Number Of Ciliates Research Articles

Chemical Defense by Erythrolactones in the Euryhaline Ciliated Protist, Pseudokeronopsis erythrina.

Pseudokeronopsis erythrina produces three new secondary metabolites, erythrolactones A2, B2 and C2, and their respective sulfate esters (A1, B1, C1), the structures of which have been recently elucidated on the basis of NMR spectroscopic data coupled to high resolution mass measurements (HR-MALDI-TOF). An analysis of the discharge of the protozoan pigment granules revealed that the non-sulfonated erythrolactones are exclusively stored in these cortical organelles, which are commonly used by a number of ciliates as chemical weapons in offense/defense interactions with prey and predators. We evaluated the toxic activity of pigment granule discharge on a panel of free-living ciliates and micro-invertebrates, and the activity of each single purified erythrolactone on three ciliate species. We also observed predator-prey interactions of P. erythrina with unicellular and multicellular predators. Experimental results confirm that only P. erythrina cells with discharged pigment granules were preferentially or exclusively hunted and eaten by at least some of its predators, whereas almost all intact (fully pigmented) cells remained alive. Our results indicate that erythrolactones are very effective as a chemical defense in P. erythrina.

Ecology of ciliates in microbial mats in meltwater streams, King George Island, maritime Antarctica

Microbial communities living in microbial mats are known to constitute early indicators of ecosystem disturbance, but little is known about their response to environmental factors in the Antarctic. This paper presents the first major study on ciliates from microbial mats in streams on King George Island (Antarctica). The objective of the study is to investigate the structure and spatial distribution of ciliate communities and to identify the environmental factors determining the structure of the assemblages. Additionally, we compared ciliate communities inhabiting streams on King George Island with other isolated islands of the maritime Antarctic. Samples of microbial mats for ciliate analysis were collected from three streams fed by Ecology Glacier. Sampling was carried out three times from 17 January to 24 February 2012. The total numbers of ciliates were dominated by small taxa recognized as cosmopolitan, also recorded on other islands of the maritime Antarctic. The species richness, abundance, and biomass of ciliates differed significantly between the stations studied, with the lowest numbers in the middle course of the stream and the highest numbers in the microhabitats closest to the glacier and at the site where the stream empties into the pond. Variables that significantly explained the variance in ciliate communities in the transects investigated were total organic carbon, total nitrogen, temperature, dissolved oxygen, and conductivity. Further research is required to explain the impact of biotic factors on the presence of ciliates, including the abundance of bacteria, microalgae, and small metazoa.

Trichodinosis associated with pathology of the reproductive tract in waterfowl

ABSTRACTTrichodinid ciliophorans are opportunistic parasites of many species of fish, amphibians, and molluscs, but yet never reported in association with lesions in birds. Postmortem and histopathological evaluation of a commercial adult Toulouse gander and female goose, and a wild Mallard drake revealed the presence of severe pathological parasitic colonization of their reproductive tracts. Histopathological findings included moderate to severe granulocytic inflammation, acanthosis, accentuation of the rete pegs, and proliferative hyperplastic squamous metaplasia of the mucosa of the ejaculatory ducts and groove, sulcus spermaticus, glandular part of the phallus (cavum penis), and oviduct in association with large numbers of ciliated protozoa anchored to the tissues or free in the lumen. These protozoa had characteristic morphological features analogous to the family of Trichodinidae. The source of this parasitism could not be determined. To our knowledge, this is the first report of trichodinosis associated with pathology in birds.

Spatiotemporal variation in community structure of marine benthic ciliates in the Yellow Sea during and after macroalgal and giant jellyfish blooms

The annual bloom of the green macroalgal Ulva prolifera from May through July since 2008 and another of giant jellyfish Nemopilema nomurai from June through September have been frequent events in the Yellow Sea. However, the patterns of benthic ciliate communities during and after the blooms are still not known. In combination with analyses of benthic environmental factors, we investigated the distribution and community composition of benthic ciliates in the Yellow Sea in July and November 2011. In July, ciliates had high standing crops and diversity in the northern Yellow Sea, and in the inshore area off the southern Shandong Peninsula, where large numbers of green macroalgae accumulated. In November, the abundance, biomass and diversity of ciliates were high in the sea areas off the Shandong Peninsula and Changjiang estuary, where a large quantity of jellyfish occurred in August. Neither the abundance nor the biomass had significant difference between seasons, or between different compartments of the Yellow Sea. The species number, and both Margalef and Shannon-Wiener indices of ciliates were all significantly higher in November than in July. In both seasons, prostomateans and karyorelicteans consistently constituted the first and second most important ciliate groups in biomass; and carnivorous ciliates constituted the primary feeding type in terms of biomass as well as species richness, followed by bacterivores, algivores and omnivores. Compared with that in June 2007 when no macroalgae occurred, the percentage of small-sized bacterivores (e.g. Metacystis spp., Euplotes spp. and scuticociliates) increased in July 2011. The proportion of carnivorous ciliates increased in November, and this increased dominance of carnivorous ciliates may be a response to the increase in predominance of heterotrophic nanoflagellates, which might in turn be ascribed to an effect of green macroalgal and giant jellyfish blooms in the Yellow Sea.

Rumen ciliate biota of water buffalo (Bubalus bubalis Linnaeus, 1758) in Kastamonu, Turkey

Species composition and distribution of rumen ciliates were investigated in the rumen contents of six Anatolian water buffaloes living in Kastamonu, Turkey. Thirty-seven species and 19 morphotypes belonging to 11 genera were identified, all being first reports of rumen ciliates from Anatolian water buffaloes. The mean number of ciliates was 70.5 ± 62.3 × 104 cells in 1 mL of rumen contents, while the average number of ciliate species per host was 17.5 ± 3.6. Dasytricha ruminantium, Entodinium simulans, and En. longinucleatum were found to be the dominant species occurring in all animals. Entodinium ellipsoideum, Eudiplodinium dilobum, and Ostracodinium munham were isolated from buffaloes for the first time. No previously unknown species were observed.

Fecal Ciliate Composition of Domestic Horses (Equus caballus Linnaeus, 1758) Living in Kyrgyzstan.

Species composition and distribution of intestinal ciliates were investigated in the feces from 15 domestic horses living in Bishkek, Kyrgyzstan. Twenty-three species belonging to 14 genera were identified. This is the first study on intestinal ciliates in domestic horses living in Kyrgyzstan. The mean number of ciliates was 14.1 ± 6.8 x10(4) cells ml(-1) of feces and the mean number of ciliate species per host was 6.0 ± 3.2. No endemic or new species were detected. Blepharocorys was the major genus as these ciliates were detected in high proportions. In contrast Holophryoides, Allantosoma were only observed at low frequencies. Recorded ciliate species in this investigation had almost the same characteristics as those described in previous studies. There was no important geographic variation in the intestinal ciliate fauna of equids.

Organic carbon and microbial food web assemblages in an oligotrophic alpine lake

<p>Picoplankton, both autotrophic (APP) and heterotrophic (HPP), ciliates and heterotrophic nanoflagellates (HNF) were counted and their biovolume measured monthly over a 3 year period in Lake Paione Superiore (LPS), a high mountain lake in the Italian alpine region. Analyses of organic carbon, particulate and dissolved, were performed at the same time. APP were negligible and picocyanobacteria almost absent. HPP showed seasonal variations, with low numbers in winter/spring and maxima of nearly 10<sup>6 </sup>cell ml<sup>-1</sup> in August/September, corresponding to 60μg C l<sup>-1</sup>. Free-living, non- pigmented flagellates showed a density range from 10<sup>4</sup> l<sup>-1 </sup>to 10<sup>6</sup> l<sup>-1 </sup>with a prevalence of cells <3 μm. Their carbon ranged between 0.1-9 μg C l<sup>-1</sup>. Ciliate numbers ranged from 0.02 to 11 10<sup>3</sup> l<sup>-1</sup>. For much of the year different species of <em>Urotricha</em> were found. Conversely, <em>Strombidium</em> appeared during the ice-free period and <em>Halteria</em> <em>grandinella</em> under the ice, indicating a strict dependence on temperature. Carbon in the microbial loop of LPS (near the bottom) was mainly confined to bacteria (73%), with 20% in HNF and only 7% in ciliates. Total organic carbon (TOC) concentration, measured after the removal of net plankton, ranged from 0.26 to 1.77 mgC l<sup>-1 </sup>with a prevalence of the dissolved form (87% av.). The average particulate organic carbon (POC) concentration was 0.24 mg C l<sup>-1</sup>. All the components of the microbial loop showed a decline under the ice-cover. Bacterial carbon concentration was three times lower under the ice than in the ice-free season (7.9-24.4 μgC l<sup>-1</sup>, respectively); protozoa carbon too declined under the ice-cover (3.1-5.8 μgC l<sup>-1</sup> for HNF and 0.4-1.7μgC l<sup>-1</sup> for ciliates in the ice-cover and ice-free periods, respectively). The drop in the microbial-loop carbon occurring in late summer may be related to the presence of a <em>Daphnia</em> population peak. At that moment, the structure of the microbial loop is transformed by a top-down control of <em>Daphnia</em>.</p>

THE IMPACT OF THE SEAWEED-WRACK DECOMPOSITION OUTPUTS ON THE INTERSTITIAL CILIATES COMMUNITY UNDER EXPERIMENTAL CONDITIONS

The effect of decomposition of macroalgae products on interstitial ciliates was studied in the laboratory. Three experiments were conducted: living fresh macroalgae (control) and decaying macrophytes from storm emissions. 61 taxa of ciliates were registered. The pairwise similarity in species composition (by index Sorensen) in all variants was low; it made 35.5 and 63.2% in pairs 1↔2 1↔3 respectively, and 42.7% in pair 2↔3. The formation of a set of species involved in the utilization of macrophytes decomposition depends not only on the stage of algae decay, but on expectancy of bringing of ciliates` resting stages to the coastal zone with a spray of waves, birds, invertebrates, etc. In the control on the initial stages of the experiment an increase of speed of the succession changes was observed; in the second variant there was a gradual decline till the fourth stage of the experiment, and in third variant – the decrease in the rate of succession changes was observed at the end of experiment. On the second week of the experiment inhibitory effect was observed, in a month – stimulating effect. The sharp rise of the number of ciliates by the end of the experiment (week 5) was registered, which can testify the stage of algal mass` decomposition when its products are available for most ciliates, both directly and through the trophic chain. Fresh macrophytes compared with dead, have a more expressed and prolonged inhibitory effect due to the excretion of any chemicals.

Effects of the algicide, thiazolidinedione derivative TD49, on microbial communities in a mesocosm experiment.

We investigated the effects of the algicide thiazolidinedione derivative TD49 on microbial community in mesocosm experiments. The TD49 concentration exponentially decreased over time, with half-life of 3.5 h, following addition in the seawater (R2=0.98, P<0.001). Among microbial communities, heterotrophic bacteria and heterotrophic nanoflagellates (HNFs) grew well in all treatments following the addition of TD49. The abundance of HNFs lagged behind the increase in heterotrophic bacteria by 24 h in the 0.2 and 0.4 μM TD49 concentrations (R2=0.28, P<0.05), and by 48 h in the 0.6 and 1.0 μM TD49 concentrations (R2=0.30, P<0.05). This implies a strong concentration-dependent top-down effect of TD49 on microbial communities, with indications that the degradation of planktonic organisms, including the target alga, led to high heterotrophic bacteria concentrations, which in turn stimulated the population growth of predatory HNF. However, total ciliate numbers remained relatively low in the TD49 treatments relative to the control and blank groups, suggesting limited carbon flow from bacteria to these grazers even though the abundance of aloricate ciliates gradually increased toward the end of the experimental period, particularly at the high TD49 concentrations. TD49 appears to provide an environmentally safe approach to the control of harmful algal blooms (HABs) in aquatic ecosystems.

Changes in the Structure of Activated Sludge Protozoa Community at the Different Oxygen Condition / Zmiany W Strukturze Zbiorowiska Pierwotniaków Osadu Czynnego W Zróżnicowanych Warunkach Tlenowych

Abstract Several experiments were performed in the laboratory condition using an SBR bioreactor modelling the expected conditions, created by malfunction of certain bioreactor elements, thus the different oxygen condition. In the course of the experiments, the concentrations of ammonia nitrogen, nitrates(III), nitrates(V), TOC, and TC were systematically measured. Besides physico-chemical parameters, the structure of activated sludge community was analyzed. In the samples, the number and species composition of protozoa (ciliates) were determined. Each of the three measuring series conducted for various types of process conditions was repeated three times. The activated sludge used for inoculation of the bioreactor was sampled at Hajdow WWTP in Lublin. The results obtained are the average of three repetitions of every experimental series. On this ground, we may conclude that the number of ciliates shows a high correlation with the O2 concentration, pH and TOC.

SEASONAL DYNAMICS OF SOIL CILIATES OF SAMUR-YALAMA NATIONAL PARK

The article describes the seasonal dynamics, as well as a comparison of the species composition and structural analysis of communities of soil ciliates. Methods . Assembled with standard collection points soil samples delivered to the laboratory for further processing. Comparison of species composition of soil ciliates two different sites was carried out by Czekanowski-Sorensen, and to analyze the community structure of soil ciliates are normally used in environmental studies-dominance indices Simpson, Margalef species diversity. Results .Studies have shown that the species composition and abundance of soil ciliates individual species consistently changing seasons of the year. In general it can be noted that the total number of seasonal dynamics of soil ciliates is a bimodal curve with peaks in spring and autumn and minima in winter and summer. Main conclusions. Species composition and the total number of soil ciliates in the territory of the Samur-Yalama National Park varies both qualitatively and quantitatively depending on the time of year. Some regularities in the change of species of soil ciliates in forest soils Samur - Yalama National Park. Studies have shown the presence of certain seasonal faunal assemblages in communities of soil ciliates. The qualitative and quantitative distribution of ciliates pedobiontov affect environmental factors (both abiotic and biotic) causing microzonation distribution of these free-celled animals within a few centimeters.

Abundance and diversity of rumen protozoa in lambs fed Gliricidia sepium silage

The objective of this study was to evaluate changes in ruminal protozoa in lambs after partial replacement of feed concentrates in their diets with Gliricidia sepium silage. Twenty-four male Santa Ines lambs with an average initial weight of 14.5 kg were used. The experimental design was completely randomized, with four treatments and six replications. Treatments (given as a percentage of dry matter) were as follows: control - corn silage (600 g kg-1 as fed) + concentrate (400 g kg-1 as fed); GS133 - corn silage (600 g kg-1 as fed) + G. sepium silage (133 g kg-1as fed) + concentrate (267 g kg-1 as fed); GS267 - corn silage (600 g kg-1 as fed) + G. sepium silage (267g kg-1as fed) + concentrate (133 g kg-1 as fed); and GS400 - corn silage (600 g kg-1 as fed) + G. sepium silage (400 g kg-1as fed). Samples of rumen contents were obtained at slaughter, and analysis revealed the presence of nine genera of rumen protozoa that were present in all animals, with the exception of Enoploplastron and Eremoplastron. There were no significant differences in the average total numbers of rumen ciliates or in the composition of species between lambs. Inclusion of up to 400 g kg-1 (as fed) G. sepium silage in the diet of lambs does not affect the diversity or density of rumen protozoa.

Effect of dietary fructose polymers or sucrose on microbial fermentation, enzyme activity, ciliate concentration and diversity of bacterial flora in the rumen of rams

Five rumen-cannulated Polish Merino rams were used in a 5×5 Latin square design to investigate the effect of sucrose and polymers of fructose on the activity and characteristics of rumen protozoa and bacteria. The animals were fed concentrate and timothy hay containing either 33g or 163g fructan/kg. The low-fructan hay was supplied in the control diet and in the diets supplemented with sucrose and inulins. The high-fructan hay was the component of diet rich in timothy grass fructan. The control diet supplied 39.6g fructan/day. The remaining diet offered 195.6g of fructose-containing carbohydrates/day. The concentration of total SCFA was 7.2–9.5mM/100ml rumen fluid independently of diet and sampling time (P>0.05). The increase in sucrose or fructan contents lowered the proportions of acetate from 73.1 to 64.2mM/100mM (P≤0.002) and increased those of propionate and butyrate from 16.4 to 21.5 (P=0.003), and from 9.8 to 15.6mM/100mM (P≤0.004), respectively. The sampling time affected the proportions of propionate (P=0.01). The diets did not affect pH of rumen fluid except in the ration with timothy grass fructan (P=0.029).Irrespective of diet and sampling time (P≥0.05), the digestion velocities of timothy grass fructan, inulin, sucrose, starch, pectins, carboxymethylcellulose, and xylan were 1.3–2.9; 0.7–2.1; 4.8–9.6; 1.9–2.4, 0.3–0.5, 0.7–1.2, and 0.7–1.4mM reducing sugars/g dry matter (DM) of rumen fluid per hour, respectively. A positive correlation was found between the degradation rate of timothy grass fructan and inulin or sucrose (P≤0.045). The total number of ciliates was 261–475×103/ml, that of Entodinium, 231–439×103/ml. The concentrations of Epidinium, Isotricha and Dasytricha were 14–24×103/ml, 2.6–7.0×103/ml, and 3.2–8.1×103/ml, respectively (P≥0.05). The Diplodinium counts varied from 1.4 to 3.1×103/ml in control animals to 4.0–7.3×103/ml in sheep fed the diet rich in timothy grass fructan and Beneo P95 (P≤0.008). A postprandial decrease in the concentration of Diplodiniuum was found in animals fed the control ration and the rations rich in timothy grass fructan and Beneo HPX (P=0.017). It was stated that the sampling time influenced the composition of bacterial flora. The experiment showed that the applied doses of the examined carbohydrates did not affect the majority of the quantified parameters. The studies shall be continued using enlarged doses of fructose-containing carbohydrates.

Most ciliated protozoa in extreme environments are cryptic in the ‘seed bank’

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 72:187-193 (2014) - DOI: https://doi.org/10.3354/ame01699 FEATURE ARTICLE Most ciliated protozoa in extreme environments are cryptic in the ‘seed bank’ Andréa Galotti1,2, Bland J. Finlay3, Francisco Jiménez-Gómez2, Francisco Guerrero2, Genoveva F. Esteban1,* 1Bournemouth University, Faculty of Science and Technology, Conservation Ecology and Environmental Science Group, Talbot Campus, Poole, Dorset BH12 5BB, UK 2Universidad de Jaén, Departamento de Biología Animal, Biología Vegetal y Ecología and Centro de Estudios Avanzados en Ciencias de la Tierra, Campus de las Lagunillas, s/n, Jaén 23071, Spain 3Queen Mary University of London, School of Biological and Chemical Sciences, The River Laboratory, Wareham, Dorset BH20 6BB, UK *Corresponding author: gesteban@bournemouth.ac.uk ABSTRACT: This study focuses on the species richness of ciliated protozoa in inland saltpans. A low number of ciliates were found thriving under extreme high salinity; however, a diverse assemblage of ciliate species was revealed by gradually diluting the salt concentration, meaning that most ciliate species in these environments are hidden in the seed bank awaiting favourable growth conditions. In some saltpan samples, up to 100% of the ciliate species found were retrieved from the seed bank. Our results highlight the importance of ciliate seed banks as repositories of microbial diversity in the natural environment, enabling ecosystems to react to environmental change. The ability of microbial communities to respond to a changing environment depends on a large local diversity of rare and encysted species. KEY WORDS: Ciliates · Cryptic biodiversity · Hypersaline · Saltpans Full text in pdf format Information about this Feature Article NextCite this article as: Galotti A, Finlay BJ, Jiménez-Gómez F, Guerrero F, Esteban GF (2014) Most ciliated protozoa in extreme environments are cryptic in the ‘seed bank’. Aquat Microb Ecol 72:187-193. https://doi.org/10.3354/ame01699 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 72, No. 3. Online publication date: June 12, 2014 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2014 Inter-Research.

The effects of predation by planktivorous juvenile fish on the microbial food web

The feeding impact of planktivorous fish on microbial organisms is still poorly understood. We followed the seasonal dynamics of the food web in two natural fishponds for two years: one was stocked with planktivorous whitefish while the other had no planktivorous fish. The aim of the study was the simultaneous assessment of the feeding behaviours of planktivorous fish and of bacterivorous meta-/protozooplankters. We hypothesized that in the presence of planktivorous fish there would be fewer metazooplankton, more protozoans and decreased numbers of bacteria. Our results showed that the amount of metazooplankton eaten by the fish was indeed negatively correlated with metazooplankton biomass. The feeding impact of planktivorous fish in shaping the microbial loop was remarkable. The main grazers of bacteria in the fishpond were ciliates, whereas in the pond without fish these were heterotrophic nanoflagellates. In the fishless pond the role of the top predator shifted to the predaceous metazooplankter Leptodora kindtii which controlled the abundance of herbivorous metazooplankters. We found a negative relationship between the number of bacteria and flagellates in the fishless pond, while the number of bacterivorous ciliates was suppressed by predaceous ciliates. Therefore the bacteria-grazing activity was higher in the absence of planktivorous fish.

Rumen ciliate fauna (Ciliophora, Protista) of Turkish domestic goats living in İzmir, Turkey

Species composition and distribution of rumen ciliates were investigated in the rumen contents of 15 domestic goats living in İzmir, Turkey. Nineteen species and 10 morphotypes belonging to 7 genera were identified. The mean number of ciliates was (94.3 ± 33.4) × 10^4 cells mL^{-1} rumen contents, which is higher than that of other goat hosts reported from Turkey and the world. The mean number of ciliate species per host was 9.2 ± 3.4. Entodinium semahatae, E. rostratum, and Ophryoscolex purkynjei m. bifidoquadricinctus are new host records for goats. This is only the second reported occurrence of E. semahatae in herbivorous mammals. E. nanellum was found to be the dominant species occurring in all animals.

Quantitative and differential analysis of ciliate protozoa in rumen content samples filtered before and after fixation

The objective of this study was to assess whether the straining of rumen content samples influences the estimation of protozoal density. Ninety rumen samples were obtained from 30 cattle (three samples per animal). The samples were subjected to one of three treatments at the moment of collection: 1) fixation informalin without straining(control treatment), 2) straining before fixation informalin, or 3)straining after fixation informalin.To test the hypothesis of the variation in the protozoa composition in the samples, multivariate analyses with non-metric multidimensional scaling (NMDS) were carried out. The diversity and density of rumen protozoa were negatively affected by straining before fixation.In the pre-filtered sample, the number of ciliates from the genus Entodinium was reduced, and no individuals from the Diploplastron, Elytroplastron and Eudiplodinium genera were detected; these effects were not observed in the other two treatments. Straining after fixation did not interfere with the diversity of the ruminal community, but the abundance of protozoa was greater thanin the control treatment and significantly greater than in the samples filtered before fixation. These factors suggest that post-fixation straining is the recommended technique to analyze rumen protozoa.

Community structure of psammon ciliates in sandy beaches of lakes

Abstract Ciliate abundance and species composition were studied in the sandy beaches of six lakes of different trophic status (Poland). Samples of wet sand were taken in June 2007 from the euarenal (emergent sand), hygroarenal (sand wetted by lake waves) and hydroarenal (submerged sand) zones. The numbers of ciliates ranged from 105 to 2933 ind. cm−3 of sand and did not show any visible trend with lake productivity. In all the studied lakes, ciliates were much more numerous in the euarenal than in the hydroarenal. Small bacterivorous scuticociliates dominated in the euarenal, while Hymenostomatida, Cyrtophorida, Hypotrichida as well as Scuticociliatida comprised a significant part of the ciliate community in the hygro- and hydroarenal zones. There were positive correlations between ciliates and the concentrations of chlorophyll a and total nitrogen.

The ability of rumen ciliates, Eudiplodinium maggii, Diploplastron affine, and Entodinium caudatum, to use the murein saccharides

Murein polysaccharides may contribute to a considerable part of the dry matter of bacterial cells. Their utilization by protozoa inhabiting the rumen is, however, poorly recognized. The objective of this study was to examine the ability of three species of ciliates, i.e., Eudiplodinium maggii, Diploplastron affine, and Entodinium caudatum of digest, and ferment these saccharides. The cultivation experiments showed that the enrichment of growth medium with bacterial cell wall β-glycans increased the ciliate number (p < 0.05). A statistically significant increase (p < 0.01) was followed by a continuous decrease (p < 0.01) in the percentage of individuals containing β-glycans particles after 4- and 24-h incubation of ciliates with this substrate, respectively. The enzymatic experiments confirmed the ability of the examined protozoa to digest murein. E. caudatum exhibited the highest activity (8.2 unit (U)/mg protein per min), and E. maggii, the lowest (3.0 U/mg protein per min). The production rates of volatile fatty acids by starved and fed ciliate species were 0.7 and 1.6 (E. caudatum) pmol/ciliate cell per h, 30.5 and 42.5 (E. maggii) pmol/ciliate cell per h, and 8.3 and 19.2 (D. affine) pmol/ciliate cell per h (p < 0.05).

Abundance and trophodynamics of surface microbial loop populations in the northern Red Sea

The population densities of filter feeding ciliates in the water of the three marine protectorates of Ras Mohammed, Nabq and Abu Galoum in the northern Red Sea, were calculated during the period from November 2006 to November 2007. Also, autotrophic nanoflagellates, heterotrophic nanoflagellates and heterotrophic bacteria were enumerated to gain some indication of the food resources available for ciliates. The abundance of ciliates in the three protectorates were found to follow an annual cycle with the highest ciliate numbers of 25.3 cells ml−1 observed in the spring, and the lowest numbers of 2.1 cells ml−1 in the summer. Abundances were at times 8-fold higher than those found in comparable studies on nutrient-poor pelagic systems and, astonishingly, approached those observed in coastal waters and in more productive open ocean systems. Nanoflagellates that could provide a food supply for the filter feeding ciliates were especially numerous in the spring, while the production of bacteria was presumably a more important component at the base of this food chain in the three protectorates’ water. The filtration activities of heterotrophic flagellates and filter feeding ciliates were compared with the population densities of bacteria, nanoflagellates and ciliates in spring and summer. Moreover, filtration rates from the literature were used to calculate the potential rate of capture of prey of different categories, as well as to calculate the time required for the whole water body to be filtered by heterotrophic nanoflagellates and filter feeding ciliates.