Predatory Ciliate Research Articles

Protists: Key Ecosystem Regulators

abundance and production directly correlate to those of phytoplankton during the winter, spring, and summer. Ciliate predation on flagellates is a major regulatory mechanism, particularly during summer and among more productive lakes. The rapid generation rates of protists belie the modest instantaneous biomass of their communities. Flagellate growth rates are much greater than those of ciliates. In addition, flagellate densities are greater by a factor of approximately 1000 in comparison with ciliates (Wetzel 2001). As a result, heterotrophic flagellate production equals or exceeds that of ciliates in both planktonic and benthic habitats. The “microbial loop,” a model of pathways of organic carbon and nutrient cycling through the microbial communities, indicates many direct links among algae, bacteria, and heterotrophic protists. Protistan bacterivores can function largely as decomposers and efficient nutrient remineralizers. Some of the fixed organic carbon can be converted into larger microorganisms that may be consumed by larger metazoans and zooplankton. Under many conditions, however, the microbial loop functions as both a carbon and nutrient sink by which organic matter is respired. This appreciable organic matter is not directly available to higher animals and the nutrients are recycled without ever entering a metazoan gut. The bottom line is that in addition to their significant contributions to biodiversity, the protists are major decomposers and mediators of nutrient recycling in ecosystems. It is apparent that more than 90% of organic carbon mineralization and nutrient recycling is effected by microorganisms under 100 µm in size, largely protists. Yet less than 10% of our exploration of heterotrophic metabolism and regulation of material and energy fluxes has focused in this area. What a fantastic opportunity for young biologists to make significant contributions to our understanding of the operation of ecosystems! Were I starting over, I would devote my career to this area, to help fill one of the most important voids in contemporary understanding of the biosphere.

Defence function of pigment granules in Stentor coeruleus

Pigment granules in Stentor coeruleus are extrusive organelles containing the pigment, stentorin, which provides the blue-green colouration to this ciliate. We studied the defence function of these organelles by 1) observing the interaction between S. coeruleus and the predatory ciliate Dileptus margaritifer; 2) comparing normally-pigmented cells and artificially-bleached cells of S. coeruleus as prey for the predator; and 3) measuring the toxicity of chemically-synthesized stentorin to D. margaritifer, S. coeruleus, and 7 other ciliates. When a Dileptus attacked a Stentor, the Stentor released a mass of bluish material and the Dileptus retreated. Bleached cells of S. coeruleus were more vulnerable than normally pigmented cells to the predator. Stentorin was highly toxic to D. margaritifer (LD50, 0.6—1.0 μg/ml) in the dark, but much less toxic to S. coeruleus (LD50, 90 μg/ml). Under certain conditions, Dileptus was killed by normally pigmented Stentor, but not by bleached ones. We conclude that pigment granules of S. coeruleus function as organelles of defence against D. margaritifer and that the chemical basis of this defence is the pigment stentorin.

Climacostol, a defense toxin of the heterotrich ciliate Climacostomum virens against predators

A toxic substance (climacostol) of the protozoan ciliate Climacostomum virens against the predatory ciliate Dileptus margaritifer was established as 1,3-dihydoxy-5-[(Z)-2′-nonenyl]benzene. The structure was rigorously confirmed by the total synthesis.

The Role of Ciliated Protozoa in Subsurface Flow Wetlands and their Potential as Bioindicators

The role of ciliated protozoa in the root zone method of wastewater treatment was assessed by analyzing ciliate community structure in four experimental subsurface flow wetlands (planted or unplanted in either soil or gravel) and estimating Escherichia coli removal due to ciliate predation. A total of 22 different ciliate taxa were isolated from the four reed beds. The first third of each bed contained a higher abundance and diversity than the final third of the bed. There was a qualitative correlation between physicochemical conditions and ciliate community structure: microaerophilic species dominated the organic-rich and oxygen-poor environment of the unplanted soil bed; aerobic and facultative bacterivorous species dominated the better oxygenated gravel beds; a combination of these two communities was found in the planted soil bed. The average grazing rates of ciliates was around 5 times higher in the planted gravel bed (49 bacteria/ciliate/hour) than in the unplanted soil bed (9.5 bacteria/ciliate/hour). Taking into account the retention time and ciliate abundance, it was calculated that ciliates, by their predatory activities, are capable of removing up to 2.35 × 105 and 0.45 × 105E. coli in the first third of the planted gravel bed and unplanted soil bed, respectively. These results are discussed in relation to variation in E. coli removal kinetics. The potential for using ciliate communities as indicators of conditions within constructed wetlands is also assessed.

The role of ciliated protozoa in subsurface flow wetlands and their potential as bioindicators

The role of ciliated protozoa in the root zone method of wastewater treatment was assessed by analyzing ciliate community structure in four experimental subsurface flow wetlands (planted or unplanted in either soil or gravel) and estimating Escherichia coli removal due to ciliate predation. A total of 22 different ciliate taxa were isolated from the four reed beds. The first third of each bed contained a higher abundance and diversity than the final third of the bed. There was a qualitative correlation between physicochemical conditions and ciliate community structure: microaerophilic species dominated the organic-rich and oxygen-poor environment of the unplanted soil bed; aerobic and facultative bactenvorous species dominated the better oxygenated gravel beds; a combination of these two communities was found in the planted soil bed. The average grazing rates of ciliates was around S times higher in the planted gravel bed (49 bacteria/ciliate/hour) than in the unplanted soil bed (9.5 bacteria/ciliate/hour). Taking into account the retention time and ciliate abundance, it was calculated that ciliates, by their predatory activities, are capable of removing up to 2.35 × 105 and 0.45 × 105E. coli in the first third of the planted gravel bed and unplanted soil bed, respectively. These results are discussed in relation to variations in E. coli removal kinetics. The potential for using ciliate communities as indicators of conditions within constructed wetlands is also assessed.

Chemical defense by means of pigmented extrusomes in the ciliate Blepharisma japonicum

Summary The defensive function of pigment granules in Blepharisma japonicum against the predatory ciliate Dileptus margaritifer was further investigated by 1) observing the discharge of pigment granules of Blepharisma as a response to the attack by the predator and 2) measuring the toxicity of purified blepharismin, the red pigment localized in pigment granules. When a Blepharisma was attacked by the toxicysts-bearing proboscis of a Dileptus , the Blepharisma instantly released a mass of reddish material at the attacked site. The Dileptus retreated and the Blepharisma swam away. The observation suggested that the Blepharisma discharged pigment granules as a response to the attack. This assumption was confirmed by scanning-electronmicroscopic observations; many pigment granules near the attacked site were discharged at the moment of the attack. Purified blepharismin was highly toxic to Dileptus and several other ciliates, but was not toxic to Blepharisma . We also showed that blepharismin is toxic in the dark. These results strongly support the previously presented hypothesis that the defensive function of pigment granules in B. japonicum against D. margaritifer is based on the discharge of blepharismin as a response to the attack by the predator. We conclude that pigment granules of B. japonicum are extrusomes (extrusive organelles in protists) for chemical defense.

Benefits and costs of predator-induced morphological changes in the ciliate Colpidium kleini (Protozoa, Ciliophora)

Summary Phenotypic transformation of C. kleini occurred when the prey coexisted with the predatory ciliate Lembadion bullinum for at least 24 hours, and was completed after 36–48 h. Net-separated predator medium caused visible shape changes in the prey. The induced phenotype was about 60% wider and 20% shorter than the typical one and had an almost spherical shape. The results showed that the induced morphological changes are a defense against L. bullinum, which is a raptorial feeder. In the presence of 100 predators, on an average 132 of 150 induced phenotypes survived for 2 h, but in the same conditions only 33 of 150 normal phenotypes did. The predator needed significantly more time and had to repeat attacks many times to catch and engulf the morphologically transformed prey. Only 16% of the attacks ended in ingestion of the transformed prey in less than 15 min, while in 54% of the cases the typical C. kleini form was ingested during the first predator attack, which occurred in the first 2 min. The growth rate of induced C. kleini phenotypes was on an average about 25% less than that of typical ones, indicating the substantial cost of the defense mechanism. Other predacious ciliates such as Dileptus margaritifer, Homalozoon vermiculare and Stylonychia mytilus did not cause any morphological changes in C. kleini.

Primary structure and origin of a predator released protein that induces defensive morphological changes in Euplotes

Summary The predatory ciliate Lembadion bullinum releases a chemical compound (L-factor) which induces morphological changes in another ciliate, Euplotes octocarinatus, and some of its relatives. The changes render Euplotes so extended that Lembadion has difficulties engulfing this prey. We have previously shown that the L-factor is a protein with a mass of 31.5 kDa. Here we report the primary structure of the L-factor deduced from cDNA, the heterologous expression of the Lembadion gene encoding the L-factor, the production of an antibody directed against this factor and the labeling of the cell surface of Lembadion with this antibody. From this and from peculiarities in the amino acid composition of the L-factor we conclude that the L-factor is a surface protein of Lembadion or at least a major part of it. To our knowledge the L-factor is the first kairomone whose origin and structure has been identified.

Microzooplankton Community Structure in the North-Eastern Atlantic: Trends with Latitude, Depth and Date, Between May and Early August

Microzooplankton from water samples collected from depths of between 10 and 50 m at four stations between 47° and 60°N along the 20°W line of longitude during each of three cruises were classified into taxonomic groups and measured to estimate their abundance and biomass. Metazoan members of the microzooplankton were rarely found and their overall biomass was negligible in comparison with protists. The mean numbers of protistan microzooplankton cells >15 μn ranged between 3 and 11 cells ml-1, with mean biomass values between 2 and 14 μgC 1-1. Numbers and biomass increased towards midsummer and then decreased again, except at the most northerly station where the values were highest in the early August sample. The ratio of dinoflagellate to ciliate biomass tended to increase through the summer to levels of three or four and then decrease again, with later changes further north; this ratio also tended to be higher at deeper levels than in the mixed layer. Gymnodinioid forms usually dominated dinoflagellate numbers and biomass, but they were overshadowed by Protoperidinium and others at the two southern stations in June and July samples. Strombidium species were the dominant ciliates, commonly providing 25–50% of total microzooplankton biomass, while predatory haptorid ciliates were occasionally numerous, but tintinnids never formed more than 10% of the biomass.

Defensive function of trichocysts in Paramecium against the predatory ciliate Monodinium balbiani

Summary Defensive function of trichocysts in Paramecium was recently verified against the predatory ciliate Dileptus margaritifer. Until then, however, their defensive function had been repeatedly questioned based on the observation that trichocysts are of little use against Didinium nasutum . We tested whether trichocysts can defend Paramecium against Monodinium , a predatory ciliate closely related to Didinium . Cells of trichocyst-non-discharge (tnd) mutants, artificially induced trichocyst-deficient cells, and intact wild-type cells of Paramecium were compared as prey for M. balbiani . In both P. caudatum and P. tetraurelia , mutant cells were much more vulnerable than wild-type cells (killed 12–40 times more often by the predator under a certain condition). Cells of P. tetraurelia with reduced numbers of trichocysts, obtained by treating wild-type cells with lysozyme, were almost as vulnerable as mutant cells. On the contrary, when tested against D. nasutum , wild-type and mutant cells of P. tetraurelia were equally vulnerable. We conclude that discharge of trichocysts defends Paramecium against M. balbiani but not against D. nasutum . These results strongly suggest that trichocysts in Paramecium function as defensive organelles against many toxicyst-bearing predatory ciliates with a few exceptions such as D. nasutum .

Subantarctic copepods in an oceanic, low chlorophyll environment:ciliate predation, food selectivity and impact on prey populations

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 130:85-96 (1996) - doi:10.3354/meps130085 Subantarctic copepods in an oceanic, low chlorophyll environment: ciliate predation, food selectivity and impact on prey populations Atkinson A Copepod feeding rates and food selectivity were measured at an oceanic subantarctic site over 5 d in February 1994. A series of gut fluorescence and gut evacuation experiments was carried out for species ranging in size from Oithona similis to Pleuromamma robusta. The copepods were also incubated in ambient seawater to compare their clearance rates on ciliates, diatoms and total chlorophyll a (chl a), using microscope counts and chlorophyll budgets. Mesozooplankton were concentrated into the top 50 m layer where biomass was high (5.5 g dry mass m-2) and comprised mainly (65%) of copepods. Copepod biomass was dominated by copepodite CV of Calanus simillimus. Numerically, however, Oithona spp. (mainly O. similis) constituted 85% of the copepods. These 2 species dominated copepod grazing and contributed to community grazing in about equal proportions. Chl a concentrations were low (~0.7 mg m-3) and were comprised of mostly nano- and picoplankton. Low daily phytoplankton carbon rations were derived from the 2 methods which measured total chl a consumption. These ranged from 1.5% (female CVI C. simillimus) to 34% of body carbon (late stage copepodites of Oithona spp.). These values were generally well below their estimated respiratory requirements, and probably reflected phytoplankton shortage because clearance rates were fairly high. Clearance rates for total chl a in the incubations tended to be less than those for the counted taxa &GT10 um, suggesting that some of the chl a was in cells too small to be eaten. Feeding selectivity followed a similar pattern across the 4 incubations. Highest clearance rates were on ciliates (~15 um), dinoflagellates (~20 um) or the diatom Corethron sp. (~200 um). Ciliates and dinoflagellates were cleared faster than centric diatoms of similar overall dimensions. It is suggested that the copepods were preying on protozoans preferentially, in response to phytoplankton shortage. Allometric relationships were used to derive the grazing and predation impact of the whole copepod community on primary production and estimated ciliate production. Less than 4% of primary production was removed per day. Copepod predation on ciliates was higher: 57% of daily production, assuming a net growth rate for ciliates of 0.1 d-1. Subantarctic . Copepods . Selective feeding . Ciliates . Allometry Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 130. Publication date: January 11, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Adaptation of inducible defense in Euplotes daidaleos (Ciliophora) to predation risks by various predators

The extent of induced morphological defense in Euplotes daidaleos correlates to this ciliate's predation risk from the defense-inducing predator species. Euplotes daidaleos responded by morphological transformation only to organisms that are able to feed on typically formed Euplotes cells (63 ± 5 μm cell width in E. daidaleos). Three of those potential predator species caused defensive changes to various degrees (Student's t-test, P < 0.1 to P < 0.0001): Lembadion bullinum (Ciliata) induced 82 ± 6 μm cell width in E. daidaleos; Chaetogaster diastrophus (Oligochaeta) induced 85 = 6 μm width; and Stenostomum sphagnetorum (Turbellaria) induced 89 ± 8 μm width (at a density of 10 predators per milliliter, respectively). At higher predator densities (50 or 100 organisms per milliliter), Euplotes developed a correspondingly larger width (to a maximum of 103 ± 10 μm in the presence of S. sphagnetorum). Euplotes did not respond to organisms (e.g., Blepharisma japonicum, Colpidium campylum, Didinium nasutum, Paramecium caudatum, Spirostomum ambiguum, Stentor coeruleus) that cannot feed on this ciliate species. Daphnia longispina and Bursaria truncatella predators, which can feed on large prey of ≥125, or ≥200 μm in diameter, respectively, also had no effect on the morphology of Euplotes. The extent of defense in Euplotes that was induced by 10 predators per milliliter during 24 h decreased the predation risk from those predators to 67% in the presence of S. sphagnetorum, to 50% with L. bullinum, and to 15% with C. diastrophus, compared to the typical form of Euplotes. In a natural population, the defensive form of E. daidaleos was found with average cell widths of 88 ± 8 μm. The results indicate that predator-induced defense in natural Euplotes populations is beneficial to this prey and that it is adapted to the predation abilities of Euplotes predators, whereby energetical costs related to defensive changes may be saved.

Highly active microbial communities in the ice and snow cover of high mountain lakes

An exploratory study carried out in Pyrenean and Alpine lakes shows that a rich, active microbial community lives in the slush layers of the winter cover of such lakes in spite of the low temperature and the seasonal occurrence of the habitat. Bacteria were very diverse in morphology, with filaments reaching up to 100 (mu)m long; flagellates, both autotrophic (chrysophytes, cryptophytes, dinoflagellates, and volvocales) and heterotrophic, and ciliates were abundant, reaching biovolume values up to 2.7 x 10(sup6) (mu)m(sup3) ml(sup-1). Species composition was very variable, with dominance depending on date and depth. Although many species were typical of lake plankton communities, some were restricted to the slush, for instance the predatory ciliates Dileptus sp. and Lacrymaria sp., and others were restricted to the surface pools, such as the snow algae Chlamydomonas nivalis. Microbial biomasses and usually bacterial and algal activities were greater in the slush layers than in the lake water. Photosynthesis rate in the upper cover layers reached values up to 0.5 (mu)g of C liter(sup-1) h(sup-1), and high bacterial activities up to 226 pmol of leucine incorporated liter(sup-1) h(sup-1) and 25 pmol of thymidine incorporated liter(sup-1) h(sup-1) were measured. For most species, lake water flooding the ice and snow cover could provide an inoculum. Differential growth depending on the environmental conditions (nutrients, organic matter, light) of a particular slush layer could provide dominance of different groups or species. However, there was no obvious colonizing mechanism for those species not appearing either in plankton or in communities on top of the snowpack.

Predation on Ciliates by the Suspension-Feeding Calanoid CopepodAcanthodiaptomus denticornis

The effects of prey size, hunger, and algal presence on the predation of the suspension-feeding calanoid copepod Acanthodiaptomus denticornis on the ciliates Tetrahymena corlisii (32 μm mean length), Paramecium aurelia (114 μm), P. caudatum (124 μm), Loxodes sp. [Formula: see text], and Stentor coeruleus[Formula: see text] and the flagellate Astasia longa (14 μm) were evaluated in laboratory experiments. Adult Acanthodiaptomus consumed all species, but not in proportion to their size. At low concentrations (prey &lt; 200 μg C∙L−1), mean clearance rates ranged from 80 mL∙copepod−1∙d−1(for Paramecium) to 13 mL∙copepod−1∙d−1(for Loxodes). Clearance rates declined with increasing concentration of the same prey, as expected. Prey capture and ingestion was determined by cell width and prey escape reactivity. Hunger significantly increased predation rates at high prey levels. The presence of algae enhanced ciliate predation by hungry copepods at low prey levels, but had no other significant effects. Protozoan predation by Acanthodiaptomus generally exceeds its feeding on algae and nanoplankton. Results suggest that ciliates can be a significant part of the diet of some suspension-feeding freshwater copepods in situ, confirming the importance of ciliates as mediators of energy transfer from the microbial loop to higher trophic levels.

Predator‐induced morphological changes in Euplotes (Ciliata): Isolation of the inducing substance released from Stenostomum sphagnetorum (turbellaria)

AbstractThe turbellarian Stenostomum sphagnetorum releases a morphogenetically active substance (S‐factor) into the surrounding medium. Ciliates of the genus Euplotes, which are potential prey of Stenostomum, are able to recognize the S‐factor. In response to this factor, each Euplotes cell becomes transformed into an enlarged circular morph with extended lateral wings that make its engulfment by the predator more difficult. The S‐factor was purified to chromatographic and electrophoretic homogeneity. From the observation that its biological activity can be eliminated by treatments with proteases and from the absorption spectrum of the purified S‐factor, it appears that the S‐factor is a protein. Upon heating at 95°C for 10 min, the S‐factor lost 50% of its biological activity, and after 30 min at 95°C the activity had disappeared completely. Electrophoretic analysis revealed that the S‐factor has a molecular mass of 17.5 kDa. It is active at concentrations as low as 10–11 M. The factor from Stenostomum is not identical to the Lembadion factor, which is released from the predatory ciliate Lembadion bullinum and has a morphogenetic effect on Euplotes. © 1993 Wiley‐Liss, Inc.

Anaerobic predatory ciliates track seasonal migrations of planktonic photosynthetic bacteria

Caenomorpha medusula was the dominant anaerobic ciliated protozoon in the anoxic water of a stratified freshwater lake. The population distribution was non-random, often with a peak in the middle of the hypolimnion. Abundance was closely correlated with numbers of the photosynthetic bacterium Thiopedia sp., and the latter was selectively eaten. There was no apparent correlation with the distribution of the total bacterial count, nor with dissolved sulphide. These observations strongly suggest that planktonic anaerobic ciliates seek out specific food sources.

Anaerobic predatory ciliates track seasonal migrations of planktonic photosynthetic bacteria

Caenomorpha medusula was the dominant anaerobic ciliated protozoon in the anoxic water of a stratified freshwater lake. The population distribution was non-random, often with a peak in the middle of the hypolimnion. Abundance was closely correlated with numbers of the photosynthetic bacterium Thiopedia sp., and the latter was selectively eaten. There was no apparent correlation with the distribution of the total bacterial count, nor with dissolved sulphide. These observations strongly suggest that planktonic anaerobic ciliates seek out specific food sources.

Participation of a Specific Substrate Degrading Strain in a Mixed Bacteria Culture as a Result of Ciliate Grazing

AbstractParticipation of nitrilotriacetic acid degrading bacterial strain NTA‐1 in the continuous‐cultivated mixed culture was studied under different conditions including predation pressure of the ciliate Dexiostoma campyla (STOKES, 1886). From the viewpoint of dispersed/flocculated biomass distribution, significant relationships between NTA‐1 and total bacteria ratio, and dispersed and total biomass ratio were proved in the systems without high concentrations of ciliates. The ciliate concentrations reaching 104 ml−1 stabilized flocculated biomass growth without directly affecting NTA‐1 portion. Using fluorescently labelled NTA‐1 bacteria, filter feeding rates of ciliates were evaluated (maximum individual uptake rate upon NTA‐1 bacteria as a number of bacteria per ciliate per hour being 120 h−1 and 260 h−1 under ciliate division rate of 0.3 day−1 and 1 day−1, respectively). Biomass balance showed that dispersed NTA‐1 bacteria should not serve as the sole feeding source for these free‐swimming ciliates. The role of diversity of mixed bacterial diet in ciliate growth and the role of ciliate predation in stabilizing bacterial assemblage structure was proved.

Isolation of the Lembadion‐factor, A morphogenetically active signal, that induces Euplotes cells to change from their ovoid form into a larger lateral winged morph

AbstractA morphogenetically active substance released by the predatory ciliate Lem‐badion bullinum is recognized by ciliates of the genus Euplotes, which are potential prey organisms of Lembadion. The substance (L‐factor) induces cells of the genus Euplotes to become less compact, which reduces their likelihood of becoming engulfed. Under the influence of this Lembadion‐ derived signal, E. octocarinatus develops extended wings and dorsal and ventral ridges and transforms within a few hours from its typical ovoid morph into an enlarged circular morph. This takes place without cell division. We have isolated the L‐factor and report that it is a protein with a mass of 31,500 Da. The factor has been purified to chromatographic and electrophoretic homogeneity and was found to be active at concentrations as low as 10−12 mol/L. © 1992 Wiley‐Liss, Inc.

Local trichocyst exocytosis provides an efficient escape mechanism for Paramecium cells

More than 1000 secretory organelles (trichocysts) are docked at the plasma membrane of Paramecium cells. After stimulation, the trichocyst contents are expelled as needle-like structures in an exocytotic response. Neither the function nor the natural stimulus of trichocyst exocytosis are known in this well established system. Several hypotheses have been put forward during the last 100 years, but as yet, none has withstood critical experimental testing. Using video-aided light microscopic evaluation of the explosive trichocyst exocytosis we have obtained conclusive evidence for a defensive mechanism. When stimulated locally by a non-cytotoxic chemical secretagogue, cells were rapidly propelled in the opposite direction by vigorous local trichocyst discharge. The same phenomenon was observed during encounter with a predatory ciliate, Dileptus. Whereas exocytosis-competent paramecia escaped by rapid propulsion away from the attacking predator, cells non-competent for exocytosis were paralysed and engulfed. Thus, oriented locomotion by locally stimulated trichocyst exocytosis serves as a rapid escape mechanism of Paramecium.