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Cap 11

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organellar complexes (e.g., 
Discotricha ) (Figs. 11.1, 11.2). 
 The cell surface of these ciliates is undoubt-
edly covered by a glycocalyx , although it has only 
been clearly demonstrated in Pseudomicrothorax
(Hausmann, 1979). Underlying the plasma membrane 
is a typical alveolar layer with the unusual feature that 
the alveoli may send invaginations through the epi-
plasm into the cortex of the ciliate. These alveolocysts 
are typically paired and on either side of the somatic 
kinetids (Eisler, 1989; Eisler & Bardele, 1983). We 
recognize these structures as a synapomorphy for the 
class NASSOPHOREA although they remain to be 
demonstrated in synhymeniids . 
 Some nassophoreans have a conspicuous epi-
plasm (e.g., Pseudomicrothorax – Peck, 1977b; 
Furgasonia – Eisler, 1988; Nassula – de Puytorac 
& Njiné, 1980; Tucker, 1971a). Pseudomicrothorax
can be prepared as an “epiplasmic” ghost , retaining 
its cell shape without any of the cell membranes or 
cortical microtubular structures – a clear demon-
stration of the shape-maintaining function of the 
 epiplasm (Peck, 1977b; Peck, Duborgel, Huttenlauch, 
& Haller, 1991). Immunocytochemistry has demon-
strated that proteins from the ciliate epiplasm share 
common epitopes with those proteins from the 
pellicles of euglenoids and dinoflagellates (Vigues, 
Bricheux, Metivier, Brugerolle, & Peck, 1987). 
The epiplasm , especially adjacent to the inner alve-
olar membrane, has higher concentrations of glyco-
proteins (Curtenaz & Peck, 1992; Huttenlauch 
& Peck, 1991). The middle layer is composed 
of articulins , a novel kind of cytoskeletal protein 
found also in euglenoids , which is characterized 
by unique repeating valine-proline-valine (VPV) 
motif, presumed to provide stability to this layer 
(Huttenlauch, Geisler, Plessmann, Peck, Weber, & 
Stick, 1995; Huttenlauch, Peck, Plessmann, Weber, 
& Stick, 1998b). In addition, another class of pro-
teins, the epiplasmins , are also found in the micro-
thoracid epiplasm and related to epiplasmins in the 
 peniculine epiplasm . Epiplasmins , although rich in 
valine and proline, do not show the VPV-motif of 
the articulins (Coffe, Le Caer, Lima, & Adoutte, 
1996; Huttenlauch et al., 1998a). 
 The somatic kinetid of the nassophoreans has 
been resummarized by Eisler (1988). Monokinetids 
can now be characterized as follows: a divergent 
postciliary ribbon at triplet 9; an anterior and 
laterally-directed kinetodesmal fibril at triplets 
5 and 6; and a small tangential transverse ribbon 
at triplets 3 and 4, arising from some dense material
(Figs. 11.3, 11.4) (Lynn, 1991). Dikinetids can 
occur: a posterior ciliated kinetosome with the 
typical fibrillar pattern is connected to an ante-
rior ciliated kinetosome with a single postciliary 
 microtubule and sometimes a transverse ribbon 
(Fig. 11.3) (Eisler, 1988). The kinetosomes of nas-
sulids have a distal B-cartwheel and may also have 
a proximal and standard A-cartwheel , while micro-
thoracids may lack both cartwheels (Eisler; Njiné 
& Didier, 1980; Peck, 1977b; Tucker, 1971a). 
 The contractile vacuole system of nassophore-
ans is a Type A system (Patterson, 1980) with the 
 contractile vacuole surrounded by a spongiome of 
irregularly arranged tubules, 20–80 nm in diameter 
(Hausmann, 1983; Prelle, 1966). Microthoracids 
may have an elongated contractile vacuole pore 
canal that extends into the cytoplasm. 
 Nassophoreans have rod-shaped extrusomes that 
have been called fibrocysts or fibrous trichocysts 
(Hausmann, 1978). Their structure and devel-
opment have been particularly well studied in 
Pseudomicrothorax . Its trichocysts have anchor-
like tips that splay out upon ejection. The 50-nm 
periodicity of the ejected shaft is very similar 
to that of the ejected trichocysts of Paramecium
(Hausmann, 1978), which also show remarkable 
similarities in their constituent proteins (Eperon 
& Peck, 1993). Fibrocyst development occurs in 
Golgi vesicles and involves the unusual fusion of 
two types of vesicles, one containing shaft precur-
sors and the other containing tip precursors (Peck, 
Swiderski, & Tourmel, 1993a, 1993b). Once devel-
oped, the trichocyst docks in the cortex by local-
ized dissolution of the epiplasm and penetration 
of the alveolar layer before contacting the inner 
surface of the plasma membrane (Eisler & Peck, 
1998). Although classified here as a microthoracid , 
Discotricha does not have anchor-like tips on its 
 extrusomes (Wicklow & Borror, 1977). Does this 
mean that it is truly not a microthoracid although 
its oral structures suggest otherwise (see below)? 
 11.4 Oral Structures 
 Nassophoreans possess some kind of oral basket 
of nematodesmata – “nasse” or cyrtos , which 
can be quite conspicuous and well-developed. 
Ciliary structures may be associated with this 
basket in nassulids and microthoracids . The 
 nassulid Furgasonia has a paroral of stichodyads 
and three adoral polykinetids (Figs. 11.1, 11.2) 
(Eisler, 1988). In Pseudomicrothorax , the paroral 
 dikinetids dissociate during stomatogenesis so that 
“posterior” kinetosomes remain associated with the 
 nematodesmata while a few “anterior” kinetosomes 
that are not resorbed remain as “residual kineto-
somes” posterior to the cytostome (Peck, 1975; 
Thompson & Corliss, 1958). In most Nassula
species, the “oral” polykinetids course on the left 
ventral surface, posterior to the cytostome, and 
may extend onto the dorsal surface. 
 “Oral” structures in the synhymeniids differ 
from that of nassulids in two ways. First, they 
extend across the entire ventral surface, even encir-
cling the entire body as the so-called synhymenium 
(e.g., Nassulopsis ). Second, they are composed of 
dikinetids or polykinetids of typically no more than 
six kinetosomes (Fig. 11.1). However, in scaphidi-
odontids and orthodonellids , the extension of the 
 synhymenium into the anterior suture recalls the 
overall pattern of cyrtophorians (cf. Figs. 10.1, 
11.1) (Deroux, 1994b). There has been no detailed 
ultrastructural description of the synhymenium
kinetids nor of the cytopharyngeal basket of syn-
hymeniids to determine that it shows strong simi-
larities to other nassophoreans (i.e., presence of 
 nematodesmal lamellae ). 
 On the other hand, several studies have detailed 
 nassulid and microthoracid oral ultrastructure. 
Eisler’s (1988) detailed study has demonstrated 
that the kinetosomes of the paroral dikinetids of 
Furgasonia and probably Nassula are oriented 
perpendicular to each other: the right or “anterior” 
kinetosome is oriented in the long axis of the 
paroral while the left or “posterior” kinetosome is 
oriented at right angles to the paroral. The Z or cys-
tostomal lamellae arise from the postciliary ribbons 
of the “posterior” kinetosomes (Eisler, 1988). The 
 oral polykinetids of nassulids are square-packed 
organellar complexes of three rows. Kinetosomes 
of the posterior row bear postciliary ribbons 
and all kinetosomes bear presumably a single 
 transverse microtubule at triplet 4. Parasomal sacs 
are distributed throughout the structure (Eisler, 
1988; de Puytorac & Njiné, 1980). 
 The nassophorean cytopharyngeal basket or 
 cyrtos has received the most detailed analysis by 
cell biologists who were attracted to it as perhaps the 
most complicated microtubular organellar complex 
Fig. 11.3. Schematics of the somatic kinetids of the Class 
 NASSOPHOREA . ( a ) Monokinetid of Pseudomicrothorax . 
(b ) Monokinetid of Furgasonia . c . Dikinetid of Furgasonia . 
(d ) Monokinetid of Nassula . ( e ) Dikinetid of Nassula (from 
Lynn, 1981, 1991) 
11.4 Oral Structures 239
of any cell! Eisler (1988) has noted that nassulids 
and microthoracids have the X or nematodesmal 
 lamellae , which are absent in phyllopharyngeans