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Ruffolo, 1978) and stichotrichs 
(Wirnsberger-Aescht et al., 1989). Of unkown 
function, they can be composed of calcium salts 
(Hausmann & Walz, 1979). 
 7.4 Oral Structures 
 Spirotrichs , like the heterotrichs , are character-
ized by a prominent adoral zone of polykinetids 
or membranelles , which are typically composed 
of three or four rows of kinetosomes. Because of 
the tremendous diversity in form of members of 
this class, there are few general statements that can 
be made about the pattern of the oral structures. 
Benthic forms with dorsoventrally flattened bod-
ies typically have an adoral zone of polykinetids 
that extend along the left side of the oral region 
and may extend over the anterior end and a short 
distance down the right side of the oral region 
(Figs. 7.2, 7.4). Planktonic forms, which are gener-
ally spherical or conical, have an adoral zone of 
polykinetids that wraps incompletely or completely 
around the anterior end of the cell (Figs. 7.3, 7.4). 
De Puytorac and Grain (1976) suggested the term 
 paramembranelle to describe the oral polykinetids 
of heterotrichs and some spirotrichs . As noted 
for the heterotrichs (see Chapter 6 and also 
below), conspicuous variations in ultrastructure 
argue against inventing a new term for the organel-
lar complexes of each taxon. We now briefly char-
acterize the oral structures of the seven subclasses, 
referring to the structures in a taxonomic fashion 
(e.g., protocruziid paroral). 
 The sole representative of the Subclass 
 Protocruziidia (i.e., Protocruzia ) has six adoral 
polykinetids and a paroral of dikinetids (Fig. 7.2) 
(Grolière et al., 1980a; Song & Wilbert, 1997). 
There are typically four rows of square-packed 
kinetosomes in the oral polykinetids with the first 
two rows more widely separated from each other 
than the last three. The posterior kinetosomes bear 
postciliary ribbons while the anterior kinetosomes 
may have radially oriented transverse ribbons. 
The paroral is composed of dikinetids, having 
postciliary ribbons extending from the left-most 
kinetosome. The paroral dikinetids form a file 
along the right and posterior sides of the oral region 
(Grolière et al., 1980a). 
Phacodinium , the sole representative of the 
Subclass Phacodiniidia , has an extensive adoral 
zone of polykinetids along the left side of the oral 
region and a short paroral on the right side of the 
oral cavity (Fig. 7.2). The oral polykinetids are 
composed of four rows of hexagonally-packed 
kinetosomes (Fernández-Galiano & Calvo, 1992). 
The kinetosomes on the right side of the oral 
polykinetids bear divergent postciliary ribbons 
while those of the anterior row apparently bear con-
vergent postciliary ribbons (Da Silva Neto, 1993a). 
The paroral is a unique structure, a polymerized 
 stichomonad termed a polybrachystichomonad by 
Fernández-Galiano and Calvo. It consists of a 
series of oblique rows of 6-7 kinetosomes, lying 
at the base of a ridge. The left-most file of kineto-
somes, which bear a postciliary ribbon, extends as 
a single file deeper into the oral cavity adjacent to 
the first oral polykinetids (Da Silva Neto, 1993a). 
Licnophora is a representative of the Subclass 
 Licnophoria . The anterior portion of its hour-glass 
shaped body is encircled by an adoral zone of oral 
polykinetids (Fig. 7.2) that have the structure of 
 paramembranelles (Da Silva Neto, 1994a). The 
paroral is a single file of monokinetids (Song, 
Warren, Ji, Wang, & Al-Rasheid, 2003). 
 Members of the Subclass Oligotrichia , typi-
fied by Strombidium , have an adoral zone of 
polykinetids divided into the “lapel” or oral cav-
ity polykinetids and the “collar” or anterior oral 
polykinetids, which encircle the anterior end of the 
cell (Fig. 7.3). These oral polykinetids have three 
rows of kinetosomes while the paroral extends 
along the right side of the oral cavity as a single file 
of kinetosomes (Agatha, 2004a; Lynn et al., 1988; 
Petz & Foissner, 1992; Song, Wang, & Warren, 
2000). There has been no ultrastructural study of 
oligotrich oral organelles. 
 The Subclass Choreotrichia includes such genera 
as Strobilidium , Pelagostrobilidium , Lohmanniella , 
Leegaardiella , Strombidinopsis , and the tintinnids , 
in which an adoral zone of polykinetids completely 
encircles the anterior end of the cell (Fig. 7.3). 
These oral polykinetids are typically composed of 
three rows of kinetosomes, but they may be divided 
into two parts as in Leegaardiella (Dale & Lynn, 
1998; Lynn & Montagnes, 1988; Petz & Foissner, 
1992; Song & Bradbury, 1998). Some of these 
polykinetids may extend into the oral cavity (e.g., 
Strobilidium , tintinnids ; Foissner & Wilbert, 1979; 
Petz & Foissner, 1992) or there may be separate, 
smaller polykinetids that line the oral cavity (e.g., 
Lohmanniella , Leegaardiella , Strombidinopsis ; 
Dale & Lynn, 1992; Lynn & Montagnes, 1988). 
When appropriately stained, the paroral appears 
to be composed of a file of monokinetids (Petz & 
Foissner). This is confirmed by study of choreotrich 
oral ultrastructure: the paroral is a file of monoki-
netids bearing transverse (?) microtubules (Grim, 
1987). The kinetosomes of the oral polykinetids 
appear to be square-packed. Kinetosomes of the 
morphologically “anterior” row may bear a trans-
verse (?) ribbon while those of the posterior row 
bear a postciliary (?) microtubular ribbon (Grim, 
7.4 Oral Structures 161
1987). Clearly, a detailed ultrastructural study of 
choreotrich oral structures is needed. The cell 
surface between the oral polykinetids of tintinnids 
bears evaginations called tentaculoids , which con-
tain the “ capsules torquées ” or twisted capsules. 
Along the oral polykinetid cilia of tintinnids are the 
 striae or streaks, bulge-like evaginations that may 
also contain the twisted capsules, which may func-
tion as extrusomes in prey capture (Laval-Peuto, 
1994; Laval-Peuto, Gold, & Storm, 1979). 
 The adoral polykinetids of members of the 
Subclasses Hypotrichia and Stichotrichia were 
characterized as paramembranelles (de Puytorac & 
Grain, 1976). Their polykinetids are composed of 3-
4 rows of kinetosomes, depending upon the position 
along the adoral zone. The kinetosomes are square-
packed with the anterior row kinetosomes bearing 
transverse ribbons and the posterior row kineto-
somes bearing postciliary ribbons, in such genera as 
Euplotidium , Halteria , Kahliella , Parastrongylidium , 
Paraurostyla , Stylonychia (Figs. 7.2, 7.4) 
(Bakowska & Jerka-Dziadosz, 1980; Fleury et al., 
1985a, 1985b, 1986; Grain, 1972; Lenzi & Rosati, 
1993; de Puytorac, Grain, & Rodriguez de Santa 
Rosa, 1976; Tuffrau & Fleury, 1994). Foissner and 
Al-Rasheid (2006) have provided a detailed descrip-
tion of the stichotrich oral cavity and revealed an 
unusual structure, the buccal seal , which can appar-
ently cover the entire oral opening like a sheet. They 
also identify lateral membranellar cilia , which 
derive from the fourth row of membranellar kineto-
somes, extend rightward across the oral cavity, 
and may be used in prey selection and feeding. 
 Paroral structures are typically a polykinetid-like 
structure in hypotrichs (Curds, 1975a; Grim, 1982; 
Tuffrau, 1960; Wicklow, 1983). In stichotrichs , de 
Puytorac and Grain (1976) apply the term diplosti-
chomonad to the paroral and endoral files, which 
are typically composed of single kinetosomes with 
associated microtubular rootlets (Albaret & Grain, 
1973; de Puytorac & Grain, 1976). The halteriids 
are an exception among the stichotrichs as they 
have apparently lost either the endoral or paroral 
and bear only a single file of paroral kinetosomes 
(Grain, 1972). 
 The physiology of oral cilia in the stichotrich 
Stylonychia appears to be different from that of 
the somatic cilia. Oral cilia are continually active,