Abstracts and Proceedings

Spring Conference 2007:

This meeting took place at Warwick University, on 29th-31st March 2007. Abstracts and proceedings from this meeeting are given below.

Plenary

Evolution of cAMP Signaling in Amoebas

Pauline Schaap
School of Life Sciences, University of Dundee, MSI/WTB/JBC complex, Dundee DD1 5EH, UK p.schaap@dundee.ac.uk

The social amoebas represent a simple form of multicellular life, where starving amoebas aggregate to build a fruiting body. A molecular phylogeny based on two conserved genes was constructed for all 75 known species of social amoebas. A set of 20 morphological characters was plotted onto the phylogeny, showing novel and unexpected trends in the evolution of morphological complexity. The evolutionary youngest taxon, group 4, shows a trend towards formation of large unbranched fruiting bodies that are buttressed by novel support structures. This trend is correlated with the use of cyclic AMP (cAMP) as a secreted chemoattractant to coordinate cell aggregation. I will discuss recent work aimed to trace the evolutionary history of cAMP signaling. This work shows that the chemoattractant role of cAMP in aggregation arose through recruitment of a pathway that originally served to coordinate fruiting body morphogenesis. A second role for intracellular and extracellular cAMP in spore formation and regulation of spore dormancy appears to be derived from an ancestral role in encystation of solitary amoebas.

Amoebae and the evolution of cell movement

Robert Insall
School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K. R.H.Insall@bham.ac.uk

The mechanisms that drive crawling cell migration are surprisingly well conserved between Dictyostelium, other amoebas, and the cells of higher animals. I will discuss current models of how actin drives cell migration, the proteins involved (in particular regulators of the Arp2/3 complex such as WASP and SCAR/WAVE), and the implications for the evolution of cell movement and actin biology.

Why doesn’t cheating pay? Genetics of conflict, cooperation and cell fate in Dictyostelium

Chris Thompson
Faculty of Life Sciences, Michael Smith Building, Oxford Road, Manchester M13 9PT christopher.thompson@manchester.ac.uk

Developmental and sociobiology are major areas of interest in the biomedical and biological sciences due to their fundamental importance in shaping life. These fields are often considered distinct. However, in the slime mould Dictyostelium discoideum they are interlocked so that the cell communication pathways that control cell fate choice, patterning and proportioning also regulate social behaviour.

Dictyostelium amoebae normally exist as single cells. However, a magnificent social cycle is induced in response to starvation. Up to several hundred thousand amoebae aggregate together, initially forming a migratory slug with its major cell types organized into tissues. Ultimately a fruiting body forms, in which about 20% of cells vacuolise and die to make a cellular stalk. Developmental biologists consider this a problem of cell fate choice: how do cells choose between the stalk and spore fate? Sociobiologists consider this a problem of altruism and cheater control: since stalk cells sacrifice themselves to aid spore dispersal, what prevents the emergence of cheaters that gain the benefit without paying their fair share of the cost?

Major social and developmental questions are therefore interlinked in Dictyostelium. For example, one cheating mechanism would be to ignore the normal controls of cell fate choice and pattern formation. Those cells more likely to become prespore should cheat in chimera. Thinking about Dictyostelium development in this way has illustrated novel concepts in social evolution whilst contributing to our understanding of cell signaling.

I will present the results of recent findings that illustrate the power of using genetic approaches to identify the signaling pathways that control cell fate choice and social behaviour. These data not only contribute to our understanding of cooperative behaviour and cell signaling in Dictyostelium, but should also provide insights into the principles of cell fate choice and social evolution in other organisms.

Evolution of Entamoeba's unique tRNA gene arrays

C. Graham Clark
Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine. Keppel Street, London WC1E 7HT, England, GB

Genome sequencing of Entamoeba histolytica revealed that almost all its tRNA genes are organised into tandem arrays that make up over 10% of the genome. There are 25 distinct array units containing up to 5 tRNA genes each. Between adjacent genes in array units are complex short tandem repeats. To investigate the origins and evolution of this unique gene organisation, we have determined the short tandem repeat structure in other isolates of E. histolytica and have undertaken genome surveys to obtain the array unit organisation for four other species of Entamoeba: E. dispar, E. moshkovskii, E. terrapinae and E. invadens. The results of those studies will be presented.

Reconstructing the Network Controling Commitment to Cell Differentiation in the Eukaryote Physarum polycephalum

Wolfgang Marwan
, Lehrstuhl für Regulationsbiologie, Otto-von-Guericke-Universität and Max-Planck-Institut für Dynamik komplexer technischer Systeme, Sandtorstraße 1, 39106 Magdeburg, Gemany marwan@mpi-magdeburg.mpg.de

Somatic complementation by fusion of two mutant cells and mixing of their cytoplasms occurs when the genetic defect of one fusion partner is cured by the functional gene product provided by the other. We have found that complementation of mutational defects in the network mediating stimulus-induced commitment and sporulation of Physarum polycephalum may reflect time-dependent changes in the signaling state of its molecular building blocks. Network perturbation by fusion of mutant plasmodial cells in different states of activation, and the time-resolved analysis of somatic complementation effects can be used to systematically probe network structure and dynamics. Time-resolved somatic complementation quantitatively detects regulatory interactions between the functional modules of a network, independent of their biochemical composition or subcellular localization, and without being limited to direct physical interactions. The regulatory network controling commitment and sporulation is reconstructed from experimental results using a hierarchical stochastic Petri Net-based modeling and simulation framework. The Petri Net consistently represents network structure and dynamics and quantitatively reproduces genetic, biochemical, physiological and time-resolved somatic complementation data [1-3]. In cooperation with A. Wagler and R. Weismantel (Magdeburg), we have most recently developed a proof-based exact mathematical procedure for the automatic reconstruction of networks from experimental time series data.

  1. Marwan, W. 2003. Detecting functional interactions in a gene and signaling network by time-resolved somatic complementation analysis BioEssays. 25:950-960.
  2. Marwan, W. 2003. Theory of time-resolved somatic complementation and its use for the analysis of the sporulation control network of Physarum polycephalum Genetics. 164:105-115.
  3. Marwan, W., A. Sujatha, and C. Starostzik 2005. Reconstructing the regulatory network controling commitment and sporulation in Physarum polycephalum based on hierarchical Petri net modeling and simulation J. Theor. Biol. 236:349-365.

Evolution of morphology in Myxomycetes

Anna-Maria Fiore-Donno
Department of Biology, University of York, Box 373, Heslington YO10 5YW, UK afiore-donno6@infomaniak.ch

The Myxomycetes are a major component of soil amoebae, displaying a complex life-cycle that terminates in the formation of macroscopic fruiting-bodies. The classification of Myxomycetes is controversial and strongly depends on the weight given by different authors to morphological and developmental characters. We used a molecular approach to establish the phylogenetic relationships in the dark-spored orders Stemonitales and Physarales and in the colorless-spored order Echinosteliales. Twenty-five small subunit ribosomal RNA gene sequences were obtained, with focus on two Stemonitales genera, Lamproderma and Comatricha. Unexpectedly, our results show that Stemonitales are paraphyletic with Physarales arousing from within a Lamproderma clade. The genus Lamproderma itself is polyphyletic and can be divided into two distinct clades. Our study allows the reappraisal of morphological and developmental characters in the light of molecular data and set foundations for a new classification of Myxomycetes.

Studies on motility in the net slime mould Labyrinthula

Conrad A.King and Terence M.Preston
Department of Biology,University College London, London WC1E 6BT conrad.king@ucl.ac.uk

Under natural conditions Labyrinthula behaves as a saprophytic/parasitic protozoon whose plasmodial stage is characterised by the production of structurally distinct trackways. Spindle cells glide along these tracks. Severe invasive pathological events can occur particularly involving Zostera and Spartina as host-cell targets. However Labyrinthula can be grown on serum-supplemented agar plates to produce ‘plasmodia’. Filopodial extension at the edge of the colony can occur at a very rapid rate (up to 50 µm min-1). Addition of Cytochalasin D (10µg ml-1) annuls this. Gliding by the spindle cells (approx. 1µm sec-1) located within the more centrally located trackways was inhibited by 10mM BDM (a myosin ATPase inhibitor) but not Cytochalasin D. A key role is proposed for specialised connections (termed bothrosomes) between the actin trackways and spindle cells to generate gliding. An isoform of myosin heavy chain was detected by immunoblotting with a molecular weight of 96-97 kDa.

In vitro and in vivo studies of Acanthamoeba ecology, revealed by microscopy, real-time PCR and 18S rDNA clone libraries.

Gaze WH, Krsek M, Morgan G and Wellington EM.
Department of Biological Science, University of Warwick, Coventry, CV4 7AL, UK W.H.Gaze@warwick.ac.uk

A study of Acanthamoeba polyphaga interactions with Salmonella typhimurium in a model biofilm was undertaken using light microscopy, digital image capture and image analysis. Microscopy studies using GFP reporter constructs of S. typhimurium were used to elucidate feeding behaviour and the possibility of intracellular growth in A. polyphaga. Invasion of the contractile vacuole was observed in a proportion of acanthamoebae and persistence observed within acanthamoebae cysts.

Population dynamics of A. polyphaga and S. typhimurium were studied in sterile and non-sterile soil microcosms at different soil moisture levels using real-time PCR for enumeration of both organisms. Grazing pressure as measured by decreasing salmonellae numbers was greatest in non-sterile and high water content soils.

Acanthamoeba numbers and species diversity in soil and digested sewage sludge were also studied using real-time PCR and 18S rDNA clone libraries. Approximately 103 - 104 acanthamoebae per gram were present in soil and sludge, although clone libraries revealed greater species diversity in soil. Acanthamoebae were isolated from the same soil and sludge samples, and screened for visible intracellular organisms. One sewage sludge isolate contained large numbers of particles resembling the giant DNA virus known as the Microbe Mimicking virus or Mimivirus.

The Choanoflagellate Lorica: Basic Structure and Evolutionry Patterns

Barry SC Leadbeater
School of Biological Sciences, University of Birmingham b.s.c.leadbeater@bham.ac.uk

The basket-like choanoflagellate lorica consists of silicified costal strips attached end-to-end to form costae. The basic organisation of the lorica comprises two layers of costae; the outer costae are orientated parallel to the long axis of the cell and the inner costae perpendicular to the long axis. This arrangement allows for a mechanically stable structure and is achieved during construction by a clockwise spiral and forward (anterior) movement of the enclosed cell. This pattern of costae and mode of assembly is fundamental to all choanoflagellate loricae. However, by a variety of ‘ingenious’ nuances, choanoflagellates have modified this apparently ‘limited’ structure and mechanism to produce a diversity of patterns which have made it possible for loricate choanoflagellates to exploit the myriad of niches in the marine environment.

A Multi-gene Phylogeny of The Choanoflagellates And The Opisthokonts

Martin Carr1, Ruhanna Hassan2, Barry Leadbeater2, Sandie Baldauf1
1. Department of Biology, University of York, UK. 2. Department of Biology, University of Birmingham

The choanoflagellates are a broadly distributed group of ecologically important eukaryotes. Due to morphological similarities between the choanoflagellates and the choanocyte cells of poriferans, a close relationship between the choanoflagellates and the metazoa has long been suspected. Current classification of choanoflagellates is based on morphological characteristics, a system which appears to be overly simplistic and prone to species misidentification. A molecular approach is therefore necessary to examine the phylogeny of the choanoflagellates and understand their relationships with the other Opisthokont lineages.

Most current phylogenies of the Opisthokonta have relied upon ribosomal RNA genes. Here we present a multi-gene phylogeny, using both ribosomal RNA and protein-coding genes, of the choanoflagellates. The results of our phylogenetic analyses show that the traditional classification was heavily based on non-informative characters and requires a radical overhaul. The new Choanoflagellate phylogeny informs our interpretation of morphological evolution in these complex single-celled eukaryotes. In addition, the use of concatenated sequence based phylogeny helps address the question of relationships among the numerous Opisthokont groups. We find that the Opisthokont protist lineages are paraphyletic, and that choanoflagellates are more closely related to the metazoa than they are to other protists.

The developmental cycle of Trypanosoma brucei in the tsetse fly

Wendy Gibson, Lori Peacock and Vanessa Ferris
School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK W.Gibson@bristol.ac.uk

The basic developmental cycle of Trypanosoma brucei in the tsetse vector was reported nearly a century ago, and various details were further elucidated by subsequent researchers. However, it has remained unclear how trypanosomes migrate to the salivary glands from the midgut. Despite a clear description in 1947 of the route and the life cycle stages involved in this journey, an alternative route via the haemolymph was proposed, leading to uncertainty about what actually happened. A widely copied diagram of the life cycle simply omits these migratory forms altogether. More recently the migratory stages have been re-examined, confirming the 1947 description of the lifecycle, but also adding important new information gleaned by the application of modern methods of analysis. Coupled with other data on visualizing living trypanosomes in the fly by fluorescence, we now have a much better understanding of the complete lifecycle of T. brucei in its vector. The latest findings about the sequence of events during the T. brucei lifecycle will be reviewed, along with the questions still unanswered.

Effects of bacterial prey species and state on the growth of Acanthamoeba castellanii and Hartmannella vermiformis

Zoë L Pickup1, Roger Pickup2 and Jacqueline D Parry1
1. Department of Biological Sciences, The Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK; 2. Centre for Ecology and Hydrology, Lancaster University, Lancaster LA1 4RA, UK j.parry@lancaster.ac.uk

Biofilms form on any surface that has contact with liquid but there has been a long-held assumption that the bacterial cells within them are afforded refuge from protozoan predation due to the bacterial cells being embedded in an exopolymer matrix. This assumption may hold true for the smaller flagellates but it does not appear to hold true for the larger ciliates and amoebae. In fact, amoebae are particularly well designed to exploit attached bacteria because their trophozoites can only move and feed whilst on a surface. Yet, despite this knowledge, quantitative data on amoeba-bacterial interactions on surfaces is scarce and previous studies have used a range of techniques that makes comparison between data sets difficult. The form of the bacterial prey employed constitutes one of the main methodological differences, with some researchers using live bacterial prey cells while others use dead, and often stained, bacterial cells. This study evaluated whether the form of the bacterial prey (live, heat-killed, heat-killed/DTAF-stained) significantly affected calculated amoebic growth parameters; and if so, why.

Carbohydrate-Binding Specificity of a Planktonic Protozoan Feeding Receptor

Emily C. Roberts, Emma C. Wootton & Jane Manning
Department of Biological Sciences, University of Wales Swansea, UK E.Roberts@swansea.ac.uk

Through selective feeding, protists play a fundamental role in structuring bacterial and phytoplankton communities within the marine environment. Although recent evidence indicates that protozooplankton can select food based on cell surface properties of their prey, the underlying mechanisms are poorly understood.

Previously, using haemagglutination experiments, we identified a Ca2+-dependent, mannose-binding lectin (MBL) on the marine dinoflagellate Oxyrrhis marina. Feeding experiments, involving live and bead prey, demonstrated the employment of this lectin as a feeding receptor, used for recognizing and selecting prey.

Further characterization of the lectin has revealed it is highly specific in terms of its carbohydrate-binding properties. The lectin has a much higher affinity for glycoproteins and polysaccharides relative to monosaccharides. These results highlight the necessity of purifying protozoan receptors if detailed investigations into biochemical feeding mechanisms are to be undertaken. The purified high specificity receptor is particularly valuable in determining the composition of prey cell surface glycoconjugugates, and in establishing which ligands are involved in the predator-prey interaction.

The potential of ClearEarthTM as a bioremediation agent of crude oil-contaminated sand.

Timothy Lowe, Stephen Coupe, Humphrey Smith & Gillian Spicer
Intelligent Paving Systems Ltd., Coventry University Technology Park, Puma Way, Coventry CV1 2TT apx191@coventry.ac.uk

ClearEarthTM (Also known as “Zander”) is organic lacustrine sediment, dredged from lakes in Ukraine and elsewhere. Its potential as a bioremediation agent, by enhancing microbial biodegradation of crude oil contamination of sand, was experimentally assessed in 2006. CO2 and temperature of four experimental treatments and their controls (three replicates each) were continuously monitored for 12 weeks. At the end of this period, the eukaryotic microfauna and hydrocarbon content of each treatment were determined.

There is therefore strong evidence for ClearEarth to be considered an effective bioremediation agent. Outstanding questions are:

Digestion of prey by the freshwater ciliate Tetrahymena pyriformis

Jill Thurman & Jackie Parry
Biological Sciences Department, Lancaster University, Lancaster, LA1 4YQ, UK j.thurman@lancaster.ac.uk

Protozoa are major predators of bacteria in the environment, however it is well documented that not all bacteria which are ingested are necessarily digested. Research in recent years has considered the escape mechanisms of bacteria e.g. Legionella pneumophila, however relatively little work has focused upon the protozoan predator itself. The events which occur during digestion in protozoan food vacuoles and the efficiency of this process are not well understood yet this has important implications for bacterial community structure and protozoan yield. This study examined the digestion of prey by the freshwater ciliate Tetrahymena pyriformis. Using four heterotrophic species of heat killed DTAF stained bacteria, live Synechococcus sp. and fluorescently labelled microspheres, the pulse chase technique allowed the observation of digestion within the vacuole passage time of the ciliate. The results indicate that digestion occurs immediately upon formation of a food vacuole. The extent of digestion is dependant on both prey type and concentration of prey within the food vacuole with indications it may also be influenced by the feeding history of the ciliate. This work forms a solid basis in our understanding of protozoan digestion in this species which should now be investigated with live bacterial prey.

Morphology and diversity of marine free-living peritrich ciliates.

Alan Warren1, Daode Ji2,3 Ping Sun2 and Weibo Song2
1. Department of Zoology, Natural History Museum, Cromwell Road, London SW7 5BD, UK; 2. Laboratory of Protozoology, Ocean University of China, 266003 Qingdao, P.R. China; 3. School of Ocean, Yantai University, Yantai 264005, China a.warren@nhm.ac.uk

Peritrichs are among the oldest-known groups of ciliates having first been observed by Antony van Leeuwenhoek in 1676. Some are free-swimming while others are sessile, being attached to a substrate via a stalk, scopula or lorica. They have colonised a wide range of habitats, marine, freshwater and terrestrial, and may either be free-living or ectocommensal. They form one of the most specious groups of ciliates with around 1,000 species representing 12 families and over 50 genera. Although genus identification among peritrichs is relatively straightforward, species identification is often difficult mainly due to inadequate species descriptions and morphological variation. Historically, species descriptions were based only on in vivo observations. In recent years, however, modern methods such a silverstaining have been routinely applied revealing taxonomically informative characters such as the pellicular silverlines and oral infraciliature. Using such techniques, extensive surveys of peritrichs have been carried out in NE coastal regions of China. These have revealed over 100 species which represents more than10% of the global peritrich species diversity. This talk provides a brief overview of the morphology and diversity of marine free-living peritrichs based on studies carried out in coastal waters near Qingdao, China.

This study was supported by the Darwin Initiative Programme (project no. 14-015) which is funded by the UK Department for Environment, Food and Rural Affairs.

Posters

Phagosome processing in Acanthamoeba castellanii and Acanthamoeba polyphaga

Claire Dixon, Roger Pickup, Paul McKean & Jackie Parry
Biological Science Department, Lancaster University, Lancaster, LA1 4YQ, UK. c.dixon1@lancaster.ac.uk

Protozoan grazing is commonly recognised as a major factor in shaping the structure and composition of bacterial communities. However, there is a well documented inconsistency in phagosome efficiency which means that ingestion does not necessarily result in digestion. This variability particularly favours survival of pathogenic bacterial species which have developed systems to avoid the host microbicidal mechanisms and even thrive under these conditions. In order to understand why this mechanism is prone to exploitation, it is important to understand the events which would ordinarily occur with a digestible prey type.

Although digestion mechanisms have received a broadened interest within both Dictyostelium discoideum and mammalian macrophage cells, the cross-over of techniques used to study these cells into other protozoa has proved challenging. Subsequently, research into phagosome processing in many protozoan species is under-represented. This study is concerned with food vacuole processing in Acanthamoeba castellanii and Acanthamoeba polyphaga and aims to further our understanding of both the trafficking of phagosomes within the cell and the biochemical changes that occur alongside these movements. Labelling of the cytoskeleton elements actin and microtubules alongside vacuole demarcation highlights the elements involved and the movement resulting from … (apologies from the organizer…)

Is the C-type lectin in Monosiga brevicollis used as a feeding receptor?

Jane Manning, Emma Wootton, Emily Roberts
Department of Biological Sciences, University of Wales Swansea, UK, SA2 8PP

This multidisciplinary project investigates the biochemical mechanisms used by unicellular plankton to recognize their prey.

Ciliates and flagellates are the two principle groups of marine plankton involved in consuming bacteria and phytoplankton at the base of the aquatic food web. In order to better understand carbon cycling and nutrient regeneration in the ocean, it is important to first understand the mechanisms used by these microscopic predators to distinguish their prey.

Ubiquitous in nature, lectins are carbohydrate binding proteins, with a frequent role in cell to cell recognition. In several protists, feeding experiments involving live and bead prey have demonstrated the employment of various lectins as feeding receptors used for detection and selection of prey items.

The first set of experiments involves the choanoflagellate, Monosiga brevicollis. Previous research has shown that Monosiga does possess a C-type lectin, however the discovery was made using molecular techniques; the function of this lectin is therefore still unknown.

Choanoflagellates are thought to be among the closest living relatives of animals, suggesting that animals evolved from a choanoflagellate ancestor. Monosiga brevicollis therefore makes an exciting subject to begin research on, and could perhaps give some insight to the evolutionary origins of animals and their innate immunity.

Soil Protozoa Populations Related to Pathogen Inactivation in Sewage-Sludge Amended Agricultural Soil

Felipe Perez Viana, James Cass, Michael Rogers and Stephen R. Smith
Centre for Environmental Control & Waste Management, Department of Civil & Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ

Soil protozoa have a critical role in soil ecological systems for maintaining soil health and fertility. Soil protozoa control bacterial populations in soil through predation, and this may also be important for the removal of enteric bacteria applied to agricultural soil in biosolids. Protozoa populations, soil microbial biomass carbon (MBC) and bacteria populations were measured in a series of field experiments on two agricultural soils with contrasting physico-chemical properties to examine the effects of different sludge application treatments on long-term soil ecological processes. The sizes of the protozoa populations were similar in both soil types. Sludge application consistently increased the size of the protozoa population overall. These results imply that sludge application potentially increases the grazing activity of protozoa, and thus, reduces the survival of enteric bacteria applied in sludge. This suggests that the survival of enteric organisms may be potentially a self-limiting process, due to the stimulation of soil predator activity in amended soil. The results provide insights to the ecological mechanisms in soil responsible for inactivating pathogenic bacteria following the application of conventionally treated biosolids to agricultural soil.

Taxonomic redescriptions of two ciliates, Gastrostyla pulchra and Hemigastrostyla enigmatica (Ciliophora: Spirotrichea: Stichotrichia), with 18S rRNA gene sequences and phylogenetic analyses

Jun Gong1,2,3, David McL. Roberts1 , Alan Warren1, Sun-Young Kim2, Joong-Ki CHoi2
1. Department of Zoology, Natural History Museum, London, UK; 2. Department of Oceanography, Inha University, Korea; 3. Laboratory of Protozoology, College of Life Science, South China Normal University, China

The morphology and infraciliature of two stichotrichid ciliates, Gastrostyla pulchra (Perejaslawzewa, 1886) Kahl, 1932 and Hemigastrostyla enigmatica (Dragesco & Dragesco-Kernéis, 1986) Song & Wilbert, 1997, collected from marine and brackish sediments, were reinvestigated by using living observation and protargol impregnations. The 18S rRNA genes were sequenced, showing high identities (98.4-99.7%) between populations of each species. While there is about 94% sequence identity between G. pulchra and G. steinii, the type species of the genus Gastrostyla which has been confirmed to be an oxytrichid by previous studies. Both G. pulchra and H. enigmatica are consistently placed outside the well-established oxytrichid clade in our phylogenetic trees. Based on our analyses and previous ontogenetic data, we conclude that these two species should not be included in the family Oxytrichidae, but may represent some lower groups in the subclass Stichotrichia.

Coccolith morphometric response to temperature

Sam Fielding1, D.J.S. Montagnes2 and J.O. Herrle3
1. Earth & Ocean Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP, UK; 2. School of Biological Sciences, University of Liverpool, BioSciences Building, Crown Street, Liverpool, L69 7ZB, UK; 3. Department of Earth & Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, Alberta, T6G 2E3, Canada

Emiliania huxleyi (Lohm) Hay & Mohler is a major component of oceanic algal blooms in waters ranging from fjords and coastal seas to the true pelagic, and is widely used as a tool for interpreting past environments. In the past sea surface temperature has varied causing not only changes in coccolithophore bloom intensity and dynamics but also in organismal size.

Existing palaeoecological studies of Emiliania huxleyi attempt to relate increased coccolith size to lower temperatures. Here we present preliminary data from culture experiments showing that the size of coccoliths of Emiliania huxleyi does not differ with changing temperature between 10 and 20oC. Growth rate change precludes the potential effect of changing coccolith growth rate on morphometry.