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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 \u201clapel\u201d or oral cav- ity polykinetids and the \u201ccollar\u201d 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 \u201canterior\u201d row may bear a trans- verse (?) ribbon while those of the posterior row bear a postciliary (?) microtubular ribbon (Grim, 7.4 Oral Structures 161 162 7. Subphylum 2. INTRAMACRONUCLEATA: Class 1. SPIROTRICHEA 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 \u201c capsules torquées \u201d 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,