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the lorica can cover a portion or the entire cell body. Sometimes it is an extension of the outer covering of the stalk with loose fibrous mate- rial \u201cgluing\u201d it to the cell body (Batisse, 1967a; Bardele, 1968). The lorica or \u201cshell\u201d of Metacineta species has an exceedingly complex crystalline nodal substructure (Batisse, 1967b). Fig. 10.7. Schematics of the somatic kinetids of the Class PHYLLOPHARYNGEA . ( a ) Monokinetid of the cyr- tophorian Chilodonella . ( b ) Monokinetid of the cyrtophorian Brooklynella . ( c ) Monokinetid of the chonotrich Chilodochona . ( d ) Monokinetid of the chonotrich Spirochona . ( e ) Monokinetid of the rhynchodian Hypocoma . ( f ) Monokinetid of the rhynchodian Ignotocoma . ( g ) Monokinetid of the suctorian Trematosoma . ( h ) Monokinetid of the suctorian Trichophrya (from Lynn, 1981, 1991) 10.3 Somatic Structures 223 224 10. Subphylum 2. INTRAMACRONUCLEATA: Class 4. PHYLLOPHARYNGEA Mitochondria are the typical tubular mitochon- dria. Batisse (1994b) reported that Allantosoma , the endosymbiotic suctorian of the horse cecum , contains hydrogenosomes , while Foissner and Foissner (1995) described hydrogenosomes in Enchelyomorpha , an anaerobic suctorian collected from domestic sewage . Contractile vacuoles are present throughout the class. Indeed, the sessile habit of suctorians made them fruitful models for our basic understanding of contractile vacuole function in the protozoa (Kitching, 1967). Patterson (1980) characterized them as having an irregular network of spongiome tubules, and this has been confirmed for the chonot- richs (Fahrni, 1983; Karadzhan, 1976). Contractions of the vacuole of Heliophrya were correlated with spontaneous depolarizing potentials of the plasma membrane (Eagles, Gregg, & Spoon, 1980). The cytoproct is found in cyrtophorians , chonot- richs , and rhynchodians . In cyrtophorians it is not a defined area, but egestion typically occurs through the right posterior dorsal surface (Deroux, 1994a). In the chonotrich Spirochona , the cyto- proct opens at the base of a 20 µm long \u201cexcretory\u201d canal (Fahrni, 1983). The rhynchodian Hypocoma has a cytoproct canal about 1 µm long (Grell & Fig. 10.8. Somatic cortex of a typical phyllopharyngean cyrtophorian whose postciliary microtubules extend as \u201ctriads\u201d alongside each other into the right cortical ridges. Note that the transverse microtubules extend slightly pos- teriorly into the left cortical ridge. (Adapted from So\u142ty ska, 1971.) Meister, 1983). As noted above, suctorians do not have a cytoproct , but they may dispose of wastes by pinching off portions of the cytoplasm that are laden with wastes. 10.4 Oral Structures The phyllopharyngeans represent a class where there is dramatic adaptive divergence in the struc- tures of the oral region related to very different feeding functions. Nevertheless, their common ancestry is supported both by the strong simi- larities in the somatic kinetids (see above Somatic Structures ) and by the presence of phyllae , or arm- bearing microtubular ribbons, lining the ingestatory apparatus, either as a true cytopharynx or a tentacle (see Lynn & Foissner, 1994). Cyrtophorians tend to be substrate-oriented, encounter feeders , ingesting single diatoms or several bacteria at once as they \u201cbrowse\u201d along the substrate (Epstein & Shiaris, 1992; Sawicka, Kaczanowski, & Kaczanowska, 1983). Chonotrichs are suspension feeders , using the entire ciliature, both somatic and oral, which lines the oral cone, to create feeding currents to bring particles to the cytostome. Rhynchodians and suctorians both have suctorial tube-like oral struc- tures or tentacles. Rhynchodians are encounter feeders, attaching to the host, whether it be another ciliate or a metazoan . Their haptotrichocysts in their suctorial tube function in some fashion, not yet known, to aid ingestion of host cytoplasm. Suctorians can be characterized as passive encoun- ter feeders \u2013 they are either sessile or float freely \u201cwaiting\u201d for prey to contact the feeding tentacles . If appropriate, this contact will elicit extrusion of the toxic haptocysts that ensure fusion of predator- prey cells and paralysis of the prey (see below; Hausmann, 1978). Cyrtophorians have an oral region that is typi- cally bordered on its right by two circumoral kineties or kinetofragments and anteriorly by a preoral kinety or multiple preoral kinetofragments (Fig. 10.1). However, there is considerable vari- ation on this \u201cbasic\u201d plan: the dysteriid Pithites may have 5 or more small kinetofragments sur- rounding the cytostome while some Lynchella species may have oral kinetofragments that extend almost across the entire ventral surface of the cell (see Deroux, 1970, 1976a, 1977; Deroux & Dragesco, 1968). Early ultrastructural observa- tions demonstrated the inverted nature of these oral kineties, predicted by their counter-clockwise migration occurring during cell division (Lom & Corliss, 1971; de Puytorac & Grain, 1976) (see below Division and Morphogenesis ). Subsequent descriptions have confirmed this (Hofmann, 1987; Hofmann & Bardele, 1987). These oral kinetids are characterized as follows: a \u2018posterior\u2019 or right- most ciliated kinetosome with which are associated a slightly convergent postciliary ribbon and occa- sionally a transverse fibre; and an \u2018anterior\u2019 or left-most, non-ciliated kinetosome with which is associated a transverse fibre (Lynn, 1981; Grain, de Puytorac, & Bohatier, 1973). Parasomal sacs may occur on either side of these kinetosomes and addi- tional dense fibres may be present (see Hofmann, 1987; Hofmann & Bardele, 1987). These oral kinetofragments are associated with the cyrtos , the complex cytopharyngeal \u201cbasket\u201d of these ciliates, which shares strong similarities to the oral bas- ket of nassophoreans (see Chapter 11 ). It is not certain that the cyrtos in both groups represents a demonstration of deep common ancestry or of convergent evolution. Although phylogenies based on small subunit ribosomal RNA genes clearly separate phyllopharyngeans and nassophoreans (see Strüder-Kypke, Wright, Fokin, & Lynn, 2000b), they are nevertheless topologically close on these trees suggesting the cyrtos could be homologous. In addition to the palisade of nematodesmata, three groups of microtubular ribbons (i.e., cytostomal or cytopharyngeal or Z lamellae ; subcytostomal or Y lamellae ; and nematodesmal or X lamellae , Eisler, 1988; Kurth & Bardele, 2001; Tucker, 1968) are associated with the cyrtos . Two of these, the Y and Z lamellae, are shared by nassophoreans and cyrtophorians . Ingestion is likely aided by dense differentiations at the outermost ends of the oral nematodesmata, variously called capitula , \u201cteeth\u201d, \u201cmaxillae\u201d, or dens, while the arm-bearing micro- tubules of the cytopharyngeal lamellae propel food vacuole membrane enclosing food into the endoplasm (Tucker, 1972). A system of complex elongated tubules, found also in chonotrichs, is associated with the cyrtophorian cyrtos . These may function in food vacuole formation, although direct evidence for this hypothesis is still needed (Chilodonella \u2013 Pyne & Tuffrau, 1970; chonotrichs \u2013 Fahrni, 1982; Grain & Batisse, 1974). 10.4 Oral Structures 225 226 10. Subphylum 2. INTRAMACRONUCLEATA: Class 4. PHYLLOPHARYNGEA As suspension feeders , chonotrichs engage the entire body ciliature in creating feeding currents. It is therefore likely that there have not been strong selective pressures to retain an organized and adap- tive oral ciliature. Indeed, it was only through elec- tron microscopy that the chonotrich Chilodochona was shown to have an oral ciliature. Grain and Batisse (1974) described a single inverted oral kinety composed of dikinetids patterned identically