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Stephen J. Hawkins - One of the best experts on this subject based on the ideXlab platform.
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Barnacle cover modifies foraging behaviour of the intertidal limpet Patella Vulgata
Journal of the Marine Biological Association of the United Kingdom, 2019Co-Authors: Giacomo Santini, R. G. Hartnoll, Stuart R. Jenkins, Guido Chelazzi, Richard C. Thompson, Suzanne Kay, Stephen J. HawkinsAbstract:Limpets and barnacles are important components of intertidal assemblages worldwide. This study examines the effects of barnacles on the foraging behaviour of the limpet Patella Vulgata , which is the main algal grazer in the North-west Atlantic. The behaviour of limpets on a vertical seawall on the Isle of Man (UK) was investigated using autonomous radio-telemetry, comparing their activity patterns on plots characterized by dense barnacle cover and plots from which the barnacles had been removed. Limpet behaviour was investigated at mid-shore level, but two different elevations were considered. This experiment revealed a significant effect of barnacle cover on the activity of P. Vulgata . Limpets on smooth surfaces spent a greater proportion of total time active than did limpets on barnacles. Movement activity was also greater in areas that were lower down in the tidal range. In general, limpets were either predominantly active during diurnal high or nocturnal low tides and always avoided nocturnal high tides. Individuals on barnacles at the higher elevation concentrated their activity during nocturnal low water. All the other groups of limpets (smooth surfaces on the upper level and all individuals on the lower shore) had more excursions centred around daylight hours with an equal distribution of activity between periods of low and high water. Inter-individual variability was, however, pronounced.
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ORIGINAL PAPER Determinants of reproductive potential and population size in open populations of Patella Vulgata
2015Co-Authors: Stuart R. Jenkins, Carl Johan Svensson, Jane Delany, Stephen J. HawkinsAbstract:Abstract The importance of external and internal popu-lation processes in determining variation in reproductive output and variation in population size were quantified with model simulations for open populations of the sequentially hermaphroditic limpet Patella Vulgata using field data from the Isle of Man and South West Ireland. Cross-correlation analyses of model outputs and elasticity analyses show that population dynamics are dominated by the effects of large females, and that recruitment adds little to reproductive output. However, populations experiencing low but highly variable recruitment appear male limited and recruitment pulses carrying young males into the population are correlated to reproductive output with a 2–5-year lag. We conclude that pulses in recruitment can be a major structuring force in these limpet populations, but site-specific post-recruitment processes will determine the relative importance of recruit-ment to population dynamics and the lag between recruitment and reproductive output
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Determinants of reproductive potential and population size in open populations of Patella Vulgata
Marine Biology, 2009Co-Authors: Andreas Sundelöf, Stephen J. Hawkins, Stuart R. Jenkins, Carl Johan Svensson, Jane Delany, Per ÅbergAbstract:The importance of external and internal population processes in determining variation in reproductive output and variation in population size were quantified with model simulations for open populations of the sequentially hermaphroditic limpet Patella Vulgata using field data from the Isle of Man and South West Ireland. Cross-correlation analyses of model outputs and elasticity analyses show that population dynamics are dominated by the effects of large females, and that recruitment adds little to reproductive output. However, populations experiencing low but highly variable recruitment appear male limited and recruitment pulses carrying young males into the population are correlated to reproductive output with a 2–5-year lag. We conclude that pulses in recruitment can be a major structuring force in these limpet populations, but site-specific post-recruitment processes will determine the relative importance of recruitment to population dynamics and the lag between recruitment and reproductive output.
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Artificial oocyte maturation in Patella depressa and Patella Vulgata using NaOH-alkalinized seawater
Marine Biology Research, 2009Co-Authors: Rosana Aquino De Souza, Paul A. Tyler, Stephen J. HawkinsAbstract:Abstract Laboratory investigations of environmental factors controlling early development and larval survival of free-spawning marine invertebrates are often limited by the difficulty of inducing spawning under laboratory conditions. Patellid gastropod species must be dissected in order to obtain the gametes from the gonads, often yielding unfertilizable immature eggs. The artificial maturation of oocytes through NaOH-alkalinization methods was investigated in order to improve laboratory experiments on larval ecology of Patella depressa and Patella Vulgata. Maturation was accelerated above pH 9.0. Alkalinizing oocytes at pH 9.5 significantly enhanced in vitro fertilization rates, especially at higher sperm concentrations. pH 10 was harmful to eggs. Sperm dilution experiments using alkalinized oocytes suggest the use of sperm concentrations proximate to 106 spermatozoa ml−1.
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Negative effects of sediment deposition on grazing activity and survival of the limpet Patella Vulgata
Marine Ecology Progress Series, 2007Co-Authors: Laura Airoldi, Stephen J. HawkinsAbstract:Sediments are likely to influence the distribution of limpets and dominant sessile spe- cies on intertidal rocky shores by smothering and interfering with feeding activity. This hypothesis was tested by field observations and laboratory experiments in which the effects of different amounts and grain sizes of sediments on the grazing and survival of the limpet Patella Vulgata L. were mea- sured. On rocky shores close to Plymouth (south-west UK), natural patchiness of sediment deposits was related to the distribution of P. Vulgata and macroalgae. Sediments severely impaired P. Vulgata. Even a ~1 mm thick layer of sediment (equivalent to 50 mg cm -2 ) decreased grazing activity by 35%, with total inhibition and mortality at loads of 200 mg cm -2 of fine sediments. Coarse sediments had
Michel Vervoort - One of the best experts on this subject based on the ideXlab platform.
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expression of a soxb and a wnt2 13 gene during the development of the mollusc Patella Vulgata
Development Genes and Evolution, 2004Co-Authors: Martine Le Gouar, Michel Vervoort, Aurélien GuillouAbstract:We cloned and analysed the expression of a SoxB gene (PvuSoxB) in the marine mollusc, Patella Vulgata. Like its orthologues in deuterostomes, after an early broad ectodermal distribution, PvuSoxB expression only persists in cells competent to form neural structures. In the post-gastrulation larva, PvuSoxB is expressed in the prospective neuroectoderm in the head and in the trunk. No expression can be seen dorsally, around the mouth and the anus, or along the ventral midline. We also report the expression of a Wnt2/13 orthologue (PvuWnt2) in Patella. After gastrulation, PvuWnt2 is expressed in the posterior part of the mouth, along the ventral midline and around the anus. This expression seems to be complementary to that of PvuSoxB in the trunk. We suggest the existence of a fundamental subdivision of the Patella trunk ectoderm into midline (mouth, midline, anus) and more lateral structures.
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Expression of a SoxB and a Wnt2/13 gene during the development of the mollusc Patella Vulgata.
Development genes and evolution, 2004Co-Authors: Martine Le Gouar, Aurélien Guillou, Michel VervoortAbstract:We cloned and analysed the expression of a SoxB gene (PvuSoxB) in the marine mollusc, Patella Vulgata. Like its orthologues in deuterostomes, after an early broad ectodermal distribution, PvuSoxB expression only persists in cells competent to form neural structures. In the post-gastrulation larva, PvuSoxB is expressed in the prospective neuroectoderm in the head and in the trunk. No expression can be seen dorsally, around the mouth and the anus, or along the ventral midline. We also report the expression of a Wnt2/13 orthologue (PvuWnt2) in Patella. After gastrulation, PvuWnt2 is expressed in the posterior part of the mouth, along the ventral midline and around the anus. This expression seems to be complementary to that of PvuSoxB in the trunk. We suggest the existence of a fundamental subdivision of the Patella trunk ectoderm into midline (mouth, midline, anus) and more lateral structures.
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The expression of a caudal homologue in a mollusc, Patella Vulgata.
Gene expression patterns : GEP, 2003Co-Authors: Martine Le Gouar, Nicolas Lartillot, André Adoutte, Michel VervoortAbstract:We cloned and analyzed the expression of a caudal homologue (PvuCdx) during the early development of the marine gastropod, Patella Vulgata. PvuCdx is expressed at the onset of gastrulation in the ectodermal cells that constitute the posterior edge of the blastopore, as well as in the paired mesentoblasts, the stem cells that generate the posterior mesoderm of the trochophore larva. During larval stages, PvuCdx is expressed in the posterior neurectoderm of the larva, as well as in part of the mesoderm. This is the first report of the expression of a caudal gene in a lophotrochozoan species. The striking similarities with the expression of caudal in other organisms, such as chordates, suggest that a posterior expression of caudal is ancestral to Bilateria.
Wim J.a.g. Dictus - One of the best experts on this subject based on the ideXlab platform.
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A lophotrochozoan twist gene is expressed in the ectomesoderm of the gastropod mollusk Patella Vulgata.
Evolution & development, 2002Co-Authors: Alexander J. Nederbragt, Andrée. Van Loon, André Adoutte, Olivier Lespinet, Sake Van Wageningen, Wim J.a.g. DictusAbstract:SUMMARY The twist gene is known to be involved in mesoderm formation in two of the three clades of bilaterally symmetrical animals: viz. deuterostomes (such as vertebrates) and ecdysozoans (such as arthropods and nematodes). There are currently no data on the spatiotemporal expression of this gene in the third clade, the lophotrochozoans (such as mollusks and annelids). To approach the question of mesoderm homology across bilaterians, we decided to analyze orthologs of this gene in the gastropod mollusk Patella Vulgata that belongs to the lophotrochozoans. We present here the cloning, characterization, and phylogenetic analysis of a Patella twist ortholog, Pv-twi, and determine the early spatiotemporal expression pattern of this gene. Pv-twi expression was found in the trochophore larva in a subset of the ectomesoderm, one of the two sources of mesoderm in Patella. These data support the idea that twist genes were ancestrally involved in mesoderm differentiation. The absence of Pv-twi in the second mesodermal source, the endomesoderm, suggests that also other genes must be involved in lophotrochozoan mesoderm differentiation. It therefore remains a question if the mesoderm of all bilaterians is homologous.
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Cell-lineage and clonal-contribution map of the trochophore larva of Patella Vulgata (mollusca).
Mechanisms of Development, 1997Co-Authors: Wim J.a.g. Dictus, Peter DamenAbstract:Abstract Molluscan development is characterised by its extremely regular cleavage pattern. In numerous molluscs the fate of various early-cleavage stage blastomeres has been determined and fate maps have been constructed. On the basis of similarities between these fate maps, a generalised molluscan cell-lineage map has been constructed. Recently, the validity of this map has been challenged. In this study, the cell-lineage of the first-, second-, and third-quartet micromeres and third-generation macromeres of the equally-cleaving gastropod mollusc Patella Vulgata was studied by fluorescent cell-lineage tracer injection followed by epifluorescence microscopy and confocal laser scanning microscopy. For the first time, a complete cell-lineage map, in the form of a clonal-contribution map of the trochophore, has been constructed with the use of fluorescent cell-lineage tracers. This map both agrees and differs in a number of respects with the generalised cell-lineage map of molluscs. The most important deviation is that the micromere 2d, formerly referred to as the first somatoblast, is not the only cell that forms the foot and shell gland in Patella.
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ORGANISER ROLE OF THE STEM CELL OF THE MESODERM IN PROTOTROCH PATTERNING IN Patella Vulgata (MOLLUSCA, GASTROPODA)
Mechanisms of development, 1996Co-Authors: Peter Damen, Wim J.a.g. DictusAbstract:During early development of the gastropod mollusc Patella Vulgata, the stem cell of the mesoderm (3D-macromere) is induced. As a result of this induction, the embryo becomes dorsoventrally organised. At about the same time in development, ciliated cells, so-called trochoblasts, are formed. Later in development, some trochoblasts deciliate and, together with the ciliated trochoblast, form the dorsoventrally organised prototroch, the locomotory organ of the larva. In order to study the role of the 3D-macromere in the specification of trochoblasts and in the induction of the dorsoventral organisation of the prototroch, induction of 3D has been prevented in various ways. it is shown that preventing 3D-induction results in the formation of a radially symmetrical prototroch. The trochoblasts of all four quadrants developed like corresponding trochoblasts of the A-quadrant. Somewhere between 30 and 120 min after fifth cleavage the 3D-macromere induces the formation of specific trochoblasts and organises the dorsoventral pattern of the prototroch. Besides a role of the 3D-macromere, a role of other cells has been demonstrated in the conditionally specified deciliation of trochoblasts.
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Cell lineage of the prototroch of Patella Vulgata (Gastropoda, Mollusca)
Developmental biology, 1994Co-Authors: Peter Damen, Wim J.a.g. DictusAbstract:The trochophore larva of the archaeogastropod mollusc Patella Vulgata has a well-developed locomotory organ, the ciliated prototroch. This structure is formed from specific founder cells, the trochoblasts. Two methods were employed to determine the composition and cell lineage of the prototroch. Fluorescent cell-lineage tracer injection in trochoblasts and trochoblast founder cells was used to show how the various trochoblasts became incorporated into the prototroch. Scanning electron microscopy was used to study both differentiation, more specifically ciliation, of trochoblasts and localization of trochoblasts in the prototroch. The results obtained with both methods are in accordance with each other. During early development all trochoblasts involved in prototroch formation become cell cycle-arrested and develop cilia. Subsequently, the trochoblasts shift in position to form a circular prototroch and a number of trochoblasts deciliate. As a result of these processes the mature prototroch consists of a number of heavily ciliated cells as well as a number of deciliated cells. Comparison of prototrochs from a number of spiralian species shows that this structure is very conserved during evolution. The significance of this is discussed.
A. E. Van Loon - One of the best experts on this subject based on the ideXlab platform.
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Protein Synthesis Controls Cyclin Stability in Metaphase I-Arrested Oocytes of Patella Vulgata
Experimental cell research, 1993Co-Authors: P. Colas, C. Launay, A. E. Van Loon, P. GuerrierAbstract:The metaphasic block of Patella Vulgata oocytes depends on protein synthesis as an emetine treatment triggers metaphase/anaphase transition and leads to the sequential disappearance of cyclin A and B. Both cyclins are stable in metaphase-arrested oocytes which indicates that inhibition of protein synthesis activates cyclin proteolysis. The use of extracts prepared from metaphase-arrested oocytes and from emetine-treated oocytes fully confirms these in vivo findings. Considering previous observations about the regulation of protein synthesis throughout the cell cycle, we propose the involvement of a transient inhibition of translation in the activation of cyclin proteolysis and in exit from the M-phase arrest.
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Microinjection of suc1 transcripts delays the cell cycle clock in Patella Vulgata embryos.
The International journal of developmental biology, 1993Co-Authors: P. Colas, Florenci Serras, A. E. Van LoonAbstract:The suc1 protein is a cell cycle regulator whose precise function remains to be elucidated. The suc1 cDNA of the mollusk Patella Vulgata was cloned and sequenced. It encodes a 9 kD protein showing a strong similarity with its human counterparts and to a lesser extend with its yeast counterparts. The expression of suc1 in maturing oocytes was shown to be tightly cell cycle-regulated. The abundance of the suc1 transcripts is high in prophase- and metaphase-arrested oocytes but drops dramatically upon exit from M-phase, after fertilization. The microinjection of suc1 synthetic messengers into embryonic blastomeres delayed the cell cycle clock, thus disrupting the perfect cell cycle synchrony exhibited by the blastomeres of early Patella embryos. Interestingly, this suc1 delaying effect was significantly reversed when cyclin B messengers were co-injected with suc1 messengers. These results show that Patella embryos offer a quite valuable model to study cell cycle regulation. Moreover, they support the existence of a negative control exerted by suc1 on the cell cycle traverse in a higher eukaryote.
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The role of cyclins in the maturation of Patella Vulgata oocytes.
The EMBO journal, 1991Co-Authors: A. E. Van Loon, Pierre Colas, H.j. Goedemans, I. Néant, P. Dalbon, P. GuerrierAbstract:We have cloned and sequenced the cDNAs encoding Patella Vulgata cyclins A and B. The cDNA clones contain an open reading frame of 426 and 408 amino acids respectively, which present similarity with cyclins from other species. Cyclin A and B RNAs are present as polyadenylated and non-polyadenylated RNA in prophase oocytes and are completely polyadenylated in metaphase I. During the first cleavages after fertilization the level of cyclin A and B mRNAs is high and drops when the free swimming stage is reached. Using p13suc1-Sepharose bead precipitation we demonstrate that cyclin synthesis is triggered during maturation and that inhibition of protein synthesis makes the cyclins disappear rapidly from the metaphase I oocytes, which shift to interphase condition. By microinjecting antisense oligonucleotides into metaphase I oocytes, we demonstrate that in vivo ablation of cyclin A and B messengers together gives the same result, whereas microinjection of only one oligonucleotide does not show any effect.
Andrée. Van Loon - One of the best experts on this subject based on the ideXlab platform.
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A lophotrochozoan twist gene is expressed in the ectomesoderm of the gastropod mollusk Patella Vulgata.
Evolution & development, 2002Co-Authors: Alexander J. Nederbragt, Andrée. Van Loon, André Adoutte, Olivier Lespinet, Sake Van Wageningen, Wim J.a.g. DictusAbstract:SUMMARY The twist gene is known to be involved in mesoderm formation in two of the three clades of bilaterally symmetrical animals: viz. deuterostomes (such as vertebrates) and ecdysozoans (such as arthropods and nematodes). There are currently no data on the spatiotemporal expression of this gene in the third clade, the lophotrochozoans (such as mollusks and annelids). To approach the question of mesoderm homology across bilaterians, we decided to analyze orthologs of this gene in the gastropod mollusk Patella Vulgata that belongs to the lophotrochozoans. We present here the cloning, characterization, and phylogenetic analysis of a Patella twist ortholog, Pv-twi, and determine the early spatiotemporal expression pattern of this gene. Pv-twi expression was found in the trochophore larva in a subset of the ectomesoderm, one of the two sources of mesoderm in Patella. These data support the idea that twist genes were ancestrally involved in mesoderm differentiation. The absence of Pv-twi in the second mesodermal source, the endomesoderm, suggests that also other genes must be involved in lophotrochozoan mesoderm differentiation. It therefore remains a question if the mesoderm of all bilaterians is homologous.
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Spatio-temporal expression of a gene encoding a putative RNA-binding protein during the early larval development of the mollusc Patella Vulgata.
Development Genes and Evolution, 2001Co-Authors: Anke H.e.m. Klerkx, Esther De Boer, Andrée. Van LoonAbstract:In the mollusc Patella Vulgata a cDNA clone named Esther 32 (E32) was found to be expressed in a specific spatio-temporal pattern. DNA sequence analysis showed that E32 represents a putative RNA-binding protein containing a KH domain. In early trochophore larvae, expression of E32 was found in all cells except the already differentiated trochoblasts and the apical tuft cells. Later on in development, expression was also abolished in the presumptive shell gland and restricted to specific areas, among which were the head and foot anlage. This suggests that E32 is involved in maintaining cells in an undifferentiated state via a post-transcriptional mechanism.
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cyclin a cyclin b and stringlike are regulated separately in cell cycle arrested trochoblasts of Patella Vulgata embryos
Development Genes and Evolution, 1998Co-Authors: Annemieke Van Der Kooij, Christiaan P W M Veraart, Andrée. Van LoonAbstract:Trochoblasts are the first cells to differentiate during the development of spiralian embryos. Differentiation is accompanied by a cell division arrest. In embryos of the limpet Patella Vulgata, the participation of cell cycle-regulating factors in trochoblast arrest was analysed as a first step to unravel its cause. We determined the cell cycle phase in which the trochoblasts are arrested by analysing the subcellular locations of mitotic cyclins. The results show that the trochoblasts are most likely arrested in the G2 phase. This was supported by measurement of the DNA content in trochoblast nuclei after the last division. Trochoblasts complete their final division at the sixth mitotic cycle. This mitotic cycle resembles the first postblastoderm cell cycle of Drosophila, in which mitotic activity is controlled by expression of the string gene. As failure of string expression results in cell cycle arrest in the G2 phase, negative regulation of a Patellastring homolog could be responsible for trochoblast arrest. Although Stl messengers disappeared from trochoblasts during their final division, expression was observed again 20 min later. Messengers remained present in all trochoblasts at low levels during further development. Thus, expression of the stringlike gene allows the cell cycle arrest of these cells, whereas in Drosophila cells arrested in division lack string messengers.
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The stringlike genes of the limpet Patella Vulgata
Gene, 1996Co-Authors: Annemieke Van Der Kooij, Alexander J. Nederbragt, Hans J. Goedemans, Andrée. Van LoonAbstract:As a first step in analyzing the function of a cdc25 homolog during the embryonic development of Patella Vulgata (Pv), genomic clones encoding these stringlike proteins (Stl) were isolated and characterized. These clones belong to four groups which are derived from different regions of the Pv genome. As the sequences of Stl genes from two of these groups are almost identical, we suggest that these genes represent copies of the same gene. The Stl3 gene, which has been analyzed in detail, consists of four exons separated by three introns. Its sequence encodes a 250-amino-acid protein with a calculated weight of 28 kDa. The Stl protein contains regions conserved in all other cdc25 proteins. Stl messengers are not stored maternally in Pv oocytes and Stl transcription only starts after the first embryonic cleavages.
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Onset of transcription in Patella Vulgata coincides with cell cycle elongation and expression of tubulin genes
Roux's archives of developmental biology : the official organ of the EDBO, 1995Co-Authors: Andrée. Van Loon, Hans J. Goedemans, Mo E M Weijtens, A J J M DaemenAbstract:In this study we show that the onset of embryonic transcription in the marine snail Patella Vulgata coincides with the start of the sixth cleavage, when the cell-cycle elongates and divisions become asynchronous. Changes in mRNA content before and after onset of transcription were initially demonstrated by in vitro translation of isolated mRNA from different stages. Before the sixth cleavage, three major mRNAs encoding proteins of 36, 50 and 52 kDa were present. These proteins probably correspond to cyclin A and B and ribonucleotide reductase. After this stage, three major proteins with molecular weights of 36.5, 52.5 and 53 kDa were found after in vitro translation. Via hybrid selected translation and differential screening cDNAs corresponding to the 52.5 and 53 kDa proteins were cloned. The encoded proteins resemble tubulins from other animals to a high extent (between 96.5 and 93.1% identity for α-tubulin and 97.9 and 75.9% for β-tubulin). The 36.5 kDa protein is the previously described actin. Both tubulins were expressed at or shortly after the first asynchronous division after the fifth cleavage.