Nanoflagellates Research Articles

Micromonas, a small pigmented flagellate, predominates the nanoflagellate and photosynthetic picoeukaryote communities in the northern South China Sea.

A small pigmented flagellate, Micromonas, is prevalently distributed in coastal and pelagic waters. However, there have been few studies conducted to quantify their abundance in the marginal seas of the Northwest Pacific Ocean. In this study, we used fluorescent in situ hybridization with tyramide signal amplification (TSA-FISH) to reveal the spatial distribution of Micromonas in the northern South China Sea (SCS). On average, the abundance of Micromonas was 317 cells mL-1, with the average proportions in the nanoflagellates (NF) and photosynthetic picoeukaryotes (PPE) communities being 10.94% and 15.39%, respectively. This indicates a wide distribution and dominance of this genus in the studied area. The relationships between Micromonas abundance and various environmental factors suggested that biotic correlations play more important roles than physicochemical filtering on Micromonas assemblage. This may indicate a broad environmental adaptation spectrum of this genus through its flexibility in terms of resource acquisition strategies. In summary, this study provides insight into the spatial distribution pattern of Micromonas and highlights its crucial contribution to the composition of NFs and PPE communities, which rely on biological interaction to respond to the changing environmental conditions in the northern SCS.

The first arctic strain of Rhizochromulina: Morphology, ultrastructure, and position in the evolutionary tree of the order Rhizochromulinales (Heterokontophyta, Dictyochophyceae)

Rhizochromulina marina is a unicellular amoeboid alga capable of forming flagellate cells; it is a single validly named species in the genus. Besides, there are numerous environmental sequences and undescribed strains designated as Rhizochromulina sp. or R. marina. The biogeography of the genus is understudied: rhizochromulines from the Indian, Southern, and Arctic Oceans are unknown. Here, we present the description of Rhizochromulina sp. B44, which was for the first time isolated from an arctic habitat. Biofilms of this microalga grow at the bottom of a culture vessel, where neighbouring amoeboid cells form associations through a common network of pseudopodia, i.e. meroplasmodia. Pseudopodia branch, anastomose mainly during meroplasmodia formation, and are supported by microtubules that arise from the perinuclear zone. Actin filaments are localized in the cytoplasm and can be revealed only near the bases of pseudopodia. We succeeded in inducing the transformation of amoeboid cells into flagellates using a prolonged agitation of cultures. Morphological and molecular analyses revealed that the studied strain is most closely related to the type strain of R. marina. At the same time, 18S rDNA sequences of early branching-off rhizochromulinids differ significantly from Rhizochromulina sp. B44, suggesting a high divergence at the genus level.

Behavior and surface properties of microalgae indicate environmental changes

We conducted a microcosm experiment under near-natural conditions to investigate the effects of environmental stressors temperature and salinity on the response of three microalgal species. The response of microalgae to increased temperature and altered salinity is species-specific, with cell barrier complexity playing an important protective role. At decreasing salinity, the green flagellate cells of Dunaliella tertiolecta vibrate around the point and become stiff while their physiological activity is at its highest, which may indicate that organic matter is being released into the medium. At the highest salinity, Tetraselmis suecica showed the highest growth rate along with the hydrophobic behavior of the cells, which is a favorable condition for the formation of aggregates. Under these conditions, the cells could enter the cyst stage, while the content of polar lipids could mediate cell adhesion to the natural interfaces. Cylindrotheca closterium, a diatom with an organosilicate cell wall, also showed the highest physiological activity at decreasing salinity. However, the cells were softest and exhibited hydrophilic behavior, implying that released organic material could alter the surface properties of the diatom. This study provides insight into the behavioral, mechanical, and molecular changes of microalgae under near-natural conditions, which may contribute to a fundamental understanding of how biochemistry and mechanics interact to control the functional behavior of microalgal cells in climatically altered aquatic systems.

Morphological, molecular, and life cycle characteristics of Phaeocystis globosa Scherffel (Prymnesiophyceae) in the Southeast China Sea

Phaeocystis globosa blooms frequently occur in the Southeast China Sea and cause significant negative impacts on coastal ecology and mariculture. The P. globosa blooms in southeastern China are very different compared to those of European strains, suggesting that differences may exist in their morphological, phylogenetic, and life history traits. In this study, seven strains of P. globosa isolated from Southeast China Sea that were typical strains of algal blooms in the region, in addition to one strain from the Gulf of Mexico (CCMP629), were comprehensively evaluated to better understand region-specific differences of the species. Significant differences were not observed in the internal cell structures and other characteristics compared to those of European strains, while differences in cell surface structures were apparent. For example, small and large flagellated Chinese P. globosa cells exhibited two flagella with slightly unequal lengths and a short haptonema, the surfaces of small flagellated cells were not covered by scales, and colony cell diameters were smaller. 18S rRNA sequence phylogenetic analysis also revealed that P. globosa comprised a species complex with two ecotypes (warm- and cold-water types), of which the strains from the southeastern coast of China and CCMP629 belonged to the warm-water type. In addition, the life cycles and variable modes of P. globosa colony formation were evaluated in detail. The algal bloom may be due to the rapid colonies formation by budding and colony fragments. These results provide new insights into the life cycle of P. globosa and highlight the differences in morphological and phylogenetic relationships between strains from the southeast coast of China and those from coastal European regions.

Generation of Reactive Oxygen Species (ROS) by Harmful Algal Bloom (HAB)-Forming Phytoplankton and Their Potential Impact on Surrounding Living Organisms.

Most marine phytoplankton with relatively high ROS generation rates are categorized as harmful algal bloom (HAB)-forming species, among which Chattonella genera is the highest ROS-producing phytoplankton. In this review, we examined marine microalgae with ROS-producing activities, with focus on Chattonella genera. Several studies suggest that Chattonella produces superoxide via the activities of an enzyme similar to NADPH oxidase located on glycocalyx, a cell surface structure, while hydrogen peroxide is generated inside the cell by different pathways. Additionally, hydroxyl radical has been detected in Chattonella cell suspension. By the physical stimulation, such as passing through between the gill lamellas of fish, the glycocalyx is easily discharged from the flagellate cells and attached on the gill surface, where ROS are continuously produced, which might cause gill tissue damage and fish death. Comparative studies using several strains of Chattonella showed that ROS production rate and ichthyotoxicity of Chattonella is well correlated. Furthermore, significant levels of ROS have been reported in other raphidophytes and dinoflagellates, such as Cochlodinium polykrikoides and Karenia mikimotoi. Chattonella is the most extensively studied phytoplankton in terms of ROS production and its biological functions. Therefore, this review examined the potential ecophysiological roles of extracellular ROS production by marine microalgae in aquatic environment.

Living particulate fluxes in throughfall and stemflow during a pollen event

Pollen shedding can produce rapid, abundant exchanges of nutrient-rich biomass from plant canopies to the surface. When pollen deposits onto understory plants, it can be washed off during storms via throughfall (a drip flux) and stemflow (a flux down plant stems). Pollen deposition may also alter the organismal community on plant surfaces, changing other biological particulates transported by throughfall and stemflow. We report concentrations and fluxes of pollen and other biological particulates (flagellate cells, nematodes, rotifers, mites and hexapodans) in throughfall and stemflow from an understory forb, Eupatorium capillifolium (Lam. dogfennel), during a Pinus palustris (Mill. longleaf pine) pollen shedding event, then compare these results to observations collected when pollen was absent. Pollen flux was 95.6 × 106 grains ha−1 season−1 from dogfennel canopies (63% and 37% transported by throughfall and stemflow, respectively), representing 0.1–3.2 g ha−1. Median concentrations in flagellates, nematodes and rotifers for throughfall and stemflow were higher during pollen shedding; however, mites and hexapodan concentrations were similar regardless of pollen presence. This is the first report of flagellate and hexapodan concentrations in canopy drainage waters. Flagellate concentrations were higher than for other organisms—being similar to those reported for streams, 105–107 cells L−1—and hexapodan fluxes were ~ 50 individuals m−2 per 1 cm of rainfall. These results indicate that throughfall and stemflow can (i) transport ecologically relevant amounts of pollen and organisms from the phyllosphere to the surface, and (ii) that the composition and flux of biological particulates can change markedly during pollen shedding.

Eyespot structure and its function in photobehaviors of phytoflagellate

Eyespot structure and its function in photobehaviors of phytoflagellate

Colony formation in <i>Phaeocystis antarctica</i>: connecting molecular mechanisms with iron biogeochemistry

Abstract. Phaeocystis antarctica is an important phytoplankter of the Ross Sea where it dominates the early season bloom after sea ice retreat and is a major contributor to carbon export. The factors that influence Phaeocystis colony formation and the resultant Ross Sea bloom initiation have been of great scientific interest, yet there is little known about the underlying mechanisms responsible for these phenomena. Here, we present laboratory and field studies on Phaeocystis antarctica grown under multiple iron conditions using a coupled proteomic and transcriptomic approach. P. antarctica had a lower iron limitation threshold than a Ross Sea diatom Chaetoceros sp., and at increased iron nutrition (> 120 pM Fe') a shift from flagellate cells to a majority of colonial cells in P. antarctica was observed, implying a role for iron as a trigger for colony formation. Proteome analysis revealed an extensive and coordinated shift in proteome structure linked to iron availability and life cycle transitions with 327 and 436 proteins measured as significantly different between low and high iron in strains 1871 and 1374, respectively. The enzymes flavodoxin and plastocyanin that can functionally replace iron metalloenzymes were observed at low iron treatments consistent with cellular iron-sparing strategies, with plastocyanin having a larger dynamic range. The numerous isoforms of the putative iron-starvation-induced protein (ISIP) group (ISIP2A and ISIP3) had abundance patterns coinciding with that of either low or high iron (and coincident flagellate or the colonial cell types in strain 1871), implying that there may be specific iron acquisition systems for each life cycle type. The proteome analysis also revealed numerous structural proteins associated with each cell type: within flagellate cells actin and tubulin from flagella and haptonema structures as well as a suite of calcium-binding proteins with EF domains were observed. In the colony-dominated samples a variety of structural proteins were observed that are also often found in multicellular organisms including spondins, lectins, fibrillins, and glycoproteins with von Willebrand domains. A large number of proteins of unknown function were identified that became abundant at either high or low iron availability. These results were compared to the first metaproteomic analysis of a Ross Sea Phaeocystis bloom to connect the mechanistic information to the in situ ecology and biogeochemistry. Proteins associated with both flagellate and colonial cells were observed in the bloom sample consistent with the need for both cell types within a growing bloom. Bacterial iron storage and B12 biosynthesis proteins were also observed consistent with chemical synergies within the colony microbiome to cope with the biogeochemical conditions. Together these responses reveal a complex, highly coordinated effort by P. antarctica to regulate its phenotype at the molecular level in response to iron and provide a window into the biology, ecology, and biogeochemistry of this group.

The Physiology of Leishmania.

The metabolism of all members of the genus Leishmania is characterized by aerobic fermentations, which lead to the excretion of various partly oxidized metabolic endproducts. The flagellates utilize several carbohydrates freely, but hardly anything is known about the intermediate carbohydrate metabolismo At suitably low pH they are able to consume intermediates of the Krebs cycle, but the presence of a functional tricarboxylic acid cycle has not yet been demonstrated conclusively. Recent data on lipid metabolism and biosynthesis have revealed interesting paralleles to phytoflagellates, as have newer studies on nucleic acids. The composition of the proteins of Leishmania is essentially unknown, but the fact that under certain experimental conditions numerous amino acids are leaked into the medium, indicates that probably all common amino acids are leaked into the medium, indicates that probably all common amino acids are present. The respiration of the flagellates is probably characterized by heavy metal catalysis, but it is uncertain whether or not they contain a fully functional cytochrome system.

A population of giant tailed virus-like particles associated with heterotrophic flagellates in a lake-type reservoir

Using transmission electron microscopy (TEM), a population of giant virus-like par- ticles (VLPs) with a head diameter of ca. 405 nm and a flexible ca. 1100 nm long tail was detected in a lake-type reservoir. These giant VLPs were abundant in situ at the start of a survey period (3.3 × 10 4 particles ml �1 ) and increased by 7-fold within 96 h. This VLP population vanished in dialysis bag incubations of 0.8 µm-filtered reservoir water (free of bacterivorous flagellates) but increased markedly in the enhanced bacterivory treatment, i.e. 5 µm filtered water. In the latter, incubation, heterotrophic nanoflagellate (HNF) abundance increased approximately 15-fold dur- ing the study. A multiple regression analysis using microbial abundances and grazing rates as parameters indicated that 78% of the variability in the abundance of giant VLPs was explained by HNF abundance and grazing rates. Our data support the hypothesis that this virus population infects flagellates. Observation of a presumptive lysing flagellate cell suggests a viral burst size of 15. Estimations of decay and net production rates from dialysis bag incubations indicate that lysis due to giant viruses could cause between 10 to 60% of the mortality of the total flagellate commu- nity and, thus, viruses are potentially a significant factor shaping the population dynamics of fl a gellates in freshwater.

Eukaryotic Microbial Communities Associated with Rock- dwelling Foliose Lichens: A Functional Morphological and Microecological Analysis

Lichens are widely recognized as important examples of a fungal-algal or fungal-cyanophyte symbiosis; and in some cases they are a major food source for some animal grazers such as caribou ( Rangifer tarandus ), especially in the Arctic during winter. However, relatively little is known about the ecology of their co-associated bacterial and protistan communities. This is one of the first reports of an analysis of microbial communities associated with rock-dwelling foliose lichens ( Flavoparmelia sp.), including a more detailed analysis of the microbial communities associated with segments of the shield-like, radially arranged lobes. Samples were taken from lichens on granite boulders beneath an oak and maple tree stand on the Lamont-Doherty Earth Observatory Campus, Palisades, N.Y. The bacteria and protist members of the lichen associated microbial communities are comparable to recently reported associations for foliose lichens growing on tree bark at the same locale, including the presence of large myxomycete plasmodial amebas, heterotrophic nanoflagellates, and naked and testate amebas. To obtain evidence of possible differences in the microecology of different portions of each radial lobe, three segments of the radial lobe in the shield-like lichen were sampled: 1) inner, more mature, central segment; 2) middle section linking the central and peripheral segments; and 3) outer, peripheral, usually broader, less closely attached segment. The mean densities (number/g) and biomasses (µg/g) of bacteria and heterotrophic nanoflagellates were highest in the older central segment and lowest in the peripheral segment of the radial lobes, especially when expressed on moist weight basis. Large myxomycete plasmodial amebas were typically located in the outermost segment of the radial lobe. The proportion of vannellid amebas ( Vannella spp. and Cochliopodium spp.) were significantly more abundant in the samples of the inner lobes compared to non-vannellid amebas that were more prevalent in the outer lobes. The outer segment of the thallus lobe was typically more spongiose and absorbed more water per unit weight (based on a wet/dry-weight ratio) than the innermost segment. In general, patterns of densities and taxonomic composition of bacteria and eukaryotic microbes intergraded from the inner most segment to the outer part of each lobe – indicating a possible microecological gradient, coincident with the age-related and morphological radial gradations of the lobe. Overall, the evidence shows that the radial variation in the morphology and age-related variables of the three lobe segments may affect the microenvironment of the lobe segments and hence influence the organization of the microbial communities within each segment.

황토와 화학물질 살포에 의한 적조생물Cochlodinium polykrikoides 제어에 따른 미소생물그룹의 단주기변화

본 연구는 마이크로코즘에서 적조생물 Cochlodinium polykrikoides을 살조하기 위해 사용된 화학물질과 황토의 처리 후 미소생물그룹의 단주기 변화를 파악하였다. 황토 4g 과 10g에서 적조생물의 살조효과는 20%이하로 낮게 관찰된 반면, 화학물질(TD49)의 0.8 μM 에서는 대상생물이 85%이상 제어되었다. 미소생물그룹에서 박테리아는 모든 실험군에서 조사 1 일 후 현저하게 증가하였고, 2일 후 가장 높게 관찰된 후 점차적으로 감소하는 경향을 관찰하였다. 대조적으로 종속영양편모 충은 조사 3-5일 경과 후 현저하게 높게 증가하였다. TD49처리군에서 박테리아가 2일후 점차적으로 감소한 것은 포식자인 HNF의 증가로 기인된 것으로 파악되었다. 또한 피각을 형성하지 않는 섬모충 Uronema sp.,의 증가는 박테리아의 증가 후 2-3일의 시간차를 두고 반응하는 특색을 관찰하였다. 즉 이는 적조생물이 살조된 후 분해되는 과정에서 박테리아의 현저한 증식을 일으켰고, 이와 함께 포식자 HNF와 Uronema sp.는 일정의 시간차를 두고 높은 개체수를 유지 한 것으로 판단되었다. 이와 같은 경향은 살조물질 TD49처리군에서 두드려졌다. 특히. 사이즈가 큰 무각섬모충 Euplotes sp. 개체수는 HNF와 Uronema sp.의 현저한 증가 후 높게 관찰되는 특성을 보였다. 결과적으로 살조제 TD49물질은 미소생물그룹에 긍정적인 효과 를 가져왔고, 이는 박테리아, HNFs 섬모충으로 이어지는 먹이망의 에너지 흐름이 효율적으로 작용하고 있다는 것을 시사할 수 있었다.

Male gonads morphology, spermatogenesis and sperm ultrastructure of the seahorse Hippocampus guttulatus (Syngnathidae)

AbstractTestes morphology, spermatogenetic process and mature sperm ultrastructure were analysed in Hippocampus guttulatus, using both light and transmission electron microscopy. Both testes were organized in a single large germinal compartment, with a central lumen. Spermatocysts only contained spermatogonia and primary spermatocytes. Inside the testis lumen, together with mature sperm, two types of large mono‐nucleate cells, flagellate and aflagellate, were present. Both types of cells were interpreted as developing germ cells precociously released inside the testis lumen, where their maturation was completed. According to the different morphological features of the nuclei, such as chromatin condensation degree, aspect of the nuclear fossa and others, the flagellate cells were unquestionably developing spermatids. On the contrary, the developmental stage of the aflagellate was more difficult to interpreted. They could be secondary spermatocytes or young spermatids. No dimorphic sperm were recognizable, the only sperm type observed have features typical of the intro‐sperm reports in other syngnathids species. They had a cylindrical head, a short midpiece, characterized by two mitochondrial rings housed inside a cytoplasmic collar, and a long flagellum. These and previous data about the same topic reported on other syngnathids species were compared and discussed.

Effects of freshwater input and mariculture (bivalves and macroalgae) on spatial distribution of nanoflagellates in Sungo Bay, China

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 6:191-203 (2015) - DOI: https://doi.org/10.3354/aei00124 Effects of freshwater input and mariculture (bivalves and macroalgae) on spatial distribution of nanoflagellates in Sungo Bay, China Jiachang Lu1, Lingfeng Huang2,*, Yuanrong Luo2, Tian Xiao3, Zengjie Jiang4, Linnan Wu1 1College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, PR China 2Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, Xiamen University, Xiamen 361102, PR China 3Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China 4Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, PR China *Corresponding author: huanglf@xmu.edu.cn ABSTRACT: Sungo Bay in northern China has been used for rearing bivalves and macroalgae for several decades. The bivalve culture areas (B-area) are located in the bay head, and the macroalgae culture areas (M-area) are located outside of the B-area. In field investigations, we compared the nanoflagellates (NF) in the B-area and the M-area during 4 seasons. After the field investigations, enclosure experiments were conducted during summer to study the effects of mariculture (bivalves and macroalgae) on NF. In the warm seasons (summer and autumn), during which there was an obvious freshwater input to the bay (especially during summer), NF abundance was negatively related to salinity and was higher in the B-area than in the M-area. In the enclosure experiments, an increase in NF abundance was observed after Day 4 in the bivalve enclosure, but not in the macroalgae enclosure. Considering that the B-area was the area of lower salinity, and the season of largest freshwater input was also the optimal growth season for bivalves, we suggest that the spatial distribution of NF in the warm seasons in Sungo Bay may be influenced by both freshwater input and mariculture. KEY WORDS: Nanoflagellates · Mariculture · Freshwater input · Sungo Bay Full text in pdf format PreviousCite this article as: Lu J, Huang L, Luo Y, Xiao T, Jiang Z, Wu L (2015) Effects of freshwater input and mariculture (bivalves and macroalgae) on spatial distribution of nanoflagellates in Sungo Bay, China. Aquacult Environ Interact 6:191-203. https://doi.org/10.3354/aei00124 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 6, No. 2. Online publication date: February 26, 2015 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2015 Inter-Research.

Distribution of nanoflagellates in five water masses of the East China Sea in autumn and winter

The variations of abundance, biomass and trophic structure of nanoflagellates (NF) among five typical water masses in the East China Sea were investigated in autumn (November 19–December 23, 2006) and winter (February 22–March 11, 2007). It was found that water mass had a significant impact on the distribution of NF. Either in autumn or in winter, the highest abundance and biomass of NF were recorded in the East China Sea Shelf Mixing Water (ECSSMW), and the lowest in the Kuroshio Subsurface Water (KSSW). While in the East China Sea Coastal Water (ECSCW), the abundance and biomass of both heterotrophic nanoflagellates (HNF) and pigmented phototrophic nanoflagellates (PNF) were only slightly higher than that in Taiwan Strait Water (TSW) and Kuroshio Surface Water (KSW). In respect to the seasonal variation, the abundance and biomass of NF in TSW declined in winter, while in other 4 water masses, they showed an increasing trend from autumn to winter, mainly due to the decrease (in TSW) or increase (in ECSCW, ECSSMW, KSW and KSSW) of HNF. The distribution pattern of abundance- or biomass-based PNF/HNF ratio was found to be correlated to the nutrient level of the water mass. Results of Pearson correlation analysis and principle component analysis indicated that PNF was mainly constrained by nutrient supply, and HNF was controlled by food availability in the East China Sea.

Ultrastructure of the Algivorous Amoeboflagellate Viridiraptor invadens (Glissomonadida, Cercozoa)

The family Viridiraptoridae represents a morphologically and ecologically distinct lineage of glissomonad flagellates (Cercozoa, Rhizaria). It currently comprises two highly specialised, algivorous genera inhabiting freshwater ecosystems, Orciraptor and Viridiraptor, for which ultrastructural data were lacking. In this study, the ultrastructure of Viridiraptor invadensHess et Melkonian, the sole described species of the viridiraptorid type genus, has been studied by transmission and scanning electron microscopy. In particular the flagellar transitional region and basal apparatus, both reconstructed from serial sections, revealed ultrastructural traits, that agree with the phylogenetic placement of the viridiraptorids within Glissomonadida: The transitional region contains a distal plate/collar complex and the basal apparatus comprises two ventral posterior roots and an anterior root, all known from other glissomonads. However, two additional small microtubular roots, two conspicuous rhizoplasts and probasal bodies present during interphase represent novel characteristics. Furthermore, an acorn/V-shaped filament system was discovered at the proximal end of the flagellar transitional region and used to establish a basal body triplet numbering system for flagellate cells of the Rhizaria. Finally, ultrastructural data on perforated algal cell walls suggest that the previously described reticulocyst of Viridiraptor represents an extrusome-derived, mesh-like coat supporting the invasion/feeding process.

Studies on woloszynskioid dinoflagellates VI: description of Tovellia aveirensis sp. nov. (Dinophyceae), a new species of Tovelliaceae with spiny cysts

A new species of Tovellia, T. aveirensis, is described on the basis of light (LM) and scanning electron microscopy (SEM) of motile cells and resting cysts, complemented with transmission electron microscopy (TEM) of flagellate cells and phylogenetic analysis of partial sequences of the large subunit ribosomal rRNA gene. Both vegetative cells and several stages of a life cycle involving sexual reproduction and the production of resting cysts were examined in cultures established from a tank in the University of Aveiro campus. Vegetative cells were round and little compressed dorsoventrally; planozygotes were longer and had a proportionally larger epicone. Chloroplast lobes were shown by TEM to radiate from a central, branched pyrenoid, although this was difficult to ascertain in LM. The amphiesma of flagellate cells had mainly 5 or 6-sided vesicles with thin plates, arranged in 5–7 latitudinal series on the epicone, 3–5 on the hypocone. The cingulum had 2 rows of plates, the posterior row extending into the hypocone and crossed by a series of small projecting knobs along the lower edge of the cingulum. A line of narrow amphiesmal plates extended over the cell apex, from near the cingulum on the ventral side to the middle of the dorsal side of the epicone. Eight or 9 narrow amphiesmal plates lined each side of this apical line of plates (ALP). Resting cysts differed from any described before in having numerous long, tapering spines with branched tips distributed over most of the surface. Most mature cysts showed an equatorial constriction. Neither cysts nor motile cells were seen to accumulate red cytoplasmic bodies in any stage of the cultures. The phylogenetic analysis placed, with high statistical support, the new species within the genus Tovellia; it formed a clade, with moderate support, with T. sanguinea, a species notable for its reddening cells.

Promastigote Existence in Infected Lesions of Cutaneous Leishmaniasis

Leishmaniasis is an endemic parasitic disease in 88 countries. It is widely distributed throughout the world, caused by vector-borne, obligate, intracellular hemoflagellates of the genus leishmania. The parasite continues its life cycle transforming to promastigote in the midgut of the sandfly vector and is transmitted to the human host in the form of promastigote through the bite of the sandfly. Other less encountered forms of transmissionare because of a laboratory accident, direct person-to-person transmission, organ transplant and blood transfusion. There is evidence that leishmaniasis may be transmitted either in utero or during the peripartum period. The promastigote form is considered the primary organism of disease transmission between the vector and the host. By not having a chance to continue its life cycle and transform into promastigote within the vector sandfly, and considering the many different routes of transmission other than the sandfly bites, it is reasonable to assume an alternative possible existence of the promastigote form of the parasite in the infected lesion of cutaneous leishmaniasis in human host. The information presented below indicates that a real transformation of amastigote to promastigote form occurs within the human host cutaneous lesion in the extracellular fluid after the macrophage membrane eruption and the amastigote release. New techniques are recommended for future studies to confirm these findings including realtime Polymerase chain reaction (PCR) and applying the immunohistochemistry techniques using novel monoclonal antibody (mAb) against the parasite flagellate (promastigote form) cell wall component.

Evidence for Sex and Recombination in the Choanoflagellate Salpingoeca rosetta

Nearly all animals reproduce sexually through the production and fusion of sperm and egg cells, yet little is known about the ancestry of animal sexual reproduction. Moreover, the sexual cycle of the closest living relatives of animals, the choanoflagellates, remains completely unknown. The choanoflagellate Monosiga brevicollis possesses a "meiotic toolkit" of genes, but the lack of polymorphisms detected during genome sequencing precluded inferences about its ploidy or sexual cycle. Here, we report that a related choanoflagellate, Salpingoeca rosetta, has a sexual life cycle and transitions between haploid and diploid states. Haploid cultures of S. rosetta became diploid in response to nutrient limitation. This ploidy shift coincided with anisogamous mating, during which small flagellated cells fused with larger flagellated cells. Distributions of polymorphisms in laboratory strains of S. rosetta provided independent evidence of historical recombination and mating. The ability of S. rosetta to produce morphologically differentiated gametes and to engage in sexual reproduction has implications for both reconstructing the evolution of sex in the progenitors of animals and establishing classical genetics in choanoflagellates.

Mixotrophic haptophytes are key bacterial grazers in oligotrophic coastal waters

Grazing rate estimates indicate that approximately half of the bacterivory in oligotrophic oceans is due to mixotrophic flagellates (MFs). However, most estimations have considered algae as a single group. Here we aimed at opening the black-box of the phytoflagellates (PFs) <20 μm. Haptophytes, chlorophytes, cryptophytes and pigmented dinoflagellates were identified using fluorescent in situ hybridization or by standard 4',6-diamidino-2-phenylindole staining. Their fluctuations in abundance, cell size, biomass and bacterivory rates were measured through an annual cycle in an oligotrophic coastal system. On average, we were able to assign to these groups: 37% of the total pico-PFs and 65% of the nano-PFs composition. Chlorophytes were mostly picoplanktonic and they never ingested fluorescently labeled bacteria. About 50% of the PF <20 μm biomass was represented by mixotrophic algae. Pigmented dinoflagellates were the least abundant group with little impact on bacterioplankton. Cryptophytes were quantitatively important during the coldest periods and explained about 4% of total bacterivory. Haptophytes were the most important mixotrophic group: (i) they were mostly represented by cells 3-5 μm in size present year-round; (ii) cell-specific grazing rates were comparable to those of other bacterivorous non-photosynthetic organisms, regardless of the in situ nutrient availability conditions; (iii) these organisms could acquire a significant portion of their carbon by ingesting bacteria; and (iv) haptophytes explained on average 40% of the bacterivory exerted by MFs and were responsible for 9-27% of total bacterivory at this site. Our results, when considered alongside the widespread distribution of haptophytes in the ocean, indicate that they have a key role as bacterivores in marine ecosystems.