Ref ID : 7590
Barry J. Wicklow; Evolution within the Order Hypotrichida (Ciliophora, Protozoa): Ultrastructure and Morphogenesis of Thigmokeronopsis jahodai (N. Gen., N. Sp.); Phylogeny in the Urostylina (Jankowski, 1979). Protistologica XVII(3):331-351, 1981
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Using light optical and both scanning and transmission electron microscopy I describe cortical morphogenesis through cell division and interphase cortical ultrastructure of a benthic, estuarine ciliate, Thigmokeronopsis jahodai n. g. n. sp. The morphogenetic pattern is of the Urostyline type: frontal ciliature develops from a longitudinal series of oblique streaks. Frontal streaks differentiate into malar, migratory, midventral, transverse, and a unique kind of ciliature, thigmotactic cirri. The thigmotactic cirral field, used for adhesion to substrate, occupies the left ventral side of the cell, posterior to the buccal cavity. The adoral membranelles are paramembranelles; postciliary microtubular ribbons originate at the first (posteriormost) row of membranellar kinetosomes, course laterally along the intermembranellar ridge to join similar ribbons from other membranelles, thus formig a postmembranellar fiber. I interpret this fiber as homologous with the postciliodesmata of somatic kineties heterotrich and karyorelictid ciliates. The endoral membrane is a stichomonade whereas the paroral apparatus is a polystichomonade. Each right midventral cirrus is connected to a left midventral cirrus is connected to a left midventral cirrus by an anterior microtubular bundle; right, left, and posterior microtubular bundles are also present. In addition to transverse and postciliary microtubular ribbons, a unique kind of microtubular ribbing (reminiscent of that found in Plagiotoma) exists in the cirri of Thigmokeronopsis. I consider cirri and membranelles as oligomerized organellar complexes having evolved by amplification (polymerization) of kinetosomal pairs with concommitant reduction of microtubular elements and a general decrease in the number of organellar complexes per cell as more complex hypotrichs evolved. I propose a phylogeny, based on morphogenetic and structural characters, for Urostyline hypotrichs (those hypotrichs possessing a midventral ciliature): Bakuella, Holosticha, Keronopsis, Pseudourostyla, Thigmokeronopsis, Uroleptus, and Urostyla. Due to possession of a divergent type of developmental primordium (ventral primordium), I separate Pseudourostyla from other Urostylines at the superfamilial level. I present a classification of the Uostylines that includes 2 superfamilies: Urostyloidea (fam. Urostylidae, subfam. Holostichinae and Urostylinae; fam. Keronopsidae, subfam. Keronopsinae and Thigmokeronopsinae) and Pseudourostyloidea (fam. Pseudourostylidae).