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Fig. 7.4. Stylized drawings of representative genera from subclasses in the Class SPIROTRICHEA . Subclass Stichotrichia : Plagiotoma , Stichotricha, Stylonychia , Urostyla , and Halteria , formerly an oligotrich (compare to Strombidium and Laboea ). Note that the bristles of Halteria have been shortened to accommodate the space on the page the oral primordium in an intracellular tube or neo- formation organelle (Petz & Foissner, 1992) or on the cell surface (Song & Wang, 1996). Oligotrichs , such as Cyrtostrombidium , Strombidium , Laboea , and Tontonia , demonstrate a considerable diversity of somatic ciliary patterns. Agatha (2004a) has pro- vided a detailed analysis of these patterns and used this to justify establishment of several new families and genera (see Chapter 17 ). Oral anlagen development is epiapokinetal , that is it occurs on the cell surface of the halteriids Halteria (Petz & Foissner, 1992; Song, 1993) and Meseres (Petz & Foissner, 1992), and these two \u201cclassical oligotrich\u201d genera undergo a complete turn-over or replacement of somatic ciliature during division (Agatha, 2004b; Petz & Foissner, 1992; Song, 1993). Consistently, the \u201cclassical oligotrich\u201d Halteria falls among the stichotrich clade, based on the SSUrRNA gene (Foissner et al., 2004; Snoeyenbos-West et al., 2002; Strüder-Kypke et al., 2002), ITS1 and ITS2 , 5.8S rRNA , and the large subunit rRNA gene (Hewitt et al., 2003), DNA polymerase \u3b1 (Hoffman & Prescott, 1997), and actin (Croft et al., 2003). These morphoge- netic and molecular features support their affinities to the stichotrichs . Agatha (2004b) argued that halteriids are related to strombidiids (= oligotrichs ) sensu lato on two main synapomorphies: (1) the enantiotropic division mode; and (2) the de novo origin of the paroral. We suggest that both these features are strongly convergent: the enantiotropic division mode is found in a form in the distantly- related prostome Balanion (Foissner, Oleksiv, & Müller, 1990), while many taxa may differentiate the paroral de novo . Instead, we would emphasize the importance of epiapokinetal stomatogenesis , the complete turnover of the somatic ciliature, and the molecular affinities, all of which relate halteriids to the stichotrichs . Thus, the proposed oligotrich taxo nomies (e.g., Agatha, 2004b; Laval-Peuto, Grain, & Deroux, 1994; Lynn & Small, 1997; Petz & Foissner) are refuted: the Family Halteriidae must be transferred to the Subclass Stichotrichia (see Chapter 17 ). Halteriids can be considered as stichotrichs , highly adapted to the planktonic habitat. We only recognize the Order Strombidiida in the Subclass Oligotrichia (see Chapter 17 ). The tintinnids deserve special mention because of their long-standing independent status as a group, their conspicuousness in the marine plankton, and the exceedingly large number of described species, well over 1,200. Stomatogenetic (Dale & Lynn, 1998; Petz & Foissner, 1992) and molecular fea- tures (Strüder-Kypke et al., 2002; Snoeyenbos-West et al., 2002) place them in the Subclass Choreotrichia alongside their aloricate relatives. In addition to the lorica , they are distinguished by a number of peculiar features: tentaculoids , a contractile body, a lateral cytoplasmic lobe apparently used in lorica construction, short somatic cilia arranged in char- acteristic patterns dependent upon species, and a perilemma surrounding the entire body and cili- ature. Doubts have been cast on the taxonomic util- ity of lorica morphology, both since the description by Laval-Peuto (1977) of a Favella species making a Coxliella -like lorica and by quantitative analyses of lorica variation that conclude it is not feasible to objectively distinguish many species based on lorica form (Davis, 1981). Despite the recent suc- cess in automatic categorization by lorica form of five species of Cymatocylis by an artificial neural network (Culverhouse et al., 1994) and linear discriminant analysis (Williams, McCall, Pierce, & Turner, 1994), we support Laval-Peuto and Brownlee (1986) who recommended a systematic approach based on cytology as revealed by pro- targol staining. Only a handful of species have been stained so far, but clear somatic kinetid patterns are emerging, such as the presence of longer dor- sal and ventral kineties that separate left and right fields of shorter kineties (e.g., Agatha & Riedel- Lorjé, 2006; Agatha & Strüder-Kypke, 2007; Choi, Coats, Brownlee, & Small, 1992; Foissner & Wilbert, 1979; Laval-Peuto & Brownlee, 1986). Nevertheless, lorica form has been the major diagnostic feature for the only new family of tin- tinnids established since 1979 (Sniezek, Capriulo, Small, & Russo, 1991; Snyder & Brownlee, 1991)! Because of the lack of comparative data on kinetid patterns , we believe it is premature to redistribute tintinnid genera among families. In the Subclass Choreotrichia , we therefore continue to recognize the loricate Order Tintinnida with its classical \u201cloricate\u201d families while genera in the aloricate Order Choreotrichida are divided into four mono- typic orders based primarily on variations in somatic kinetid patterning (see Chapter 17 ). Finally, researchers continue to explore rela- tionships within the stichotrichs . The exceedingly complex ventral cirral patterns of stichotrichs 7.1 Taxonomic Structure 149 150 7. Subphylum 2. INTRAMACRONUCLEATA: Class 1. SPIROTRICHEA have lead taxonomists to use features of division morphogenesis as a means to resolve relation- ships among taxa. This approach is premised on the conservative nature of developmental pat- terns as argued by Fauré-Fremiet (1948a) and Corliss (1961, 1967, 1968, 1979). There is a rich literature using these morphogenetic patterns to resolve relationships within the stichotrichs (e.g., Berger & Foissner, 1997; Borror, 1979; Borror & Hill, 1995; Eigner, 1997, 1999, 2001; Fleury et al., 1985a, 1985b, 1986; Martin, 1982; Wicklow, 1982). Other researchers have primarily used the SSUrRNA genes. While the Subclass Stichotrichia appears to be monophyletic and now includes the halteriids (see above), it is still quite difficult to rec- oncile morphological and molecular approaches at the family and genus levels, although current molec- ular evidence at least supports a clade of Stylonychia - related species (Bernhard et al., 2001; Berger & Foissner; Foissner et al., 2004; Hewitt et al., 2003; Schmidt, Bernhard, Schlegel, & Foissner, 2007), suggested already in a cladistic analysis of morphological traits (Berger & Foissner). We have done our best to reconcile these data, but the effort is obviously unfinished as there is a considerable amount of convergence in morphological traits (see Wiackowski, 1988). We have remained conservative in our taxonomic treatment of this subclass and rec- ognize three orders: (1) Order Stichotrichida , includ- ing genera such as Plagiotoma and Stichotricha , whose cirri are arranged, often in many, linear files; (2) Order Sporadotrichida , such as Stylonychia , in which cirri are distributed \u201csporadically\u201d in con- spicuous frontal, ventral, and transverse groupings; and (3) Order Urostylida , such as Urostyla , in which the frontoventral cirri are arranged in two or more zig-zag files on the ventral surface (Fig. 7.4) (see Chapter 17 ). In conclusion, we recognize seven subclasses in the Class SPIROTRICHEA : (1) Subclass Protocruziidia ; (2) Subclass Phacodiniidia ; (3) Subclass Licno- phoria ; (4) Subclass Hypotrichia ; (5) Subclass Oligotrichia ; (6) Subclass Choreotrichia ; and (7) Subclass Stichotrichia . Molecular phylogenetics suggests that the taxa are ordered in this manner with Protocruzia at the base of the spirotrich lineage and various stichotrichs , like Stylonychia and Sterkiella , at the tip (Bernhard