Spatial genetic variation, phylogeography and barcoding of the peritrichous ciliate Carchesium polypinum

Most recent studies of geographic distribution of microbial eukaryotes have focused on marine rather than freshwater protists. Here, we used the freshwater peritrich ciliate Carchesium polypinum to quantify the degree of genetic diversity of four closely related and previously described lineages and to determine whether patterns of genetic differentiation showed geographic partitioning. Using an expanded dataset of 100 isolates and employing the mitochondrial marker cytochrome oxidase c subunit I (cox-1), we enriched the 6 previously identified clades of Carchesium polypinum. We found a large degree of geographic overlap among the different clades (e.g. to the level of range of sampling), but also a spatially restricted clade (e.g. to the level of one river basin). Furthermore, we present evidence of a clear geographic separation in one of the lineages with Canadian and North Carolinian isolates grouping in two distinct clusters.     

Observations on the peritrichous ciliate Scyphidia ubiquita from the west coast of Wales and a description of a new species

The peritrichous ciliate, Scyphidia ubiquita Hirshfield has been recorded on the west coast of Wales from the mantle cavity of snails belonging to the genus Littorina. The ultrastructure is similar to that described for specimens from the Pacific coast of the United States, but the scopula lacks a pellicular crest. Scyphidia acanthophora sp.n. from the mantle cavity of the top shells, Gibbula umbilicalis (da Costa) and Monodonta lineata (da Costa) is described on the basis of light, surface and transmission electron microscopy. It is distinguished from other scyphidians principally by the general body shape, form of the macronucleus and the ultrastructure of the scopula disc. Comparisons are made between this species and S. ubiquita particularly with respect to the ultrastructure of the scopula and the mode of attachment to the host.     

Grazing rates of the freshwater ciliate Balanion planctonicum determined by flow cytometry

Feeding of Balanion planctonicum on the cryptomonad Rhodomonassp. was recorded in vivo at 2–3 min intervals by flowcytometry. Ingestion rates were 1.6–1.7 algal cells ciliate^–1h^–1. On average, 20–30 min elapsed between ingestionand egestion.     

Description of a marine peritrichous ciliate, Pseudovorticella sinensis n. sp. (Ciliophora, Peritrichia) from China

A new marine peritrich ciliate, Pseudovorticella sinensis n. sp. was isolated from a shrimp-farming pond in the littoral area of Qingdao, China. The morphology, infraciliature, and silverline system were studied based on living and silver-impregnated specimens. This species is characterized by (1) an elongated bell-shaped body that measures 50-60 x 35-45 microm in vivo, (2) one large, ventrally located contractile vacuole, and (3) a pellicle covered by a layer of transparent, cortical vesicles. The number of transverse silverlines from the peristomial area to the aboral ciliary wreath is 26-32, and from the aboral ciliary wreath to the scopula is 12-15. The stalk measures about 160-250 microm long x 5-6 microm wide. The spasmoneme has one row of conspicuous thecoplasmic granules, which are about 0.8 microm in diameter.     

Indicator value of the genus Opercularia (Ciliata)

Résumé Des cultures de Chara fragilis et Chara vulgaris ont été réalisées sur milieu naturel additionné de phosphate de sodium sous diverses concentrations. Les ions H₂PO₄ ^– qui, à 2 mmol/l, ont un effet bénéfique sur la croissance de Chara fragilis sont tolérés par cette espèce à dose beaucoup plus élevée que par Chara vulgaris.La teneur en phosphore des deux végétaux s'élève avec la concentration du milieu, sans accroissement concomitant du taux de calcium insoluble.

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Chara fragilis and Chara vulgaris were grown in a natural medium containing sodium phosphate at different levels. The H₂PO₄ ^– ions, at a concentration of 2 mmol/l, are beneficial for the growth of Chara fragilis. The toxic effect of H₂PO₄ ^– appears at 5 mmol/l. Tolerance of Chara vulgaris is inferior.The phosphorus content of the plants were somewhat higher by increasing concentration of the medium, the insoluble calcium content was not enhanced.

     

Light sensitivity of the ciliate Tetrahymena vorax induced by the fluorescent dye acridine orange.

The ciliate Tetrahymena vorax is normally insensitive to light. However, after uptake of acridine orange, blue light evokes instant backward swimming. The dye accumulates mainly in posterior vacuoles, with half-maximal uptake after 1 min. Illumination for 10 s induced a depolarisation of approximately 15 mV lasting less than 2 s, followed by a sustained hyperpolarisation of approximately 20 mV. Deciliated cells displayed a similar response. The hyperpolarisation was linked to reduced membrane resistance, showed a reversal potential of approximately -55 mV and was blocked by 1 mmol l(-1) TEA. The rate of rise of electrically evoked Ca(2+)-spikes was reduced during the hyperpolarisation, which is compatible with elevated cytosolic Ca(2+) concentration. This suggests that the hyperpolarisation may be caused by activation of Ca(2+)-sensitive K(+) channels. The depolarisation was abolished in Ca(2+)-free medium, whereas the hyperpolarisation was unaffected. Illumination for 2 s, or prolonged stimulation restricted to the anterior part of the cell, induced depolarisation only. Illumination of the posterior part caused delayed hyperpolarisation with no preceding depolarisation. We conclude that the induced backward swimming is associated with Ca(2+) influx through anterior channels, while Ca(2+) released from intracellular stores activates K(+) channels responsible for the delayed hyperpolarisation.     

小球藻绿钟虫--中国东北淡水生缘毛类纤毛虫的形态学重述

小球藻绿钟虫 (VorticellachlorellataStiller ,194 0 )采自哈尔滨附近水域。本文在活体观察基础上 ,利用蛋白银染色技术对其形态学进行了研究 ,给出了该种染色后的特征。小球藻绿钟虫因其细胞内充满共生小球藻呈鲜绿色而得名。该种自然伸展时呈稳定的矮钟状 ,体长 5 3- 6 3× 4 1- 6 2 μm ;大核“J”型 ,两端明显盘绕 ,纵贯于体内。细胞表面具横纹 ,蛋白银制片后可见从口围唇到反口纤毛环之间有 33- 36条纹 ,从反口纤毛环到帚胚有条纹 15 - 18条 ;第三咽膜 (P3)由三列毛基列组成 ,最内侧一列长度仅是另外两列的一半 ,并显著分离 ;口围盘纤维斜向并呈轮辐式放射状排列 ,纤维末端分叉。通过对本文描述的绿色钟虫—小球藻绿钟虫的研究 ,发现对绿色钟虫的描述与归属问题仍存在一些混淆。本文认同将小球藻绿钟虫与绿钟虫严格分立的观点     

Light sensitivity of the ciliate Tetrahymena vorax induced by the fluorescent dye acridine orange

The ciliate Tetrahymena vorax is normally insensitive to light. However, after uptake of acridine orange, blue light evokes instant backward swimming. The dye accumulates mainly in posterior vacuoles, with half-maximal uptake after 1 min. Illumination for 10 s induced a depolarisation of approximately 15 mV lasting less than 2 s, followed by a sustained hyperpolarisation of approximately 20 mV. Deciliated cells displayed a similar response. The hyperpolarisation was linked to reduced membrane resistance, showed a reversal potential of approximately −55 mV and was blocked by 1 mmol l⁻¹ TEA. The rate of rise of electrically evoked Ca²⁺-spikes was reduced during the hyperpolarisation, which is compatible with elevated cytosolic Ca²⁺ concentration. This suggests that the hyperpolarisation may be caused by activation of Ca²⁺-sensitive K⁺ channels. The depolarisation was abolished in Ca²⁺-free medium, whereas the hyperpolarisation was unaffected. Illumination for 2 s, or prolonged stimulation restricted to the anterior part of the cell, induced depolarisation only. Illumination of the posterior part caused delayed hyperpolarisation with no preceding depolarisation. We conclude that the induced backward swimming is associated with Ca²⁺ influx through anterior channels, while Ca²⁺ released from intracellular stores activates K⁺ channels responsible for the delayed hyperpolarisation.     

Growth of the Peritrich Opercularia coarctata in Axenic Culture*

A synthetic medium for Opercularia coarctata was developed that contains 20 amino acids, 10 vitamins, an 8-component balanced salt solution, Fe₂(SO₄)₃·(NH₄)₂SO₄·24H₂O, Tween 80, stigmasterol, a 7-component nucleic acid mixture, phenol red as an indicator, and 2,500 U.S.P. units/ml penicillin to maintain sterility. This medium supported axenic survival for 96 hr. Multiple supplements of thioctic acid, niacin, niacinamide, inositol, PABA, oleic acid, and Fe(NO₃)₂·9H₂O instead of Fe₂(SO₄)₃·(NH₄)₂SO₄·24H₂O coverted the survival medium into a growth medium, which permitted 36–45 days continuous cultivation of populations in excess of 4 × 10³ cells/3.0 ml final volume. Five generations were produced during the 48 hr logarithmic growth period. Serial transfers at 72 hr and during periods of greatest cell density produced a maximum of 8 generations 96 hr after initiation but the medium failed to sustain growth through more than 6 serial transfers. Extension of this investigation to formulating a minimal axenic medium is discussed.     

Colonization dynamics of biofilm-associated ciliate morphotypes at different flow velocities

The impact of flow velocity on initial ciliate colonization dynamics on surfaces were studied in the third order Ilm stream (Thuringia, Germany) at a slow flowing site (0.09 m s^?1) and two faster flowing sites (0.31 m s^?1) and in flow channels at 0.05, 0.4, and 0.8 m s^?1. At the slow flowing stream site, surfaces were rapidly colonized by ciliates with up to 60 cells cm^?2 after 24 h. In flow channels, the majority of suspended ciliates and inorganic matter accumulated at the surface within 4.5 h at 0.05 m s^?1. At 0.4 m s^?1 the increase in ciliate abundance in the biofilm was highest between 72 and 168 h at about 3 cells cm^?2 h^?1. Faster flow velocities were tolerated by vagile flattened ciliates that live in close contact to the surface. Vagile flattened and round filter feeders preferred biofilms at slow flow velocities. Addition of inorganic particles (0, 0.6, and 7.3 mg cm^?2) did not affect ciliate abundance in flow channel biofilms, but small ciliate species dominated and number of species was lowest (16 species cm^?2) in biofilms at high sediment content. Although different morphotypes dominated the communities at contrasting flow velocities, all functional groups contributed to initial biofilm communities implementing all trophic links within the microbial loop.     

Grazing by the Antarctic sea-ice ciliate Pseudocohnilembus

Potential uptake and clearance rates of fluorescent microspheres (FM) from 0.25 to 4.05 μm diameter were determined for the non-loricate ciliate Pseudocohnilembus sp. from Antarctic sea ice. The percentage of ciliate cells that ingested FM after 20 min incubation decreased with increasing particle diameter. Pseudocohnilembus sp. ingested FM between 0.25 and 4.05 μm in diameter. We offered FM at concentrations less than natural concentrations for plankton plus detrital material and obtained clearance rates less than those previously reported for bactivorous ciliates. Clearance rates were 3.6–5.4 nl cell⁻¹ h⁻¹ for FM 0.5 and 1 μm diameter, respectively, but decreased to 1.1 nl cell⁻¹ h⁻¹ for 1.97 μm diameter and 1.4 nl cell⁻¹ h⁻¹ for 4.05-μm-diameter FM. Clearance and uptake rates of FM 0.5 and 1 μm diameter indicate that Pseudocohnilembus sp. principally grazes on bacteria-sized particles. However, it can also ingest organisms as large as nanoplankton and may graze particles as small as femtoplankton and colloids. This suggests a feeding strategy that may suit the temporal and spatial changes in food availability in the sea-ice habitat. Accepted: 13 August 2000     

Analysis of the flow field of the krill,Euphausia pacifica

Velocity measurements were performed for the flow field generated by tethered krill Euphausia pacifica. The particle image velocimetry (PIV) technique was used to measure the velocity field in vertical planes aligned with the krill body axis. The krill generates a narrow jet-like flow behind and below the pleopods (roughly 25° below horizontal). The volume of fluid moving at greater than 10% of the maximum velocity near the pleopods is roughly 18 times larger than the volume of the krill. Thus, the hydrodynamic disturbance occupies a significantly larger region than the animal body. Other krill, sensing the flow disturbance, may take advantage of the flow induced by a neighbor to locate a mate or to draft for efficient propulsion.     

Analysis of the flow field of the krill, Euphausia pacifica

Velocity measurements were performed for the flow field generated by tethered krill Euphausia pacifica. The particle image velocimetry (PIV) technique was used to measure the velocity field in vertical planes aligned with the krill body axis. The krill generates a narrow jet-like flow behind and below the pleopods (roughly 25° below horizontal). The volume of fluid moving at greater than 10% of the maximum velocity near the pleopods is roughly 18 times larger than the volume of the krill. Thus, the hydrodynamic disturbance occupies a significantly larger region than the animal body. Other krill, sensing the flow disturbance, may take advantage of the flow induced by a neighbor to locate a mate or to draft for efficient propulsion.     

Restricted distribution and limited gene flow in the model ciliate Tetrahymena thermophila

The biogeography of microbial eukaryotes has long been debated, but few phylogeographic data have been available to assess whether protists tend to have ubiquitous or endemic distributions. We addressed this issue in the ciliate Tetrahymena thermophila, a highly successful model system in cell and molecular biology. We found that this species has a distribution that is restricted to the Eastern United States, with high diversity in the northeast and low diversity across the rest of its distribution. We find high levels of population subdivision, low rates of migration and significant isolation by distance, supporting the moderate endemicity model of protist biogeography. This restricted gene flow may be a result of small population size, which would reduce the probability of migration events, or the inability to establish after migration. This work lays the foundation for T. thermophila to become a valuable model system for studying population biology.     

Surface modifications by field induced diffusion

By applying a voltage pulse to a scanning tunneling microscope tip the surface under the tip will be modified. We have in this paper taken a closer look at the model of electric field induced surface diffusion of adatoms including the van der Waals force as a contribution in formations of a mound on a surface. The dipole moment of an adatom is the sum of the surface induced dipole moment (which is constant) and the dipole moment due to electric field polarisation which depends on the strength and polarity of the electric field. The electric field is analytically modelled by a point charge over an infinite conducting flat surface. From this we calculate the force that cause adatoms to migrate. The calculated force is small for voltage used, typical 1 pN, but due to thermal vibration adatoms are hopping on the surface and even a small net force can be significant in the drift of adatoms. In this way we obtain a novel formula for a polarity dependent threshold voltage for mound formation on the surface for positive tip. Knowing the voltage of the pulse we then can calculate the radius of the formed mound. A threshold electric field for mound formation of about 2 V/nm is calculated. In addition, we found that van der Waals force is of importance for shorter distances and its contribution to the radial force on the adatoms has to be considered for distances smaller than 1.5 nm for commonly used voltages.     

Behavioural changes induced by the conjugation-inducing pheromones,gamone 1 and 2, in the ciliate Blepharisma japonicum

Preconjugant interactions between complementary mating-type cells in ciliates occur before sexual reproduction. The interactions include retardation of swimming behaviour, courtship dancing, chemoattraction, nuclear activation, cell division, or cell agglutination, depending on ciliate species. In Blepharisma japonicum, chemoattraction of mating-type I by mating-type II has been reported previously. It has been shown that chemoattraction here is caused by a conjugation-inducing substance called gamone 2 secreted by mating-type II cells. In this study, we show that mating-type II cells accumulate near the site where gamone 1 secreted by mating-type I cells is present at a high concentration. We also show that the behaviour of individual cells changes when exposed to the complementary mating-type gamone; cells begin to rotate and swim slowly, thus shortening their minimum path length (final displacement of a cell from its origin). These results suggest that gamones 1 and 2 induce behavioural changes in type II and I cells, respectively, and that gamone-stimulated cells may accumulate at the site with the highest activity of the complementary gamone, after repetition of swimming changes in the gradient of gamone concentration. This reciprocal induction of the changes in behaviour may increase the probability of sexual encounters for conjugation.     

Rediscovery and redescription of the marine peritrichous ciliate Epicarchesium abrae (Precht, 1935) nov. comb. (Protozoa, Ciliophora, Peritrichia)

The morphology, infraciliature and silverline system of the marine peritrichous ciliate, Epicarchesium abrae (Precht, 1935) nov. comb., isolated from an abalone-farming pond off the coast of Qingdao, China, are investigated. E. abrae is characterized by: size of zooid in vivo 68 μm×48 μm on average; macronucleus usually J-shaped; one dorsally-located contractile-vacuole; colony regularly dichotomously branched with 4–16 zooids; total number of transverse silverlines 62–72, from peristome to aboral ciliary wreath 41–47, from aboral ciliary wreath to scopula 21–25; outer kinety of peniculus 3 prolonged and converges with peniculus 1.