An Analysis of Macrostome Production in Tetrahymena vorax Strain V2S-Type*

SYNOPSIS. Tetrahymena vorax is a small polymorphic holotrichous ciliate capable of transforming to macrostomes when microstomes are washed and suspended with prey in distilled water. Extrinsic factors having an effect on this transformation were examined; maximum yields of macrostomes (in excess of 90%) were obtained under the following conditions: populations of both prey, T. pyriformis, and potential predator, T. vorax microstomes, were grown on Loefer's medium for 48 hours prior to washing in distilled water. The density of the prey was adjusted to 300,000 cells/ml and the predator density to 2,000–3,000 cells/ml. Five ml of prey suspension and 5 ml of T. vorax microstome suspension were mixed together in a large petri dish because a high surface-volume ratio is important for high yields of macrostomes. The pH was adjusted to 6.0 and the petri dish was placed at 20 C for 12 hr. Macrostomes then appeared about 6 hr after addition of the prey. A dialyzable, heat stable substance released by the prey which can induce the microstome-macrostome transformation was isolated. This material was effective after being stored for weeks in the cold; its activity was not affected by the protein digesting enzymes pepsin or trypsin. This factor was called stomatin because its first visible effect in producing microstome-macrostome transformation appeared to be to incite reorganization of the oral structures.     

The Effect of 2-Mercapto-1-(Beta-4-Pyridethyl) Benzimidazole (MPB) on Cell Differentiation and RNA Synthesis in the Protozoon Tetrahymena vorax1

SYNOPSIS. Differentiation of small-mouthed cells (microstomes) into large-mouthed, potentially carnivorous cells (macrostomes) in Tetrahymena vorax is prevented by 2-mercapto-1-(β-4-pyridethyl) benzimidazole (MPB). This differentiation, induced by the transforming principle, stomatin, isolated from the potential prey, Tetrahymena pyriformis, is a synchronous process in which 70–95% of the population of T. vorax microstomes transform into macrostomes within 450 min. MPB also inhibits RNA synthesis in transforming microstomes while having little effect on protein synthesis. Finally, the effect of MPB on both transformation and RNA synthesis is reversible.     

Preuves Cinétiques de l'Existence d'une Période de Compétence pour la Transformation Microstome-Macrostome dans le Cycle Cellulaire de Tetrahymena paravorax

RÉSUMÉ. Des expérimentations portant sur des cellules isolées ont montré que 77% des microstomes de Tetrahymena paravorax, prélevés au hasard dans des cultures en phase logarithmique de croissance, se transforment directement en macrostomes en présence de “stomatine.” Ces macrostomes apparaissent à des moments variés entre 1,5 et 9 h après l'addition de la stomatine (“point 50% de transformations” vers 2,5 h). La compétence pour le remplacement oral est en relation avec la position dans le cycle cellulaire. Les pourcentages de transformation les plus élevés sont observés avec les populations testées pendant la première moitié de la période moyenne d'interfission. La formation des macrostomes est d'autant plus rapide que l'ǎge initial des microstomes est plus proche du point médian du cycle cellulaire (“point de compétence”). Dans la seconde moitié de ce cycle, le temps moyen de transformation reste à peu près constant, mais le pourcentage de divisions augmente: le “point de transition” (50% de divisions) se trouve au début d'une phase terminale représentant 19–20% de la durée totale du cycle. La transformation des produits de bipartition antérieur et postérieur est nettement asynchrone: dans la majorité des paires cellulaires, l'opisthe se transforme avant le proter. Les cellules-soeurs se divisent aussi de manière asynchrone: le temps de génération du proter est plus long que celui de l'opisthe. Le problème de l'acquisition de la compétence pour le changement de phénotype est discuté en envisageant les corrélations éventuelles avec certains processus majeurs du cycle cellulaire. SYNOPSIS. Seventy-seven percent of the microstomes of Tetrahymena paravorax taken from random samples of log-phase cultures transform directly into macrostomes in the presence of “stomatin.” These macrostomes appear between 1.5 and 9 h after addition of stomatin (“50% transformation point,”～ 2.5 h). Competence for oral replacement is related to the position in the cell cycle. The highest percentages of transformation are observed in populations tested during the first half of the mean interfission period. Formation of macrostomes is more rapid when the initial age of the microstomes is nearer to the midpoint of the cell cycle (“competence point”). In the 2nd half of this cycle, the mean transformation time remains approximately constant, but the percentage of cells undergoing division is increasing. The “transition point” (50% divided cells) is found at the beginning of a terminal phase which accounts for 19–20% of the cell cycle. Transformation of anterior and posterior fission products is fairly asynchronous; in the majority of individual pairs, the opisthe is transformed before the proter. The daughter cells also divide asynchronously, the generation time of the proter being longer than that of the opisthe. The problem of acquisition of competence for phenotypic change is discussed in light of possible correlations with certain major processes of the cell cycle.     

Microstome-Macrostome Transformation in Tetrahymena vorax Strain V2 Type S Induced by a Transforming Principle, Stomatin

SYNOPSIS. Microstome →macrostome transformation in Tetrahymena vorax was induced by suspending microstomes in a transforming principle, stomatin, released by a potential prey, T. pyriformis. It was found that 70–90% of the microstomes formed macrostomes within 7 hours following suspension in this transforming principle. Macrostome formation occurred by the process of oral replacement. This process involved resorption of the microstome oral apparatus and its replacement with a larger (macrostome) one, which arose from an anarchic field that formed behind the resorbing oral area. Ninety-five percent of those microstomes which were destined to form macrostomes were in some stage of oral replacement 195 minutes after their suspension in stomatin. Several commercially produced products were tested over a wide range of concentrations to determine their ability to act as an inducer of macrostomes. Only 2, Trypticase and Bactocasitone, had any activity, and it was too small to be considered really effective. An attempt was also made to destroy the activity of stomatin by using enzymes. RNAse was effective but only in very high concentrations, so it was suggested that this activity might be related to the destruction of RNA within the transforming cell and not related to hydrolysis of stomatin. None of the other enzymes tested had any effect in reducing the activity of stomatin.     

The Effects of Purine and Pyrimidines Upon Transformation in Tetrahymena vorax,Strain V2S1

Column chromatography with Biogel P2 (molecular exclusion of 1800 daltons) indicates that the transforming principle causing microstomes to become macrostomes is a small molecule. Absorbance tests show that only those fractions with high absorbance at 260 nm have biological activity, indicating that the active principle is a component of nucleic acids. Tests of purines and pyrimidines show that purines are active, with hypoxanthine having the highest activity. The combination of hypoxanthine with uridine shows a synergistic reaction. As these two compounds are the natural catabolic excretory products from nucleic acids in Tetrahymena, the fact that they induce transformation in concentrated, starving cells may be a survival mechanism allowing cannibalism to be induced when nutrients are depleted, thereby allowing the survival of the transformed cells until such time as adequate nutritional conditions are restored.     

Frasnian bryozoans (Late Devonian) from the Khoshyeilagh Section,Alborz Mountains (northern Iran)

A bryozoan fauna containing seven species is described from the Upper Frasnian (Upper Devonian) rocks in the Khoshyeilagh Section, Alborz Mountains (northern Iran). The studied bryozoan assemblage includes one new trepostome species, Eridotrypella alborzensis sp. nov., an additional four species identified at species level: two trepostomes, Minussina akkayaensis Volkova, 1974 and Leptotrypella inaudita Morozova, 1961, and two rhabdomesine cryptostomes, Bigeyella mariae (Morozova, 1961) and Saffordotaxis multispinata (Morozova, 1955). Furthermore, two species are described in open nomenclature: the trepostome Schulgina sp. and the rhabdomesine cryptostome Nicklesopora sp. The studied fauna shows a close similarity at the species level between northern Iran and the Altai-Sayan Folded Belt (Russia), south China, and Transcaucasia.     

Unusual skeletal morphology and systematic description of a new Devonian cryptostome bryozoan from the Western Sahara

Palaeozoic bryozoan colonies display a large variety of skeletal elements. Various types of rod-like styles are mainly built by laminated and non-laminated (hyaline) skeleton. Typical styles consist of hyaline cores and surrounding laminated sheaths. They usually protrude on the colony surface as spines. In a new bryozoan genus from the Middle Devonian of the Western Sahara described here, styles do not protrude on the colony surface and are embedded within the laminated skeleton. They consist of fibrous material. This new type of styles, unknown from other bryozoans, is here called a “cryptostyle”. A special characteristic of these structures is their intensive reddish-brown colouration. This colouration is apparently caused by the presence of ferric iron between the individual fibres. The function of cryptostyles was apparently weight reduction and stabilising the skeleton. The general morphology of the new bryozoan, Cryptostyloecia hexapuncta gen. et n. sp., implies its systematic position within ptilodictyine cryptostomes, specifically the Family Ptilodictyidae Zittel, 1880.     

A Comparison of Cortical Proteins in Tetrahymena vorax Microstomes and Macrostomes1

Proteins of surface membranes and surface-related cytoskeletons in Tetrahymena vorax microstomes and macrostomes were compared by one-dimensional SDS polyacrylamide gel electrophoresis to see if protein differences could be detected that correlate with the transformation from one phenotype to the other. Some differences were observed. However, these alterations appear to result from the heat-shock procedure used to synchronize the microstome-to-macrostome transition. The apparent lack of transformationspecific changes in cortical proteins is discussed. Similarities and differences between cytoskeletal proteins of T. pyriformis GL-C and T. vorax are also noted and discussed.     

Studies of Macrostome Formation of Low-Transforming Tetrahymena vorax. Transformation Enhancers,Generation Time,and Membrane Fluidity1

ABSTRACT. Periodically, stocks of Tetrahymena vorax, which normally yield 70–90% macrostomes when subjected to heat shock or other induction methods, become low-transformers and yield ≥30% macrostomes. The addition to the post-heat-shock wash buffer (pH 6.8) of 2.7 × 10^-4 M Fe³⁺, 1.6 × 10^-5 M Cu²⁺, 1 × 10^-4 M retinol palmitate or the adjustment of the buffer to a pH of 4 to 5 boosts transformation significantly over controls in inorganic medium alone. The addition of Fe²⁺ or Cu¹⁺ has a similar, but less pronounced effect on transformation. Ferric ion (2.7 × 10^-4 M) will significantly increase transformation in starved non-heat-shocked cells, whereas Fe²⁺, copper, retinol palmitate, and hydrogen ion concentration have no effect. The agents that boost transformation appear to act by delaying cell division in pre-transformants. Membrane fluidity, as inferred by fluorescence polarization measurements of 1,6-diphenyl-1,3,5-hexatriene, is altered in a consistent manner by starvation and heat shock. Enhancing agents, including compounds previously shown to boost heat-shock-induced macrostome formation, produce diverse shifts in membrane fluidity. Their effect on transformation of these low-transforming cells therefore appears to be attributable to some mechanism or mechanisms other than a direct alteration of membrane physical properties.     

Morphology and ontogenesis of Platyophrya bromelicola nov. spec., a new macrostome-forming colpodid (Protists,Ciliophora) from tank bromeliads of Jamaica

Platyophrya bromelicola nov. spec. was discovered in tanks of bromeliads from Jamaica. Its morphology, ontogenesis, and small-subunit rDNA were studied using standard methods. Platyophrya bromelicola differs from its congeners mainly by the pyriform, unflattened body (vs. reniform and flattened); the free-swimming (planktonic) habit (vs. biofilm creepers); and the unique ability to form two distinct morphs, i.e., small, bacteriophagous microstomes and large, predaceous macrostomes. Microstomes and macrostomes can be distinguished not only by body size and feeding preferences but also by the postoral pseudomembrane composed of two vs. three to four dikinetids per kinety. The ability to form macrostomes is considered as an adaptation to the highly competitive habitat. Ontogenesis closely resembles that of other members of the family. Platyophrya bromelicola is distinct not only morphologically but also genetically (3.7% in the small-subunit rDNA) from P. vorax, a common, cosmopolitan moss and soil species.     

The structure of the nervous system of the pluteus larva of Strongylocentrotus purpuratus

Summary Tissues that have the ultrastructural characteristics of nervous tissues are associated with ciliary and muscular elements of the pluteus larva of Strongylocentrotus purpuratus. The nerve cells are found along the margins of the ciliary bands, which are composed predominantly of spindle-shaped ciliated cells. The nerve cells contribute axonal processes to a tract of axons, which runs at the base of the ciliary band throughout its length. Axonal tracts, in the esophagus, lie beneath the circumesophageal muscles. Branched microvilli, which have been interpreted as sensory receptors, are located on the oral side of the main ciliary band and connect with the nerve cells in the ciliary band. The nervous structures described here, and other tissues of the pluteus that have been previously described as nervous, are compared on the basis of their association with receptor and effector organs, and their ultrastructural characteristics.     

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.     

Electrophysiological Properties of the Microstome and Macrostome Morph of the Polymorphic Ciliate Tetrahymena vorax

Polymorphic ciliates, like Tetrahymena vorax, optimize food utilization by altering between different body shapes and behaviours. Microstome T. vorax feeds on bacteria, organic particles, and solutes, whereas the larger macrostome cells are predators consuming other ciliates. We have used current clamp and discontinuous single electrode voltage clamp to compare electrophysiological properties of these morphs. The resting membrane potential was approximately ?30 mV in both morphs. The input resistance and capacitance of microstomes were approximately 350 MΩ and 105 pF, whereas the corresponding values for the macrostomes were 210 MΩ and 230 pF, reflecting the larger cell size. Depolarizing current injections elicited regenerative Ca²⁺ spikes with a maximum rate of rise of 7.5 Vs^?1 in microstome and 4.7 Vs^?1 in macrostome cells. Depolarizing voltage steps from a holding potential of ?40 mV induced an inward Ca²⁺ ‐current (I_ca) peaking at ?10 mV, reaching approximately the same value in microstome (?1.4 nA) and macrostome cells (?1.2 nA). Because the number of ciliary rows is the same in microstome and macrostome cells, the similar size of I_Ca in these morphs supports the notion that the voltage‐gated Ca²⁺ channels in ciliates are located in the ciliary membrane. In both morphs, hyperpolarizing voltage steps revealed inward membrane rectification that persisted in Na⁺‐free solution and was only partially inhibited by extracellular Cs⁺. The inward rectification was completely blocked by replacing Ca²⁺ with Co²⁺ or Ba²⁺ in the recording solution, and is probably due to Ca²⁺ ‐activated inward K⁺ current secondary to Ca²⁺ influx through channels activated by hyperpolarization.     

Development of Chemoreceptor Cells in Oral Epithelium of Adult Jelly-Fish Beroë cucumis

In oral epithelium of adult jelly-fish Beroë cucumis, the main stages of differentiation of chemoreceptor cells replacing damaged degenerating chemoreceptors are described. The initial stages are connected with transformation of the so-called precursor cells that on transformation into juvenile cells, are inserted from mesoglea into basal epithelial areas. In the juvenile chemoreceptor cells, there continue ultrastructural transformations connected with differentiation of the apical sensory apparatus, central process, and innervation. Consecutive spatial translocations of these cells in epithelium are traced, up to their insertion into the superficial layer and replacement of degenerated chemoreceptors. The literature and the authors' own data about possible sources of origin and ways of utilization of damaged jelly-fish chemoreceptor cells are discussed.     

Ultrastructure of tentacles in the sipunculid worm <Emphasis Type="Italic">Thysanocardia nigra</Emphasis> Ikeda, 1904 (Sipuncula)

The ultrastructure of the tentacles was studied in the sipunculid worm Thysanocardia nigra. Flexible digitate tentacles are arranged into the dorsal and ventral tentacular crowns at the anterior end of the introvert of Th. nigra. The tentacle bears oral, lateral, and aboral rows of cilia; on the oral side, there is a longitudinal groove. Each tentacle contains two oral tentacular canals and an aboral tentacular canal. The oral side of the tentacle is covered by a simple columnar epithelium, which contains large glandular cells that secrete their products onto the apical surface of the epithelium. The lateral and aboral epithelia are composed of cuboidal and flattened cells. The tentacular canals are lined with a flattened coelomic epithelium that consists of podocytes with their processes and multiciliated cells. The tentacular canals are continuous with the radial coelomic canals of the head and constitute the terminal parts of the tentacular coelom, which shows a highly complex morphology. Five tentacular nerves and circular and longitudinal muscle bands lie in the connective tissue of the tentacle wall. Similarities and differences in the tentacle morphology between Th. nigra and other sipunculan species are discussed.Original Russian Text Copyright © 2005 by Biologiya Morya, Maiorova, Adrianov.     

Mitotic arrest by melatonin

We are testing the hypothesis that migration of the newly formed mouth (i.e., oral membranellar band) in stentor is homologous to mitotic chromosomal movement and that both types of movement within single cells depend directly on microtubule elongation. The following compounds synchronously delay the migration of the oral membranellar band as an exponential function of concentration: Colcemid, podophyllotoxin, β-peltatin and vinblastine. Delay for these compounds can be described by the equation, y = kxⁿ, where y is delay in hours and x is concentration of mitotic spindle inhibitor in moles/l. We discovered that the animal pineal gland hormone, melatonin (5-methoxy n-acetyl tryptamine), also specifically and reproducibly delays oral band regeneration according to an equation of this form. Thus we predicted that melatonin would arrest mitosis. We report here a colchicine-type disruption of the mitotic apparatus in onion root tips by melatonin. Two closely related tryptamine derivatives, n-acetyl serotonin and serotonin were inactive in both the stentor and onion assays: they neither delayed band migration in stentor as an exponential function nor induced mitotic arrest in onion.     

Localization of sensory mechanisms utilized by coral planulae to detect settlement cues

Coral planulae are induced to settle and metamorphose by contact with either crustose coralline algae or marine bacterial biofilms. Larvae of two coral species, Pocillopora damicornis and Montipora capitata, which respond to different metamorphic cues, were utilized to investigate the sensory mechanisms used to detect metamorphic cues. Because the aboral pole of the coral planula is the point of attachment to the substratum, we predicted that it is also the point of detection for cues. To determine where sensory cells for cues are localized along the body, individual larvae were transversely cut into oral and aboral portions at various levels along the oral–aboral axis, and exposed to settlement‐inducing substrata. Aboral ends of M. capitata metamorphosed, while oral ends continued to swim. However, in larvae of P. damicornis, ¾ oral ends (i.e., lacking the aboral pole) were also able to metamorphose, indicating that the cells that detect cues may be distributed along the sides of the body. These cells do not correspond to FMRFamide‐immunoreactive cells that are present throughout the body. Cesium ions induced both aboral and oral ends of larvae of both species to settle, suggesting that oral ends have not lost their capacity to metamorphose, despite lacking sensory cells to detect natural cues. To determine whether sensory cells in larvae of P. damicornis are restricted to one side of the body, swimming behavior over substrata was observed in larvae labeled with diI, a red fluorescent lipophilic membrane stain. The larvae were found to rotate around the oral–aboral axis, with their surface against the substratum, not favoring a particular side for detecting cues. While clarifying the regions of the larval body important for settlement and metamorphosis in coral planulae, we conclude that significant differences between coral species may be due to differences in the distribution of sensory structures in relation to different planular sizes.     

安徽滁州琅琊山下奥陶统弗洛阶(红花园组上部)的苔藓动物

寒武纪没有化石苔藓动物的任何记录.最老的、毫无疑问的、真正的苔藓动物,发现于我国峡东地区的下奥陶统特马豆克阶地层中.这类苔藓动物以丰富但多样性低的变口目和少量的隐口目为代表.弗洛期的一些苔藓动物,在北美,英国和波罗的海地区(俄罗斯西北部)已相继发现,这时以Ceramopora?unapensis为代表的泡孔目苔藓动物开始出现,有一定的多样性.中奥陶世初期,苔藓动物迅速崛起,古生代狭唇纲的四个目--变口目、隐口目、泡孔目和管孔目(=环口目)苔藓动物都已经有了代表.由于奥陶纪是苔藓动物发生、演化发展和辐射的重要时期,因此,奥陶纪,特别是早奥陶世苔藓动物的任何新的发现,都有重要的意义.本文描述和解释的一个新的苔藓动物群,发现于安徽滁州琅琊山弗洛阶的红花园组上部.这个苔藓动物群由变口目爱沙尼亚苔虫亚目的两个种:Dianulites hexaporites(Pander),Orbiramus grandis sp.nov.和隐口目翼网苔虫亚目的一个种:Prophyllodi-ctya putilovensis Lavrentjeva组成.尽管这个苔藓动物群在局部地区可能还是低多样性的,但就整个世界范围而言,有一定的多样性,类似于同样以变口目苔藓动物占优势的比林根苔藓动物群,后一苔藓动物群产于波罗的海以东地区(俄罗斯西北部)同时代的地层中.