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Contrary to Small and Lynn (1985), the molecular genetic evidence now strongly links the peniculines to the other oligohymenophoreans (Strüder-Kypke et al., 2000a, 2000b). Moreover, Beran (1990) has made the most recent compelling argument for ontoge- netic homologies between peniculines and other oligohymenophoreans in his investigations of the early development of the oral anlage. Beran (1990) considered as homologues the following structures involved in oligohymenophorean stomatogenesis : the ophryokineties of the peniculine Frontonia , the anarchic field of the peniculine Paramecium , and the scutica of the scuticociliates , and this may be extended to the germinal row of peritrichs (Figs. 15.10, 15.11). With this assumption of homology, these ontogenetic features corroborate the mono- phyly of this class. Peniculine stomatogenesis has been charac- terized as ophryobuccokinetal (Foissner, 1996b). While there is no doubt on molecular and morpho- logical grounds that the frontoniids and parameciids are sister taxa, there are differences in their division Fig. 15.10. Division morphogenesis of representatives from subclasses of the Class OLIGOHYMENOPHOREA . A In the Subclass Peniculia , represented by Frontonia , stomatogenesis is considered ophryobuccokinetal because it involves proliferation of kinetosomes from the parental paroral and from several \u201cophryokineties\u201d to the right of the oral region ( a , b ). As stomatogenesis proceeds, a new paroral differentiates on the left of the field for the proter while the opisthe\u2019s oral apparatus differentiates into the three peniculi and a paroral as it migrates posteriorly ( c , d ). (from Song, 1995.) B In the Subclass Scuticociliatia , Philaster represents the Order Philasterida . Stomatogenesis begins by proliferation of kinetosomes from the parental paroral and the scutica , which resides in the director meridian between Kineties 1 and n ( a , b ). Kinetosomes from the paroral migrate posteriorly along the right to form the opisthe\u2019s paroral and part of the oral polykinetids ( c ). As the proter\u2019s paroral reconstitutes itself ( d , e ), the opisthe\u2019s oral structures take shape with the scutica appearing as a \u201chook-like\u201d attachment at the posterior end of the developing paroral. (from Coats & Small, 1976.) 316 15. Subphylum 2. INTRAMACRONUCLEATA: Class 9. OLIGOHYMENOPHOREA Fig. 15.11. Division morphogenesis of representatives from subclasses of the Class OLIGOHYMENOPHOREA . A In the Subclass Scuticociliatia , Pleuronema represents the Order Pleuronematida . A large portion of the parental paroral dedifferentiates and kinetosomal replication occurs along this c segment or scutica , categorizing the stoma- togenesis as scuticobuccokinetal ( a , b ). The oral polykinetids and paroral for the opisthe begin to differentiate as they migrate posteriorly, leaving the paroral of the proter to reassemble ( c , d ). Near the final stages, the scutica appears as a J-shaped structure at the posterior end of the paroral in each cell ( e ). (From Ma et al., 2003a.) B In the Subclass Hymenostomatia , Tetrahymena is the classic example of parakinetal stomatogenesis . Kinetosomes proliferate along the equator of what is defined as Kinety 1 or the stomatogenic kinety ( a , b ). As this proliferation continues, devel- opment of the oral structures takes place from the anterior towards the posterior and from the right towards the left (c\u2013e ) (redrawn after Grolière, 1975a). C In the Subclass Apostomatia , Hyalophysa shows what have been interpreted as stomatogenesis during tomite development. Three closely spaced kineties, designated a , b , and c , overly a small kinetofragment (* in a ), which develops as the rosette . These three kineties themselves undergo dedifferentiation and redifferentiation to produce the kinetal structures of the mature tomite ( b\u2013e ). The homologies with other oligohy- menophoreans are very difficult to see. (from Bradbury et al., 1997.) morphogenesis . The oral apparatus of frontoniids develops, in some species, by participation of a set of special kineties to the right of the oral cav- ity \u2013 the ophryokineties \u2013 and in all species, by participation of the parental paroral, which serves as a site for kinetosomal replication for opisthe structures (Fig. 15.10) (Beran, 1990; Song, 1995). In parameciids , an anarchic field to the right of the paroral serves as the site for replication of kineto- somes that construct the oral organellar complexes. Upon completion of stomatogenesis , a new anar- chic field differentiates in readiness for the next cell division (Jones, 1976). UV-irradiation studies suggest that this area of the oral cortex is crucial in formation of a functioning oral apparatus (Hanson, 1962). Parental structures in peniculines may be partially or completely reorganized (Fig. 15.10) (Foissner; Roque, 1961a; Shi, 1980). Dividing Paramecium also assembles longitudinal, supraepi- plasmic microtubules in the somatic cortical ridges (Sundararaman & Hanson, 1976). Fluorescently- labelled tubulin antibodies have demonstrated that these microtubules, collectively termed the cyt- ospindle , assemble early in cell division correlated with the disassembly of other components of the cytoskeleton (Cohen, Adoutte, Grandchamp, Houdebine, & Beisson, 1982; Delgado, Romero, & Torres, 1990; Iftode et al., 1989). Hymenostomes and scuticociliates , at least among other oligohy- menophoreans , have longitudinal, supraepiplasmic microtubules throughout the cell cycle. Is this con- dition in Paramecium a recapitulation of an ances- tral pre- oligohymenophorean state, since it may also occur in dividing nassophoreans (Tucker, 1971b) ( see Chapter 11 ) or is it a presage for a derived neo- tenous state, which is exhibited by hymenostomes and scuticociliates ? Urocentrum turbo , a ciliate whose SSUrRNA gene sequence places it outside the peniculine clade (Strüder-Kypke et al., 2000b), shows parameciine features in its stomatogenesis (Foissner; Martín-González, Serrano, Guinea, & Fernández-Galiano, 1986). Thus, until the rDNA gene sequence data are corroborated by other genes, we maintain Urocentrum as a peniculine . The scuticociliates were recognized as a group by Small (1967) who demonstrated homologies in the stomatogenesis of a number of hymenostome -like ciliates that he had assigned to his newly conceived order Scuticociliatida . During stomatogenesis, the paroral or a grouping of kinetosomes associated with the posterior end of the paroral \u2013 the scuticovestige \u2013 gives rise to kinetosomes for the opisthe\u2019s oral apparatus (Figs. 15.10, 15.11). The scutica itself is a transient structure, and often takes the form of a \u201cwhip-lash\u201d or \u201cJ\u201d during philasterine scuticociliate stomatogenesis , hence its name (Fig. 15.10). In some cases, kinetosomal involvement in stomatogenesis also includes participation of kinetosomes derived from the dedifferentiating parental oral polykinetids (Dolan & Antipa, 1985; Small). With these two features, Foissner (1996b) characterized this type as scuticobuccokinetal . The literature has grown consid- erably since Small\u2019s review, providing support for at least two major stomatogenetic types, correlated with the orders in the subclass (Figs. 15.10, 15.11). While there is considerable variability in the details of the stomatogenic pattern, Coats and Small (1976) proposed a schema in which the paroral plays a central role. They viewed it to be composed of an anterior or a segment, a middle or b segment, and a posterior or c segment. The philasterine scuticocili- ates have been much more extensively studied than representatives from the other orders. The philaster- ines typically have a paroral with a and b segments, and a scuticovestige