Regulation of ciliary pattern in ciliates.

The modes of pattern regulation found in the ciliates Dileptus and Paraurostyla are compared. These forms are systematically distant but both possess very extensive regenerative capacities. They are characterized by 2 types of ciliary patterns: the ciliature of Dileptus has largely a simple pattern composed of single kinetosomes while that of Paraurostyla has a complex pattern composed of aggregates of kinetosomes interconnected by amorphic matter. In both ciliates a change in cell size evokes pattern regulation which differs substantially in the extent of pattern replacement, timing, and localization of morphogenetic activities. It is concluded that these differences result from the pattern constituents.     

Fine structure of the dorsal bristle complex and pellicle of Euplotes

The fine structure of the dorsal bristle complex and pellicle of non-developing Euplotes eurystomus is described in detail by scanning and transmission electron microscopy. The bristle-pit unit is a highly differentiated complex of organelles. The bristle complex is composed of a pair of kinetosomes (basal bodies) joined by a connective. The anterior kinetosome bears the bristle cilium, which contains a polarized network of particles (“lasiosomes”). The posterior kinetosome bears a very short, knob-like “condylocilium,” and has an associated striated fiber. Accessory ribbons of microtubules are also associated with the kinetosome couplets. Parasomal sacs, a septum connecting the bristle cilium to the anterior wall of the pit, core granules of the kinetosomes, and large membranous ampules are described. The organization of the bristle complex bears many similarities to the somatic ciliature of other ciliates. The pellicle of Euplotes is composed of a continucus outer cell membrane subtended by membranous alveoli, which contain a “fibrous mat.” Two sheets of subpellicular microtubules (longitudinal and transverse) are located just beneath the alveoli. The “epiplasm” seen in some other ciliates is apparently absent in Euplotes. The texture of the cell surface is a pattern of folds or rugae composed of the outer cell membrane and the upper membrane of the alveolus. The pattern of rugae probably defines the “silverline-system” of light microscopy.     

Morphogenesis and Cortical Ultrastructure of Brooklynella hostilis,a Dysteriid Ciliate Ectoparasitic on Marine Fishes*

SYNOPSIS. Morphogenesis, and the cortical structures of Brooklynella hostilis, a cyrtophorine gymnostome ciliate ectoparasitic on marine fishes, were studied from protargol silver-impregnated preparations and with the aid of electron microscopy. The pattern of morphogenesis of Brooklynella is close to that found in less differentiated species of the families Chlamydodontidae (e.g., in the genus Trithigmostoma) and Dysteriidae (e.g., in the genus Hartmanula). The full number of kineties in the opisthe is restored after division from a segment of the left one of the 3 kinetics producing the oral rows. The oral rows consist of a double row of kinetosomes arranged in a zig-zag pattern; only the outer row is ciliated, the inner one being barren. However, the positions of the postciliary and transverse fibers indicate that the oral rows are not homologs of an undulating membrane but are akin to a membranelle. In association with the ventral somatic kinetosomes there are 4 postciliary fibers; a rather aberrant, transversally oriented kinetodesma; 2 microtubular, transverse fibers plus a transverse fibrousspur; and one to several ribbons of subkinetal microtubular fibers. Not directly associated with the kinetosomes are fibrous strands running subpellicularly between the kinetosomes and also deep into the cytoplasm. The cortical structures of Brooklynella are compared with those of some other groups of ciliates of about the same phylogenetic level in which the subkinetal microtubules can also be found– rhynchodine, suctorian, and chonotrich ciliates. The nasse consists of 6–8 nematodesmata not closely associated with the microtubular cytopharyngeal tube. The former have a distinctly developed densely fibrous capitulum containing barren kinetosomes which originally produced the nematodesma during stomatogenesis; the capitulum is connected by a fibrous link to the microtubular shaft. Extending from the oral rows to the capitula are fibrous structures strongly reminiscent of filamentous reticulum in hymenostome and peritrich ciliates. The structure of the posterio-ventral glandular organelle is also described and discussed.     

Preparatory changes and the development of the conjugation junction in a ciliate,Dileptus

Summary The present observations concern changes in the cortical structure of the ciliateDileptus prior to and during conjugation. The results can be summarized as follows: (1) Mating cells join each other in heteropolar configuration, i.e., the distal part of the oral apparatus of one partner faces the proximal part of the oral apparatus of another partner. (2) The structural changes prior to conjugation occur in the area of the oral apparatus. (3) The bonding area is situated within the oral apparatus, while the oral ciliature that encircles the oral apparatus remains outside the bonding area. (4) The fusion area is formed within the bonding area as a newly formed zone, without cortical organelles typically associated with the cell membrane. Two aspects of the formation of cell-to-cell union inDileptus are discussed: firstly, the heteropolar configuration of mating cells and its possible bearing upon an ability to form double cells when partners separation is inhibited. Secondly, the bonding area ofDileptus is compared to bonding areas of peniculine and hymenostome ciliates. A striking likeness in structural changes was found within the bonding areas of all three ciliates, in spite of the fact that the changes in question are localized within the oral apparatus ofDileptus, while inParamecium andTetrahymena the changed territory is situated between the oral apparatus and the anterior pole of the cell.     

The Cytology of Sheep Rumen Ciliates. III. Ultrastructure of the Genus Entodinium (Stein)1

This study examines previously undescribed general and cytopharyngeal features of the genus Entodinium. The cytopharynx contains three types of microtubular ribbons underlying the cytostomal membrane as well as a loose palisade of nematodesmata. A protoesophagus composed of microtubular bundles associated with a fibrous wall lies internally to one side of an extrusible peristome on which the adoral zone of syncilia (AZS) is mounted. Macronuclear structures are very similar to those of other ophryoscolecids. The micronucleus has chromatin bodies forming a compact mass but lacks the thick wall found in other species. A tubular spongiome surrounds the contractile vacuole and the cytoproct is relatively undifferentiated. Cortical structure follows the usual five-layered ophryoscolecid pattern with subcortical barren kinetosomes arranged into indistinct kineties. The infraciliature of the AZS has kinetosomes set upon a subkinetal rod and with associated bifurcated kinetodesmata and transverse microtubules, some of which extend into the cytopharynx. Components newly described for Entodinium are the one to three postciliary microtubules and the interkinetosomal centro-lateral strand, all of which are present in other species of ophryoscolecid ciliates. The infraciliature of the paralabial ciliary tuft shows similar components to that of the main AZS, but lacks the subkinetal rod. The microtubular components of the cytopharynx are discussed in relation to the “alimentary” structures in other ophryoscolecids, and a relationship of these structures to dietary differences is suggested.     

Assessment of cell proportions during regeneration ofDileptus anser (Ciliata)

Summary Following transection ofDileptus regulation of cell shape and cortical pattern was studied during regeneration in an attempt to understand the interrelations of these two regulation processes. The cell ofDileptus consists of two regions, proboscis and trunk, with the oral structures marking the border between them. The isolated proboscis is able to reorganize into a complete and correctly proportioned organism and the course of this reorganisation has been observed.Correct cell proportions take more than 24h to be established. Three hours after the operation the new border between proboscis and trunk is formed. Initially, the proportions of the cell are far from normal; moreover, they can temporarily change towards a more abnormal state. This indicates that the localisation of the border between the two cell regions and the assessment of final cell proportions are separate phenomena possibly controlled by different mechanisms.     

Redefinition of the Urostylidae (Ciliophora,Hypotrichida) on the Basis of Morphogenetic Characters*

SYNOPSIS Examination of stained specimens (protargol and nigrosinbutanol) of hypotrich ciliates during division allows understanding of morphogenesis of buccal structures and cirri. Midventral, frontal, and transverse cirri in both proter and opisthe of Urostyla marina differentiate from a longitudinal series of numerous oblique ciliary streaks in a manner similar to that of Bakuella, Holosticha, Keronopsii. Pseudourostyla, and Uroleptus. This pattern differs markedly from that in Amphisiella, Kahliella, Paraholosticha, and Paraurostyla, in which the fronto-ventral and transverse cirri arise from a series of fewer (2–5) ciliary streaks in a longitudinal or fan-like array. Rows of marginal cirri in U. marina arise independently, as in Urostyla grandis. On the basis of comparisons of both structural and morphogenetic features of this and other hypotrichs, the family Urostylidae is redefined to contain Urostyla (type), Bakuella, Holosticha, Keronopsis, Pseudourostyla, and Uroleptus. Other genera formerly contained in the families Holostichidae and Urostylidae are placed in synonymy, assigned to other families, or held in uncertain familial relationship pending their rediscovery and further investigation.     

Morphology and Morphogenesis of Fuscheria terricola n. sp. and Spathidium muscorum (Ciliophora: Kinetofragminophora)1

The morphology and morphogenesis of the kinetofragminophoran soil ciliates, Fuscheria terricola n. sp. and Spathidium muscorum Dragesco & Dragesco-Kerneis, 1979, are described. Stained specimens (protargol) are characterized biometrically. The new species differs from the other species of the genus in its body size, body shape, number of kineties, length of extrusomes, and habitat. Both species have telokinetal stomatogenesis, which commences with a proliferation of kinetosomes at those kineties which bear the brosse. Fuscheria terricola does not have a complex perioral ciliature; indeed, it might be that this species has only monokinetids. Thus only a proliferation of kinetosomes and the separation of the kineties takes place in the prospective division furrow. In contrast, S. muscorum differentiates short dikinetid kinetofragments in the region of the division furrow, which are arranged to form the perioral kinety of the opisthe in the intermediate and late stages of the stomatogenesis. The right part of the perioral kinety develops first. This and other studies show that telokinetal stomatogenesis proceeds very differently depending on the differentiation of the oral ciliature; however, detailed studies on the morphogenesis of kinetofragminophoran ciliates are still too few in number for subtypes to be defined.     

Brooklynella hostilis n. g., n. sp., a Pathogenic Cyrtophorine Ciliate in Marine Fishes*

SYNOPSIS. Brooklynella hostilis is a new genus and new species of highly lethal Chilodonella-like parasite in the gills of marine fishes. It differs from other dysteriid ciliates by a combination of these features: 1) posterior-ventral adhesive apparatus consisting of a single glandular organelle that lacks a distinct discharging canal or podite; 2) the kinetosomes cover the entire ventral surface, except the left posterior portion of the body; the outer right kinety is divided into 2 segments; the middle postoral kinetyues as a row of kinetosomes without cilia around the glandular organelle; 3) there are never more than 9 nematodesmata; and 4), there are numerous small micronuclei. The lesions caused by the infection vary from a mild inflammatory reaction to extreme tissue damage resulting in severe hemorrhages, desquamation, and fusion of the gill lamellae.     

Morphogenesis of infraciliature in the entodiniomorphid ciliate Eudiplodinium maggii

The morphogenesis of ciliary zones has been studied in the ciliate Eudiplodinium maggi which has a vestigial somatic infraciliature consisting of subcortical barren kinetosomes. These replicate and migrate into the subequatorial ciliary anlagen of the dividing cells. The kinetid pattern of the barren kinetosomes changes sequentially to that of the ciliary zones. Postciliary and transverse microtubules are derived from basal and cortically directed microtubules while a dense spur coincides with the origin of the kinetodesma. All kinetics produce potential cytopharyngeal components. Nematodesmata originate in granular subkinetosomal dense plates, while two of the three types of cytopharyngeal ribbon are formed from tansverse microtubules. A spatial selectivity ensures that these components extend only from specific kinetids. It is concluded that 91) morphogenesis of the intricate cytoskeletal network of infraciliature involves a “pattern generator” in the vestigial somatic kinetids; and 92) entodiniomorph stomatogenesis in not truly apokinetal but is more like the telokinetal process of related ciliates.     

The Fine Structure of the Mature Tomite of Hyalophysa chattoni

SYNOPSIS. The fine structure of the tomite stage of Hyalophysa chattoni was examined with particular attention to its kinetal apparatus. The pellicle, thick and dense compared with that of other ciliates, is formed of three layers. The inner layer is composed of short fibrils oriented perpendicular to the surface. The cytoplasm around the oral passage and beneath falciform field 8 is crowded with dense inclusion bodies of unknown function. Dorsal to the oral passage is the rosette, a disc-shaped organelle subdivided by septa in the form of incomplete radii about a central chamber containing a tuft of cilia. The septa are composed of 3 membranes enclosing a fine layer of cytoplasm. At their inner ends 20 mμ fibers run dorsally and ventrally. Dense clumps of fibrous material line the luminal surface of the septa. Rows of fusiform trichocysts parallel the kineties. The trichocysts are composed of a finely periodic, moderately electron-dense material surrounded by 20 mμ fibrils oriented along the long axis of the trichocyst. Between and below the kinetosomes and the rows of trichocysts are electron-dense vesicles 300 mμ in diameter and bounded by a loose membrane. The large “trichocysts,” the “gros trichocystes” of Chatton and Lwoff, whose appearance heralds the beginnings of trichocystogenesis, prove to be canaliculi opening to the surface. Four separate ciliary membrane systems—the oral ciliature (XYZ), falciform field 8, falciform field 9, and the ogival field—are located on the ventral surface of the tomite. Each differs from the others and from the somatic kineties in the fibrillar organization around its kinetosomes. In the somatic kineties the kinetodesmos is a dense, periodic fiber which is formed of stacks of up to 18 subfibers, each arising from the base of a kinetosome. The kinetosomes are short (300 mμ) and contain dense central granules. In some kineties, alternating between the kinetosomes, are elliptical kinetosome-like structures which do not bear cilia and perhaps provide a reservoir of kinetosomes for future growth of the kinety.     

Observations on the Ultrastructure of the Buccal Apparatus in Thigmotrich Ciliates and their Bearing on Thigmotrich-Peritrich Affinities*

SYNOPSIS. In the first use of electron microscopy in a comparative investigation of ciliates belonging to the order Thigmotrichida, ultrastructural data were collected on ciliary organelles of the buccal area. Species studied included members of the genera Ancistrum and Boveria. Analysis of the findings suggest close affinities between thigmotrich and peritrich ciliates. Further comparison with studies on hymenostome (sensu lato) ciliates supportes the hypothesis of a common ancestral stock in the phylogenetic history of all 3 of these groups. Structures very likely homologous in species of hymenostomes, thigmotrichs, and peritrichs include: the undulating membrane, the polykineties, the oral ribs, the filamentous reticulum, and a small field of barren kinetosomes.     

Reevaluation of the ‘well-known’ Paraurostyla weissei complex,with notes on the ontogenesis of a new Paraurostyla species (Ciliophora,Hypotrichia)

Two hypotrichous ciliates, Paraurostyla wuhanensis nov. spec. from Wuhan (China) and a new North American population of the Paraurostyla weissei complex, were studied based on live observations and protargol impregnation. Paraurostyla wuhanensis nov. spec. differs from the congeners by the combined features of having six or seven frontal cirri, 2–4 frontoventral cirri, 5–7 ventral rows, and yellow-greenish cortical granules. Ontogenesis proceeds as in the type species, except that fewer frontoventral cirri are formed in the new species. The morphology of the new population of the Paraurostyla weissei complex corresponds well with other American populations. In the phylogenetic trees based on the 18S rRNA gene, Paraurostyla sequences nest in a large clade together with Apoamphisiella and Notohymena. Monophyly of Paraurostyla is rejected by the results of the approximately unbiased test analyses. Morphological, morphogenetic, and phylogenetic analyses show a close relationship between the North American populations of the Paraurostyla weissei complex and Apoamphisiella, indicating that the taxonomic position of the former needs to be reassigned. A new combination, viz. Apoamphisiella polymicronucleata (Merriman, 1937) comb. nov., a reevaluation of the Paraurostyla weissei complex, and emended diagnoses of Paraurostyla and Apoamphisiella, are provided.     

Metamorphosis from the Phoront to the Trophont in Hyalophysa*

SYNOPSIS. The nature and sequence of changes involved in the metamorphosis of the phoront of Hyalophysa have been examined in the light microscope using both living and silver-impregnated ciliates. The phoront's infraciliature, which resembles that of the migratory tomite, differentiates to the trophont (feeding stage) infraciliature without an intervening dedifferentiation. The primary visible event of metamorphosis is the growth of the metastomial area that distorts the meridional somatic kineties so that they curve or spiral around it. The distinct borders and intense argentophilia of the metastomial area suggest that it is a discrete organelle which is probably involved in the management and concentration of a large volume of dilute food. The anterior ventral field of kinetosomes, whose presence distinguishes Hyalophysa from Gymnodinioides, forms from a disorganized anterior segment of falciform field 9. The rapid and pronounced elongation of the somatic kineties supports our view that the kinetodesmos elongates by the sliding of its component subfibrils upon one another, and that the accessory kinetosomes seen in the electron microscope become functional at metamorphosis. The movement of the kineties and contractile vacuole pore during metamorphosis suggests that differentiation in this instance is not directed by pellicular “fields” but by morphogenetic movements of the underlying cytoplasm.     

Buccal and Somatic Infraciliature of Lagynus elegans (Engelmann, 1862) Quennersted, 1867 (Ciliophora, Prostomatea): Remarks on its Systematic Position

The somatic and buccal infraciliature of Lagynus elegans are described, and aspects of its division and conjugation are reported. Its somatic infraciliature is made up of 37–46 meridianal kineties composed of isolated kinetosomes that have thick and long kinetodesmal fibers. In the anterior zone of the cell, the circumoral infraciliature can be observed: it is composed of short, slightly oblique kinetal segments, which are formed of three kinetosomes each. The brosse of this species consists of 3 or 4 groups that possess 4 to 6 ciliated kinetosomes each; these kinetosomes lack kinetodesmal fibers. On the apical pole of the cell, surrounding the oral opening, a crown of nematodesmata is observed; these nematodesmata are connected to each other by a fibrillar structure. Taking into account these features, we propose that this genus be transferred from the order Prostomatida to a new family, Lagynidae, of the order Prorodontida.     

New Aspects of the Morphology of Pleurotricha lanceolata (Ciliophora, Hypotrichida): Cirral and Membranellar Patterns and Fibrillar Systems

In Pleurotricha lanceolata, the ventral somatic infraciliature presents 13 frontoventral cirri, 5 transverse cirri, one row with 18–19 left marginal cirri and two rows of right marginal cirri of different length. On the dorsal side there are six longitudinal rows of dorsal bristles, four of them bipolar and the other two less than half body length. The oral infraciliature includes the adoral zone of membranelles, with 45–55 membranelles of three or four rows of kinetosomes each, and two undulating membranes (paroral and endoral membranes), each with two rows of kinetosomes. Some structures of the oral and somatic fibrillar systems have also been examined and are similar to those described in other species of hypotrichous ciliates.     

Fine Structure and Molecular Phylogeny of Parametopidium circumlabens (Ciliophora: Armophorea), Endocommensal of Sea Urchins

Metopid armophoreans are ciliates commonly found in anaerobic environments worldwide; however, very little is known of their fine structure. In this study, the metopid Parametopidium circumlabens (Biggar and Wenrich 1932) Aescht, 1980, a common endocommensal of sea urchins, is investigated for the first time with emphasis on transmission electron microscopy, revealing several previously unknown elements of its morphology. Somatic dikinetids of P. circumlabens have a typical ribbon of transverse microtubules, an isolated microtubule near triplets 4 and 5 of the anterior kinetosome, plus two other microtubules between anterior and posterior kinetosomes, a short kinetodesmal striated fiber and long postciliary microtubules. In the dikinetids of the perizonal stripe, the kinetodesmal fiber is very pronounced, and there is a conspicuous microfibrillar network system associated with the kinetosomes. A new structure, shaped as a dense, roughly cylindrical mass surrounded by microtubules, is found associated with the posterior kinetosome of perizonal dikinetids. The paroral membrane is diplostichomonad and the adoral membranelles are of the “paramembranelle” type. Bayesian inference and maximum‐likelihood analysis of the 18S‐rDNA gene unambiguously placed P. circumlabens as sister group of the cluster formed by ((Atopospira galeata, Atopospira violacea) Metopus laminarius) + Clevelandellida, corroborating its classification within the Metopida.     

Morphologie,Infraciliatur und Ökologie der limnischen Tintinnina: Tintinnidium fluviatile Stein,Tintinnidium pusillum Entz,Tintinnopsis cylindrata Daday und Codonella cratera (Leidy) (Ciliophora,Polyhymenophora)*

Synopsis. Structure, infraciliature, and ecology of 4 fresh-water Tintinnina were investigated. The lorica of Tintinnidium fluviatile is gelatinous, fragile, and contains some agglutinated material mainly of biologic origin. Its infraciliature consists of ? 10 kineties. with kinetosomes arranged in pairs. Only one basal body of a pair is ciliated, except for the uppermost 1–4 pairs which have 2 slightly elongated cilia. In Tintinnidium fluviatile. Tintinnidium pusillum, and Tintinnopsis cylindrata there are 2 prominent ventral organelles. The lorica of T. pusillum is gelatinous and coated with much agglutinated material of biologic and nonbiologic origin. Its infraciliature is similar to that of T. fluviatile, but the uppermost pair of kinetosomes has elongated cilia. The firm loricae of T. cylindrata and Codonella cratera are, built mainly of sharp-cornered structures. The infraciliature of T. cylindrata is composed of ? 10 kineties with kinetosomes not arranged in pairs. The infraciliature of C. cratera consists of ? 32 kineties, in some of which the kinetosomes are paired, e.g. ventral kinety, and in others not paired, e.g. cilia of the very prominent lateral field and of the other somatic kineties. The uppermost kinetosomes of each somatic kinety are paired and have elongated cilia. In addition, there is an unusual ventro-lateral kinety. The oral apparatus consists of adoral membranelles and a paroral membrane. The membranelles that enter the praecral cavity are very elongate, a feature perhaps unique to Polyhymenophora. The fibrillar system consists of a prominent praeoral ring formed by fibrils extending from the adoral membranelles. A finely meshed silverline system extends over the entire cell. A review of the ecology of the fresh-water Tintinnina indicated that water temperature seems to be the most essential ecologic factor. The systematic position of the Tintinnina is discussed in light of their infraciliature. It is concluded that these organisms are most closely related to Oligotrichina, and probably to Heterotrichina.     

The Fine Structure of the Trophont and Stages in Telotroch Formation in Circolagenophrys ampulla (Ciliophora,Peritrichida)1

ABSTRACT. Ultrastructural studies of the trophont of the epizooic loricate peritrich, Circolagenophrys ampulla, show that the body conforms to the basic peritrich pattern. The lorica is dome-shaped, and the trophont is joined to it by attachment organelles. A single row of barren aboral kinetosomes is present. In telotroch formation, as cytokinesis proceeds, a band of aboral kinetosomes develops, running posteroventrally in an arc from the base of the epistomial disc. In one instance, postciliary microtubules were seen associated with the kinetosomes of the adoral polykinety in a dividing organism. In the fully developed telotroch there are several distinctive structures. In the midaboral region there is a scopula with numerous barren kinetosomes in the epiplasm underlying the pellicle. Surrounding the rim of the aboral surface is a tripartite fringe which overlies the base of the aboral ciliary girdle. The outer layer of this fringe contains regularly spaced electron-dense striations and the middle region contains microfilaments. The aboral ciliary girdle forms a complete ring. It is composed of diagonal rows of kinetosomes, 8–9 in each row. Striated fibers run between the rows of kinetosomes. They bend at the ends of the rows and continue for some distance below the outer rim of the aboral surface. Running beside each striated fiber is a band of paracrystalline material. Several distinctive structures are associated with the kinetosomes and striated fibers of the aboral girdle. In the telotroch many of the adoral cilia are absent but the adoral kinetosomes are still present. The possible functions of the specializations of the aboral surface in settlement of the telotroch, and the relationship between telotroch formation and the molting behavior of the crustacean host are discussed.