Exclusive Gut Flagellates of Serritermitidae Suggest a Major Transfaunation Event in Lower Termites: Description of Heliconympha glossotermitis gen. nov. spec. nov.

The guts of lower termites are inhabited by host‐specific consortia of cellulose‐digesting flagellate protists. In this first investigation of the symbionts of the family Serritermitidae, we found that Glossotermes oculatus and Serritermes serrifer each harbor similar parabasalid morphotypes: large Pseudotrichonympha‐like cells, medium‐sized Leptospironympha‐like cells with spiraled bands of flagella, and small Hexamastix‐like cells; oxymonadid flagellates were absent. Despite their morphological resemblance to Pseudotrichonympha and Leptospironympha, a SSU rRNA‐based phylogenetic analysis identified the two larger, trichonymphid flagellates as deep‐branching sister groups of Teranymphidae, with Leptospironympha sp. (the only spirotrichosomid with sequence data) in a moderately supported basal position. Only the Hexamastix‐like flagellates are closely related to trichomonadid flagellates from Rhinotermitidae. The presence of two deep‐branching lineages of trichonymphid flagellates in Serritermitidae and the absence of all taxa characteristic of the ancestral rhinotermitids underscores that the flagellate assemblages in the hindguts of lower termites were shaped not only by a progressive loss of flagellates during vertical inheritance but also by occasional transfaunation events, where flagellates were transferred horizontally between members of different termite families. In addition to the molecular phylogenetic analyses, we present a detailed morphological characterization of the new spirotrichosomid genus Heliconympha using light and electron microscopy.     

Protistan bacterivory in an oligomesotrophic lake: Importance of attached ciliates and flagellates

Seasonal and depth variations of the abundance, biomass, and bacterivory of protozoa (heterotrophic and mixotrophic flagellates and ciliates) were determined during thermal stratification in an oligomesotrophic lake (Lake Pavin, France). Maximal densities of heterotrophic flagellates (1.9 × 10³ cells ml^–1) and ciliates (6.1 cells ml^–1) were found in the metalimnion. Pigmented flagellates dominated the flagellate biomass in the euphotic zone. Community composition of ciliated protists varied greatly with depth, and both the abundance and biomass of ciliates was dominated by oligotrichs. Heterotrophic flagellates dominated grazing, accounting for 84% of total protistan bacterivory. Maximal grazing impact of heterotrophic flagellates was 18.9 × 10⁶ bacteria 1^–1h^–1. On average, 62% of nonpigmented flagellates were found to ingest particles. Ciliates and mixotrophic flagellates averaged 13% and 3% of protistan bacterivory, respectively. Attached protozoa (ciliates and flagellates) were found to colonize the diatom Asterionella formosa. Attached bacterivores had higher ingestion rates than free bacterivorous protozoa and may account for 66% of total protozoa bacterivory. Our results indicated that even in low numbers, epibiotic protozoa may have a major grazing impact on free bacteria. Correspondence: C. Amblard.     

An Ultrastructural Study of Phytomonas davidi Lafont (Trypanosomatidae)1

Phytomonas davidi (Trypanosomatidae) possesses typical trypanosomatid organelles: subpellicular microtubules, kinetoplast-mitochondrial complex, K-DNA, and four subflagellar pocket microtubules. A greater concentration of subpellicular microtubules was observed in the latex forms than in those found in the salivary glands of its insect vector. Only in the latex flagellates (the stage with postnuclear torsion) were subpellicular microtubules interconnected by crossbridges observed. Morphology and development of mitochondrial aristae varied according to the source of the flagellates. Organisms taken from culture medium had extensively developed plate-like cristae; sparse tubular cristae were observed in the latex forms; and highly developed tubular cristae were seen in flagellates from the lumen of the vector's salivary glands, though organisms in the salivary gland channels had few or none.     

Effect of Filtered Cultures of Flagellate Ochromonas sp. on Colony Formation in Microcystis aeruginosa

The possible effect of filtered cultures of flagellate Ochromonas sp. on colony formation in M. aeruginosa was investigated in this paper. The results show that filtered cultures of flagellates fed with M. aeruginosa could induce colony formation in M. aeruginosa. Furthermore, induction strength is clearly dependent on the concentration of flagellates and filtered cultures. However, no colonial M. aeruginosa was found in the treatments of filtered cultures of flagellates fed with Microcystis wesenbergii, filtered cultures of flagellate fed with Chlorella pyrenoidosa, and algae homogenates. This suggests that infochemicals released from flagellates fed with M. aeruginosa may be a trigger for colony formation in M. aeruginosa. The clearance rates of flagellates on algae were markedly decreased when they were cultivated with induced colonial M. aeruginosa. These indicate that colony formation in M. aeruginosa is a predator‐induced defense which could reduce predation risk from flagellates (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Reduced Growth of Blastocrithidia culicis and Crithidia oncopelti Freed of Intracellular Symbiotes by Chloramphenicol*

The intracellular symbiotes of Blastocrithidia culicis and Crithidia oncopelti can be eliminated from cultures of the flagellates by a single chloramphenicol (CAP) treatment. Effective dosages were determined to be 0.01–0.08% (w/v) CAP after a treatment for 2 weeks or more for B. culicis and 0.08% (w/v) after 1 month for C. oncopelti in most cases. Ineffective dosages only lowered the numbers of symbiote-bearing flagellates. Growth of both species of flagellates in the presence of CAP was reduced in proportion to the drug concentration. Repeated subcultures at effective dosages yielded symbiote-free flagellates, which maintained a low level of growth rate. After repeated subcultures at ineffective dosages, the growth rate rose and the symbiote-bearing cells, initially very few, increased in number. The lowest effective dosages proved to be marginal, often producing symbiote-free cultures, but occasionally cultures with a few symbiote-bearing cells. After repeated subcultures at these drug concentrations, symbiote-containing cultures grew faster than the symbiote-free cultures. Hence, the symbiotic bacteria benefit the growth of their hosts, perhaps by supplying essential factors that are inadequate even in a rich blood medium.     

CURRENT KNOWLEDGE OF THE LIFE CYCLES OF PHAEOCYSTIS GLOBOSA AND PHAEOCYSTIS ANTARCTICA (PRYMNESIOPHYCEAE)1

Despite continuous efforts since the 1950s and more recent advances in culturing flagellates and nonflagellate cells of the prymnesiophyte Phaeocystis, a number of different life‐cycle models exist today that appear to apply for P. globosa Scherff. and P. antarctica G. Karst., both spherical colony formers. In one such model, this life cycle consists of three different flagellates and one nonmotile cell stage that is embedded in carbohydrate matrix‐forming colonies of different sizes and forms. Recently, noncolonial aggregates of diploid nonmotile cells attached to surfaces of diatoms were put forward as a new stage in the sexual life cycle of P. antarctica. However, it can be discussed that these “attached aggregates” (AAs) are an intermediate between motile diploid flagellates, with their well‐known tendency to adhere to surfaces, and the young spherical colony with its diploid nonmotile cells, which in nature is commonly found attached to diatoms. A life‐cycle model pertaining to both P. globosa and P. antarctica is presented.     

Ultrastructural study of the relations between Leptomonas oncopelti (Noguchi and Tilden), protozoa trypanosomatidae,and the rectal wall of adults of Oncopeltus fasciatus dallas,hemiptera lygaeidae

A laboratory colony of Oncopeltus fasciatus was found to be infected by Leptomonas oncopelti. The flagellates form a carpet attached to the cuticular intima of the rectal glands of adult bugs. The epithelial cells of these glands are characterized by infolded apical plasma membranes associated with mitochondria; the overlying cuticular intima shows endocuticular canals. The Leptomonas are attached by hemidesmosomes, located most often at the tip of the flagella. The Protozoa multiply by budding and the resultant straphangers cling to the parental flagellum. Adhesion of the flagellates to the cuticular lining is so strong that detaching flagellates carry with them the outer part of the epicuticle. Epicuticle repair presumably occurs through the endocuticular canals.     

Relationships between dynamics of red tide-causing raphidophycean flagellates and algicidal micro-organisms in the coastal sea of Japan

Temporal fluctuations of algicidal micro-organisms against the red tide causing raphidophycean flagellates Chattonella antiqua (Hada) Ono and Heterosigma akashiwo (Hada) Hada ex Hara et Chihara were investigated using the microplate most probable number (MPN) method in northern Hiroshima Bay and Harima-Nada, the Seto Inland Sea, in 1992 and 1993. In Har-ima-Nada, both flagellates appeared at low levels (< 1 cell mL^?1), and killer micro-organisms against the two flagellates (C-killer for C. antiqua and H-killer for H. akashiwo) also appeared at low densities (< 2 mL^?1). In northern Hiroshima Bay, C. antiqua cells were scarce (< 1 cell mL^?1), and C-killers occurred at a low level (≤ 3.4 mL^?1). Conversely, red tides of H. akashiwo occurred there in June of both years. The dynamics of H-killers revealed a close relationship with that of H. akashiwo populations. H-killers followed the increase of H. akashiwo cells, reached a maximum level after the beginning of decline of H. akashiwo, maintained a high level for at least 1 week after the crash of bloom, and then decreased. C-killers consistently remained at low densities during the period of H. akashiwo red tides in both 1992 and 1993. Hence, algicidal micro-organisms specifically associated with the occurrence and crash of H. akashiwo red tides, and presumably contributed to the rapid termination of the red tides in the coastal seas such as northern Hiroshima Bay.     

Transmission of Herpetomonas in Laboratory Populations of Drosophila melanogaster

Methods of transmission and the effects of temperature and mites on ageledeme development of Herpetomonas were examined in populations of Drosophila melanogaster maintained in the laboratory. Herpetomonas was observed in feces of infected adults taken from population cages and in the vomitus of clean flies shortly after feeding on a saline suspension of flagellates. Free-swimming flagellates were found in the moist areas of food cups. Adult D. melanogaster became infected when they fed on flagellates taken from the endoperitrophic space, the ectoperitrophic space or the Malpighian tubules. At 25°C the flagellates infected approximately 90% of the host population within 20 days. The high transmission rate was prematurely disrupted if host populations were subjected to changes in temperature. Free-swimming flagellates did not appear to be affected at these temperature changes. Food mites (Tyrophagus) established in the growth media of the fly nearly eliminated the Herpetomonas from Drosophila populations.     

Microbial Community Structure and Dynamics in the Largest Natural French Lake (Lake Bourget)

We investigated the dynamics and diversity of heterotrophic bacteria, autotrophic and heterotrophic flagellates, and ciliates from March to July 2002 in the surface waters (0–50 m) of Lake Bourget. The heterotrophic bacteria consisted mainly of “small” cocci, but filaments (>2 μm), commonly considered to be grazing-resistant forms under increased nanoflagellate grazing, were also detected. These elongated cells mainly belonged to the Cytophaga-Flavobacterium (CF) cluster, and were most abundant during spring and early summer, when mixotrophic or heterotrophic flagellates were the main bacterial predators. The CF group strongly dominated fluorescent in situ hybridization–detected cells from March to June, whereas clear changes were observed in early summer when Beta-proteobacteria and Alpha-proteobacteria increased concomitantly with maximal protist grazing pressures. The analysis of protist community structure revealed that the flagellates consisted mainly of cryptomonad forms. The dynamics of Cryptomonas sp. and Dinobryon sp. suggested the potential importance of mixotrophs as consumers of bacteria. This point was verified by an experimental approach based on fluorescent microbeads to assess the potential grazing impact of all protist taxa in the epilimnion. From the results, three distinct periods in the functioning of the epilimnetic microbial loop were identified. In early spring, mixotrophic and heterotrophic flagellates constituted the main bacterivores, and were regulated by the availability of their resources mainly during April (phase 1). Once the “clear water phase” was established, the predation pressure of metazooplankton represented a strong top-down force on all microbial compartments. During this period only mixotrophic flagellates occasionally exerted a significant bacterivory pressure (phase 2). Finally, the early summer was characterized by the highest protozoan grazing impact and by a rapid shift in the carbon pathway transfer, with a fast change-over of the main predators contribution, i.e., mixotrophic, heterotrophic flagellates and ciliates in bacterial mortality. The high abundance of ciliates during this period was consistent with the high densities of resources (heterotrophic nanoflagellates, algae, bacteria) in deep layers containing the most chlorophyll. Bacteria, as ciliates, responded clearly to increasing phytoplankton abundance, and although bacterial grazing impact could vary largely, bacterial abundance seemed to be primarily bottom-up regulated (phase 3).     

Some Dinophycean Red Tide Plankton Species Generate a Superoxide Scavenging Substance

Recent studies indicate that some raphidophycean red tide flagellates produce substances able to scavenge superoxide, whereas there have been no reports on superoxide scavenger production by dinophycean red tide flagellates. In this study, we examined the superoxide-scavenging activity of aqueous extracts from dinophycean red tide flagellates, Gymnodinium spp., Scrippsiella trochoidea, and Karenia sp., by a luminol analog L-012-dependent chemiluminescence (CL) method and an electron spin resonance (ESR)-spin trapping method, and compared the activity to that of raphidophycean red tide flagellates, Chattonella spp., Heterosigma akashiwo, and Fibrocapsa japonica. In the experiment applying the L-012-dependent CL method, only the aqueous extracts from raphidophycean red tide flagellates showed superoxide-scavenging activity. On the other hand, applying the ESR-spin trapping method, we found that the aqueous extracts from dinophycean red tide flagellates also showed superoxide-scavenging activity. This is the first report on the production of a superoxide-scavenger by dinophycean red tide flagellates.     

The Life Cycle of Trypanoplasma bullocki (Zoomastigophorea: Kinetoplastida)1

The leech Calliobdella vivida (Verrill) is the vector of Trypanoplasma bullocki. At 10°C, infective-stage flagellates were first present in the leech's proboscis sheath five days after feeding. At 5°C, infective-stage flagellates were not present in the leech's proboscis sheath until 10 days after feeding, but at 20°C, flagellates were located there as early as 24 h after feeding. Infected leeches retained flagellates through three subsequent feeds on uninfected fish. When flagellates were first observed in hogchoker, Trinectes maculatus (Bloch & Schneider), they were much larger than infective stages from the leech. Average flagellate length then decreased during early acute phase, but gradually increased thereafter. Peak parasitemia was greater in a hogchoker inoculated by only one leech but held at colder temperature than in a hogchoker inoculated by 45 leeches, suggesting that temperature may be more important than inoculum in determining peak parasitemia. Cell division in the fish host is described. SEM studies of fish blood flagellates revealed a pre-oral ridge and a cytostome.     

Herpetomonas,with Bacterium-like Inclusions,in Malaysian Aedes aegypti and Aedes albopictus*

SYNOPSIS Herpetomonas sp. was found repeatedly in the Malpighian tubules of laboratory-reared male and female Aedes aegypti and Aedes albopictus in Malaysia. The flagellates occurred irregularly, in batches, and were absent during long periods. The data suggest an exogenous source of infection for the mosquitoes, presumably from another insect, probably of another genus. Thirty to 40% of the flagellates of Aedes contained intracytoplasmic rod-shaped structures strongly resembling bacteria. These were found often in groups suggesting intracellular multiplication. They were passed to the Herpetomonas daughter cells during division. Parasitism of Aedes by Herpetomonas is extremely unusual, only one previous record, an inconclusive one, having been found. Parasitism by Herpetomonas containing bacterium-like rods has apparently never been reported.     

Influence of Mercury on the Green Alga Haematococcus lacustris. Inhibition Effects and Recovery of Impact

The influence of mercury ions on germination of the resting cells (aplanospores) and on cell division, cell structure, phototaxis, and photosynthesis during the flagellate stage of Hoemotococcus lacustris was investigated. Aplanospores possess a higher tolerance against mercury ions than flagellates. The reason could be seen in the thicker wall of the resting cells which possibly provide a detoxifying effect by immobilisation of Hg²⁺. This is confirmed by a normal phototactic orientation of flagellates formed from Hg ²⁺-influenced aplanospores. In contrast, a direct addition of Hg²⁺ (0.1 to 1 /*M) to the flagellate stage induced an immediate loss of the flagellates to react phototactically, but it was interesting that the inhibition was overcome with time. Obviously, these Hg²⁺ concentrations influence only the sensory transduction chain, whereas the energetic background is not injured because the velocity of movement and the percentage of motile cells were scarcely affected. This is supported by the high level of the photochemical efficiency of photosystem II, which remains unchanged at 1 uM Hg²⁺. Recovery of photosynthesis from inhibition by 10/iM Hg²⁺ suggests a connection between Hg²⁺ influence and metabolism of the D, protein in the reaction centre of photosystem II. The Hg²⁺ effect was reversed with time in light, but not in darkness, and streptomycin, an inhibitor of chloroplast protein synthesis, prevented recovery. In flagellates, showing no reactivation, exposure to 10uA/l Hg²⁺ caused cell swelling, a loss of the flagella, and a disorganisation in structure of the chloroplast and of nucleus.     

Fine Structure and Taxonomic Position of the Giant Amoeboid Flagellate Pelomyxa palustris1,2

ABSTRACT Specimens of Pelomyxa palustris from five collecting sites had numerous nonmotile flagella. The structures are called flagella because of morphological similarities to flagella and because P. palustris has affinities with amoeboid flagellates. Flagella were photographed on living cells and studied by transmission and scanning electron microscopy. From 64 to 742 flagella per cell were estimated from scanning electron microscopy of ten cells 204 to 1269 μm in length. The nonmotile flagella arise from basal granules which were, in one strain, surrounded by radiating electron-dense microtubules. This strain also had excess axonemal microtubules. Abundant cytoplasmic microtubules were arranged in several different patterns. In about half of the P. palustris cells in which nuclei were studied, microtubules were either apposed to the nuclear membrane in a parallel alignment (with some also radiating) or radiating from the nuclear membrane (with none parallel). Bacteria associated with nuclei were of three characteristic types: Gram-negative rods, Gram-positive rods, and large rods. All nuclei within a given trophozoite had similar perinuclear features. Recent proposals for separation of Pelomyxa to its own phylum (based on its proposed primitive, unique nature) can not be justified. Pelomyxa is a complex, highly specialized organism adapted to live in a specific fresh-water environment. Mastigamoebid amoeboid flagellates of the genera Mastigamoeba, Mastigella, Mastigina, and possibly Dinamoeba are placed with Pelomyxa within the order Pelobiontida Page, 1976, emend., containing two families. Pelomyxidae Schulze, 1877, and Mastigamoebidae Goldschmidt, 1907.     

Effects of grazing and excretion by pelagic mysids (Mysis spp.) on the size structure and biomass of the phytoplankton community

The aim of this study was to determine the effects of pelagic mysids (Mysis mixta and M. relicta) on the biomass and size-structure of the phytoplankton community during the period following the spring bloom. Mysids excreted phosphate (4.5 ± 0.7 nmol ind⁻¹ h⁻¹) and ammonium (123.6 ± 31.6 and 45.0 ± 3.2 nmol ind⁻¹ h⁻¹) and increased the total chlorophyll-a concentration of phytoplankton slightly. However, the presence of mysids affected different size-classes of phytoplankton differently. Mysids mainly grazed on large-sized (>10 μm) phytoplankton cells. Small-sized (<10 μm) algal cells avoided grazing, gained a competitive advantage and were able to utilize the nutrients excreted by mysids. According to this study, both top-down and bottom-up mechanisms simultaneously mould the structure of the phytoplankton community. A large zooplankton biomass might promote the increase of small flagellates by a combination of repleting nutrient stores, selective grazing on large algal cells and heavy predation on protozoa which, consequently, might have a cascading effect on the most favoured protozoan food source, small flagellates.

     

Elucidating the evolution and diversity of Uroglena-like colonial flagellates (Chrysophyceae): polyphyletic origin of the morphotype

ABSTRACT

The Uroglena-like morphotype represents a prototype of a colonial naked chrysophyte, comprising plastid-bearing cells that are arranged as the surface monolayer of the spherical colony. So far, insufficient molecular characterization appears to be the most significant brake on the modern taxonomic revision of this ecologically and morphologically coherent group of organisms. The general aim of this work was to conduct a modern taxonomic revision of Uroglena-like flagellates by using combined molecular, morphological and ultrastructural methodology, complemented by exploring type localities of Uroglena volvox and Uroglenopsis americana in Europe and North America, respectively. On the basis of phylogenetic analysis of concatenated nuclear SSU rDNA and plastid rbcL sequences we show that Uroglena-like colonial flagellates form three genetically and morphologically distinct lineages within the Ochromonadales (Chrysophyceae), distinguished here as Uroglena, Uroglenopsis and Urostipulosphaera gen. nov. The taxonomic status of the other chrysophyte genera with spherical colonies is discussed in light of our findings.     

Light and electron microscopical studies onHafniomonas gen. nov. (Chlorophyceae,Volvocales), a genus resemblingPyramimonas (Prasinophyceae)

Based on light and electron microscopical studies ofPyramimonas reticulata the genusPyramimonas is shown to contain a number of unrelated flagellates.P. reticulata andP. montana are transferred to the new genusHafniomonas, cells of which differ fromPyramimonas in shape, in the absence of scales and hairs on the body and flagellar surfaces, in details of the chloroplast, the position of the nucleus, the Golgi apparatus, the internal structure of the flagellar apparatus, and in cell division. The prasinophytePyramimonas contains a characteristic association of a large microbody and a rhizoplast, situated on the nuclear surface. A similar association is being found in an increasing number of prasinophycean flagellates, but is absent inHafniomonas, which is considered related to chlorophycean rather than prasinophycean flagellates. The phylogenetic position ofHafniomonas is discussed, based in particular on details of the unique flagellar apparatus.     

Chemosensory behavioural response of freshwater phytoplanktonic flagellates

Unlike behavioural responses to physical gradients, active responses to chemical gradients, and their physiological and ecological implications, have rarely been studied in freshwater phytoplanktonic flagellates. This study used microscale preference chambers to investigate the population and individual cell responses of five species exposed to four chemical gradients which commonly develop with depth in lakes: phosphate, oxygen, carbon dioxide and pH. Upon exposure of nutrient‐replete and ‐depleted cells to a phosphate gradient, only nutrient‐depleted cells of the autotrophic Chlamydomonas moewusii responded, accumulating at high concentrations. In contrast, all species responded to an oxygen gradient with Ceratium furcoides, Chlamydomonas moewusii, Dinobryon sertularia and Plagioselmis nannoplanctica preferring high concentrations whereas Euglena gracilis preferred low concentrations. In addition, all species displayed a strong affinity for carbon dioxide which was not mediated by detecting pH. Analysis of the swimming trajectories of individual cells showed that directed chemotaxes, rather than speed‐dependent chemokineses, were responsible for the observed preferences. These complex and diverse species‐dependent chemosensory responses may optimize photosynthesis, facilitate nutrient retrieval during migration, increase growth rate and may influence spatial and temporal distribution, contributing to the delineation of niche separation in phytoplanktonic flagellates.     

Small but Manifold – Hidden Diversity in “Spumella‐like Flagellates”

Colourless, nonscaled chrysophytes comprise morphologically similar or even indistinguishable flagellates which are important bacterivors in water and soil crucial for ecosystem functioning. However, phylogenetic analyses indicate a multiple origin of such colourless, nonscaled flagellate lineages. These flagellates are often referred to as “Spumella‐like flagellates” in ecological and biogeographic studies. Although this denomination reflects an assumed polyphyly, it obscures the phylogenetic and taxonomic diversity of this important flagellate group and, thus, hinders progress in lineage‐ and taxon‐specific ecological surveys. The smallest representatives of colourless chrysophytes have been addressed in very few taxonomic studies although they are among the dominant flagellates in field communities. To overcome the blurred picture and set the field for further investigation in biogeography and ecology of the organisms in question, we studied a set of strains of specifically small, colourless, nonscaled chrysomonad flagellates by means of electron microscopy and molecular analyses. They were isolated by a filtration‐acclimatisation approach focusing on flagellates of around 5 μm. We present the phylogenetic position of eight different lineages on both the ordinal and the generic level. Accordingly, we describe the new genera Apoikiospumella, Chromulinospumella, Segregatospumella, Cornospumella and Acrispumella Boenigk et Grossmann n. g. and different species within them.