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Michel Vervoort - One of the best experts on this subject based on the ideXlab platform.

  • morphological cellular and molecular characterization of posterior regeneration in the marine annelid Platynereis dumerilii
    Developmental Biology, 2019
    Co-Authors: Anabelle Planques, Michel Vervoort, Julien Malem, Julio Parapar, Eve Gazave
    Abstract:

    Abstract Regeneration, the ability to restore body parts after an injury or an amputation, is a widespread but highly variable and complex phenomenon in animals. While having fascinated scientists for centuries, fundamental questions about the cellular basis of animal regeneration as well as its evolutionary history remain largely unanswered. Here, we present a study of regeneration of the marine annelid Platynereis dumerilii, an emerging comparative developmental biology model, which, like many other annelids, displays important regenerative abilities. When P. dumerilii worms are amputated, they are able to regenerate the posteriormost differentiated part of their body and a stem cell-rich growth zone that allows the production of new segments replacing the amputated ones. We show that posterior regeneration is a rapid process that follows a well reproducible path and timeline, going through specific stages that we thoroughly defined. Wound healing is achieved one day after amputation and a regeneration blastema forms one day later. At this time point, some tissue specification already occurs, and a functional posterior growth zone is re-established as early as three days after amputation. Regeneration timing is only influenced, in a minor manner, by worm size. Comparable regenerative abilities are found for amputations performed at different positions along the antero-posterior axis of the worm, except when amputation planes are very close to the pharynx. Regenerative abilities persist upon repeated amputations without important alterations of the process. We also show that intense cell proliferation occurs during regeneration and that cell divisions are required for regeneration to proceed normally. Finally, 5-ethynyl-2’-deoxyuridine (EdU) pulse and chase experiments suggest that blastemal cells mostly derive from the segment immediately abutting the amputation plane. The detailed characterization of P. dumerilii posterior body regeneration presented in this article provides the foundation for future mechanistic and comparative studies of regeneration in this species.

  • morphological cellular and molecular characterization of posterior regeneration in the marine annelid Platynereis dumerilii
    bioRxiv, 2018
    Co-Authors: Anabelle Planques, Michel Vervoort, Julien Malem, Julio Parapar, Eve Gazave
    Abstract:

    Regeneration, the ability to restore body parts after an injury or an amputation, is a widespread but highly variable and complex phenomenon in animals. While having fascinating scientists since centuries, fundamental questions about the cellular basis of animal regeneration as well as its evolutionary history remain largely unanswered. We study regeneration of the marine annelid Platynereis dumerilii , an emerging comparative developmental biology model, which, like many other annelids, displays important regenerative abilities. If the posterior part of the body is amputated, P. dumerilii worms are able to regenerate the posteriormost differentiated part of the body and stem cell-rich growth zone that allows to make new segments to replace amputated ones. We show that posterior regeneration is a rapid process that follows a well reproducible paths and timeline, going through specific stages that we thoroughly defined. Wound healing is achieved by one day post-amputation and a regeneration blastema forms one day later. At this time point, some tissue specification already occurs, and a functional posterior growth zone is re-established as early as three days after amputation. Regeneration is only influenced in a minor manner by worm size and position of the amputation site along the antero-posterior axis of the worm and regenerative abilities persist upon repeated amputations without important alterations of the process. We also show that intense cell proliferation occurs during regeneration and that cell divisions are strictly required for regeneration to normally proceed. Finally, we provide evidence, through several 5-ethynyl-2′-deoxyuridine (EdU) pulse and chase experiments, in favor of a local origin of the blastema, whose constituting cells mostly derive from the segment immediately abutting the amputation plane. The detailed characterization of P. dumerilii posterior body regeneration presented in this article provides the foundation for future mechanistic and comparative studies of regeneration in this species.

  • cell lineage and cell cycling analyses of the 4d micromere using live imaging in the marine annelid Platynereis dumerilii
    eLife, 2017
    Co-Authors: Duygu B Ozpolat, Michel Vervoort, Mette Handbergthorsager, Guillaume Balavoine
    Abstract:

    : Cell lineage, cell cycle, and cell fate are tightly associated in developmental processes, but in vivo studies at single-cell resolution showing the intricacies of these associations are rare due to technical limitations. In this study on the marine annelid Platynereis dumerilii, we investigated the lineage of the 4d micromere, using high-resolution long-term live imaging complemented with a live-cell cycle reporter. 4d is the origin of mesodermal lineages and the germline in many spiralians. We traced lineages at single-cell resolution within 4d and demonstrate that embryonic segmental mesoderm forms via teloblastic divisions, as in clitellate annelids. We also identified the precise cellular origins of the larval mesodermal posterior growth zone. We found that differentially-fated progeny of 4d (germline, segmental mesoderm, growth zone) display significantly different cell cycling. This work has evolutionary implications, sets up the foundation for functional studies in annelid stem cells, and presents newly established techniques for live imaging marine embryos.

  • posterior elongation in the annelid Platynereis dumerilii involves stem cells molecularly related to primordial germ cells
    Developmental Biology, 2013
    Co-Authors: Eve Gazave, Adrien Demilly, Michel Vervoort, Guillaume Balavoine, Julien Behague, Lucie Laplane, Aurelien Guillou, Laetitia Preau
    Abstract:

    Like most bilaterian animals, the annelid Platynereis dumerilii generates the majority of its body axis in an anterior to posterior temporal progression with new segments added sequentially. This process relies on a posterior subterminal proliferative body region, known as the “segment addition zone” (SAZ). We explored some of the molecular and cellular aspects of posterior elongation in Platynereis, in particular to test the hypothesis that the SAZ contains a specific set of stem cells dedicated to posterior elongation. We cloned and characterized the developmental expression patterns of orthologs of 17 genes known to be involved in the formation, behavior, or maintenance of stem cells in other metazoan models. These genes encode RNA-binding proteins (e.g., tudor, musashi, pumilio) or transcription factors (e.g., myc, id, runx) widely conserved in eumetazoans. Most of these genes are expressed both in the migrating primordial germ cells and in overlapping ring-like patterns in the SAZ, similar to some previously analyzed genes (piwi, vasa). The SAZ patterns are coincident with the expression of proliferation markers cyclin B and PCNA. EdU pulse and chase experiments suggest that new segments are produced through many rounds of divisions from small populations of teloblast-like posterior stem cells. The shared molecular signature between primordial germ cells and posterior stem cells in Platynereis thus corresponds to an ancestral “stemness” program.

  • involvement of the wnt β catenin pathway in neurectoderm architecture in Platynereis dumerilii
    Nature Communications, 2013
    Co-Authors: Adrien Demilly, Patrick R H Steinmetz, Eve Gazave, Lauriane Marchand, Michel Vervoort
    Abstract:

    The Wnt/β-catenin pathway has important roles during neurogenesis in bilaterian animals. The authors show that this pathway regulates the transition from proliferating neural progenitors to differentiating neurons in the annelid Platynereis dumerilii, suggesting a conserved role in the last common bilaterian ancestor.

Detlev Arendt - One of the best experts on this subject based on the ideXlab platform.

  • whole head recording of chemosensory activity in the marine annelid Platynereis dumerilii
    bioRxiv, 2018
    Co-Authors: Thomas F Chartier, Gaspar Jekely, Joran Deschamps, Wiebke Duerichen, Detlev Arendt
    Abstract:

    Abstract Chemical detection is key to various behaviours in both marine and terrestrial animals. Marine species, though highly diverse, have been underrepresented so far in studies on chemosensory systems, and our knowledge mostly concerns the detection of airborne cues. A broader comparative approach is therefore desirable. Marine annelid worms with their rich behavioural repertoire represent attractive models for chemosensory studies. Here, we study the marine worm Platynereis dumerilii to provide the first comprehensive study of head chemosensory organ physiology in an annelid. By combining microfluidics and calcium imaging, we record neuronal activity in the entire head of early juveniles upon chemical stimulation. We find that Platynereis uses four types of organs to detect stimuli such as alcohols, esters, amino acids and sugars. Antennae, but not nuchal organs or palps as generally hypothesised in annelids, are the main chemosensory organs. We report chemically-evoked activity in possible downstream brain regions including the mushroom bodies, which are anatomically and molecularly similar to insect mushroom bodies. We conclude that chemosensation is a major sensory modality for marine annelids, and propose early Platynereis juveniles as a model to study annelid chemosensory systems.

  • whole organism cellular gene expression atlas reveals conserved cell types in the ventral nerve cord of Platynereis dumerilii
    Proceedings of the National Academy of Sciences of the United States of America, 2017
    Co-Authors: Hernando Martinez Vergara, Paola Bertucci, Peter Hantz, Maria Antonietta Tosches, Kaia Achim, Pavel Vopalensky, Detlev Arendt
    Abstract:

    The comparative study of cell types is a powerful approach toward deciphering animal evolution. To avoid selection biases, however, comparisons ideally involve all cell types present in a multicellular organism. Here, we use image registration and a newly developed “Profiling by Signal Probability Mapping” algorithm to generate a cellular resolution 3D expression atlas for an entire animal. We investigate three-segmented young worms of the marine annelid Platynereis dumerilii, with a rich diversity of differentiated cells present in relatively low number. Starting from whole-mount expression images for close to 100 neural specification and differentiation genes, our atlas identifies and molecularly characterizes 605 bilateral pairs of neurons at specific locations in the ventral nerve cord. Among these pairs, we identify sets of neurons expressing similar combinations of transcription factors, located at spatially coherent anterior-posterior, dorsal-ventral, and medial-lateral coordinates that we interpret as cell types. Comparison with motor and interneuron types in the vertebrate neural tube indicates conserved combinations, for example, of cell types cospecified by Gata1/2/3 and Tal transcription factors. These include V2b interneurons and the central spinal fluid-contacting Kolmer-Agduhr cells in the vertebrates, and several neuron types in the intermediate ventral ganglionic mass in the annelid. We propose that Kolmer-Agduhr cell-like mechanosensory neurons formed part of the mucociliary sole in protostome-deuterostome ancestors and diversified independently into several neuron types in annelid and vertebrate descendants.

  • neurotrophin p75 and trk signaling module in the developing nervous system of the marine annelid Platynereis dumerilii
    BioMed Research International, 2016
    Co-Authors: Antonella Lauri, Paola Bertucci, Detlev Arendt
    Abstract:

    In vertebrates, neurotrophic signaling plays an important role in neuronal development, neural circuit formation, and neuronal plasticity, but its evolutionary origin remains obscure. We found and validated nucleotide sequences encoding putative neurotrophic ligands (neurotrophin, NT) and receptors (Trk and p75) in two annelids, Platynereis dumerilii (Errantia) and Capitella teleta (Sedentaria, for which some sequences were found recently by Wilson, 2009). Predicted protein sequences and structures of Platynereis neurotrophic molecules reveal a high degree of conservation with the vertebrate counterparts; some amino acids signatures present in the annelid Trk sequences are absent in the basal chordate amphioxus, reflecting secondary loss in the cephalochordate lineage. In addition, expression analysis of NT, Trk, and p75 during Platynereis development by whole-mount mRNA in situ hybridization supports a role of these molecules in nervous system and circuit development. These annelid data corroborate the hypothesis that the neurotrophic signaling and its involvement in shaping neural networks predate the protostome-deuterostome split and were present in bilaterian ancestors.

  • effects of low seawater ph on the marine polychaete Platynereis dumerilii
    Marine Pollution Bulletin, 2015
    Co-Authors: Janine Wage, Detlev Arendt, J D Hardege, Tomas Larsson, Oleg Simakov, Emma C Chapman, Jeanette M Rotchell
    Abstract:

    An important priority for any organism is to maintain internal cellular homeostasis including acidbase balance. Yet, the molecular level impacts of changing environmental conditions, such as low pH, remain uncharacterised. Herein, we isolate partial Na+/H+ exchangers (NHE), carbonic anhydrase (CA), and calmodulin (CaM) genes from a polychaete, Platynereis dumerilii and investigate their relative expression in acidified seawater conditions. mRNA expression of NHE was significantly down-regulated after 1 h and up-regulated after 7 days under low pH treatment (pH 7.8), indicating changes in acid-base transport. Furthermore, the localisation of NHE expression was also altered. A trend of down regulation in CA after 1 h was also observed, suggesting a shift in the CO2 and HCO3- balance. No change in CaM expression was detected after 7 days exposure to acidified seawater. This study provides insight into the molecular level changes taking place following exposure to acidified seawater in a non-calcifying, ubiquitous, organism.

  • linking micro and macro evolution at the cell type level a view from the lophotrochozoan Platynereis dumerilii
    Briefings in Functional Genomics, 2013
    Co-Authors: Oleg Simakov, Tomas Larsson, Detlev Arendt
    Abstract:

    Ever since the origin of the first metazoans over 600 million years ago, cell type diversification has been driven by micro-evolutionary processes at population level, leading to macro-evolution changes above species level. In this review, we introduce the marine annelid Platynereis dumerilii, a member of the lophotrochozoan clade (a key yet most understudied superphylum of bilaterians), as a suitable model system for the simultaneous study, at cellular resolution, of macro-evolutionary processes across phyla and of micro-evolutionary processes across highly polymorphic populations collected worldwide. Recent advances in molecular and experimental techniques, easy maintenance and breeding, and the fast, synchronous and stereotypical development have facilitated the establishment of Platynereis as one of the leading model species in the eco ^ evo ^ devo field. Most importantly, Platynereis allows the combination of expression profiling, morphological and physiological characterization at the single cell level. Here, we discuss recent advances in the collection of ^ omics data for the lab strain and for natural populations collected world-wide that can be integrated with population-specific cellular analyses to result in a cellular atlas integrating genetic, phenotypic and ecological variation. This makes Platynereis a tractable system to begin understanding the interplay between macro- and micro-evolutionary processes and cell type diversity.

J D Hardege - One of the best experts on this subject based on the ideXlab platform.

  • the sibling polychaetes Platynereis dumerilii and Platynereis massiliensis in the mediterranean sea are phylogeographic patterns related to exposure to ocean acidification
    Marine Biology, 2017
    Co-Authors: J D Hardege, Janine Wage, Giulia Valvassori, Anja Schulze, Maria Cristina Gambi
    Abstract:

    High pCO2 environments, such as volcanic carbon dioxide (CO2) vents, which mimic predicted near-future scenarios of ocean acidification (OA), offer an opportunity to examine effects of low pH conditions on marine biodiversity and adaptation/acclimatization of marine organisms to such conditions. Based on previous field studies in these systems, it is predicted that the stress owing to increasing CO2 concentrations favours the colonization by invertebrate species with a brooding habit. The goal of this study was to investigate the relative occurrence of the two sibling species Platynereis dumerilii (Audouin & Milne-Edwards, 1834) (free spawner) and Platynereis massiliensis (Moquin-Tandon, 1869) (egg brooder) in two shallow CO2 vents off Ischia and Vulcano islands (Italy, Tyrrhenian Sea), and in various areas with ambient pH conditions, where they represent one of the dominant genera. Phylogeographic analyses were integrated with reproductive biology and life-history observations on some selected populations thriving in the vent areas. This approach revealed the presence of four distinct Platynereis clades. Whereas two clades primarily inhabit CO2 vents and are presumably all brooders, the other two clades dominate the non-acidified sites and appear to be epitokous free spawners. We postulate that one of the brooding, vent-inhabiting clades represents P. massiliensis and one of the free spawning, non-vent-inhabiting clades represents P. dumerilii, although confirmation of the species status with sequence data from the respective-type localities would be desirable.

  • short term effects of co induced low ph exposure on target gene expression in Platynereis dumerilii
    Journal of Marine Biology & Oceanography, 2016
    Co-Authors: Janine Wage, J D Hardege, Silvia Rohr, Jeanette M Rotchell
    Abstract:

    Short-Term Effects of CO2- Induced Low pH Exposure on Target Gene Expression in Platynereis dumerilii Objective: Increasing atmospheric CO2 concentration are causing changes to the seawater carbonate chemistry, lowering the pH and we study potential impacts of these changes at the molecular level in a non-calcifying, marine polychaete species Platynereis dumerilii. Methods: We investigate the relative expression of carbonic anhydrase (CA), Na+/H+ exchangers (NHE), and calmodulin (CaM) genes from P. dumerilii under acidified seawater conditions (pH 7.8) induced by CO2 using qPCR. Results: mRNA expression of CA in the CO2-induced worms was significantly up-regulated at low pH conditions (pH 7.8, 1h), suggesting changes in acid-base balance. In contrast, the expression of NHE and CaM showed no significant change. In addition, we compare these results to a previous study using inorganic acid (HCl)-induced pH changes. Conclusions: Results suggest that carbonate chemistry has an impact on gene expression that differs from pH-associated change. To our knowledge, this is the first study that compares low pH exposure experiments using HCl and CO2 as the inducing agents.

  • Short-term effects of CO₂-induced low pH exposure on target gene expression in Platynereis dumerilii
    Journal of Marine Biology & Oceanography, 2016
    Co-Authors: Janine Wage, J D Hardege, Silvia Rohr, Jeanette M Rotchell
    Abstract:

    Short-Term Effects of CO2- Induced Low pH Exposure on Target Gene Expression in Platynereis dumerilii Objective: Increasing atmospheric CO2 concentration are causing changes to the seawater carbonate chemistry, lowering the pH and we study potential impacts of these changes at the molecular level in a non-calcifying, marine polychaete species Platynereis dumerilii. Methods: We investigate the relative expression of carbonic anhydrase (CA), Na+/H+ exchangers (NHE), and calmodulin (CaM) genes from P. dumerilii under acidified seawater conditions (pH 7.8) induced by CO2 using qPCR. Results: mRNA expression of CA in the CO2-induced worms was significantly up-regulated at low pH conditions (pH 7.8, 1h), suggesting changes in acid-base balance. In contrast, the expression of NHE and CaM showed no significant change. In addition, we compare these results to a previous study using inorganic acid (HCl)-induced pH changes. Conclusions: Results suggest that carbonate chemistry has an impact on gene expression that differs from pH-associated change. To our knowledge, this is the first study that compares low pH exposure experiments using HCl and CO2 as the inducing agents.

  • exposure to low ph induces molecular level changes in the marine worm Platynereis dumerilii
    Ecotoxicology and Environmental Safety, 2016
    Co-Authors: Janine Wage, J D Hardege, Adelaide Lerebours, Jeanette M Rotchell
    Abstract:

    Fossil fuel emissions and changes in net land use lead to an increase in atmospheric CO2 concentration and a subsequent decrease of ocean pH. Noticeable effects on organisms' calcification rate, shell structure and energy metabolism have been reported in the literature. To date, little is known about the molecular mechanisms altered under low pH exposure, especially in non-calcifying organisms. We used a suppression subtractive hybridisation (SSH) approach to characterise differentially expressed genes isolated from Platynereis dumerilii, a non-calcifying marine polychaeta species, kept at normal and low pH conditions. Several gene sequences have been identified as differentially regulated. These are involved in processes previously considered as indicators of environment change, such as energy metabolism (NADH dehydrogenase, 2-oxoglutarate dehydrogenase, cytochrome c oxidase and ATP synthase subunit F), while others are involved in cytoskeleton function (paramyosin and calponin) and immune defence (fucolectin-1 and paneth cell-specific alpha-defensin) processes. This is the first study of differential gene expression in a non-calcifying, marine polychaete exposed to low pH seawater conditions and suggests that mechanisms of impact may include additional pathways not previously identified as impacted by low pH in other species.

  • effects of low seawater ph on the marine polychaete Platynereis dumerilii
    Marine Pollution Bulletin, 2015
    Co-Authors: Janine Wage, Detlev Arendt, J D Hardege, Tomas Larsson, Oleg Simakov, Emma C Chapman, Jeanette M Rotchell
    Abstract:

    An important priority for any organism is to maintain internal cellular homeostasis including acidbase balance. Yet, the molecular level impacts of changing environmental conditions, such as low pH, remain uncharacterised. Herein, we isolate partial Na+/H+ exchangers (NHE), carbonic anhydrase (CA), and calmodulin (CaM) genes from a polychaete, Platynereis dumerilii and investigate their relative expression in acidified seawater conditions. mRNA expression of NHE was significantly down-regulated after 1 h and up-regulated after 7 days under low pH treatment (pH 7.8), indicating changes in acid-base transport. Furthermore, the localisation of NHE expression was also altered. A trend of down regulation in CA after 1 h was also observed, suggesting a shift in the CO2 and HCO3- balance. No change in CaM expression was detected after 7 days exposure to acidified seawater. This study provides insight into the molecular level changes taking place following exposure to acidified seawater in a non-calcifying, ubiquitous, organism.

Janine Wage - One of the best experts on this subject based on the ideXlab platform.

  • the sibling polychaetes Platynereis dumerilii and Platynereis massiliensis in the mediterranean sea are phylogeographic patterns related to exposure to ocean acidification
    Marine Biology, 2017
    Co-Authors: J D Hardege, Janine Wage, Giulia Valvassori, Anja Schulze, Maria Cristina Gambi
    Abstract:

    High pCO2 environments, such as volcanic carbon dioxide (CO2) vents, which mimic predicted near-future scenarios of ocean acidification (OA), offer an opportunity to examine effects of low pH conditions on marine biodiversity and adaptation/acclimatization of marine organisms to such conditions. Based on previous field studies in these systems, it is predicted that the stress owing to increasing CO2 concentrations favours the colonization by invertebrate species with a brooding habit. The goal of this study was to investigate the relative occurrence of the two sibling species Platynereis dumerilii (Audouin & Milne-Edwards, 1834) (free spawner) and Platynereis massiliensis (Moquin-Tandon, 1869) (egg brooder) in two shallow CO2 vents off Ischia and Vulcano islands (Italy, Tyrrhenian Sea), and in various areas with ambient pH conditions, where they represent one of the dominant genera. Phylogeographic analyses were integrated with reproductive biology and life-history observations on some selected populations thriving in the vent areas. This approach revealed the presence of four distinct Platynereis clades. Whereas two clades primarily inhabit CO2 vents and are presumably all brooders, the other two clades dominate the non-acidified sites and appear to be epitokous free spawners. We postulate that one of the brooding, vent-inhabiting clades represents P. massiliensis and one of the free spawning, non-vent-inhabiting clades represents P. dumerilii, although confirmation of the species status with sequence data from the respective-type localities would be desirable.

  • short term effects of co induced low ph exposure on target gene expression in Platynereis dumerilii
    Journal of Marine Biology & Oceanography, 2016
    Co-Authors: Janine Wage, J D Hardege, Silvia Rohr, Jeanette M Rotchell
    Abstract:

    Short-Term Effects of CO2- Induced Low pH Exposure on Target Gene Expression in Platynereis dumerilii Objective: Increasing atmospheric CO2 concentration are causing changes to the seawater carbonate chemistry, lowering the pH and we study potential impacts of these changes at the molecular level in a non-calcifying, marine polychaete species Platynereis dumerilii. Methods: We investigate the relative expression of carbonic anhydrase (CA), Na+/H+ exchangers (NHE), and calmodulin (CaM) genes from P. dumerilii under acidified seawater conditions (pH 7.8) induced by CO2 using qPCR. Results: mRNA expression of CA in the CO2-induced worms was significantly up-regulated at low pH conditions (pH 7.8, 1h), suggesting changes in acid-base balance. In contrast, the expression of NHE and CaM showed no significant change. In addition, we compare these results to a previous study using inorganic acid (HCl)-induced pH changes. Conclusions: Results suggest that carbonate chemistry has an impact on gene expression that differs from pH-associated change. To our knowledge, this is the first study that compares low pH exposure experiments using HCl and CO2 as the inducing agents.

  • Short-term effects of CO₂-induced low pH exposure on target gene expression in Platynereis dumerilii
    Journal of Marine Biology & Oceanography, 2016
    Co-Authors: Janine Wage, J D Hardege, Silvia Rohr, Jeanette M Rotchell
    Abstract:

    Short-Term Effects of CO2- Induced Low pH Exposure on Target Gene Expression in Platynereis dumerilii Objective: Increasing atmospheric CO2 concentration are causing changes to the seawater carbonate chemistry, lowering the pH and we study potential impacts of these changes at the molecular level in a non-calcifying, marine polychaete species Platynereis dumerilii. Methods: We investigate the relative expression of carbonic anhydrase (CA), Na+/H+ exchangers (NHE), and calmodulin (CaM) genes from P. dumerilii under acidified seawater conditions (pH 7.8) induced by CO2 using qPCR. Results: mRNA expression of CA in the CO2-induced worms was significantly up-regulated at low pH conditions (pH 7.8, 1h), suggesting changes in acid-base balance. In contrast, the expression of NHE and CaM showed no significant change. In addition, we compare these results to a previous study using inorganic acid (HCl)-induced pH changes. Conclusions: Results suggest that carbonate chemistry has an impact on gene expression that differs from pH-associated change. To our knowledge, this is the first study that compares low pH exposure experiments using HCl and CO2 as the inducing agents.

  • exposure to low ph induces molecular level changes in the marine worm Platynereis dumerilii
    Ecotoxicology and Environmental Safety, 2016
    Co-Authors: Janine Wage, J D Hardege, Adelaide Lerebours, Jeanette M Rotchell
    Abstract:

    Fossil fuel emissions and changes in net land use lead to an increase in atmospheric CO2 concentration and a subsequent decrease of ocean pH. Noticeable effects on organisms' calcification rate, shell structure and energy metabolism have been reported in the literature. To date, little is known about the molecular mechanisms altered under low pH exposure, especially in non-calcifying organisms. We used a suppression subtractive hybridisation (SSH) approach to characterise differentially expressed genes isolated from Platynereis dumerilii, a non-calcifying marine polychaeta species, kept at normal and low pH conditions. Several gene sequences have been identified as differentially regulated. These are involved in processes previously considered as indicators of environment change, such as energy metabolism (NADH dehydrogenase, 2-oxoglutarate dehydrogenase, cytochrome c oxidase and ATP synthase subunit F), while others are involved in cytoskeleton function (paramyosin and calponin) and immune defence (fucolectin-1 and paneth cell-specific alpha-defensin) processes. This is the first study of differential gene expression in a non-calcifying, marine polychaete exposed to low pH seawater conditions and suggests that mechanisms of impact may include additional pathways not previously identified as impacted by low pH in other species.

  • effects of low seawater ph on the marine polychaete Platynereis dumerilii
    Marine Pollution Bulletin, 2015
    Co-Authors: Janine Wage, Detlev Arendt, J D Hardege, Tomas Larsson, Oleg Simakov, Emma C Chapman, Jeanette M Rotchell
    Abstract:

    An important priority for any organism is to maintain internal cellular homeostasis including acidbase balance. Yet, the molecular level impacts of changing environmental conditions, such as low pH, remain uncharacterised. Herein, we isolate partial Na+/H+ exchangers (NHE), carbonic anhydrase (CA), and calmodulin (CaM) genes from a polychaete, Platynereis dumerilii and investigate their relative expression in acidified seawater conditions. mRNA expression of NHE was significantly down-regulated after 1 h and up-regulated after 7 days under low pH treatment (pH 7.8), indicating changes in acid-base transport. Furthermore, the localisation of NHE expression was also altered. A trend of down regulation in CA after 1 h was also observed, suggesting a shift in the CO2 and HCO3- balance. No change in CaM expression was detected after 7 days exposure to acidified seawater. This study provides insight into the molecular level changes taking place following exposure to acidified seawater in a non-calcifying, ubiquitous, organism.

D. R. Dixon - One of the best experts on this subject based on the ideXlab platform.

  • assessment of developmental effects cytotoxicity and genotoxicity in the marine polychaete Platynereis dumerilii exposed to disinfected municipal sewage effluent
    Mutation Research, 1998
    Co-Authors: Thomas H. Hutchinson, J.m. Mackay, Barry M. Elliott, D. R. Dixon
    Abstract:

    Abstract While sodium hypochlorite is widely used as a disinfectant for municipal sewage effluents and power station cooling waters discharged into coastal environments, there is limited information on the potential in vivo genotoxicity of such disinfection procedures to marine organisms. Using a recently developed test system based on the marine polychaete Platynereis dumerilii , we have evaluated impacts based on embryo–larval development, cytotoxicity and genotoxicity following exposure to disinfected settled (primary) effluent from a municipal sewage treatment works (STW). Sewage samples were collected from Newton Abbot STW, Devon, UK and then disinfected with sodium hypochlorite based on standard operational procedures. Exposure of polychaetes to dilutions of disinfected sewage in seawater (20±1°C) led to a marked reduction in normal embryo–larval development (7 h EC 50 from 0.57–1.88% (v/v), n =4), with a simultaneous increase in cytotoxicity. Following the calculation of the Maximum Tolerated Dose (MTD), based on developmental and cytotoxic effects, the organisms were also analysed for the induction of chromosomal aberrations. This investigation demonstrated the absence of genotoxicity in polychaetes exposed in vivo to sewage disinfected with sodium hypochlorite. These observations extend our previously published studies in which polychaetes exposed to non-disinfected sewage, while showing developmental toxicity and cytotoxicity, did not exhibit any evidence of cytogenetic damage.

  • evaluation of the genotoxicity of municipal sewage effluent using the marine worm Platynereis dumerilii polychaeta nereidae
    Mutation Research-genetic Toxicology and Environmental Mutagenesis, 1997
    Co-Authors: Thomas H. Hutchinson, J.m. Mackay, Barry M. Elliott, D. R. Dixon
    Abstract:

    Abstract Samples of settled (primary) effluent were collected from a municipal sewage treatment works at Newton Abbot, Devon, UK, a site which discharges primary effluent via long sea pipeline into the English Channel (minimum of 200-fold initial dilution). Sewage samples were collected during the period February–April 1995 and were analysed for standard physico-chemical parameters (ammonia, chemical oxygen demand, conductivity, non-purgeable organic carbon and settled solids). Samples were also tested for cytotoxicity, genotoxicity, and for developmental effects in the embryo-larval stages of the marine worm, Platynereis dumerilii . Exposure to sewage concentrations of ≥10% (v/v) in seawater at 20±1°C led to a marked reduction in normal embryo-larval development (7 h EC 50 values from 10% to 18% v/v, n =5). There was also evidence of a simultaneous delay in the cell cycle progression (as determined by sister chromatid differential staining) following embryo-larval exposures to sewage concentrations of ≥10% (v/v). Following the calculation of the Maximum Tolerated Dose (MTD), based on cytotoxic and developmental effects, cells from the same embryo-larvae were analysed for chromosomal aberrations (CAs). Results were consistent for all samples tested, demonstrating the absence of cytogenetic damage following the in vivo exposure of polychaete embryo-larvae to settled sewage.

  • The chromosomes Of Platynereis dumerilii (Polychaeta: Nereidae)
    Journal of the Marine Biological Association of the United Kingdom, 1995
    Co-Authors: Thomas H. Hutchinson, J.m. Mackay, Barry M. Elliott, P.l. Pascoe, D. R. Dixon
    Abstract:

    The chromosomes of Platynereis dumerilii (Audouin & Milne-Edwards) are described here for the first time. A modal chromosome number of 2n=28 was recorded, based on counts conducted on metaphase spreads prepared from 24-h-old larvae. The karyotype comprises seven pairs, each of relatively large median (arm ratio, p/q=l.00–0.59) and submedian (arm ratio, 0.59–0.33) chromosomes. Attempts were also made to band the chromosomes using C-banding and silver staining methods. C-band-positive regions were localized on four chromosome pairs (three median, one submedian). A further two chromosome pairs (both median) were observed to have terminal nucleolar organizer regions (NORs). To our knowledge, this is the first time that these banding methods have been successfully applied to any polychaete species. These results are discussed in relation to the karyotypic variation within the class Polychaeta, and the family Nereidae in particular. A stable karyotype consisting of a moderate number of large and morphologically well-differentiated chromosomes, coupled with the ease of culture under laboratory conditions and short generation time, suggests that P. dumerilii is a potentially suitable model for evaluating marine contaminants for genotoxic activity.