Cap 9

the cytostomal 
region of Dileptus where kinetosomes are supplied 
to the enlarging circumoral kinety and to adjacent 
elongating somatic kineties. In contrast, Golińska
(1984) examined the effects of reduced cell size 
on ultrastructural components of the cell: Dileptus
reduced in size by microsurgery had oral nema-
todesmata and transverse ribbons that contained 
fewer microtubules. However, the reduction was 
not perfectly proportional to the reduction in cell 
size , suggesting that some lower limit may exist 
for a functional organelle (Golińska, 1984). In con-
trast, in overfed Dileptus , although the number of 
oral nematodesmata might increase, the number of 
microtubules in these nematodesmata and in trans-
verse ribbons did not vary, suggesting an upper 
size-limit on these structures (Golińska, 1986). 
High temperatures can cause abnormalities in the 
oral development, probably by interfering with 
microtubule assembly (Golińska, 1988). 
 9.5 Division and Morphogenesis 
 Litostomes typically divide while swimming 
freely, although some pleurostomatids may divide 
within a cyst . Stomatogenesis is telokinetal and 
the parental oral structures are retained. Foissner 
(1996b) distinguished four subtypes in the class, 
primarily characterizing different ordinal or sub-
ordinal assemblages. The majority of taxa within 
the Subclass Haptoria are characterized as under-
going holotelokinetal stomatogenesis , with the 
“anterior” ends of all the opisthe somatic kineties 
undergoing kinetosomal differentiation and pro-
liferation to produce the oral dikinetids (Fig. 9.6) 
(e.g., Fuscheria , Spathidium – Berger, Foissner, 
& Adam, 1983; Homalozoon – Leipe, Oppelt, 
Hausmann, & Foissner, 1992). Dileptus has also 
been characterized as holotelokinetal . However, the 
development of the proboscis and its ciliary fields 
means that kinetosomal proliferation at the equa-
tor gives rise to both the proboscis infraciliature 
and the circumoral dikinetids (Golińska, 1995). 
 Pleurostomatid stomatogenesis is characterized 
as monotelokinetal as only the somatic portions 
of the oral kineties are involved (e.g., Litonotus , 
Loxophyllum – Fryd-Versavel, Iftode, & Dragesco, 
1976). The endocommensal vestibuliferids are 
characterized as undergoing intertelokinetal stoma-
togenesis (Foissner, 1996b). Kinetosomal prolifera-
tion occurs at the ends and by elineation or laterally 
to produce kinetofragments between the anterior 
ends of the somatic kineties (e.g., Balantidium
– Fauré-Fremiet, 1955; isotrichids , paraisotrichids , 
and buetschliids – Grain, 1966a). The buetschliid 
Polymorphella may be the only exception as it 
appears to have holotelokinetal stomatogenesis 
(Foissner 1996b; Grain 1966a). It might be more 
appropriate to classify the stomatogenesis of buet-
schliids as cryptotelokinetal (see below) since the 
region of oral kinetosomal proliferation usually has 
non-ciliated somatic kinetosomes. 
 The entodiniomorphids have long been con-
sidered to have apokinetal stomatogenesis since 
somatic kinetosomes were not visible by light 
microscopy. Furness and Butler (1986) have demon-
strated that proliferation of oral kinetosomes occurs 
from non-ciliated somatic kinetosomes distributed 
in the cortex of Eudiplodinium . A similar process 
may explain the appearance of the new girdles in 
the haptorian Didinium as they appear “de novo” 
at some distance from the parental girdles (Small, 
Antipa, & Marszałek, 1972). This is presumably the 
case for all entodiniomorphids (Fernández-Galiano, 
Serrano, & Fernández-Galiano, 1985; Ito & Imai, 
2005; Ito, Miyazaki, & Imai, 2001) and blepharo-
corythids (Wolska, 1966), and has lead to describing 
the process as cryptotelokinetal (Foissner, 1996b). 
Several primordial fields may develop, typically 
in cortical pockets , and then later fuse to form the 
diff erentiated oral structures (Fig. 9.6). Cameron 
and O’Donoghue (2001) have concluded that 
the stomatogenesis of Macropodinium , the genus 
endosymbiotic in kangaroos and wallabies , is 
very unusual, having features of epiapokinetal , 
 endoapokinetal , and cryptotelokinetal stomatogen-
esis depending upon the infraciliary structures 
involved. Clearly, an ultrastructural study is needed 
to resolve these questions. Moreover, stomatogen-
esis has not been studied in representatives from all 
9.5 Division and Morphogenesis 205
206 9. Subphylum 2. INTRAMACRONUCLEATA: Class 3. LITOSTOMATEA
the families in this class, so there is clearly much 
comparative work to do. 
 There is an extensive literature on the morpho-
genesis and cell biology of regeneration in 
litostomes, particularly using the genera Dileptus
and Lacrymaria (Frankel, 1989). Both ciliates can 
be sectioned by microsurgery and regeneration 
follows. If the proboscis or trunk of Dileptus is 
isolated, each part can proportionally regulate a 
smaller “body” over several days (Golińska, 1979; 
Golińska & Kink, 1977). Regeneration involves the 
proliferation of new kinetosomes in both genera 
(Bohatier, 1972; Golińska; Kink, 1972). Initially 
 regeneration stomatogenesis apparently requires 
neither RNA nor protein synthesis. However, “sta-
bilization” of the oral structures and development 
of toxicysts does require these two crucial cell 
processes (Bohatier & Kink, 1977; Golińska & 
Bohatier, 1975). A fuller discussion of this research 
can be found in Frankel (1989). 
 9.6 Nuclei, Sexuality 
and Life Cycle 
 Litostomes are typical ciliates, having at least one 
 macronucleus and one micronucleus . Macronuclear 
DNA does not appear to be fragmented into gene-
Fig. 9.6. Division morphogenesis of litostomes . A In the haptorian Spathidium , its holotelokinetal stomatogenesis 
begins with proliferation of circumoral dikinetids at the equator of all somatic kineties ( a , b ). These kinetofragments 
bend rightward to extend across the interkinetal space and so form the opisthe’s circumoral dikinetid as division 
morphogenesis is completed ( c , d ) (from Berger et al., 1983). B In the entodiniomorphid Entodinium , what appears 
to be apokinetal is now considered cryptotelokinetal because there are somatic kinetosomes scattered throughout 
the cortex. Kinetosomes first appear on the right ventral side ( a ) and as these proliferate to form a polybrachykinety
another field forms on the dorsal left side ( b ). These two primordia meet as replication continues ( c ). Ultimately, a 
portion invaginates to become the infundibular or vestibular portion ( d , e ) (from Fernández-Galiano et al., 1985.)
sized pieces (e.g., Didinium – Riley & Katz, 2001). 
Macronuclear shapes can be quite variable, ranging 
from small ovoid to very elongate and band-shaped 
(e.g., Didinium ). Pleurostomatids often have the 
 macronucleus in pairs or quartets. Some vestibulif-
erids (e.g., Isotricha ) have filaments extending from 
the ecto-endoplasmic layer to form a karyophore 
(Grain, 1966a). The macronucleus and micro-
nucleus are typically quite closely associated in 
 trichostomes with the micronucleus often residing 
in a depression in the macronucleus (Grain, 1994). 
Although appearing multiple, the macronucleus 
may in fact be moniliform, like a string of beads, 
with the number of beads increasing as cell size 
increases (Leipe & Hausmann, 1992). These beads 
condense prior to macronuclear division , while 
the more elongate and band-shaped macronuclei 
become ovoid. Macronuclear and micronuclear 
division are accomplished by intranuclear micro-
tubules (e.g., Isotricha – Grain, 1966a; Didinium
– Karadzhan & Raikov, 1977; Homalozoon – Leipe 
& Hausmann). 
 Relatively little research has been done on con-
jugation processes in litostomes , and the event is 
rarely observed in natural populations (Lucchesi & 
Santangelo, 2004). What we know derives mostly