The Contribution of Ciliated Protozoa to Zooplankton Biomass in an Acidic, Subtropical Lake

Ciliated protozoa accounted for up to 50% of the mean daily zooplankton biomass in McCloud Lake, a small (5 ha), oligotrophic, acidic (pH 4.7) lake in north-central Florida. Food resources (algae and bacterioplankton) were limiting for crustacean and rotifer zooplankton during much of the year. Myxotrophic ciliates were a dominant component of the planktonic food web. Stentor niger , an uncommon species in the plankton of lakes, dominated the ciliate assemblage and usually comprised >90% of total ciliate biomass. Stentor niger always contained high densities of photosynthetic zoochlorellae and contributed an estimated 30% to the total autotrophic biomass.     

Chlorella-bearing ciliates dominate in an oligotrophic North Patagonian lake (Lake Pirehueico, Chile): abundance, biomass and symbiotic photosynthesis

1. Large mixotrophic ciliates ( Stentor araucanus , S. amethystinus and Ophrydium naumanni ) were a characteristic component of a temperate, oligotrophic lake in North Patagonia. During a 1-year study, the abundance, biomass and primary production of these large Chlorella -bearing ciliates were compared with those of the total plankton community.
2. Mixotrophic ciliates peaked in spring and from late summer to autumn, accounting for 1.6–43% (annual average: 16.3%) and 67–99% (annual average: 92%) of total ciliate abundance and biomass, respectively. Their contribution to total zooplankton biomass, including flagellates, rotifers, ciliates and crustaceans, was 14–76%, or 47% as an annual average. Endosymbiotic algae accounted for up to 25% of total autotrophic biomass (annual mean: 3.9%).
3. Maximum cell-specific photosynthetic rates of S. araucanus and S. amethystinus at light saturation varied between 80 and 4400 pg C ciliate^–1 h^–1 with high values during autumn and winter, and low values during summer. The depth-integrated rates of photosynthesis (0–40 m) of algal endosymbionts contributed 1–25% to total photosynthesis (annual mean: 6.5%).
4. A comparison of calculated ingestion rates with photosynthetic rates of Stentor indicates that photosynthate produced by endosymbionts generally exceeded heterotrophic food supply of Stentor during autumn and winter, but was much lower during summer, when food supply was high.
5. The mixotrophic ciliates represent an important 'link' between nanoplankton and higher trophic levels within the plankton community because of their high heterotrophic biomass and considerable contribution to total photosynthesis.     

The endosymbiotic unit ofStentor polymorphus andChlorella sp. morphological and physiological studies

Summary The greenStentor polymorphus harbours unicellular coccoid chlorophycean algae. They are located in food vacuoles, where they show various states of digestion, as well as in individual so-called perialgal vacuoles. According to their characteristic morphological properties the algae belong to the genusChlorella. They can be isolated from the ciliate and cultivated in mass cultures in a sterile defined inorganic medium supplemented with vitamins B₁ and B₁₂. The algae have no secondary carotenoids and excrete maltose by a pH-dependent mechanism. They thus show a conspicuous physiological similarity to the symbiotic chlorellae ofParamecium bursaria andHydra viridis, which also excrete maltose.A comparison of the properties of the chlorellae isolated fromStentor polymorphus and of the intactStentor polymorphus-Chlorella unit with the characteristic features of symbiotic chlorellae and with endosymbiotic systems containingChlorella sp. in general, lead to the conclusion that the greenStentor polymorphus is also a true endosymbiotic system.     

Stentor tartari sp. n. from India

A species of Stenior isolated from freshwater ponds and tanks in and around Bangalore, India, showed striking differences from those that have been described so far. The ciliate is red in color and has 2 spherical macronuclei and 2 small micronuclei. On the basis of the nuclear apparatus and pigmentation of the body, it is believed to be a new species, named in honor of Professor Vance Tartar as Stentor tartari. n. sp.     

The giant zooxanthellae-bearing ciliate Maristentor dinoferus (Heterotrichea) is closely related to folliculinidae

The small subunit rDNA sequence of Maristentor dinoferus (Lobban, Schefter, Simpson, Pochon, Pawlowski, and Foissner, 2002) was determined and compared with sequences from other Heterotrichea and Karyorelictea. Maristentor resembles Stentor in basic morphology and had been provisionally assigned to Stentoridae. However, our phylogenetic analyses show that Maristentor is more closely related to Folliculinidae. Our results support the creation of a separate family for Maristentor, Maristentoridae n. fam., and also confirm the phylogenetic grouping of Folliculindae, Stentoridae, Blepharismidae, and Maristentoridae, which we informally call 'stentorids'. Maristentor, rather than Stentor itself, appears to be most significant in understanding the origins of folliculinids from their aloricate ancestors. Our analyses suggest continued uncertainty in the exact placement of the root of heterotrichs with this phylogenetic marker.     

Cytological,genetic, and biochemical characteristics of an unusual non‐Chlorella photobiont of Stentor polymorphus collected from an artificial pond close to the shore of Lake Biwa,Japan

Stentor polymorphus (Müller) Ehrenberg (Heterotrichea, Ciliophora) is a trumpet‐form ciliate with endosymbiotic green algae (photobionts). Previous reports have indicated that this photobiont has a form typical of Chlorella Beijerinck (Trebouxiophyceae), with one chloroplast and a distinct pyrenoid. We collected S. polymorphus from an artificial pond on the shore of Lake Biwa in Japan. Microscopic examination demonstrated that there was no pyrenoid in the photobiont, and thus we analyzed the cytological, genetic, and biochemical characteristics of these algal cells. Cultured photobionts were smaller than those in hospite. Phylogenetic analyses placed the photobiont within the genus Mychonastes Simpson and Van Valkenburg, a chlorophycean alga occurring in fresh/brackish waters that lacks pyrenoids. Mychonastes provided little photosynthate to its host; the quantity of carbohydrate amounted to only 2% of that provided to Paramecium bursaria (Ehrenberg) Focker by its photobiont.     

Learning in Stentor

SYNOPSIS. When placed in a vertical capillary tube of 0.5 mm inner diameter opening at the bottom end into a reservoir, Stentor coeruleus learns to escape; that is, on the 1st trial it takes a long time to find its way out and much less time on the 2nd and succeeding trials. It was found that learning did not occur in a horizontal tube, or in a vertical tube with the open end above, or in tubes of 1 or 2 mm inner diameter. To explain the results it is suggested that the response is actually a delayed geotaxis released only after a definite period of mechanical stimulation from bumping into the walls of the tube. Possibly the phenomenon is related to the process of habituation to mechanical stimuli which has been elucidated by other authors.     

Ciliary Proteins and Cytodifferentiation in Stentor coeruleus*

To elucidate further the molecular events required for cytodifferentiation in Stentor coeruleus, the effects of several chemical metabolic inhibitors were tested on the outgrowth in situ of the membranellar cilia of the oral feeding organelle. The chemicals used included several inhibitors of cytoplasmic and mitochondrial protein synthesis (cycloheximide, emetine, and chloramphenicol), and an antimitotic agent (colchicine). Ciliary growth was affected only by colchicine, suggesting that a pool of “ciliary proteins” exists in interphase Stentor of sufficient size to permit complete reformation of the membranellar cilia. The implication of these observations to an understanding of the more complicated process of oral regeneration is discussed.     

Host manipulation of a freshwater crustacean (Gammarus roeseli) by an acanthocephalan parasite (Polymorphus minutus) in a biological invasion context

Several gammarid species serve as intermediate hosts for the acanthocephalan parasite Polymorphus minutus. This parasite influences gammarid behaviour in order to favour transmission to its ultimate host, generally a bird. We investigated this host manipulation in Gammarus roeseli, a gammarid species introduced in France 150 years ago which now coexists with several exotic species from different origins. In the field, vertical distribution of G. roeseli revealed a higher proportion of infected individuals close to the water's surface and the size distribution of infected gammarids revealed predation pressure on infected individuals. However, under laboratory conditions both infected and non-infected individuals remained benthic. The addition of a second gammarid, Dikerogammarus villosus, to the experimental device involved a vertical displacement of infected G. roeseli towards the water's surface. Dikerogammarus villosus, originating from the Ponto-Caspian basin, can be considered as an aggressive predator. The substitution of D. villosus with Atyaephyra desmarestii, a planktivore decapod, did not alter the gammarids' distribution, with both infected and uninfected G. roeseli staying benthic. Thus, biotic interactions between D. villosus and G. roeseli represent selective pressure encouraging the expression of manipulated behaviour in infected amphipods. Through manipulation, P. minutus was found to increase the survival of infected G. roeseli when faced with non-host predators and to make it more vulnerable to predation by the parasite's definitive host.     

Opioid activity of beta-endorphin-like proteins from Tetrahymena

Morphine and other opioids have been reported to modulate phagocytosis in the ciliate Tetrahymena. However, the endogenous signaling molecule responsible for these effects remains uncharacterized. In this work we present evidence for the presence of beta-endorphin-like protein(s) in Tetrahymena thermophila. Subcellular extracts and cell-free culture supernatants were fractionated by hydrophobic chromatography on Sep Pack C18 columns and by affinity chromatography on polyclonal anti-beta-endorphin columns. Both preparations exhibited opioid-like effects in two different systems: 1) they inhibited phagocytosis in murine peritoneal macrophages, and 2) they blocked the response to mechanical stimuli in the ciliate Stentor. Both of these effects were reversed by naloxone, consistent with an opioid receptor-mediated mechanism. Chromatographic (HPLC) fractionation of the subcellular extracts resolved a component with beta-endorphin-like immunoreactivity, whose retention time was similar to that of the human beta-endorphin standard. Fractions were also analyzed by immunoblots using a monoclonal antibody that recognizes the N-terminus of human beta-endorphin. This antibody detected two antigenic components (corresponding to Mr 9,000 and Mr 12,000 polypeptides) in subcellular extracts, but only a single antigen (corresponding to a Mr 7,000 polypeptide) in culture supernatants. These results indicate that Tetrahymena produces one or more proteins that share some properties with beta-endorphin and that these may form part of an opioid mechanism that originated early in evolution.     

Step-up photophobic response in the ciliate,Stentor coeruleus

The avoidance by Stentor coeruleus of a light trap is caused by a step-up photophobic response. The phobic response invariably consists of a delay of about 200 ms, a stop response, a turn to one side, and resumption of swimming in the new direction. After this the cells enter a refractory period of 1–3 s following a phobic response, during which they will not give a second response. Phobic responses can be elicited by spatial and temporal increases in light intensity. The action spectrum for the step-up photophobic response resembles the absorption spectrum of stentorin, the proposed photoreceptor pigment, and of its chromophore, hypericin.The phobic response is specifically inhibited by the protonophorous uncouplers TPMP⁺ and FCCP but not by the ionophores gramicidin and A23187. Since the uncouplers block light-induced membrane potential changes at the same concentrations, it has been proposed that the primary photoreception causes a light-induced potential change, which in turn, induces a motor response.Abbreviations TPMP⁺ triphenyl methyl phosphonium bromide - FCCP carbonylcyanide p-trifluoromethoxy-phenylhydrazone     

Scanning Electron Microscopy of the Cortex of the Ciliate Stentor coeruleus. A View from the Inside*

SYNOPSIS. A microdissection procedure was developed which permits the viewing of the inside surface of the cortex of Stentor coeruleus with scanning electron microscopy. Parallel bands of myonemes cover the entire inner surface of the cortex. The myonemes of the stalk region are ribbon-shaped and lack cross connections. The myonemes of the anterior cortex are flattened against the surface and are interconnected by an extensive system of cross branches. The inner surface of the frontal field is covered with a regularly cross-branched myoneme system which follows the curved pattern of frontal field kinety. The observed branching patterns and shapes of the myonemes support the hypothesis that they cause contraction of the cell. The membranellar root system was examined. Each membranellar root makes a 90° counterclockwise twist along its vertical axis (viewed from the inside) as it descends into the cell. The outer edge of each root fuses with the inner edge of the adjacent one, forming a continuous fiber sheet linking the roots together.     

Intra- and inter-specific variations in egg survival and brood development time for Austrian populations of Gammarus fossarum and G. roeseli (Crustacea: Amphipoda)

SUMMARY. 1. Egg survival (ES, percentage of eggs hatched in vitro ), reproductive success (RS, percentage of live young released from the brood pouch) and brood development lime ( d , days) in four populations of Gammarus fossarum and two populations of Gammarus roeseli were studied, in the laboratory at water temperatures of 2.0–26.1°C. Intraspecific differences between populations were not significant, but interspecific differences were found between the two species.
2. In natural stream populations, the reproductive period of G. fossarum lasted from December to September, that of G. roeseli from March to September.
3. In the experimental temperature range 2–26°C, 73% of the total number (771) of G. fossarum females and 69% of 469 G. roeseli females were ovigerous. Of these, 45% of G. fossarum and 43% of G. roeseli females successfully released live young from their brood pouches.
4. For G. fossarum , the optimum temperatures were 11.4°C for ES, where 76% of the eggs hatched, and 11.8°C for RS, where 77% of the females released live young from their brood pouches. For G. roseli , the optimum temperatures were 13.5°C for ES (51% hatched) and 14.0°C for RS (76% released). Over 50% of eggs hatched at temperatures of 3.6–19.2°C in G. fossarum and at 1 1.9–15.1°C in G. roeseli . Development time increased from 12 days at 21.9°C to 251 days at 2.0°C in G. fossarum , and from 10 days at 24.1°C to 212 days at 4.1°C in G. roeseli .
5. interspecific differences between the effects of water temperature on ES, RS and d are used to explain the different distributional patterns of G. fossarum and G. roeseli in central European running water systems. assuming that other physico-chemical variables are suitable for both species.     

Light-adaptation in the photophobic response by Stentor coeruleus

Effects of preillumination on photophobic response (light-adaptation) and recovery of the photophobic sensitivity in the dark (dark-adaptation) in Stentor coeruleus were examined. When the cells were preilluminated with white light of 7.80 W/m² for 2 min, the fluence-rate response curve of photophobic response was shifted toward higher light intensities by half an order of magnitude compared to the one without preillumination. Preillumination with a higher light intensity resulted in a further shift of the fluencerate response curve. An action spectrum for light-adaptation showed a primary peak at 610 nm and secondary peaks at 540 and 480 nm which are almost identical to the peaks observed in the photophobic action spectrum.The light-adapted cells showed a recovery of their photophobic sensing ability following dark treatment. Dark-adaptation resulted in total recovery of photophobic sensing ability in 8 minutes for the most cases examined.     

Detection and localization of a putative cyclic-GMP-activated channel protein in the protozoan ciliate Stentor coeruleus

Summary. Immunoblotting and immunocytochemical assays were employed to identify and localize a channel protein activated by cyclic GMP (cGMP) in the protozoan ciliate Stentor coeruleus. Analysis of whole-cell homogenate with antibodies raised against the α-subunit of the cGMP-activated channel protein from bovine rod outer segments and against cGMP revealed four major protein bands with molecular masses of 40 kDa, 63 kDa, and over 120 kDa, which bound cGMP. However, only a cGMP-binding protein of 63 kDa, corresponding to the α-subunit of the cGMP-activated ion channel protein from bovine rod outer segments, was found in the ciliate cortex fraction. The functional cGMP-activated channel protein was also shown to be present in the cortex fraction of S. coeruleus by patch-clamp measurements of artificial liposomes. Incorporation of the cortex fraction into liposomes resulted in the appearance of ion channel activity related to cGMP. The reconstituted protein channels were strongly inhibited by l-cis-diltiazem, a known potent blocker of many types of cyclic-nucleotide-activated channels. The results presented here are the first demonstration of the existence and localization of a putative cGMP-activated channel protein in the ciliate S. coeruleus. Cyclic-nucleotide-activated channel proteins are nonspecific cation channels which mediate the receptor potentials in photoreceptor cells and in cells of the olfactory epithelium. On the basis of these data, we suggest that the 63 kDa protein identified in Stentor coeruleus is also a cGMP-activated ion channel and that it may be involved as an effector in the photosensory transduction pathway leading to the motile photophobic response in this ciliate protist. Correspondence and reprints: Department of Cell Biology, Nencki Institute of Experimental Biology, 3, Pasteur ulica, 02 093 Warsaw, Poland.     

Genes and structural patterns in ciliates: Vance tartar and the “cellular architects”

The one form of cytoplasmic inheritance that has not been assimilated into the Central Dogma is the inheritance of surface structural patterns, a phenomenon most clearly expressed in cilates. Vance Tartar, although he worked with a genetically undomesticated organism (Stentor coeruleus), provided early evidence for the crucial role of clonally propagated features of the cell cortex. He showed that the capacity for development of cortical organelle systems is associated with a particular relational feature, the “locus of stripe contrast” (LSC), and that clonally inherited cortical variants (homopolar doublets) could be created at will by microsurgical operations that duplicated the LSC. Tartar also hoped to demonstrate the existence of what David Nanney called “cellular architects” by provoking stentors to carry out entirely novel types of morphogenetic performances. He eventually acknowledged failure, although the bizarre juxtapositions by which he attempted to elicit such novel performances did bring about specific and illuminating defects in cortical development. Subsequent analyses of similar defects in other ciliates revealed not the unitary “pattern factor” postulated by Tartar, but rather a hierarchy of distinct patterning mechanisms. Nonetheless, by pursuing an embryological approach toward morphogenesis in a highly regulative ciliate, Tartar uncovered relational aspects of pattern-determination; this, in my view, delineates the major problem that we must solve to gain understanding of intracellular patterning. © 1992 Wiley-Liss, Inc.     

Is the host or the parasite the most locally adapted in an amphipod-acanthocephalan relationship? A case study in a biological invasion context

Manipulative endoparasites with complex life cycles can alter their intermediate host immunity and behaviour in ways that increase survival probability within the host body cavity and enhance successful transmission to the definitive host. These parasitic manipulations are variable among and within parasite species and may result from co-evolutionary processes, in which the parasite is constrained for adaptation to the local intermediate host. Hence, arrival of a new host species in a local host population may promote local parasite maladaptation. This study tested the occurrence of local adaptation in two distantly located populations of the acanthocephalan parasite Pomphorhynchus laevis and its effect on the immunity and behaviour of its gammarid intermediate host Gammarus roeseli. This was done in France (an area for which G. roeseli is a recent invader) and Hungary (an area from which G. roeseli was believed to be native). As expected, we found no alteration in G. roeseli's immune defence and behaviour associated with infection by P. laevis in localities, where the gammarid is invasive. Unexpectedly, we found similar results in Hungarian populations, where the parasite was even more exposed to the host immune response. Whilst these results suggest maladaptation of the parasite to the gammarid in both countries, they also suggest that the gammarid host might be locally adapted to the parasite. Genetic analyses were performed on both the parasite and the host and the results suggest that the two subsets of populations we studied harbour rather isolated host-parasite systems, both probably deriving from a common ancestral population. We propose that G. roeseli is also of recent acquisition in Hungary, and that a recent co-evolutionary history between P. laevis and G. roeseli in association with a long generation time in the parasite has constrained parasite adaptations in Europe or even favoured host adaptation to the parasite.     

Oxygen dependent habitat selection in surface and hyporheic environments by Gammarus roeseli Gervais (Crustacea, Amphipoda): experimental evidence

Field distributions of benthic and hyporheic invertebrates are dynamic and are influenced by many physical and chemical factors. A laboratory flume containing natural gravel substrates was used to test the hypothesis that the amphipod Gammarus roeseli Gervais actively selects habitat based on two important environmental variables, dissolved oxygen concentration and direction of water flow. Under homogeneous oxygen concentrations throughout the flume, amphipods accumulated downstream. During trials with uniformly hypoxic conditions throughout the flume, G. roeseli moved to stones and screens at the water surface and above, into the zone normally saturated with humidity. This behavior, termed aquatic surface respiration, may enhance survival during periods of oxygen deficiency. Oxygen gradients were created in the flume by injecting water of differing oxygen concentrations into the head and the center of the channel. A statistically significant response to these gradients by G. roeseli demonstrates active selection of regions with more favorable oxygen concentrations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular phylogeny of the Heterotrichea (Ciliophora, Postciliodesmatophora) based on small subunit rRNA gene sequences

A comprehensive molecular analysis of the phylogenetic relationships within the Heterotrichea including all described families is still lacking. For this reason, the complete nuclear small subunit (SSU) rDNA was sequenced from further representatives of the Blepharismidae and the Stentoridae. In addition, the SSU rDNA of a new, undescribed species of the genus Condylostomides (Condylostomatidae) was sequenced. The detailed phylogenetic analyses revealed a consistent branching pattern: while the terminal branches are generally well resolved, the basal relationships remain unsolved. Moreover, the data allow some conclusions about the macronuclear evolution within the genera Blepharisma, Stentor, and Spirostomum suggesting that a single, compact macronucleus represents the ancestral state.