Pré-visualização11 páginas
there is no consensus on subdivision within the subclass. Batisse (1975) described seven suborders within what was then the Order Suctorida . He has now supported three orders with eight included suborders in a Subclass Suctoria (Batisse, 1994b). These systems are modeled on Fig. 10.2. Stylized drawings of representatives of the Subclass Chonotrichia of the Class PHYLLOPHARYNGEA . The exogemmid Chilodochona . The exogemmid Spirochona and its bud . Note the similarity of the bud\u2019s ciliary pat- tern to the cyrtophorians . The cryptogemmids Chonosaurus , Armichona , and Spinichona 10.1 Taxonomic Structure 213 214 10. Subphylum 2. INTRAMACRONUCLEATA: Class 4. PHYLLOPHARYNGEA Fig. 10.3. Stylized drawings of representatives of the Subclasses Rhynchodia and Suctoria of the Class PHYLLOPHARYNGEA . Members of the Subclass Rhynchodia . The hypocomatid Hypocoma . The rhynchodids Raabella and Ancistrocoma . Members of the Subclass Suctoria . The highly unusual endoparasite of guinea pigs , the evaginogenid Cyathodinium . This ciliated suctorian has its tentacles reduced to small protuberances along the left border of a cortical depression. The bud of the endogenid Enchelyomorpha , exhibiting a rare condition in which the bud bears tentacles the morphogenetic analyses of Kormos and Kormos (1957a, 1957b, 1958). Jankowski (1980) listed five subclasses and 21 orders in a Class Suctoria . We conservatively follow Lynn and Small (2002) and Matthes et al. (1988) in recognizing three orders based on modes of asexual reproduction (Figs. 2.11cb\u2013d, 10.3\u201310.6). The Orders Exogenida and Endogenida were suggested by Collin (1912) Fig. 10.4. Stylized drawings of representatives of the Subclass Suctoria of the Class PHYLLOPHARYNGEA . The endogenid Acineta and its bud . The exogenid Asterifer . The evaginogenid Dendrocometes and its bud 10.1 Taxonomic Structure 215 216 10. Subphylum 2. INTRAMACRONUCLEATA: Class 4. PHYLLOPHARYNGEA while the Order Evaginogenida was suggested by Jankowski (1975). Monographic works by Dovgal (1996, 2002) support these three taxa. However, Dovgal (2002) recognized the suctorians as a class and adds a fourth taxon, the Subclass Vermigenia Jankowski, 1978, to include suctorians whose swarmers are vermiform and non-ciliated. While this is truly an unusual kind of budding , we still consider it a type of exogenous budding , and will await the demonstration by gene sequencing that these taxa are sufficiently divergent and mono- phyletic to be recognized at this taxonomic level. Nevertheless, we have relied particularly heavily on Dovgal (2002) whose numerical phenetic analysis has provided the most objective assessment of char- acter state distributions among suctorians . The exogenids reproduce by budding with cytokinesis occurring on the cortical surface of the parental cell. This order includes 17 fami- lies: Allantosomatidae , Dentacinetidae , Dendro- somididae , Ephelotidae , Manuelophryidae , Metacinetidae , Ophryodendridae , Paracinetidae , Phalacrocleptidae , Podophryidae , Praethecaci- netidae , Rhabdophryidae , Severonidae , Spelaeo- phryidae , Stylostomatidae , Tachyblastonidae , and Thecacinetidae . The Family Phalacrocleptidae , monotypic for the genus Phalacrocleptes , is the exceptional ciliate \u2013 kinetosomes have never been observed. However, it does have a macronucleus and micronuclues, and with short tentacles enclos- ing one haptocyst in each, its suctorian affini- ties are certain (Kozloff, 1966; Lom & Kozloff, 1967). Budding and cytokinesis in the endog- enids occurs in a brood pouch with the swarmer typically exiting through a \u201c birth pore .\u201d Thirteen families are placed in this order: Acinetidae , Acinetopsidae , Choanophryidae , Corynophryidae , Dactylostomatidae , Dendrosomatidae , Endos- phaeridae , Erastophryidae , Pseudogemmidae , Rhynchetidae , Solenophryidae , Tokophryidae , and Trichophryidae . The Order Evaginogenida includes suctorians in which the kinetosomes of larval kineties first replicate on the \u201cparental\u201d surface of the brood pouch while cytokinesis is com- pleted externally or exogenously. Eleven families are assigned to this order: the Cometodendridae , Cyathodiniidae , Dendrocometidae , Discophryidae , Enchelyomorphidae , Heliophryidae , Periacinet- idae , Prodiscophryidae , Rhynchophryidae , Stylocometidae , and Trypanococcidae . The Family Enchelyomorphidae includes the genus Enchelyomorpha , long-considered a tentacled, actinobolinid gymnostome (Corliss, 1961, 1979), but now known to be the swarmer of a globular suctorian (Foissner & Foissner, 1995) (Fig. 10.3). The Family Cyathodiniidae includes the genus Cyathodinium , an endosymbiont of the caecum of the guinea pig Cavia porcella . Its suctorian affinities were demonstrated by Paulin and Corliss (1964, 1969) who revealed the tentacle-like substructure of its endosprits and the presence of haptocysts (Fig. 10.3). 10.2 Life History and Ecology Members of the Class PHYLLOPHARYNGEA can be divided into those that are free-living and those that are symbiotic, either commensal or parasitic but never mutualistic. The full range of these free-living and symbiotic life histories can be found among members of the subclasses Cyrtophoria and Suctoria while members of the subclasses Rhynchodia and Chonotrichia are obligate symbionts. Rhynchodians are obligate predators or parasites and chonotrichs are obli- gate commensals. Suctorians and chonotrichs have convergently evolved dimorphic life his- tories: a sessile trophont divides to produce a motile dispersal swarmer . Distributions of the free-living members of the class are very likely global while the distributions of the symbionts, as with symbiotic forms from other classes, are likely limited by the distributions of their preferred hosts. Members of the Subclass Cyrtophoria , such as Chilodonella , Dysteria , and others, have been found around the world: in terrestrial habitats, likes soils and mosses from Europe (Foissner, 1979a, 1988b; Grolière, 1977), Africa (Buitkamp, 1977), Asia (Wang, 1977), and Antarctica (Petz & Foissner, 1997); in freshwater streams (Cleven, 2004) and ponds in Europe (Grolière, 1977; Madoni & Sartore, 2003), Africa (Dragesco, 1965; Dragesco & Dragesco-Kernéïs, 1986), and North America and Mexico (López-Ochoterena, 1966); and in marine habitats, such as sublittoral sediments from Europe (Deroux, 1976a, 1976b; Deroux & Dragesco, 1968; Dragesco, 1963) and North America (Borror, 1963), on kelps and other marine vegetation in Europe (Gismervik, 2004); in deep benthic Mediterranean sediments (Hausmann, Hülsmann, Polianski, Schade, & Weitere, 2002), and in sea ice in Antarctica (Garrison et al., 2005). Their flattened body form is particularly adapted for benthic or interstitial habitats, although some species of Pseudochilodonopsis (Foissner, 1988b) and Gymnozoum (formerly Spiroprorodon ) (Corliss & Snyder, 1986) can be found in the plankton. Cyrtophorians are typically found in the bio- films on substrates where they use the tooth-like capitula on the cytopharyngeal apparatus to browse on bacteria , diatoms , filamentous green algae , and cyanobacteria (Deroux, 1994a; Foissner, 1988b). This preference for biofilms probably leads them to exploit these films on the body surfaces of invertebrates, such as crustaceans , where they can be facultative (i.e., Chilodonella spp.) or obli- gate (i.e., Allosphaerium ) symbionts (Dobrza ska- Kaczanowska, 1963; Morado & Small, 1995). They do not likely present disease problems in crustaceans . However, two species, Chilodonella cyprini and Chilodonella hexasticha , do cause disease of freshwater and marine fishes (Hoffman,