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\u201d of the ancestral suctorian , preserved in the cecum of a vertebrate?! Finally, Foissner and Foissner (1995) conclusively demonstrated using electron microscopy that the strange tentacled \u201c haptorian \u201d Enchelyomorpha was, in fact, the swarmer of a small globular suctorian , based on the substruc- ture of its tentacles and a complete study of its life cycle. 10.5 Division and Morphogenesis Guilcher (1951) consolidated our current view that the subclasses in this class might be phyloge- netically related with her descriptions of division morphogenesis , which Dobrza ska-Kaczanowska (1963) later confirmed. Foissner (1996b) charac- terized stomatogenesis of cyrtophorians as mero- telokinetal because the opisthe anlagen form at the anterior ends of a small number of somatic kineties (Fig. 10.9). He does not characterize stomatogen- esis for the other three subclasses because no oral ciliature has been described in these ciliates. Stomatogenesis in cyrtophorians involves a coun- ter-clockwise migration of the kinetofragments, when the ventral surface is viewed from outside the cell (Fig. 10.9). Thus, at completion of stomatogen- esis , these three or more oral kinetofragments are inverted with respect to neighbouring somatic kine- ties (Deroux, 1970, 1976a, 1977; Sniezek & Coats, 1996). These movements have been confirmed and the interpretation of the inverted nature of the oral dikinetids in cyrtophorians has been verified by the 10.5 Division and Morphogenesis 227 228 10. Subphylum 2. INTRAMACRONUCLEATA: Class 4. PHYLLOPHARYNGEA detailed ultrastructural study of Trithigmostoma (Hofmann & Bardele, 1987) and Chilodonella (Hofmann, 1987). Kurth and Bardele (2001) verify the same pattern in Chlamydodon and put forward the intriguing hypothesis that the cyrtophorian oral apparatus is a secondary one based on the very divergent nature of these oral kinetids. Turning the traditional view of phylogeny within the Class PHYLLOPHARYNGEA upside-down, they claim that suctorians represent the basal branch with cyrtophorians and chonotrichs deriving \u201ctypical\u201d cytostomes and body ciliature secondarily! Clearly, sampling of more phyllopharyngean genera fol- lowed by gene sequencing will help to resolve how basal the suctorians really are. Molecular phylo- genetic analyses of SSUrRNA gene sequences do not resolve the question as suctorians are the sister clade to a cyrtophorine-chonotrich clade (Li & Song, 2006a; Snoeyenbos-West et al., 2004). Chilodonella and Trithigmostoma have also been models in understanding the global param- eters of pattern formation in ciliates (see Frankel, 1989). Contractile vacuole pore positioning at cell division suggests that new pores are positioned, in a probabilistic manner, with reference to the developing oral apparatus and the margins of the cell (Kaczanowska, 1974, 1981). Variability in the number of ventral kineties has been determined to arise in Trithigmostoma following cell division . This is primarily due to how many left-field kineties are separated by the fission furrow since kineties typically decrease in length towards the left margin of the cell (Fig. 10.1) (Radzikowski & Golembiewska-Skoczylas, 1999). At each cell division, the right-most \u201cstomatogenetic\u201d kinety releases an anterior fragment, which separates, moves to the right of this kinety, and elongates by replication. This at least compensates for the loss of one left-field kinety (Deroux, 1994a; Radzikowski & Golembiewska-Skoczylas, 1999). However, \u201cstomatogenic\u201d kineties can vary in position, lead- ing to a phenomenon similar to cortical slippage in the oligohymenophorean Tetrahymena (Frankel, 1989; Radzikowski & Golembiewska-Skoczylas). This indicates that it is not the kinety per se that has the morphogenetic \u201cpotential\u201d but rather some particular region of the cortex, specified in a proba- bilistic manner by a global patterning mechanism , like that for contractile vacuole positioning (see Frankel, 1989). Parental cytopharyngeal structures typically dedifferentiate and redifferentiate in syn- chrony with those of the opisthe. Chonotrichs reproduce by two major kinds of budding , termed exogemmous and cryptogemmous (Jankowski, 1973b, 1975). The swarmer is pro- duced probably by continuity with the ciliature of the parent in exogemmous forms. Cryptogemmous forms develop within a crypt, which may derive its kinetosomes by migration from the parental field (Gunderson, 1984). One bud is typically formed Fig. 10.9. Merotelokinetal division morphogenesis of the cyrtophorian Chlamydonella pseudochilodon . Note how the new oral structures appear in the equatorial region by kinetosomal replication of a few somatic kineties ( a ). These kinetosomes assemble as oral dikinetids ( b ) and undergo a counter-clockwise rotation as seen from outside the cell (b\u2013d ). (Redrawn from Deroux, 1970.) followed by regrowth of the parent. However, sequential reactive budding can occur at times when the host molts or dies (Batisse, 1994a; Jankowski, 1973b). Very few buds have been described from silver stained specimens. However, those that have been described remind one of a dysteriid-like cyr- tophorian with a right ventral kinety field extend- ing anteriorly over a smaller left ventral kinety field (Fig. 10.2). There is also an adhesive organelle in the posterior (see Dobrza ska-Kaczanowska, 1963; Fahrni, 1984; Guilcher, 1951; Jankowski, 1973b; Taylor, Lynn, & Gransden, 1995). Rhynchodian cell division can be equal or unequal. Since there is no oral ciliature, it is an uncomplicated division of the somatic kineties. The parental cytopha- ryngeal apparatus dedifferentiates and redifferentiates in synchrony with that of the opisthe (de Puytorac, 1994b). Sphenophryids may have a division that is so unequal that it could be called budding (Chatton & Lwoff, 1950; Dobrza ska, 1961). The suctorian bud or swarmer , like that of the chonotrichs , is a short-lived dispersal stage. It may be ciliated or it may be worm-like and non-ciliated. The bud \u201crecapitulates\u201d the phylogenetic origin of the group, under the hypothesis that suctorians are a derived group (but see Kurth & Bardele, 2001 and above). Budding can be simple or single or it can be multiple, either successive or simultaneous. Reactive budding , as in the chonotrichs , may occur under unfavourable conditions or when the host molts, possibly stimulated by ecdysone (Batisse, 1994b; Walker & Roberts, 1988). There are several schemes of classification for budding (Batisse; Collin, 1912; Corliss, 1979; Kormos & Kormos, 1957a, 1957b). We follow Corliss (1979) until molecular evidence confirms the diversity sug- gested by Batisse and Dovgal (2002). In exogenous budding , the bud infraciliature develops on the cell surface of the parent followed by an uncompli- cated cell division, sometimes almost equal (e.g., Podophrya \u2013 Fauré-Fremiet, 1945). In evaginative budding , the bud infraciliature begins development in a pocket that erupts rapidly out of the parental cell surface (e.g., Discophrya \u2013 Henk & Paulin, 1977). In endogenous budding , the bud devel- ops and is completed within a brood pouch . The swarmer then exits through a \u201c birth pore \u201d (e.g., Tokophrya \u2013 Noble, 1932) (Fig. 2.11cb\u2013d). There have been relatively few studies on the ultrastructural aspects of division morphogenesis in suctoria . Non-ciliated kinetosomes, often near the parental contractile vacuole pore, replicate to produce the infraciliature of the swarmer. The kinetal pattern of Discophrya is very reminiscent of a cyrtophorian with kineties curving around the \u201canterior\u201d end (Fig. 10.5) (Canella, 1957; Plachter, 1979; Suárez, Guinea, & Fernández- Galiano, 1987a). However, these kineties curve around the scopuloid NOT the oral region,