Morphology and Development of Mirror-Image Doublets of Stylonychia mytilus

This paper describes the cortical anatomy and development of mirror-image doublets of Stylonychia mytilus, analyzed using the protargol technique. The reversed, or “left-handed” (LH) component of these doublets is a mirror image of the normal or “right handed” (RH) component with regard to the arrangement of cortical structures. The mirror-image patterning is imperfect, however, as the individual ciliary structures of the LH component all are of normal internal asymmetry, and the orientation of membranelles is inverted. Certain structures that would be expected to form near the line of symmetry are absent. During cell division and cortical reorganization, ciliary primordia arise and become arranged in a mirror-image pattern that is more perfect than that exhibited by the mature structures. Deviations from a mirror-image pattern appear at late stages when organelle sets differentiate within ciliary primordia: for example, the membranelle set differentiates within the oral primordium of the LH component in a sequence that is an inversion rather than a mirror image of the corresponding sequence of the RH component. This mixed control of oral development by different cortical “informational systems” accounts for some of the characteristic abnormalities of the mature oral structures of the LH component.     

Morphology and development of mirror-image doublets of Stylonychia mytilus

This paper describes the cortical anatomy and development of mirror-image doublets of Stylonychia mytilus, analyzed using the protargol technique. The reversed, or "left-handed" (LH) component of these doublets is a mirror image of the normal or "right handed" (RH) component with regard to the arrangement of cortical structures. The mirror-image patterning is imperfect, however, as the individual ciliary structures of the LH component all are of normal internal asymmetry, and the orientation of membranelles is inverted. Certain structures that would be expected to form near the line of symmetry are absent. During cell division and cortical reorganization, ciliary primordia arise and become arranged in a mirror-image pattern that is more perfect than that exhibited by the mature structures. Deviations from a mirror-image pattern appear at late stages when organelle sets differentiate within ciliary primordia: for example, the membranelle set differentiates within the oral primordium of the LH component in a sequence that is an inversion rather than a mirror image of the corresponding sequence of the RH component. This mixed control of oral development by different cortical "informational systems" accounts for some of the characteristic abnormalities of the mature oral structures of the LH component.     

Description of a mirror-image doublet from a Brazilian strain of Gastrostyla setifera (Engelmann, 1862) Kent, 1882 (Ciliophora: Stichotrichia)

The present work describes a mirror-image doublet morph found in a Brazilian strain of the stichotrich ciliate Gastrostyla setifera (Engelmann, 1862) Kent, 1882, obtained from a sample of water and sediment from an urban freshwater stream in the city of Juiz de Fora (Minas Gerais, Brazil). The doublet measured 63 x 49 microm, and had two components where the right one has upside-down arranged adoral membranelles with a set of small oblique membranelles at its proximal (posterior) end. The fronto-ventral-transverse ciliature comprised 34 cirri, mostly related to the left component, as well as two marginal rows. On the dorsal surface there were eight dorsal kineties and six caudal cirri. Dorsomarginal kineties were lacking. The macronucleus comprised one irregular-shaped transverse nodule and two smaller roughly ellipsoid longitudinal nodules.     

The filaments supporting ciliary primordia and fission furrow in the hypotrich ciliateParaurostyla weissei, revealed by the monoclonal antibody 12G9: Studies on wild-type and ciliary hypertrophy mutant

Summary The unique monoclonal antibody FXXXIX 12G9 obtained againstTetrahymena cortices was used to label cytoskeletal structures related to basal body proliferation inParaurostyla weissei. The antibody binds to an amorphous material interconnecting basal bodies in compound ciliary structures: dorsal units, cirri and membranelles in interfission cells, and filamentous structures supporting the primordia of ciliary structures and fission line in dividing cells. The antibody visualized meridional filaments preceding proliferation of new basal bodies in the oral primordium and structures accompanying all developing ciliary primordia. It congregated in differentiating new procirri and membranelles, whereas another population of transient meridional structures accompanied the final distribution of new structures. A meridional filament connecting transverse cirri with the oral apparatus, marking the future stomatogenic meridian, persisted in both division products until completion of cell elongation. The fission line was found to originate from an anterior extension of the pre-oral filament toward the parental oral structures. It then encircled the cell's midbody demarcating the boundary between daughter cells; two additional circumferential structures bordering the anterior and posterior ends of differentiating division products participate in formation of the new poles. They disappear after separation of daughter cells and completion of resorption of parental ciliature. In the enhanced multi-left-marginal mutant expressing gross hyperduplication of basal bodies, the location of the 12G9 antigen corresponded to that in wild-type cells. The sequence of formation of meridional filaments in the mutant was found to be altered. The filaments in the left lateral domain preceded the formation of the preoral filament, yet the temporal pattern of basal body assembly was not modified. The fission line, as in wild-type cells, originated in connection with the oral primordium. We conclude that the nucleation of the filamentous structures bearing the 12G9 antigen and the basal body assembly occur by independent mechanisms reading the same cell cycle signals. We suggest that the 12G9-antigen-bearing protein might be similar to septins: involved in signaling the position of the oral primordium and the fission line and functioning in establishing and maintaining the asymmetric cortical domain characteristics.Abbrevations AZM zone of adorai membranelles - bb basal bodies - CC caudal cirri - FC frontal cirri - Fmf frontal meridional filament - FTV the primordia of fronto-ventro-transverse cirri - LD, RD dorsal rows of bristle units - LM, RM left or right marginal cirral row - OA oral apparatus - OP primordium of the adoral membranelles - pLM, pRM primordium of the left or right marginal cirri - pLD, pRD primordia of the left or right dorsal bristle rows - pUM primordium of the undulating membranes - TC transverse cirri - UM undulating membranes - VC ventral cirral rows     

Morphology and Development of Left-Handed Singlets Derived from Mirror-Image Doublets of Stylonychia mytilus

Mirror-image doublets of Stylonychia mytilus include 2 sets of cortical structures, one with the normal “right-handed” (RH) arrangement, the other with a reversed “left-handed” (LH) arrangement. These sets, however, are incomplete, with certain structures, most notably cirri of the right marginal type, missing near the line of symmetry. When a mirror-image doublet is bisected longitudinally to separate the RH and LH components physically, each fragment undergoes a regeneration process that restores a complete set of cortical structures, including the previously missing cirri of the right marginal type. In the resulting LH cell, all ciliary structures are present in an arrangement that is globally reversed in relation to that found in RH cells; in particular, marginal cirri of the left-marginal type are formed at the cell's right margin, and marginal cirri of the right-marginal type are produced at the cell's left margin. Whereas the regenerated RH fragment always divides and initiates a clone of normal singlets, the LH fragment, though structurally nearly complete, in all cases eventually dies without dividing. The cause of death is starvation due to the formation of an abnormal oral apparatus. In the Discussion, we consider the nature and consequences of a reversal of global positional information.     

Morphology and development of left-handed singlets derived from mirror-image doublets of Stylonychia mytilus

Mirror-image doublets of Stylonychia mytilus include 2 sets of cortical structures, one with the normal "right-handed" (RH) arrangement, the other with a reversed "left-handed" (LH) arrangement. These sets, however, are incomplete, with certain structures, most notably cirri of the right marginal type, missing near the line of symmetry. When a mirror-image doublet is bisected longitudinally to separate the RH and LH components physically, each fragment undergoes a regeneration process that restores a complete set of cortical structures, including the previously missing cirri of the right marginal type. In the resulting LH cell, all ciliary structures are present in an arrangement that is globally reversed in relation to that found in RH cells; in particular, marginal cirri of the left-marginal type are formed at the cell's right margin, and marginal cirri of the right-marginal type are produced at the cell's left margin. Whereas the regenerated RH fragment always divides and initiates a clone of normal singlets, the LH fragment, though structurally nearly complete, in all cases eventually dies without dividing. The cause of death is starvation due to the formation of an abnormal oral apparatus. In the Discussion, we consider the nature and consequences of a reversal of global positional information.     

Mirror-imaged doublets of Tetmemena pustulata: implications for the development of left-right asymmetry

Ciliated protozoa possess cellular axes reflected in the arrangement of their ciliature. Upon transverse fission, daughter cells develop an identical ciliary pattern, ensuring perpetuation of the cellular phenotype. Experimentally manipulated cells can be induced to form atypical phenotypes, capable of intraclonal propagation and regeneration after encystment. One such phenotype in the ciliate Tetmemena pustulata (formerly Stylonychia pustulata) is the mirror-imaged doublet. These cells possess two distinct sets of ciliature, juxtaposed on the surfaces in mirror image symmetry, with a common anterior-posterior axis. We have examined whether individual ciliary components of Tetmemena mirror-image doublets are mirror imaged. Ultrastructural analysis indicates that despite global mirror imaging of the ciliature, detailed organization of the membranelles is reversed in the mirror-image oral apparatus (OA), such that the ciliary effective stroke propels food away from the OA. Assembly of compound ciliary structures of both OAs starts out identically, but as the structures associated with the mirror-image OA continue to form, the new set of membranelles undergoes a 180° planar rotation on the ventral surface relative to the same structures in the typical OA. The overall symmetry of the OA thus appears to be separable from the more localized assembly of individual basal bodies. True mirror imagery of the membranelles would require new enantiomorphic forms of the individual ciliary components, particularly the basal bodies, which is never observed. These observations suggest a mechanistic hypothesis with implications for the development of left-right asymmetry not only in ciliates, but perhaps also in development of left-right asymmetry in general.     

The Structure and Morphogenesis of the Ventral Ciliature in Paraurostyla hymenophora*

SYNOPSIS. The structure and morphogenesis of the ventral ciliature of Paraurostyla hymenophora (Stokes) are described. The oral primordium apparently originates in association with transverse cirrus #6, from which it migrates anteriorly simultaneous with kinetosomal proliferation. The primordium eventually forms an elongate ciliary field from which the future opisthe's fronto-ventro-transverse (FVT) and undulating membrane primordial fields arise. Concomitantly, the future proter's FVT primordial field is initiated by the disaggregation of frontal cirri #4, #5, and #6. Primordia then develop simultaneously within marginal and ventral cirral rows by a disaggregation of cirri within the respective rows, and do not give rise to new cirri until the FVT fields complete segregation into discrete cirri. Near the completion of cirral production from the FVT primordia, each ventral cirral primordium (VCP) forms the 2 rightmost transverse cirri. Segregation of new cirri within the marginal cirral primordia and VCP then occurs, eventually replacing all old cirri within their respective marginal and ventral cirral rows. At the end of cortical morphogenesis, all old ciliary organelles, with the exception of the adoral zone of membranelles, are either reorganized or replaced. These results suggest an evolutionary affinity between the ventral and marginal cirral rows and raise questions about the control of the developmental competence of individual primordia.     

An Analysis of the Formation of Ciliary Primordia in the Hypotrich Ciliate Urostyla weissei*

SYNOPSIS. The protargol technic was used in a study of the development of oral, cirral, and dorsal primordia of Urostyla weissei fixed during division, reorganization, and regeneration following transection at different levels. While the course of development is similar in all situations, differences were observed in the way in which some primordia are initiaily formed. The primordium of the new AZM always appears posterior to the old AZM. It develops into an entire new membranellar band in dividing cells and in opimers (posterior fragments from equatorial transections), while it eventually joins with a portion of the old AZM in reorganizers, promers (anterior fragments from equatorial transections) and “large opimers” (cells whose anterior tip has been cut off). The UM-primordium of proters is derived from disaggregation of the kinetosomes of the 2 old UM's, that of opisthes and opimers is formed “de novo” to the right of the AZM-primordium, while the UM-primordium of reorganizers, promers, and “large opimers” is of composite origin, partly “de novo” and partly from the old UM's. The UM primordium differentiates into the new UM's and the 1st frontal cirrus. The primordia of the remaining frontal, ventral, transversal (F-V-T) and marginal cirri originate as “streaks” of cilia, most of which are derived from re-alignment of the constituent cilia of certain pre-existing cirri. New cirri differendiate from the streaks, and replace the remaining old cirri. The streaks are formed similarly in all developmental situations, except for the 1st 3 F-V-T streaks. In proters, reorganizers, and promers, these originate from the posterior 3 frontal cirri, while in opisthes and opimers they are formed “de novo” to the right of the UM-primordium. In the “large opimers” these streaks are formed “de novo” behind the 1st 3 frontal cirri, in spite of the continued presence of these cirri at the anterior tip of the fragments. The site of formation of these streaks thus appears to be determined by an anteriorposterior gradient, rather than by any preformed cortical structure. The new dorsal bristle rows I to III develop from the proliferation of portions of the old rows, while rows IV and V originate from short kineties formed “de novo” on the right margin. New caudal cirri differentiate at the posterior ends of the new rows I to III. The numbers of ventral cirral rows and transversal cirri are variable; these variations are correlated, and related to variations in numbers of developing streaks. A survey of hypotrich developmental patterns revealed extensive parallels, especially in the sites of appearance of primordia. The primordium site appears to be a more constant feature of cortical development than is the “source” of ciliary units. It is concluded that sites of primordia are determined by cellular gradients, with competent preformed structures being utilized if they are appropriately positioned within these gradients.     

棘尾虫对折右纵断片的再生和纤毛模式形成的研究

应用切割嫁接方法获得的棘尾虫完全对折和部分对拆右纵断片都经历了一面调整极性、一面再生和形态发生的过程。推测这两种断片在纤毛模式形成中发生的诸多现象可能与所在断片再生时的极性调整变化状态有关。     

Divisional morphogenesis in the marine ciliate, Hemigastrostyla enigmatica (Dragesco & Dragesco-Kernéis, 1986) and redefinition of the genus Hemigastrostyla Song & Wilbert, 1997 (Protozoa, Ciliophora)

Morphogenetic events during the division of the marine hypotrichous ciliate, Hemigastrostyla enigmatica (Dragesco & Dragesco-Kernéis, 1986) Song & Wilbert, 1997 are described. The morphogenesis is characterized by:(1) 5 frontoventral-transverse cirral anlagen develop into 8 frontal, 5 ventral and 5 transverse cirri after Oxytricha-pattern;(2) there may be 6 FVT-anlagen in some individuals giving rise to more cirri which, however, will be resorbed after division;(3) anlage of the right marginal row at least in the opisthe occurs de novo right to the parental structures instead of within them;(4) according to the origin, the two extra ventral cirri right to transverse ones are not ventral or transverse cirri, which are from the retained old structure;(5) dorsal kineties originate from one group of DK-anlagen in both dividers with, very uniquely, an additional fragmentation of DK1, and(6) oral primordia will be formed in both dividing parts, from which the newly-built membranelles in the proter replace the posterior part of the parental AZM with a particular 'piecing together mode.Some features during the morphogenesis (e.g. variable number of cirral anlagen, presence of primary primordia, the mode of rebuilding of the proter's adoral zone of membranelles, origin of dorsal kineties and caudal cirri etc.) indicate that the genus Hemigastrostyla might present a intermediate form between oxytrichids and other related higher taxa. Based on our new observations, an improved diagnosis for genus Hemigastrostyla is given: marine or brackish water Oxytrichidae with slightly to conspicuously cephalized body shape; mostly 8–10 frontal, 5 ventral, 5 transverse and two to several extra ventral cirri to the right of the transverse ones, which are from the retained parental structure; caudal cirri present.     

Litonotus — Euplotes (predator — prey) interaction: ciliary structure modifications of the prey caused by toxicysts of the predator (Protozoa,Ciliata)

Summary The morphological modification of ventral cilia associated with cell paralysis of Euplotes when attacked by the predator Litonotus are analyzed by electron microscopy (both SEM and TEM). The locomotory organelles of Euplotes (membranelles and cirri) lose their typical compact morphology. Single cilia of both organelles undergo a modification at their terminal portion. At this level, the axoneme becomes folded, and the ciliary membrane enlarges into a conspicuous rounded bulbus. The possible nature of this bulbus and the different behaviour of membranelles, cirri, and dorsal bristles are discussed.     

Mirror-image configuration of the cortical pattern causes modifications in propagation of microtubular structures in the hypotrich ciliateParaurostyla weissei

Analysis or the development of microtubular structures in the mirror-image doublet cell lines of a hypotrich ciliate,Paraurostyla weissei, revealed several modifications in standard morphogenesis. Ciliary primordia can be formed without prior disaggregation of the preformed marginal cirri, on the left instead of the right hand side of an old row. Two or more overlapping streak segments may originate from disaggregating old marginal cirri, giving rise to two or three cirral rows. Inverted marginal cirri occasionally develop de novo and can be propagated clonally. Thus the modifications in developmental processes concern the positioning of primordia, the number of forming structures and the polarity of these structures. The microtubular triplets in the basal bodies of normal and inverted cirri do not differ, indicating that the large-scale reversal of the overall pattern has no effect on the assembly of microtubular triplets. The study indicates that the control of cytotactic propagation of compound microtubular structures is either modified or partially suppressed in a morphogenetic field where the positional values along one of the main cellular axes (lateral) have been reversed.     

一种游仆虫无性分裂生殖的研究Ⅱ.无性分裂过程中皮层结构的形态发生

应用光学显微镜和扫描电子显微镜,观察到在一种游仆虫无性生殖周期中,新口围带发育时老口围带的更新、新波动膜原基的发生、棘毛原基发生的最早形态和背触毛发生等在其他种游仆虫中未见报道的现象。     

A Novel Healing Filament in Ciliate Regeneration

The interphase cells of the hypotrich ciliate Paraurostyla weissei possess a complex fibrillar system surrounding basal bodies in the compound ciliary assemblages, cirri and membranelles. During replacement of the ciliature at cell division, transient filaments precede and accompany the development of ciliary primordia and participate in the formation of the fission furrow. Both fibrillar systems are recognized by monoclonal antibody FXXXIX 12G9. We studied regeneration of cellular fragments after transection employing the mAb 12G9 and found a new cytoskeletal structure involved in healing of the excisional wound. The healing filament is formed at the wound edge, distally and in connection with the bases of cirri closest to the wound. It is visible 5 min after transection. Concomitant with development of new ciliary primordia, the healing filament shrinks and finally disappears together with other transient fibers formed in this process. Ultrastructural analysis of immunolabeled regenerating cells revealed that structures recognized by mAb 12G9 contain fine filaments whose packing and arrangement depends on accompanying cytoplasmic elements and the developmental status of a fragment. Assembly of the healing fiber does not depend on microtubules and microfilaments since it develops in cellular fragments exposed to cold, nocodazole, and Cytochalasin D. On Western blots of whole cell and cytoskeletal extracts of P. weissei the 12G9 antibody identified one protein band whose molecular weight corresponds to 60 kDa.     

阔口尖毛虫无性生殖和生理改组过程的比较

阔口尖毛虫无性生殖中先后发生后口围带原基,前、后的波动膜原基,额腹横棘毛原基和左、右缘棘毛原基,老口围带也在此期间更新,结果形成2套新纤毛结构,原老结构瓦解消失;生理改组时按同样顺序产生口围带原基等几类腹面纤毛原基,结果形成1套新纤毛结构,替换老结构。在这两个截然不同的过程中,新纤毛结构的分化和老纤毛结构退化时也表现出某些相似的特征。作者据此推测,这种纤毛虫无性生殖和生理改组中,纤毛原基的发生、发育和定位在细胞控制机理上可能是相同的。     

The Cortical Morphogenetic Cycle Associated with Cell Division in Diophrys Dujardin, 1841 (Ciliophora,Hypotrichida)1

Morphogenesis of cell division was investigated in Diophrys scutum, D. oligothrix, and D. appendiculata utilizing both light microscopy of living and stained specimens and SEM of preserved specimens. The cortical morphogenetic pattern of Diophrys is similar to that of other members of the family Euplotidae. The opisthe oral primordium, which develops in a subsurface pouch, forms posterior to the parental buccal cavity. The proter inherits the parental adoral zone of membranelles (AZM) apparently unchanged. The endoral membrane forms to the right of the posterior end of the AZM in the proter, in association with the developing AZM in the opisthe. The paroral cirrus and membrane develop from a single streak that first appears along the right edge of the buccal cavity in the proter to the right of the developing buccal structures of the opisthe. Frontal and transverse cirri develop in both proter and opisthe from five separate cirral primordia that form to the right of the buccal cavity. Left marginal cirri do not develop in association with the corresponding parental structures. Kinetosomes formed within the opisthe oral primordium, or kinetosomes that were part of any parental ciliary structure, do not appear to become part of any developing paroral structures, frontal, transverse, or left marginal cirri. Speciation within the genus Diophrys and evolution of the family Euplotidae as they relate to the morphogenesis of cortical structure are discussed.     

Ultrastructure and Cortical Morphogenesis in the Euplotine Hypotrich Certesia quadrinucleata Fabre-Domergue, 1885 (Ciliophora,Protozoa)1

The cortical development during cell division and the interphase ultrastructure of the marine interstitial hypotrich Certesia quadrinucleata is described using light microscopy and both scanning and transmission electron microscopy. Membranelles are paramembranelles; postciliary microtubules from rightmost membranellar kinetosomes line the buccal cavity and separate parallel arrays of pharyngeal discs that border the cytopharynx. A large paroral membrane is present; an endoral membrane is absent. Alveolar plates lie within alveolar membranes except in regions where organelles and organellar complexes (cirri, the condylopallium, dorsal bristles, membranelles, and the paroral membrane) emerge from the cortex. Muciferous-like bodies attach to the plasma membrane in these regions. Dorsal bristles possess transverse and postciliary microtubules as well as kinetodesmal fiber like those of other hypotrichs. Lasiosomes are present. A unique bulbous structure—the condylopallium—protrudes from the anterior right of the cell. The morphogenetic pattern is euplotine in that cortical development begins in one latitudinal zone, and the oral primordium of the opisthe develops within a subsurface pouch apart from the frontal primordia. Microtubular bundles appear beside (later attached to) developing frontal anlagen; they disappear after cirri are in final interphase locations. Although possessing unique characters, Certesia shares a close phylogenetic relationship with Euplotes.     

Morphology and morphogenesis of Holosticha heterofoissneri nov. spec. from the Yellow Sea,China (Ciliophora,Hypotrichida)

The morphology and morphogenesis of the marine hypotrichous ciliate Holosticha heterofoissneri nov. spec. from mollusc culture in Qingdao, China are described based on living and protargol-impregnated specimens. The new species is characterized by: adoral zone slightly bipartite, consisting of on average 43 membranelles; constantly 5 dorsal kineties, and 12 pairs of cirri in midventral rows, and 14–16 macronuclear segments, which differs from the closely related species, H. foissneri. Its morphogenetic process shows the following features: (1) the parental AZM is retained unchanged and will be inherited by the proter, only the old UM reorganized; (2) FVT-cirral anlagen in both division parts derive from the breaking of primary primordia; (3) during the formation of FVT-cirral anlagen, most midventral cirri remain intact; and there appears an 'extra' anlage (EA) between the UMA and other FVT-cirral primordia; (4) the generation type of the dorsal kineties is of 'one group mode', the leftmost one of the 4 primordia fragmentates to form a new kinety; (5) at the early stage of morphogenesis, replication bands of macronuclear segments are apparently present.