Transverse Microtubular Ribbons Research Articles

The ultrastructure of Macropodinium moiri and revised diagnosis of the Macropodiniidae (Litostomatea: Trichostomatia)

The ultrastructural features of Macropodinium moiri were investigated. The somatic cortex is composed of two lateral non-ciliated zones covered with trapezoidal plates and separated by a trough-like dorsoventral groove (DVG) which divides the cell into left and right halves. The somatic kineties occupy the margins of the DVG and are composed of monokinetids whose infraciliature shows a typical litostome pattern. The pellicular plates are lamellate, and separated by V-shaped grooves which are lined by thick-walled vacuoles. The DVG cortex is composed of electron-opaque U-shaped ribs which alternate with electron-lucent saccular structures. The DVG surface is composed of small regular pellicular sacs built up to form the ridges of the dorsal DVG. The vestibulum forms a laterally compressed cone with left/right differentiation. The basal section of its non-ciliated right side is internally lined (outer to innermost) by longitudinal fibres, nematodesmata and transverse microtubular ribbons. The left side bears the vestibular kineties and in its basal section is lined (outer to innermost) by small nematodesmata and transverse tubules. Cytoplasmic organelles include endoplasmic reticulum, starch granules and a single contactile vacuole surrounded by patches of nephridioplasm. Hydrogenosomes are absent and coccoid Gram-positive bacteria lie under the ciliated portions of the cell. This set of characteristics differs significantly from those of the all other trichostomes; Macropodiniidae is therefore designated Trichostomatia incertae sedis. A revised familial diagnosis of the Macropodiniidae is proposed.

Morphology and Ecology of Siroloxophyllum utriculariae (Penard, 1922) N. G., N. Comb. (Ciliophora, Pleurostomatida) and an Improved Classification of Pleurostomatid Ciliates

ABSTRACT. The morphology and infraciliature of Siroloxophyllum utriculariae (Penard, 1922) n. g., n. comb. were studied in live cells, with the scanning and transmission electron microscope, as well as in specimens impregnated with protargol and silver carbonate. The new genus, Siroloxophyllum, belongs to the Loxophyllidae and has a specific combination of characters, viz. an oral bulge surrounding almost the entire cell, three perioral kineties, a single brush kinety, and a single right dorsolateral kinety. The ecology and faunistics of S. utriculariae are reviewed. It is a rare and infrequent predator preferring clean freshwaters. The somatic monokinetid of S. utriculariae has typical haptorid ultrastructure, including two transverse microtubular ribbons. The oral bulge is patterned string‐like with riffles containing the transverse microtubular ribbons originating from the oral kinetids. Perioral kineties 1 and 2 consist of dikinetids having one basal body each ciliated; the nonciliated basal body is associated with a nematodesmal and a transverse microtubular ribbon. Perioral kinety 3 consists of ciliated monokinetids having a fine structure similar to the somatic kinetids; they form triads with the dikinetids from perioral kinety 2. The classification of pleurostomatid ciliates is reviewed. Two suborders (Amphileptina, Litonotina) and three families (Amphileptidae, Litonotidae, Loxophyllidae n. fam.) are recognized and defined.

Ultrastructure of Prorodon (Ciliophora, Prostomatida) Ii. Oral Cortex and Phylogenetic Conclusions

ABSTRACT. The ultrastructure of the oral region and the ultrastructural architecture of the basket of Prorodon aklitolophon and Prorodon teres are described. the oral region of Prorodon consists of: 1) A circumoral kinety at the anterior pole of the cell surrounding the typically slit‐shaped cytostomial funnel. This kinety is composed of inversely oriented dikinetids in which both kinetosomes are ciliated and are associated with a very short postciliary microtubular ribbon and a few transverse microtubules; 2) Three brush rows aligned in parallel and extended meridionally in the anterior part of the cell. the individual brush rows consist of dikinetids, but in contrast to the dikinetids around the cytopharynx they are not inverted and only the anterior kinetosomes bear specialized short brush cilia and are associated with a divergent‐tangential transverse microtubular ribbon. the posterior kinetosome is non‐ciliated and bears a prominent convergent postciliary microtubular ribbon. Schematized dikinetid patterns of both oral regions of Prorodon are provided. In addition, a three‐dimensional reconstruction of the basket of the genus Prorodon based on serial thin sections is presented. A phylogenetic tree, mainly based on stomatogenic data, is given to show the phylogenetic relationships of some prostomatid genera as well as the hypothesized sistergroup relationship of colpodid and prostomatid ciliates.

Ultrastructure of Prorodon (Ciliophora, Prostomatida) I. Somatic Cortex and Some Implications Concerning Kinetid Evolution In Prostomatid and Colpodid Ciliates

ABSTRACT. This study describes the ultrastructure of the somatic cortex of Prorodon aklitolophon and Prorodon teres. the meridionally arranged somatic kineties of both species can be separated into two parts: a short anterior part, which consists of a few somatic dikinetids (in which both kinetosomes are ciliated), and a longer posterior consisting of monokinetids. the somatic monokinetids are associated with a convergent postciliary microtubular ribbon, a transverse microtubular ribbon flatly inserted in front of the kinetosome, a short and steeply extending kinetodesmal fibre attached to kinetosomal triplet 5 and 7, and a desmose anterior to triplet 3. From this desmose, two to five prekinetosomal microtubules originate and extend anteriorly. the posterior kinetosome of the somatic dikinetids is associated with the same microfibrillar and microtubular structures as the somatic monokinetid, except that no prekinetosomal microtubules originate from the desmose. the anterior kinetosome has a single postciliary microtubule and a tangentially oriented transverse microtubular ribbon. the permanent collecting canals of the unique contractile vacuole system extend parallel and adjacent to the somatic kinetics of Prorodon. the collecting canals are supported by the prekinetosomal microtubules. A similarly organized contractile vacuole system is not yet known from any other ciliate group. One of the most surprising results of this investigation was finding a significant similarity between the somatic dikinetid pattern of Prorodon and the colpodid dikinetid pattern. A hypothesis is presented to illustrate the evolution of the somatic kinetid patterns in colpodid and prostomatid ciliates.

Light and Electron Microscopic Study of Balantidium entozoon (Ciliophora, Vestibuliferida)Somatic Cortex and Vestibular Cavity

The somatic cortex and the vcstibulum of Balantidium entozoon were studied using silver carbonatc impregnation and electron microscopy. The somatic infraciliature is composed by monokinetids with a short kinetodesmal fiber, a long posteiliary microtubular ribbon, and a long transverse microtubular ribbon directed anteriorly. Moreover, the somatic kinetids located near the vestibular aperture bear nematodesmal bundles (“oralized somatic kinetids”) that contribute to form the oral cytoskeleton. A zone with strongly argentophilic kinetosomes. which we have denominated Villeneuve-Brachon's fields, is located on the right side of the vestibular cavity. This zone is formed by kinetosomes strongly argentophilic, closely placcd, with normal cilia and long roots that penetrate into the endoplasm. The vestibular cavity possesses two ciliated margins formed by the anterior extremes of the somatic kineties. The right margin is constituted exclusively by these kinetics, while the left margin possesses numerous supernumerary kinetics. These two margins retain the ectoplasmic fibrillar derivates of the somatic cortex, but their fine structure is different. The dorsal cytoskeleton of the vestibular cavity is made up of two microtubular systems, and the ventral side is reinforced by thick periodical fibers. Our observations confirm the systematic position of the genus Balantidium within the order Vestibulilerida of the subclass Trichostomatia. © 1992, Gustav Fischer Verlag Jena. All rights reserved.

A Reexamination of the Ultrastructure of Didinium nasutum and a Reanalysis of the Phylogeny of the Haptorid Ciliates

ABSTRACT. The cilia of Didinium nasutum are restricted to two girdles encircling the cell. Each row of cilia in both girdles is made up of two to three anterior pairs of kinetosomes followed by several single kinetosomes. Each single kinetosome has two sets of transverse microtubules, an overlapping postciliary microtubular ribbon, and a laterally directed kinetodesmal fiber. The pairs of kinetosomes are homologous to the oral dikinetids of other haptorians: the nonciliated kinetosome of the pair has a transverse microtubular ribbon that extends to line the membrane of the proboscis, a single short postciliary microtubule, and a nematodesma; the ciliated kinetosome has a ribbon of postciliary microtubules and two sets of transverse microtubules. The presence of these characters in Didinium invalidates Leipe & Hausmann's conclusion that the Didiniidae should be removed from the subclass that contains the other haptorians (Leipe, D. D. & Hausumann, K. 1989. Somatic infraciliature of the haptorid ciliate Homalozoon vermiculare (Kinetofragminophora, Gymnostomata) Ditransversalia n. subcl. and phylogenetic implications. J. Protozool., 36:280–289). In light of this, the justification for a subclass Ditransversalia is challenged and shown to be unnecessary.

Bursellopsis spaniopogon n. spec. (Ciliophora: Prostomatida) : I. Infraciliature and ultrastructure of the somatic and oral cortex

A description is given of a new species of the genus Bursellopsis Corliss, 1960. Its infraciliature is studied by means of Klein's dry silver technique and Fernández-Galiano's pyridinated silver-carbonate-method. The light microscopical results are supplemented by a comparative scanning and transmission electron microscope study, with special reference to the somatic cortex, the circum-oral ciliature, and the "dorsal brush". The kineties of the somatic cortex, consisting of monokinetids, cover only the anterior four fifths of the cell. Three fibrillar systems, a kinetodesmal fibre, a postciliary microtubular ribbon, a transverse microtubular ribbon and one parasomal sac are associated with each monokinetid. The circum-oral kinety consists of dikinetids bearing only stubs of cilia. The so-called "dorsal brush" consists of dikinetids, with only their anterior kinetosomes bearing "brush cilia", which are shorter than the somatic cilia. The biometric data of Bursellopsis spaniopogon are given and the ultrastructure of the new species is compared to light microscopical and ultrastructural data of Urotricha, Holopbrya and Prorodon. The systematic position of the genus Bursellopsis is discussed and an improved diagnosis of Bursellopsis is provided.

The Ultrastructure of Chaenea teres and an Analysis of the Phylogeny of the Haptorid Ciliates

ABSTRACTChaenea teres has typical haptorid ultrastructure. The somatic monokinetid has two transverse microtubular ribbons, an overlapping postciliary microtubular ribbon, and a laterally directed kinetodesmal fiber. The evered cytopharynx forms a dome at the apical end of the cell. The base of the dome is surrounded by oral dikinetids. The left, anterior kinetosome of the oral pair is not ciliated and has a transverse microtubular ribbon, a nematodesmata and a single postciliary microtubule. The right, posterior kinetosome is ciliated and has only postciliary microtubules. The kinetosomes at the anterior ends of the somatic kinetics are close together and their transverse microtubules and nematodesmata contribute to the support of the cytopharynx. The transverse microtubules of these oralized somatic kinetosomes, together with those from the oral dikinetids, line the cytopharynx. Accessory or bulge microtubules arise perpendicular to the transverse microtubules. A dorsal brush of three kineties of clavate cilia is found on the cell surface just posterior to the oral region. Mucocysts and a single type of toxicyst are present. The toxicysts are confined to the oral region. There are multiple ovoid macronuclei that stain weakly. Micronuclei were not observed. Cladistic analysis indicates the Chaenea may be most closely related to Fuscheria and Acropisthium. The cladistic analysis also suggests that existing taxonomies of the subclass Haptoria need to be revised. We propose some modifications to Foissner & Foissner's classification that include transferring Helicoprorodon, Actinobolina, the buetschiliids, and the balantidiids to the order Haptorida and recognizing the close relationship between pleurostomes and spathidiids.

Morphogenesis and ultrastructure of the soil ciliate Engelmanniella mobilis (Ciliophora, Hypotrichida)

The morphogenetic pattern, freeze-fracture, transmission, and scanning electron-microscopy of interphasic cells were used to elucidate the enigmatic systematic position of Engelmanniella mobilis. Frontal, buccal, parabuccal, and marginal cirri are distinguishable during cortical development; transverse, frontoterminal (migratory), and caudal cirri are absent. Ontogenetic peculiarities include the conservation of parental and grandparental marginal cirri and the apokinetal origin of a dorsal kinety in the opisthe. Thus, interphasic cells of E. mobilis possess three generations of cirri. The pellicle is multilamellated. Prominent, undischargeable subpellicular granules consisting of a homogeneous osmiophilic mass develop from bundles of long fibers. Rhomboid crystal-like structures projecting from the lithosomes and regularly patterned mitoribosomes are additional remarkable ultrastructural characteristics. The somatic and frontal cirri comprise 2-10 kinetosomes. Very likely, all cirri are composed of closely adjacent "dikinetids" because their kinetosomes form pairs each possessing a transverse and a postciliary microtubular ribbon. The fourth row of kinetosomes of the adorai membranelies shows the usual transverse microtubular ribbons, while one or two transverse microtubules are closely adjacent to the third and the second row of its basal bodies. Our data suggest that Engelmanniella has descended from a kahliellid lineage. However, its placement in a well-founded (!) stichotrichid family is impossible at present.

Somatic Infraciliature in the Haptorid Ciliate Homalozoon vermiculare (Kinetophragminophora, Gymnostomata) Ditransversalia N. Subcl. and Phylogenetic Implications

ABSTRACTThe ultrastructure of the cortex of Homalozoon vermiculare is described. The ventral side bears 13–15 iongitudinal kineties composed of monokinetids. On the dorsal surface, there are 3 kineties, 2 of which are composed of dikinetids in the anteriormost part of the cell. Consequently there exist 3 different kinds of kinetids within the somatic cortex: 1) The monokinetids on the ventral side are associated with a kinctodesmal fibril, 2 transverse microtubular ribbons and 7 postciliary microtubules in a double‐row configuration; 2) The monokinetids on the dorsal side are very similar but they are associated with just 3 very ‘short postciliary microtubules; 3) The posterior kinetosome of the dorsal dikinetids bears the same fibrillar associates as the dorsal monokinetid, but it lacks the second transverse ribbon. The anterior kinetosome of each pair is associated with a single postciliary’ microtubule. The kinetid organization of Homalozoon is compared to that of other members of the Haptorida. Their phylogeny is discussed. A monophyleiic taxon within the litostomate ciliates is characterized by data on the somatic kinetids, and the new subclass Ditransversalia n. subcl. is constituted. The new subclass comprises the genera Balantidium, Bryophyllum, Enchelydium, Homalozoon, Isotricha, Lacrymaria, Lepidolrachelophyllum, Spathidium and Vestibulongum.

A Somatic Kinetid Study of the Pycnotrichid Ciliate Vestibulongum corlissi N. G., N. Sp. (Class: Litostomatea), Symbiont in the Intestines of the Surgeonfish, Acanthurus xanthopterus1

ABSTRACT The ciliate Vestibulongum corlissi n. g., n. sp. was collected from the intestines of surgeonfish, Acanthurus xanthopterus, in the summer of 1986. In has been examined in the light microscope after protargol staining and by scanning and transmission electron microscopy. Its form is distinct from that of other pycnotrichid ciliates at the generic level. Somatic kinetids were examined; these demonstrate that its cytostome is posterior and that the kinetid structures and the presence of a second transverse microtubular ribbon confirm its placement in the class Litostomatea.

The Fine Structure of Fuscheria terricolaBerger et al., 1983 and a Proposed New Classification of the Subclass Haptoria Corliss, 1974 (Ciliophora, Litostomatea)

Summary The general fine structure of Fuscheria terricola Berger, Foissner and Adam , 1983 is very similar to that of other haptorid ciliates. However, a tela corticalis and parasomal sacs are absent. Fuscheria terricola has doughnutshaped mucocysts and unique nail-shaped toxicysts. Their nail-like appearance is due to a conspicuous posterior thickening of a fibro-granular material surrounding the rod-shaped center which is very similar to the pexicysts of Acropisthium and Didinium. The somatic kinetids are monokinetids with the classical haptorian fibrillar associates. In addition, the upper 4 to 7 somatic kinetids in each kinety possess nematodesmal bundles. At the base of the oral cone there is a circumoral kinety composed of typical haptorian dikinetids. Their nematodesmal bundles and those from the upper somatic kinetids form a highly characteristic irregular rhabdos. Acropisthium and Actinorhabdos show the same oral organization as Fuscheria. Hence, these 3 genera are united in the new family Acropisthiidae nov. fam. The rhabdos of most members of the subclass Haptoria is built up of 3 microtubular components: a) the transverse microtubular ribbons which originate from the nonciliated kinetosomes of oral dikinetids or from ciliated or nonciliated oralized somatic kinetids and turn to the center of the oral bulge, where they plunge inwards to support the cytopharynx; b) the nematodesmal bundles which form an “outer rhabdos”; and c) the vertically oriented bulge microtubules which are distributed rather regularly in the marginal area of the oral bulge and grouped in nematodesmata-like bundles in the lower oral region, where they form a more or less pronounced “inner rhabdos”. Exceptions from this pattern are the Cyclotrichina which lack nematodesmata and the Archistomatida which lack bulge microtubules, probably because of the absence of toxicysts. The term “oralized somatic kinetids” is suggested for such kinetids which lie within somatic kineties, but bear nematodesmal bundles contributing to the rhabdos. Such kinetids may be monokinetids or dikinetids; they may or may not be associated with normal haptorid oral dikinetids; and they may be ciliated or nonciliated. The different kinds of kinetids which contribute to the rhabdos and the dorsal brush (presence/absence) are the clue characters for a revised classification of the Haptoria. The following new higher taxa are erected: Enchelyina nov. subord. (with nonciliated oralized somatic monokinetids), Acropisthiina nov. subord. (with oral dikinetids and ciliated oralized somatic monokinetids), Spathidiida nov. ord. (with oral dikinetids only), Litonotina nov. subord. (right oral kinety associated with somatic monokinetids), Pseudoholophryida nov. ord. and Pseudoholophryina nov. subord. (dorsal brush absent or highly aberrant), Helicoprorodontina nov. subord. (oralized somatic dikinetids, dorsal brush probably absent).

Oral Monokinetids in the Free‐Living Haptorid Ciliate Enchelydium polynucleatum (Ciliophora, Enchelyidae): Ultrastructural Evidence and Phylogenetic Implications1

ABSTRACTSpecial ultrastructural characteristics of the haptorid soil ciliate Enchelydium polynucleatum Foissner, 1984 are the restriction of the parasomal sacs to the area of the “brush” and finger‐like projections of the food vacuole membrane into the lumen of the vacuole. The general organization of the infraciliature is similar to that of Spathidium and some buetschliids because the anterior ends of the somatic kineties are condensed and obliquely bent. Enchelydium is similar to haptorids and buetschliids in possessing monokinetid somatic fibrillar structures with the classical fibrillar associates: 1) a short kinetodesmal fiber; 2) two transverse microtubular ribbons; 3) a long postciliary microtubular ribbon; and 4) a system of overlapping subkinetal microtubules, which seems to be absent in the buetschliids. Unlike Spathidium and all other haptorids so far investigated ultrastructurally, serial sections show that there are no oral dikinetids, as in the endocommensal buetschliids and balantidiids. Instead, three to six anterior kinetids in each ciliary row have nematodesmal bundles extending into the cytoplasm and surrounding the cytopharynx. These kinetids lack cilia and all fibrillar associates except enlarged transverse ribbons, which extend anteriorly and inwards to support the cytopharynx. Other similarities between the buetschliids and Enchelydium are the conspicuous rough endoplasmic reticulum and abundant sausage‐like vesicles in the oral region. As in other haptorids, Enchelydium has two types of toxicysts and one type of mucocyst. These observations strongly suggest that Enchelydium belongs to the ancestral stock of both the Haptorida and the Archistomatida. The similarities in the somatic and oral infraciliature and ultrastructure of the Haptorida and the Archistomatida suggest that they belong to the same subclass, Haptoria Corliss, 1974.

Ultrastructure of the Somatic Cortex of the Gymnostome Ciliate Spathidium spathula (O. F. M.)1

ABSTRACTThe somatic cortex of Spathidium spathula is described ultrastructurally. The pellicle consists of an outer membrane and an underlying alveolar system. Numerous membrane‐bound mucocysts and spherical electron‐opaque bodies have similar circular sites of attachment to the outer membrane. Below these are a microfibrillar zone and an underlying region of rough ER. Mitochondria are lined up under the rough ER in longitudinal cortical ridges. Parasomal sacs are found near the basal bodies and are associated with cytoplasmic membranous sacs. Various microtubular and fiber systems are associated with single basal bodies: (1) a short kinetodesmal fiber; (2) two transverse microtubular ribbons and a transverse fiber; (3) a postciliary microtubular ribbon, initially sandwiched by two fibers, which gives rise to longitudinal subpellicular microtubules extending posteriorly for a distance of some four or five basal bodies; and (4) a system of overlapping subkinetal microtubules. A three‐dimensional reconstruction is included. The somatic cortex of S spathula is similar to that reported for other Haptorida of the ciliate subclass Gymnostomata.

Ultrastructure of the Somatic and Buccal Cortex of the Tetrahymenine Hymenostome Glaucoma chattoni

SYNOPSIS The membranes, epiplasm, and fiber systems are described in the somatic cortex of Glaucoma chattoni strain HZ‐1. Kinetodesmal fibers, postciliary and transverse microtubular ribbons, basal microtubules, transverse fibers and transverse accessory material are associated with kinetosomes. Longitudinal microtubular ribbons and mitochondria occur interkinetally. In the buccal cortex, the membranes, epiplasm and fibers of the 3 membranelles, the paroral kinety, the ribbed wall, and the cytostome are described. Comparisons between G. chattoni and other ciliates reveal ultrastructural differences of possible systematic significance. In the somatic cortex of this and other tetrahymenines. Iongitudinal microtubular ribbons and basal microtubules occur concurrently. In the buccal cortex, alveoli are absent in tetrahymenine membranelles. A table is presented of the fiber systems associated with single somatic kinetosomes of various ciliates whose cortical ultrastructure has been studied to date.

Cortical Ultrastructure of the Scuticociliates Dexiotricha media and Dexiotricha colpidiopsis (Hymenostomata)*†

Cortical ultrastructure of the scuticociliates Dexiotricha media and Dexiotricha colpidiopsis was investigated. The following elements of the somatic cortex were studied: the cell membrane, alveolar membranes and the epiplasm, kinetodesmal fibers, postciliary and transverse microtubular ribbons, and transverse fibers associated with single and paired kinetosomes; mitochondria and single microtubules located in interkinetal ridges; mature and early extrusion stages of mucocysts; the expulsion vacuole pore and tube, the nephridioplasm and the cytoproct. In the buccal cortex, the paroral kinety-ribbed wall complex, the 3 polykineties, and the cytostome-cytopharynx were investigated. Comparative survey of ciliate ultrastructure indicates 2 principal orientation patterns for kinetodesmal and postciliary fibers, recognition of which leads to reevaluation of the theory of paroral kinety formation and the ideas of homology based on this theory. Ultrastructurally, the scuticociliates are not distinct from tetrahymenines and peniculines; the 3 groups appear to be 1 assemblage.

Ultrastructural alterations in Tetrahymena pyriformis induced by growth on saturated phospholipids at 40.1 °C

Structural changes in Tetrahymena pyriformis, strain WH-14, induced by growth on saturated phospholipids at 40.1 °C, were studied by electron microscopy. Alterations in the ultrastructural organization of the cell membrane and surface regions were common. These alterations were characterized in the displacement of kinetosomes, the spatial disorientation and disorganization of cortical ridges and grooves, and the spatial disorientation of longitudinal and transverse microtubular ribbons. Irregular surface protrusions and multiple invaginations of alveolar membranes were among the most common features encountered. Disorganization of longitudinal microtubular ribbons was also a frequent encounter. The integrity of the ultrastructure of cell surface membranes and of the internal organization and ultrastructure of the kinetosomes, however, appeared to be unaltered. Other alterations included those of a number of cytoplasmic organelles (e.g. mitochondria and endoplasmic reticulum), which showed characteristic changes in structural patterns.