Literatura científica selecionada sobre o tema "Hydrozoaire"
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Artigos de revistas sobre o assunto "Hydrozoaire"
Bailly, J. P., H. Girardi e P. Moulet. "Craspedacusta sowerbyi Lank., 1880 (Hydrozoaire), une station nouvelle dans le sud-est de la France et données écologiques complémentaires sur cette méduse". Bulletin mensuel de la Société linnéenne de Lyon 56, n.º 6 (1987): 192–98. http://dx.doi.org/10.3406/linly.1987.10801.
Texto completo da fonteTeses / dissertações sobre o assunto "Hydrozoaire"
Condamine, Thomas. "Étude comparative d'expression de gènes chez un scyphozoaire (Aurelia aurita) et un hydrozoaire (Clytia hemisphaerica) : nouvelles perspectives sur certaines innovations évolutives qui caractérisent leurs stades méduse". Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS384.
Texto completo da fonteThree of the five classes of cnidarians possess pelagic medusae. The latter are classically considered homologous, i.e. inherited from a planktonic stage acquired in the ancestor of all medusozoans. However, an impressive array of fundamental differences opposes hydromedusae to cubomedusae/scyphomedusae, e.g. concerning their locomotory nervous systems, sensory organs, and ontogeny. Could there have been several convergent acquisitions of a medusa stage? The research presented here is based on comparative study of a hydromedusa (Clytia hemisphaerica) and a scyphomedusa (Aurelia aurita), involving gene phylogenies, and gene expression surveys using RNA-seq, in situ hybridisation, and qPCR. The main objectives were (i) an improved characterisation of the Clytia tentacle system; and comparisons between these two medusae, of (ii) the deployment of key actors in animal development and morphogenesis, and of (iii) some proteins associated with striated muscles which are absent in polyps and convergent with those of bilaterians. Comparison of Wnt expressions supports conservation among cnidarians of the roles held by several signalling pathways downstream of the Wnt ligands, in the organisation of the oral-aboral polarity and of some elements of the nervous system, and suggests that tentacles and tetraradial symmetry may not be homologous between hydro- and scyphomedusae. Independent recruitments of tropomyosin forms specific to the striated muscles strongly advocate convergent origins of striated muscles and thereby of pelagic locomotion between hydro- and scyphomedusae. These findings challenge the classical scenario of a single medusa acquisition during cnidarian evolution
Ferraioli, Anna. "Comparison of cell types across life cycle stages of the hydrozoan Clytia hemisphaerica". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS497.
Texto completo da fonteThe hydrozoan Clytia hemisphaerica displays a typical tri-phasic hydrozoan life cycle including a vegetatively propagating polyp colony and free-swimming medusa form as the sexually reproductive life stage. Male and female jellyfish spawn daily, triggered by light and after fertilisation a ciliated planula larva forms in about one day. After three days the planula settles and metamorphoses to give rise to a primary feeding polyp, the gastrozooid, founder of the polyp colony. The colony propagates by stolon extension and a second type of polyp, the gonozooid, releases medusa by budding. Analysis of the genome and the bulk transcriptome across the three life stages revealed specific gene expression programs for each stage (Leclère et al. 2019, Nature Ecology & Evolution). We are now extending this comparison to the level of individual cell types via single-cell RNA transcriptomics of Clytia medusa and larva. Together with L. Leclère and S. Chevalier (LBDV), we generated a female medusa cell atlas in collaboration with T. Chari and J. Gehring from L. Pachter’s lab and B. Weissbourd from D. Anderson’s lab at Caltech (Chari et al. 2021, Science Advances). Analysis of the medusa cell atlas revealed eight broad cell type classes including epidermis and gastrodermis, bioluminescent cells, oocytes and the hydrozoan multipotent stem cells (i cells) and their derivatives such as neurons, nematocytes and gland cells. In situ hybridisation analysis of expression patterns revealed previously uncharacterized subtypes including 14 neuronal subpopulations. Trajectory analysis of the nematocyte lineage revealed two distinct transcriptional programs within this cell class, a “nematoblast” phase, characterised by the production of the typical nematocyte capsule, and the nematocyte differentiation phase, characterised by the production of the nematocil apparatus. ScRNAseq for the Clytia planula required refinement of cell dissociation, fixation and sorting protocols (collaboration with Arnau Sebé-Pedros’ group, Barcelona). Our planula Cell Atlas consists of 4370 cells grouped in 19 cell clusters. Following in situ hybridisation expression patterns analysis of known and novel genes at three planula developmental stages we could assign cell identities and combine the 19 clusters in 8 broad cell classes. These correspond to the two cnidarian epithelial tissue layers, the epidermis and the gastrodermis, the hydrozoan stem cells (I-cells), the nematocytes (stinging cells), neural cells, aboral neurosecretory cells and distinct population of secretory cells, mucous cells and putative excretory cells (PEC). This Clytia planula Cell Types Atlas represents the first cell atlas of an hydrozoan larva and provides characterization of previously undescribed cell populations as well as further information on already known cell types. Comparison analysis of the two Cell Atlases revealed similar nematocyte transcriptional programs between stages indicating that the two distinct developmental programs persist during life cycle transitions. We could identify shared gene expression at the cell type level between life stages. Among those, further subtypes were only found in the adult. Analysis of gene expression programs also revealed the presence of putative stage specific cell types
Leclère, Lucas. "Evolution de la reproduction sexuée des hydrozoaires : aspects historiques, analyse phylogénétique et développementale". Paris 6, 2008. http://www.theses.fr/2008PA066472.
Texto completo da fonteQuiroga, Artigas Gonzalo. "Light-induced oocyte maturation in the hydrozoan clytia hemisphaerica". Electronic Thesis or Diss., Paris 6, 2017. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2017PA066284.pdf.
Texto completo da fonteTight control of oocyte maturation and of gamete release is essential for successful sexual reproduction in the animal kingdom. These processes are precisely coordinated by endocrine and/or environmental cues, depending on the species, but much remains to be learned about their regulation. Within the Cnidaria, many hydrozoan jellyfish are known to spawn mature gametes following dark/light transitions. To characterise the cellular and molecular machinery linking light reception and oocyte maturation initiation, I have studied the hydrozoan jellyfish Clytia hemisphaerica. My thesis work had three parts, each involving the identification of a key molecular component of this process.My initial study was part of a collaboration with N. Takeda (Asamushi) and R. Deguchi (Sendai), who identified the endogenous oocyte Maturation-Inducing Hormones (MIH) in Clytia as WPRPamide-related tetrapeptides, generated by cleavage of two neuropeptide precursors. I showed by in situ hybridization and immunofluorescence that Clytia MIH is produced by neurosecretory cells of the gonad ectoderm that co-express the two precursor genes, and that it is secreted upon light stimulation. This study paved the way for identification of regulators acting upstream and downstream of MIH release in the gonads, specifically the ones involved in photoreception in the gonad ectoderm, and in MIH reception by the oocytes. To identify the Clytia MIH receptor (CheMIHR) in the oocytes, I compiled a shortlist of 16 candidate G protein-coupled receptors (GPCRs) from gonad transcriptome data. I cloned all 16 cDNAs and, using a cell culture-based "GPCR deorphanization" assay (collaboration with P. Bauknecht and G. Jékély; MPI, Tübingen), identified one GPCR that was activated by synthetic MIH peptides. Its in vivo function as the essential MIH receptor was confirmed by CRISPR/Cas9 gene editing. Introduction of a frame-shift mutation in the CheMIHR gene impaired growth of Clytia polyp colonies and also the spawning behaviour of mature medusae. Confirming the function of CheMIHR, oocyte maturation in CheMIHR mutants could not be triggered by light or by synthetic MIH, but could be restored using cell-permeable analogues of cAMP, known to act downstream of MIH reception in hydrozoan oocytes. Phylogenetic analyses showed that Clytia MIHR is related to a subset of bilaterian neuropeptide hormone receptor families involved in diverse physiological processes, including regulation of reproduction. Accordingly, in situ hybridization showed the expression of Clytia MIH precursors and MIHR in non-gonadal neural cells, suggesting a wider role of Clytia MIH-MIHR besides oocyte maturation initiation.To address gonad photoreception, I showed that Clytia spawning is selectively induced by blue-cyan light, and then identified using gonad transcriptome data an opsin photopigment (Opsin9) highly expressed in the ectoderm. Strikingly, in situ hybridization showed that Opsin9 is expressed in the MIH-secreting cells. Introduction of a frame-shift mutation into the Opsin9 gene via CRISPR/Cas9 prevented oocyte maturation and spawning of mutant jellyfish in response to light. Anti-MIH immunofluorescence and rescue experiments with synthetic MIH showed that the essential function of Opsin9 is upstream of MIH release. Spawning in Clytia thus appears to be regulated by a dual function photosensory-neurosecretory cell type, perhaps retained from a distant metazoan ancestor
Postaire, Bautisse. "Connectivité et endémisme d'espèces marines dans le sud-ouest de l'océan Indien : le cas des Aglaopheniidae". Thesis, La Réunion, 2015. http://www.theses.fr/2015LARE0006/document.
Texto completo da fonteDesigning biodiversity conservation plans requires knowledge on the biogeographic distribution of taxa but also accurate estimates of species richness and diversification processes. However, measuring the phyletic richness can be biased by the use of inappropriate taxonomical characters, leading to erroneous species delimitation and diversity estimates. This work explores the phyletic richness at several taxonomic levels (generic, specific and intraspecific) of the hydrozoan family Aglaopheniidae (Agassisz, 1862), with a particular focus on the South-Western Indian Ocean. Firstly, using several newly constructed phylogenies based on mitochondrial and nuclear markers, this study reveals that the phyletic diversity of this family is at underestimated by at least 50%: all studied genera are polyphyletic or with doubtful monophyletic status. Then, using several species delimitation methods based on molecular markers, it sheds light on the richness of cryptic diversity of this family, enlightening the potential of using an integrative taxonomic approach on these morphologically simple organisms. Finally, the population genetics of an Aglaopheniidae brooding species shows a high populations structuring with pervasive pattern of isolation by distance at several geographic scales (several to thousands of kilometres), implying a potentially high cryptic diversity existing in this family. The results of this work provide new insights on Aglaopheniidae diversity, underlining the potential influence of reproductive mode on the phyletic diversity and diversification processes of brooding hydrozoan brooders. This thesis further highlights the relevance of using several complementary species delimitation procedures to study the diversity of morphologically simple organisms
Quiroga, Artigas Gonzalo. "Light-induced oocyte maturation in the hydrozoan clytia hemisphaerica". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066284/document.
Texto completo da fonteTight control of oocyte maturation and of gamete release is essential for successful sexual reproduction in the animal kingdom. These processes are precisely coordinated by endocrine and/or environmental cues, depending on the species, but much remains to be learned about their regulation. Within the Cnidaria, many hydrozoan jellyfish are known to spawn mature gametes following dark/light transitions. To characterise the cellular and molecular machinery linking light reception and oocyte maturation initiation, I have studied the hydrozoan jellyfish Clytia hemisphaerica. My thesis work had three parts, each involving the identification of a key molecular component of this process.My initial study was part of a collaboration with N. Takeda (Asamushi) and R. Deguchi (Sendai), who identified the endogenous oocyte Maturation-Inducing Hormones (MIH) in Clytia as WPRPamide-related tetrapeptides, generated by cleavage of two neuropeptide precursors. I showed by in situ hybridization and immunofluorescence that Clytia MIH is produced by neurosecretory cells of the gonad ectoderm that co-express the two precursor genes, and that it is secreted upon light stimulation. This study paved the way for identification of regulators acting upstream and downstream of MIH release in the gonads, specifically the ones involved in photoreception in the gonad ectoderm, and in MIH reception by the oocytes. To identify the Clytia MIH receptor (CheMIHR) in the oocytes, I compiled a shortlist of 16 candidate G protein-coupled receptors (GPCRs) from gonad transcriptome data. I cloned all 16 cDNAs and, using a cell culture-based "GPCR deorphanization" assay (collaboration with P. Bauknecht and G. Jékély; MPI, Tübingen), identified one GPCR that was activated by synthetic MIH peptides. Its in vivo function as the essential MIH receptor was confirmed by CRISPR/Cas9 gene editing. Introduction of a frame-shift mutation in the CheMIHR gene impaired growth of Clytia polyp colonies and also the spawning behaviour of mature medusae. Confirming the function of CheMIHR, oocyte maturation in CheMIHR mutants could not be triggered by light or by synthetic MIH, but could be restored using cell-permeable analogues of cAMP, known to act downstream of MIH reception in hydrozoan oocytes. Phylogenetic analyses showed that Clytia MIHR is related to a subset of bilaterian neuropeptide hormone receptor families involved in diverse physiological processes, including regulation of reproduction. Accordingly, in situ hybridization showed the expression of Clytia MIH precursors and MIHR in non-gonadal neural cells, suggesting a wider role of Clytia MIH-MIHR besides oocyte maturation initiation.To address gonad photoreception, I showed that Clytia spawning is selectively induced by blue-cyan light, and then identified using gonad transcriptome data an opsin photopigment (Opsin9) highly expressed in the ectoderm. Strikingly, in situ hybridization showed that Opsin9 is expressed in the MIH-secreting cells. Introduction of a frame-shift mutation into the Opsin9 gene via CRISPR/Cas9 prevented oocyte maturation and spawning of mutant jellyfish in response to light. Anti-MIH immunofluorescence and rescue experiments with synthetic MIH showed that the essential function of Opsin9 is upstream of MIH release. Spawning in Clytia thus appears to be regulated by a dual function photosensory-neurosecretory cell type, perhaps retained from a distant metazoan ancestor
Dubé, Caroline Eve. "Life History of Millepora Hydrocorals : New Ecological and Evolutionary Perspectives from Population Genetic Approaches". Thesis, Paris, EPHE, 2016. http://www.theses.fr/2016EPHE3075/document.
Texto completo da fonteEvaluating life history of species carries important implications for conservation biology. A total of 3651 colonies of the fire coral Millepora platyphylla was measured, georeferenced and collected in 5 different habitats in Moorea to evaluate the biological and ecological context of the population maintenance and renewal. This thesis has demonstrated that the population structure of this species varies greatly between lagoonal and fore reef habitats. Using newly developed microsatellite markers, we have shown that M. platyphylla relies heavily on clonal reproduction via fragmentation (80%) and that the fragments are distributed in perfect alignment with wave energy dispersal. Clonal lineages with clones shared among habitats revealed the ability of a single genotype to express different phenotypes depending on its exposure to swell wave energy. Surprisingly, M. platyphylla invests in a vulnerable morphology to wave-induced breakage in high energy reef habitats. Furthermore, parentage analysis revealed a high contribution from self-seeding (58%), limited dispersal of sexual propagules and sibling aggregations. At last, we have demonstrated intracolonial genotypic variability, mostly from somatic mutations (mosaicism), which creates novel genetic diversity within the population. The interaction of these processes generates a high level of genetic and phenotypic variation within the population and allows for local replenishment and the persistence of this fire coral species in Moorea, a marginal habitat. These life history strategies thus increase the adaptive potential and resilience of M. platyphylla in response to rapid and unpredictable environmental changes
Peron, Sophie. "Bases cellulaires et moléculaires de la régénération chez la méduse Clytia hemisphaerica". Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS325.
Texto completo da fonteThe hydrozoan jellyfish Clytia hemisphaerica displays very efficient wound repair mechanisms after different types of injury. During my PhD, I investigated in the medusa the cellular and molecular processes involved in the regeneration of the feeding organ, called ‘manubrium’, ensuring the function of the mouth and stomach. I could define three successive phases during the wound response: wound healing, remodeling of the umbrella allowing the rapid recovery of the circular medusae shape, followed by the regeneration of some of the missing organs. Manubrium regeneration relies on local proliferation as well as cell migration from the gonads. Structural elements, especially the muscle fibers, play a key role in the repatterning process of the umbrella and the site of manubrium regeneration. I also generated transcriptomic data covering the early steps of regeneration. These data allowed the identification of markers of different cell types of the manubrium and documentation of their sequential reappearance during regeneration. They also revealed dynamic expression profiles for Wnt/β-catenin pathway components in the regenerating manubrium, strongly suggesting important roles for this pathway during regeneration. This work confirmed the potential of Clytia medusae as an experimental model for studying regeneration, allowing conserved cellular and molecular mechanisms to be uncovered, and our knowledge about the evolution of regeneration mechanisms in metazoans to be expanded