and sediments of the 
marine littoral or brackish estuaries. Karyorelicteans 
have been recorded from interstitial habitats, 
often sandy ones in the marine sublittoral, in Africa
(Dragesco, 1965), western and eastern Europe 
(Agamaliev, 1971; Azovsky & Mazei, 2003; 
Dragesco, 1963, 2002; Fernández-Leborans & 
Fernández-Fernández, 1999; Kovaleva & Golemansky, 
1979; Mazei & Burkovsky, 2003), North America 
(Borror, 1963), and the Arabian Gulf (Al-Rasheid 
& Foissner, 1999). The only recorded exception is 
Loxodes , which is found in freshwater sediments 
(Finlay, 1982; Finlay & Berninger, 1984). Most 
species are classified as microaerophilic , restricted 
to sediments because these regions contain reduced 
oxygen concentrations, often becoming anoxic 
within a few centimeters of the sediment-water 
interface. However, Loxodes can move into the 
water column if the interstitial waters of the 
sediments become anoxic (Goulder, 1980). Finlay, 
Fenchel, and Gardener (1986) suggested that cyto-
chrome oxidase is the oxygen receptor forLoxodes
whose response to oxygen concentrations is modi-
fied by light (Fenchel & Finlay, 1986b). 
 Karyorelicteans are predaceous macrophages, 
using their filiform or vermiform bodies to crawl 
between the grains in the sediments in search of 
food. They have been recorded to ingest bacteria , 
Fig. 5.1. Representative genera of the Class KARYORELICTEA. The protostomatid Kentrophoros whose body in 
cross-section is ciliated on one surface (the right?) and harbors a “kitchen garden” of epibiotic bacteria on its glabrous 
zone (after Foissner, 1995a). The loxodid Loxodes whose ventral oral region has a paroral along its right border 
and an intrabuccal kinety extending posteriorly into the tube-like oral cavity. Note the bristle kinety along the ventral 
left surface of the cell (arrow) (after Bardele & Klindworth, 1996). The protostomatid Tracheloraphis showing its 
prostomial oral region and the glabrous zone bordered by the bristle kinety (After Foissner & Dragesco, 1996b). 
The protoheterotrichid Geleia, which is holotrichous and shows a complex oral region of dikinetid files and simple 
polykinetids. (after Dragesco, 1999.)
124 5. Subphylum 1. POSTCILIODESMATOPHORA: Class 1. KARYORELICTEA – The “Dawn” 
 diatoms (e.g., Coscinodiscus , Phaeodactylum ), 
both autotrophic and heterotrophic flagellates 
(e.g., Euglena , dinoflagellates ), other ciliates (e.g., 
Euplotes , Strombidium , and smaller karyorelict-
eans ), and even micrometazoans, such as rotifers 
and copepods (Foissner, 1998b). The many species 
sharing an interstitial habitat probably coexist in 
part by partitioning food resources: different-sized 
Loxodes species coexist in the same lake as the 
larger species consumes the larger food particles 
(Finlay & Berninger, 1984). 
 Conjugation is rarely observed (see Sexuality
and Life Cycle below). Since it does occur in some 
taxa, we presume it to be an ancestral feature of the 
group. Cysts are not known. Thus, explaining the 
presumed global distribution of some of these ciliates
is problematic as it is with any group that does not 
form resistant phases in the life cycle. 
 5.3 Somatic Structures 
 The karyorelictean cell body is typically long, some-
times >5,000 µm, and frequently flattened to about 
5–10 µm in thickness. In several genera, the cell 
surface on which the organism “crawls” is more 
densely ciliated (e.g., Loxodes , Kentrophoros ). The 
body is often pigmented, brown or yellowish, possibly 
due to pigmentocysts or extrusomes . The pigmento-
cysts apparently have a defensive function, at least 
in Loxodes (Buonanno, Saltalamacchia, & Miyake, 
2005). The cell surface may have a conspicuous 
 glycocalyx , but is not underlain by a regular layer of 
cortical alveoli . When present, the alveoli are irregu-
lar and small. Parasomal sacs have not been observed. 
 The somatic dikinetids of these ciliates are com-
posed of two kinetosomes joined by desmoses 
(Fig. 5.2), and oriented at 20–40° to the kinety 
axis. Both kinetosomes may be ciliated or only the 
anterior one. The postciliary microtubular ribbon of 
the posterior kinetosome is divergent, extending up 
to the cortex and posteriorly to overlap the ribbons 
of 10 or more anterior kinetids, and so forming the 
 postciliodesma . The number of overlapping ribbons 
will vary depending upon the contractile state of the 
ciliate, as these microtubules are assumed to play 
the same role in cell elongation as those of Stentor
(Huang & Mazia, 1975; Huang & Pitelka, 1973). It 
is not clear how the organization of the postciliary 
ribbons changes from their origin as a ribbon to the 
modified structure at the cell surface. There are two 
microtubules closest to the kinetosome followed by 
a ribbon of up to 20 microtubules perpendicular to 
the cell surface, and then a single microtubule. This 
2 + ribbon + 1 pattern can be repeated for each over-
lapping set (Fig. 5.2) (Klindworth & Bardele, 1996; 
Raikov, 1994b; Raikov & Kovaleva, 1995; Raikov, 
Gerassimova-Matvejeva, & de Puytorac, 1976). 
The postciliary microtubules are accompanied by 
dense material on either side near their base. The 
posterior kinetosome may also have a tangential 
transverse ribbon associated with triplets 3–5 (Fig. 5.2). 
The kinetodesmal fibril originates near triplets 5, 6, 
and 7 and is variable in form. It is striated and elongate 
in Remanella (Raikov, 1994b), striated and shovel-
shaped in Loxodes (Bardele & Klindworth, 1996), 
and short and hooked with only a faint periodicity 
in Tracheloraphis (Raikov & Kovaleva, 1995) and 
Geleia (de Puytorac, Raikov, & Nouzarède, 1973a). 
The kinetodesmal fibril structure in the latter two 
genera is very reminiscent of Stentor ’s as described 
by Huang and Pitelka. In Loxodes, the shovel-shaped 
kinetodesmal fibril becomes branched, one branch 
of which extends to contact the postciliary ribbon 
of the next anterior kinetid. The anterior kinetosome 
has a tangential transverse ribbon associated with 
triplets 3–5. There may be ribbons of subkinetal 
microtubules that originate from the bases of the 
somatic kinetosomes and extend posteriorly beneath 
the kinety (Raikov & Kovaleva, 1995) or towards 
the left (Klindworth & Bardele, 1996). 
 There are two kineties on the left side of 
Loxodes that have been interpreted to be one 
continuous kinety. Klindworth and Bardele 
(1996) have disproved this by showing that the 
kinetodesmal fibrils are oriented in the manner 
expected for two kineties: these kineties just hap-
pen to abut near the anterior end and so appear to 
be continuous at the level of the light microscope. 
Until it is demonstrated otherwise by electron 
microscopy, we assume that the bristle kineties 
bordering the non-ciliated stripe in Kentrophoros
are bipolar, contrary to the interpretations of 
Foissner (1995a, 1998b). 
 Myonemes are arranged longitudinally and parallel
to the somatic kineties in most karyorelicteans : to 
the right of the kinety in Tracheloraphis , to the 
left of the kinety in Remanella , and on both sides 
in Geleia . Since these ciliates are often not evenly 
ciliated around the body, contraction may cause 
Fig. 5.2. Ultrastructure of the cortex of the Class KARYORELICTEA. A Somatic dikinetids. (a) The protostomatid 
Tracheloraphis (after Raikov & Kovaleva, 1995). (b) The loxodid Loxodes. (after Klindworth & Bardele, 1996.) (c) 
The protoheterotrichid Geleia (after de Puytorac, Raikov, & Nouzarède, 1973a). B Somatic cortex of the protostome 
Tracheloraphis with postciliodesmata composed of overlapping ribbons in the 2 + ribbon + 1 arrangement. (Redrawn 
after Raikov et al., 1976.)
5.3 Somatic Structures 125
126 5. Subphylum 1. POSTCILIODESMATOPHORA: Class 1. KARYORELICTEA – The “Dawn” 
the cell to become banana-shaped or roll up. In 
some species, transverse myonemes occur, possibly 
ensuring an even longitudinal contraction. 
 The contractile vacuole system is not well-
developed, except in freshwater Loxodes species, 
and is often absent. 
 Extrusomes in the karyorelicteans are very diverse. 
 Rhabdocysts have been recorded in Tracheloraphis
and Kentrophoros (Raikov, 1974b), ampullocysts 
in Kentrophoros (Raikov), and cnidocysts and 
 orthonematocysts in Remanella (Foissner, 1996a; 
Raikov, 1978, 1992, 1993). The aberrant character 
of karyorelictean extrusomes in relation to those 
of other ciliates and the apparent similarities of the 
 cnidocysts of some karyorelicteans to the extrusomes 
of dinoflagellates, another alveolate group, have 
been used as another feature to indicate the ancestral 
nature of the karyorelicteans (Raikov, 1992). 
 5.4 Oral Structures 
 The taxa in this class are distinguished from each 
other primarily on the basis of oral structures, 
which, as we learn more about the detailed cyto-
anatomy of this group, are quite diverse. Oral 
kinetosomes bear cilia that are usually slightly 
longer than the somatic cilia, and may have simple 
nematodesmata,which reinforce the cytopharyn-
geal walls. 
 Protostomatids have a dome-like oral region 
surrounded by circumoral dikinetids , which may 
form an uninterrupted ring around the cytostome 
or which may be interrupted by brosse kineto-
fragments (Fig. 5.1). Until electron microscopy 
demonstrates otherwise, we assume that the glabrous
stripe is delimited by two kineties, one on its 
left and one on its right (Fig. 5.1). Foissner and 
Dragesco (1996b) interpreted these as the bris-
tle kinety , which they assumed to be continuous 
around the glabrous stripe . Protostomatids may 
ingest food through the anterior end (Al-Rasheid & 
Foissner, 1999) or along the glabrous stripe (Lenk, 
Small, & Gunderson, 1984; Lenk, Hollander, & 
Small, 1989). We place Kentrophoros in this group 
because it has two kineties bordering the glabrous 
stripe and it ingests the symbiotic bacteria from its 
 glabrous stripe (Raikov, 1974b) in a fashion similar 
to that reported for ingestion by Tracheloraphis
(Lenk et al., 1984, 1989). Foissner and Dragesco 
(1996b) argued that protostomatids are derived 
with respect to their oral region, which they 
regarded as having become apicalized from that of 
a ventrostomous ancestor, based on the arguments 
of Eisler (1992). 
 Loxodids have a slit-like ventral oral region that 
is bordered by files of dikinetids (Fig. 5.1). There is 
a paroral of dikinetids bordering the right side of the 
oral region. Slightly inside of this is a file of dikinetids 
that extends into a posterior extension of the oral cav-
ity. This file has been called an intravestibular kinety 
(Bardele & Klindworth, 1996) or an intrabuccal 
kinety (Foissner, 1995/1996). Since these oral struc-
tures are derived from buccal structures (see below), 
this oral cavity is not a vestibulum (see Glossary ); 
therefore, we prefer the term intrabuccal kinety . The 
cytostome may be placed between the paroral and 
this kinety (Klindworth & Bardele, 1996). The left 
side of the oral region is bordered by the left pseu-
dobuccal kinety , which may have been derived from 
somatic kinety 1 (Foissner, 1995/1996), since it is an 
inverted kinety based on the inverted orientation of 
its fibrillar associates (Bardele & Klindworth, 1996). 
Just interior to this, is a file of several anterior left 
oral dikinetids. A ventral kinetofragment of several 
dikinetids extends posterior from the ventral slit; it 
behaves like a scutica during stomatogenesis (Bardele 
& Klindworth, 1996). 
 Protoheterotrichids have been recently described 
in detail by Dragesco (1999). Their oral region 
varies from slit-like to almost rounded, and is 
bordered by more complex oral structures than 
found in the previous two orders (Fig. 5.1). The 
cytostome is bounded on its right side by a paroral 
of dikinetids to the right of which are right paroral 
polykinetids . The structure of these polykinetids 
appears variable at the light microscopic level: files 
of closely spaced monokinetids lie perpendicular 
to the paroral (e.g., Geleia , Avelia , Parduczia ); and 
files of dikinetids lie parallel to the paroral (e.g., 
Gellertia ). Adoral polykinetids are arrayed perpen-
dicular to the longitudinal axis of the cell to the left 
of cytostome in all genera but Parduczia , which 
has oralized somatic kineties on this side of the 
oral region. When present, the adoral polykinetids 
appear to be composed of files of dikinetids (e.g., 
Geleia , Gellertia ) or monokinetids ( e.g ., Avelia ). 
Confirmation of Dragesco’s interpretation from 
these protargol-stained specimens must await elec-
tron microscopic examination. 
 5.5 Division and Morphogenesis 
 Karyorelicteans divide while swimming freely. 
They also have considerable powers of regenera-
tion, like the heterotrichs . Thus, they may increase 
in numbers by fragment regeneration when they 
become severed by sediment action in their natural 
habitat.
 Foissner and Al-Rasheid (1999) have classified 
 stomatogenesis in the protostomatid Sultanophrys
as parakinetal . The proter oral apparatus does not 
reorganize. The oral primordium of the opisthe 
is apparently derived from proliferation of kine-
tosomes in the somatic kinety to the right of the 
glabrous stripe (Fig. 5.3). The subequatorial pri-
mordium differentiates from an anarchic field of 
kineto somes into kinetofragments of dikinetids. 
These kinetofragments assemble as circumoral 
dikinetids and three small brosse kinetofragments. 
 Bardele and Klindworth (1996) concluded that 
stomatogenesis in Loxodes is buccokinetal . The 
parental oral apparatus is only slightly reorgan-
ized. Stomatogenesis begins with proliferation 
of kinetosomes from the ventral kinetofragment, 
just posterior to the oral region, and this is fol-
lowed by proliferation of kinetosomes from the 
 paroral and the left pseudobuccal kinety . The 
ventral kinetofragment gives rise to the opisthe 
paroral while the proliferation of the proter left 
pseudobuccal kinety gives rise to that of the 
opisthe. The intrabuccal kinety and the anterior left 
oral dikinetids, whose origin is not yet resolved, 
appear later in stomatogenesis at the anterior end 
of the opisthe oral region, as the oral anlagen 
reach the cell equator. 
 Thus, stomatogenesis among the karyorelictean 
orders demonstrates different modes: parakinetal in 
 protostomatids and buccokinetal in loxodids . What 
mode the protoheterotrichs demonstrate awaits the 
results of further investigations. However, it is clear 
that there is as much diversity in stomatogenesis in 
this class as can be found in other classes of ciliates 
(e.g., Class OLIGOHYMENOPHOREA , Foissner 
& Al-Rasheid, 1999). Stomatogenesis is therefore 
not likely to be an indicator of deep phylogenetic 
relationships.
Fig. 5.3. Stomatogenesis of the protostomatid Sultanophrys. (a) The process begins in the mid-region of the body 
as kinetosomes proliferate, forming an anarchic field to the right of the ventral (?) or right bristle kinety. (b–d) The 
process continues until a ring of circumoral dikinetids forms accompanied by 3 minute brosse kinetids. (from Foissner 
& Al-Rasheid, 1999.)
5.5 Division and Morphogenesis 127
128 5. Subphylum 1. POSTCILIODESMATOPHORA: Class 1. KARYORELICTEA – The “Dawn” 
 5.6 Nuclei, Sexuality and Life 
Cycle
 As discussed above, the karyorelicteans have the 
simplest form of nuclear dimorphism in the phylum: 
the macronucleus is diploid or paradiploid and 
non-dividing. It is rich in RNA with a conspicuous 
 nucleolus and may have proteinaceous inclusions 
(Raikov, 1982). Since it does not divide, the 
macronucleus(ei) must be replaced at each cell 
division by differentiation of the products of micro-
nuclear division. The micronucleus is presumed to 
be diploid and is capable of mitosis and meiosis. 
Both nuclei are small in size, typically globular or 
ellipsoid. They may be found in a variety of close 
associations: a single micronucleus and one macro-
nucleus (e.g., Loxodes ), a single micronucleus and 
two associated macronuclei (e.g., some protosto-
matids ), or present in clusters or complexes of 
several micronuclei and several macronuclei with 
or without a surrounding envelope. 
 It is not clear what factors stimulate conjuga-
tion in karyorelicteans . Raikov (1972) reviewed 
the general features of conjugation in kary-
orelicteans, based on observations of Loxodes
and Tracheloraphis , and summarized it thus. 
Preconjugants differ from vegetative cells by the 
incomplete differentiation of the nuclei, especially 
the macronuclei. Meiosis is typical but it may 
lead to the formation of multiple pronuclei and, 
ultimately after exchange of migratory gametic 
nuclei, multiple synkarya in Tracheloraphis spe-
cies. Thus, genetic identity of the two separating 
 exconjugants is not assured. After separation, the 
“parental” macronuclei do not degenerate. Thus, 
the exconjugant is presumed to be a genetic 
chimaerawith a “parental” phenotype expressed 
by the old macronuclei and a developing phe-
notype expressed by the genome residing in the 
“new” macronucleus. Replacement of the “paren-
tal” macronuclei occurs over several cell divisions 
following conjugation , and the new phenotype 
presumably becomes established as the “paren-
tal” macronuclei are diluted out by cell division 
cycles. Since renewal of the macronuclei is not 
directly connected with conjugation, Raikov sup-
poses this to be an ancestral feature of the conjuga-
tion process (see also Orias, 1991a, 1991b). 
 5.7 Other Features 
 Gram-negative bacteria are commonly associated with 
 karyorelicteans . Geleia species may have perhaps 
10,000 bacteria as epibionts on their cell surface 
(Epstein, Bazylinski, & Fowle, 1998). Other Gram-
negative bacteria are found in the cytoplasm. Since 
they are often not bounded by a ciliate vacuolar mem-
brane, it is assumed that they are endosymbionts. Their 
functional relationship to their hosts is unknown. 
 A novel feature restricted to the loxodid karyo-
relicteans is the organelle known as Müller’s vesicle . 
The vesicle, about 7 µm in diameter, encloses the 
 Müller’s body , which itself is bounded by a cell 
membrane that encloses barium salt-dominated 
crystals in the freshwater Loxodes and strontium salt-
dominated crystals in the marine Remanella (Rieder, 
Ott, Pfundstein, & Schoch, 1982). Movements of 
the Müller’s body , in response to gravity and the 
orientation of the ciliate, may deform ion channels 
on the cell surface and thereby modulate cell move-
ment. Movement in Loxodes is also dependent on 
external oxygen concentration in the water: Loxodes
swim faster upward when the water is anoxic and 
faster downward when the water is oxygen-saturated 
(Fenchel & Finlay, 1984, 1986b). 
 Müller’s body is suspended in the vesicle by a 
stalk that is a supported by postciliary microtu-
bules from an adjacent dorsal left somatic dikinetid 
(Fenchel & Finlay, 1986a). These dikinetids com-
prise the loxodid dorsolateral kinety that Foissner 
(1998b) has presumed to be homologous to a 
somatic kinety of kentrophorids that is in a similar 
position but does not “bear” Müller’s vesicles. 
Foissner (1998b) thus argues that loxodids and 
 kentrophorids are sister taxa. We remain skeptical 
until ultrastructural homologies of the kinetids are 
proved or until gene sequence data confirm these 
two groups as sister taxa.

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