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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 
chimaera

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