Publications by authors named "Le Moullac Gilles"

17 Publications

  • Page 1 of 1

Microplastics induce dose-specific transcriptomic disruptions in energy metabolism and immunity of the pearl oyster Pinctada margaritifera.

Environ Pollut 2020 Nov 8;266(Pt 3):115180. Epub 2020 Jul 8.

Ifremer, Institut Louis-Malardé, IRD, Univ Polynésie Française, EIO, F-98719, Taravao, Tahiti, Polynésie française, France. Electronic address:

A combined approach integrating bioenergetics and major biological activities is essential to properly understand the impact of microplastics (MP) on marine organisms. Following experimental exposure of polystyrene microbeads (micro-PS of 6 and 10 μm) at 0.25, 2.5, and 25 μg L, which demonstrated a dose-dependent decrease of energy balance in the pearl oyster Pinctada margaritifera, a transcriptomic study was conducted on mantle tissue. Transcriptomic data helped us to decipher the molecular mechanisms involved in P. margaritifera responses to micro-PS and search more broadly for effects on energetically expensive maintenance functions. Genes related to the detoxification process were impacted by long-term micro-PS exposure through a decrease in antioxidant response functioning, most likely leading to oxidative stress and damage, especially at higher micro-PS doses. The immune response was also found to be dose-specific, with a stress-related activity stimulated by the lowest dose present after a 2-month exposure period. This stress response was not observed following exposure to higher doses, reflecting an energy-limited capacity of pearl oysters to cope with prolonged stress and a dramatic shift to adjust to pessimum conditions, mostly limited and hampered by a lowered energetic budget. This preliminary experiment lays the foundation for exploring pathways and gene expression in P. margaritifera, and marine mollusks in general, under MP exposure. We also propose a conceptual framework to properly assess realistic MP effects on organisms and population resilience in future investigations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.envpol.2020.115180DOI Listing
November 2020

Toxic effects of leachates from plastic pearl-farming gear on embryo-larval development in the pearl oyster Pinctada margaritifera.

Water Res 2020 Jul 30;179:115890. Epub 2020 Apr 30.

Ifremer, Institut Louis-Malardé, IRD, Univ Polynésie française, EIO, F-98719 Taravao, Tahiti, Polynésie française, France.

Pearl-farming leads to significant plastic pollution in French Polynesia (FP) as the end of life of most farming gear is currently poorly managed. Plastic debris released into the aquatic environment accumulates, with potentially detrimental effects on the lagoon ecosystem and pearl oyster Pinctada margaritifera, a species of ecological, commercial and social value. Here, we tested the effects of leachates from new (N) and aged (A) plastic pearl-farming gear (spat collector and synthetic rope) obtained after 24 h and 120 h incubation, on the embryo-larval development of the pearl oyster using an in-vitro assay. Embryos were exposed for 24 h and 48 h to a negative control (0) and the leachate from 0.1, 1, 10 and 100 g of plastic. L. After 24 h exposure to leachate at 100 g.L, effects were observed on embryo development (-38% to -60% of formed larvae) and mortality (+72% to +82%). Chemical analyses of plastic gear indicated the presence of 26 compounds, consisting of organic contaminants (PAHs) and additives (mainly phthalates). Screening of leachates demonstrated that these compounds leach into the surrounding seawater with an additional detection of pesticides. Higher levels of phthalates were measured in leachates obtained from new (6.7-9.1 μg.L) than from aged (0.4-0.5 μg.L) plastics, which could be part of the explanation of the clear difference in toxicity observed after 48 h exposure at lower concentrations (0.1-10 g.L), associated with mortality ranging from 26 to 86% and 17-28%, respectively. Overall, this study suggests that plastic gear used in the pearl-farming industry releases significant amounts of hazardous chemicals over their lifetime, which may affect pearl oyster development that call for in-situ exploration.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.watres.2020.115890DOI Listing
July 2020

Influence of temperature and pearl rotation on biomineralization in the pearl oyster, .

J Exp Biol 2018 09 21;221(Pt 18). Epub 2018 Sep 21.

Ifremer, UMR EIO 241, Labex Corail, Centre du Pacifique, BP 49, 98719 Taravao, Tahiti, French Polynesia.

The objective of this study was to observe the impact of temperature on pearl formation using an integrative approach describing the rotation of the pearls, the rate of nacre deposition, the thickness of the aragonite tablets and the biomineralizing potential of the pearl sac tissue though the expression level of some key genes. Fifty pearl oysters were grafted with magnetized nuclei to allow the rotation of the pearls to be described. Four months later, 32 of these pearl oysters were exposed to four temperatures (22, 26, 30 and 34°C) for 2 weeks. Results showed that the rotation speed differed according to the movement direction: pearls with axial movement had a significantly higher rotation speed than those with random movement. Pearl growth rate was influenced by temperature, with a maximum between 26 and 30°C but almost no growth at 34°C. Lastly, among the nine genes implicated in the biomineralization process, only expression was significantly modified by temperature. These results showed that the rotation speed of the pearls was not linked to pearl growth or to the expression profiles of biomineralizing genes targeted in this study. On the basis of our results, we consider that pearl rotation is a more complex process than formerly thought. Mechanisms involved could include a strong environmental forcing in immediate proximity to the pearl. Another implication of our findings is that, in the context of ocean warming, pearl growth and quality can be expected to decrease in pearl oysters exposed to temperatures above 30°C.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/jeb.186858DOI Listing
September 2018

Low energy cost for cultured pearl formation in grafted chimeric Pinctada margaritifera.

Sci Rep 2018 05 14;8(1):7520. Epub 2018 May 14.

Ifremer, UMR 241 Ecosystèmes Insulaires Océaniens (EIO), Labex Corail, Centre du Pacifique, BP 49, 98719, Taravao, Tahiti, French Polynesia.

The pearl oyster is one of the rare animal models that support two distinct genomes, through the surgical graft process operated for culture pearl production. This grafted organism is assimilated to a chimera whose physiological functioning remains poorly known. The question of the energy expenditure comparison between chimera and non-chimera animals arises. To answer this question, grafted and non-grafted pearl oysters were evaluated for their energetic needs by the indirect calorimetry method. This method made it possible to measure the energy expenditure based on the respiration rate (RR) measurement, reflecting the basal metabolism. The results showed that the RR values for grafted and non-grafted pearl oysters were not significantly different (p < 0.05). The estimated cost of pearl calcification including CaCO and proteins synthesis was 0.237 ± 0.064 J h, representing 0.64% of the total energy expenditure of grafted pearl oysters. This study made it possible, for the first time, to see the energy cost of cultured pearl formation in P. margaritifera and the little impact in the energetic metabolism of the chimera organism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-018-25360-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5951858PMC
May 2018

Microplastics Affect Energy Balance and Gametogenesis in the Pearl Oyster Pinctada margaritifera.

Environ Sci Technol 2018 05 12;52(9):5277-5286. Epub 2018 Apr 12.

Ifremer, UMR Ecosystèmes Insulaires Océaniens (EIO), UMR 241 UPF/ILM/IRD/Ifremer , Centre du Pacifique , BP 49 , 98719 , Taravao , French Polynesia.

Plastic pollution in the environment is increasing at global scale. Microplastics (MP) are derived from degradation of larger plastic items or directly produced in microparticles form (< 5 mm). Plastics, widely used in structures and equipment of pearl farming, are a source of pollution to the detriment of the lagoon ecosystem. To evaluate the impact of MP on the physiology of Pinctada margaritifera, a species of ecological and commercial interests, adult oysters were exposed to polystyrene microbeads (micro-PS of 6 and 10 μm) for 2 months. Three concentrations, 0.25, 2.5, and 25 μg L, and a control were tested. Ingestion and respiration rate and assimilation efficiency were monitored on a metabolic measurement system to determine the individual energy balance (Scope For Growth, SFG). Effects on reproduction were also assessed. The assimilation efficiency decreased significantly according to micro-PS concentration. The SFG was significantly impacted by a dose-dependent decrease from 0.25 μg L ( p < 0.0001), and a negative SFG was measured in oysters exposed to 25 μg L. Gonads may have provided the missing energy to maintain animals' metabolism through the production of metabolites derived from germ cells phagocytosis. This study shows that micro-PS significantly impact the assimilation efficiency and more broadly the energy balance of P. margaritifera, with negative repercussions on reproduction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.8b00168DOI Listing
May 2018

Influence of water temperature and food on the last stages of cultured pearl mineralization from the black-lip pearl oyster Pinctada margaritifera.

PLoS One 2018 5;13(3):e0193863. Epub 2018 Mar 5.

Ifremer, UMR 241 « Ecosystèmes Insulaires Océaniens », Labex Corail, Centre du Pacifique, Tahiti, French Polynesia.

Environmental parameters, such as food level and water temperature, have been shown to be major factors influencing pearl oyster shell growth and molecular mechanisms involved in this biomineralization process. The present study investigates the effect of food level (i.e., microalgal concentration) and water temperature, in laboratory controlled conditions, on the last stages of pearl mineralization in order to assess their impact on pearl quality. To this end, grafted pearl oysters were fed at different levels of food and subjected to different water temperatures one month prior to harvest to evaluate the effect of these factors on 1) pearl and shell deposition rate, 2) expression of genes involved in biomineralization in pearl sacs, 3) nacre ultrastructure (tablet thickness and number of tablets deposited per day) and 4) pearl quality traits. Our results revealed that high water temperature stimulates both shell and pearl deposition rates. However, low water temperature led to thinner nacre tablets, a lower number of tablets deposited per day and impacted pearl quality with better luster and fewer defects. Conversely, the two tested food level had no significant effects on shell and pearl growth, pearl nacre ultrastructure or pearl quality. However, one gene, Aspein, was significantly downregulated in high food levels. These results will be helpful for the pearl industry. A wise strategy to increase pearl quality would be to rear pearl oysters at a high water temperature to increase pearl growth and consequently pearl size; and to harvest pearls after a period of low water temperature to enhance luster and to reduce the number of defects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193863PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5837120PMC
June 2018

Response of the pearl oyster Pinctada margaritifera to cadmium and chromium: Identification of molecular biomarkers.

Mar Pollut Bull 2017 May 18;118(1-2):420-426. Epub 2017 Mar 18.

Ifremer, UMR 241 EIO, UPF-ILM-IRD, Labex Corail, BP 49, 98719 Taravao, Tahiti, French Polynesia. Electronic address:

This study was designed to identify in the pearl oyster Pinctada margaritifera, used as a bio-accumulator, molecular biomarkers for the presence of heavy metals in the lagoon environment. Pearl oysters were exposed to 2 concentrations (1 and 10μgL) of cadmium (Cd) and chromium (Cr) compared to a control. Twelve target genes encoding proteins potentially involved in the response to heavy metal contamination with antioxidant, detoxification or apoptosis activities were selected. P. margaritifera accumulated Cd but not Cr, and mortality was related to the amount of Cd accumulated in tissues. In response to Cd-Cr contamination, metallothionein (MT) was significantly up-regulated by Cd-Cr at both concentrations, while 7 others (SOD, CAT, GPX, GSTO, GSTM, CASP, MDR) were down-regulated. Based on the development of these molecular tools, we propose that the pearl oyster, P. margaritifera, could be used as a sentinel species for heavy metal contamination in the lagoons of tropical ecosystems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.marpolbul.2017.03.012DOI Listing
May 2017

Growth, Survival and Reproduction of the Giant Clam Tridacna maxima (Röding 1798, Bivalvia) in Two Contrasting Lagoons in French Polynesia.

PLoS One 2017 24;12(1):e0170565. Epub 2017 Jan 24.

Direction des Ressources Marines et Minières, Fare Ute, Papeete, Tahiti, French Polynesia.

Shell growth, reproduction, and natural mortality of the giant clam Tridacna maxima were characterized over a two-year-period in the lagoon of the high island of Tubuai (Austral Archipelago) and in the semi-closed lagoon of Tatakoto (Tuamotu Archipelago) in French Polynesia. We also recorded temperature, water level, tidal slope, tidal range, and mean wave height in both lagoons. Lower lagoon aperture and exposure to oceanic swells at Tatakoto than at Tubuai was responsible for lower lagoon water renewal, as well as higher variability in temperature and water level at Tatakoto across the studied period. These different environmental conditions had an impact on giant clams. Firstly, spawning events in the lagoon of Tatakoto, detected by gonad maturity indices in June and July 2014, were timed with high oceanic water inflow and a decrease in lagoon water temperature. Secondly, temperature explained differences in shell growth rates between seasons and lagoons, generating different growth curves for the two sites. Thirdly, local mortality rates were also found to likely be related to water renewal patterns. In conclusion, our study suggests that reef aperture and lagoon water renewal rates play an integral role in giant clam life history, with significant differences in rates of shell growth, mortality and fertility found between open versus semi-closed atoll lagoons in coral reef ecosystems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0170565PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5261826PMC
August 2017

Yes, it turns: experimental evidence of pearl rotation during its formation.

R Soc Open Sci 2015 Jul 15;2(7):150144. Epub 2015 Jul 15.

Ifremer , UMR 241 EIO, UPF-ILM-IRD, Labex Corail , BP 7004, 98719 Taravao, French Polynesia.

Cultured pearls are human creations formed by inserting a nucleus and a small piece of mantle tissue into a living shelled mollusc, usually a pearl oyster. Although many pearl observations intuitively suggest a possible rotation of the nucleated pearl inside the oyster, no experimental demonstration of such a movement has ever been done. This can be explained by the difficulty of observation of such a phenomenon in the tissues of a living animal. To investigate this question of pearl rotation, a magnetometer system was specifically engineered to register magnetic field variations with magnetic sensors from movements of a magnetic nucleus inserted in the pearl oyster. We demonstrated that a continuous movement of the nucleus inside the oyster starts after a minimum of 40 days post-grafting and continues until the pearl harvest. We measured a mean angular speed of 1.27° min(-1) calculated for four different oysters. Rotation variability was observed among oysters and may be correlated to pearl shape and defects. Nature's ability to generate so amazingly complex structures like a pearl has delivered one of its secrets.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1098/rsos.150144DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4632584PMC
July 2015

Effect of temperature, food availability, and estradiol injection on gametogenesis and gender in the pearl oyster Pinctada margaritifera.

J Exp Zool A Ecol Genet Physiol 2016 Jan 20;325(1):13-24. Epub 2015 Oct 20.

Ifremer, UMR 241 Ecosystèmes Insulaires Océaniens (EIO), Labex CORAIL, Centre du Pacifique, Taravao, Tahiti, French Polynesia.

The black-lip pearl oyster Pinctada margaritifera is a protandrous hermaphrodite species. Its economic value has led to the development of controlled hatchery reproduction techniques, although many aspects remain to be optimized. In order to understand reproductive mechanisms and their controlling factors, two independent experiments were designed to test hypotheses of gametogenesis and sex ratio control by environmental and hormonal factors. In one, pearl oysters were exposed under controlled conditions at different combinations of temperature (24 and 28°C) and food level (10,000 and 40,000 cells mL(-1) ); whereas in the other, pearl oysters were conditioned under natural conditions into the lagoon and subjected to successive 17β-estradiol injections (100 μg per injection). Gametogenesis and sex ratio were assessed by histology for each treatment. In parallel, mRNA expressions of nine marker genes of the sexual pathway (pmarg-foxl2, pmarg-c43476, pmarg-c45042, pmarg-c19309, pmarg-c54338, pmarg-vit6, pmarg-zglp1, pmarg-dmrt, and pmarg-fem1-like) were investigated. Maximum maturation was observed in the treatment combining the highest temperature (28°C) and the highest microalgae concentration (40,000 cells mL(-1) ), where the female sex tended to be maintained. Injection of 17β-estradiol induced a significant increase of undetermined stage proportion 2 weeks after the final injection. These results suggest that gametogenesis and gender in adult pearl oysters can be controlled by environmental factors and estrogens. While there were no significant effects on relative gene expression, the 3-gene-pair expression ratio model of the sexual pathway of P. margaritifera, suggest a probable dominance of genetic sex determinism without excluding a mixed sex determination mode (genetic + environmental). J. Exp. Zool. 325A:13-24, 2016. © 2015 Wiley Periodicals, Inc.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jez.1992DOI Listing
January 2016

Molecular signatures discriminating the male and the female sexual pathways in the pearl oyster Pinctada margaritifera.

PLoS One 2015 27;10(3):e0122819. Epub 2015 Mar 27.

Ifremer, UMR 241 Ecosystèmes Insulaires Océaniens (EIO), Labex Corail, Centre du Pacifique, BP 7004, 98719 Taravao, Tahiti, French Polynesia.

The genomics of economically important marine bivalves is studied to provide better understanding of the molecular mechanisms underlying their different reproductive strategies. The recently available gonad transcriptome of the black-lip pearl oyster Pinctada margaritifera is a novel and powerful resource to study these mechanisms in marine mollusks displaying hermaphroditic features. In this study, RNAseq quantification data of the P. margaritifera gonad transcriptome were analyzed to identify candidate genes in histologically-characterized gonad samples to provide molecular signatures of the female and male sexual pathway in this pearl oyster. Based on the RNAseq data set, stringent expression analysis identified 1,937 contigs that were differentially expressed between the gonad histological categories. From the hierarchical clustering analysis, a new reproduction model is proposed, based on a dual histo-molecular analytical approach. Nine candidate genes were identified as markers of the sexual pathway: 7 for the female pathway and 2 for the male one. Their mRNA levels were assayed by real-time PCR on a new set of gonadic samples. A clustering method revealed four principal expression patterns based on the relative gene expression ratio. A multivariate regression tree realized on these new samples and validated on the previously analyzed RNAseq samples showed that the sexual pathway of P. margaritifera can be predicted by a 3-gene-pair expression ratio model of 4 different genes: pmarg-43476, pmarg-foxl2, pmarg-54338 and pmarg-fem1-like. This 3-gene-pair expression ratio model strongly suggests only the implication of pmarg-foxl2 and pmarg-fem1-like in the sex inversion of P. margaritifera. This work provides the first histo-molecular model of P. margaritifera reproduction and a gene expression signature of its sexual pathway discriminating the male and female pathways. These represent useful tools for understanding and studying sex inversion, sex differentiation and sex determinism in this species and other related species for aquaculture purposes such as genetic selection programs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0122819PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4376701PMC
February 2016

Temperature and food influence shell growth and mantle gene expression of shell matrix proteins in the pearl oyster Pinctada margaritifera.

PLoS One 2014 14;9(8):e103944. Epub 2014 Aug 14.

Ifremer, UMR 241 « Ecosystèmes Insulaires Océaniens », Labex Corail, Centre du Pacifique, Taravao, Tahiti, Polynésie Française.

In this study, we analyzed the combined effect of microalgal concentration and temperature on the shell growth of the bivalve Pinctada margaritifera and the molecular mechanisms underlying this biomineralization process. Shell growth was measured after two months of rearing in experimental conditions, using calcein staining of the calcified structures. Molecular mechanisms were studied though the expression of 11 genes encoding proteins implicated in the biomineralization process, which was assessed in the mantle. We showed that shell growth is influenced by both microalgal concentration and temperature, and that these environmental factors also regulate the expression of most of the genes studied. Gene expression measurement of shell matrix protein thereby appears to be an appropriate indicator for the evaluation of the biomineralization activity in the pearl oyster P. margaritifera under varying environmental conditions. This study provides valuable information on the molecular mechanisms of mollusk shell growth and its environmental control.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103944PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4133174PMC
April 2015

Gonad transcriptome analysis of pearl oyster Pinctada margaritifera: identification of potential sex differentiation and sex determining genes.

BMC Genomics 2014 Jun 18;15:491. Epub 2014 Jun 18.

Ifremer, UMR 241 EIO, Labex CORAIL, BP 7004, 98719 Taravao, Tahiti, Polynésie Française.

Background: Black pearl farming is based on culture of the blacklip pearl oyster Pinctada margaritifera (Mollusca, lophotrochozoa), a protandrous hermaphrodite species. At first maturation, all individuals are males. The female sex appears progressively from two years old, which represents a limitation for broodstock conditioning for aquaculture production. In marine mollusks displaying hermaphroditic features, data on sexual determinism and differentiation, including the molecular sex determining cascade, are scarce. To increase genomic resources and identify the molecular mechanisms whereby gene expression may act in the sexual dimorphism of P. margaritifera, we performed gonad transcriptome analysis.

Results: The gonad transcriptome of P. margaritifera was sequenced from several gonadic samples of males and females at different development stages, using a Next-Generation-Sequencing method and RNAseq technology. After Illumina sequencing, assembly and annotation, we obtained 70,147 contigs of which 62.2% shared homologies with existing protein sequences, and 9% showed functional annotation with Gene Ontology terms. Differential expression analysis identified 1,993 differentially expressed contigs between the different categories of gonads. Clustering methods of samples revealed that the sex explained most of the variation in gonad gene expression. K-means clustering of differentially expressed contigs showed 815 and 574 contigs were more expressed in male and female gonads, respectively. The analysis of these contigs revealed the presence of known specific genes coding for proteins involved in sex determinism and/or differentiation, such as dmrt and fem-1 like for males, or foxl2 and vitellogenin for females. The specific gene expression profiles of pmarg-fem1-like, pmarg-dmrt and pmarg-foxl2 in different reproductive stages (undetermined, sexual inversion and regression) suggest that these three genes are potentially involved in the sperm-oocyte switch in P. margaritifera.

Conclusions: The study provides a new transcriptomic tool to study reproduction in hermaphroditic marine mollusks. It identifies sex differentiation and potential sex determining genes in P. margaritifera, a protandrous hermaphrodite species.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1471-2164-15-491DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4082630PMC
June 2014

Pearl oysters Pinctada margaritifera grazing on natural plankton in Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia).

Mar Pollut Bull 2012 3;65(10-12):490-9. Epub 2012 May 3.

IFREMER, Centre du Pacifique, BP 7004, 98719 Taravao, Tahiti, French Polynesia.

In atoll lagoons of French Polynesia, growth and reproduction of pearl oysters are mainly driven by plankton concentration. However, the actual diet of black-lip pearl oysters Pinctada margaritifera in these lagoons is poorly known. To fill this gap, we used the flow through chamber method to measure clearance rates of P. margaritifera in Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia). We found: (i) that pearl oysters cleared plankton at a rate that was positively related to plankton biovolume, (ii) that nanoflagellates were the main source of carbon for the pearl oysters, and (iii) that the quantity and origin of carbon filtrated by pearl oysters was highly dependent on the concentration and composition of plankton. These results provide essential elements for the comprehension of growth and reproduction variability of pearl oysters in atoll lagoons of French Polynesia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.marpolbul.2012.03.026DOI Listing
November 2012

Influence of plankton concentration on gametogenesis and spawning of the black lip pearl oyster Pinctada margaritifera in Ahe atoll lagoon (Tuamotu Archipelago, French polynesia).

Mar Pollut Bull 2012 2;65(10-12):463-70. Epub 2012 May 2.

IFREMER, Centre du Pacifique, BP 7004, 98719 Taravao, Tahiti, French Polynesia.

Pearl culture industry represents one of the dominant business sector of French Polynesia. However, it still entirely relies on unpredictable spat collection success. Our aim was to assess the influence of natural plankton concentration fluctuations on maturation and spawning of the black lip pearl oyster Pinctada margaritifera, during a 4 months survey conducted in Ahe atoll lagoon. Plankton concentration was assessed by chlorophyll a extraction and by microscope counts while gonadic index, gonado-visceral dry weights and histology were used to measure pearl oysters reproduction activity. We found that (i) plankton concentration fluctuations were mainly related to wind regime, (ii) gametogenesis rate was mainly related to plankton concentration, (iii) spawning occurred when maximal gonad storage was reached, (iv) plankton concentration was the main spawning synchronizing factor. These results contribute explaining P. margaritifera spat collection variability in French Polynesian atoll lagoon.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.marpolbul.2012.03.027DOI Listing
November 2012

Transcriptomic response of the Pacific oyster Crassostrea gigas to hypoxia.

Mar Genomics 2010 Sep-Dec;3(3-4):133-43

UMR CNRS 6539-LEMAR (Laboratoire des Sciences de l'Environnement Marin), IUEM (Institut Universitaire Européen de la Mer), Université de Bretagne Occidentale, Technopôle Brest Iroise, 29280 Plouzané, France.

Marine intertidal organisms commonly face hypoxic stress during low tide emersion; moreover, eutrophic conditions and sediment nearness could lead to hypoxic phenomena; it is indeed important to understand the molecular processes involved in the response to hypoxia. In this study the molecular response of the Pacific oyster Crassostrea gigas to prolonged hypoxia (2mg O(2) L(-1) for 20d) was investigated under experimental conditions. A transcriptomic approach was employed using a cDNA microarray of 9058 C. gigas clones to highlight the genetic expression patterns of the Pacific oyster under hypoxic conditions. Lines of oysters resistant (R) and susceptible (S) to summer mortality were used in this study. ANOVA analysis was used to identify the genes involved in the response to hypoxia in comparison to normoxic conditions. The hypoxic response was maximal at day 20. The principal biological processes up-regulated by hypoxic stress were antioxidant defense and the respiratory chain compartment, suggesting oxidative stress caused by hypoxia or an anticipatory response for normoxic recovery. This is the first study employing microarrays to characterize the genetic markers and metabolic pathways responding to hypoxic stress in C. gigas.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.margen.2010.08.005DOI Listing
October 2012

Transcriptional regulation of pyruvate kinase and phosphoenolpyruvate carboxykinase in the adductor muscle of the oyster Crassostrea gigas during prolonged hypoxia.

J Exp Zool A Ecol Genet Physiol 2007 Jul;307(7):371-82

UMR 100 Physiologie et Ecophysiologie des Mollusques Marins, IFREMER, Site Expérimental d'Argenton, Presqu'île du Vivier, Argenton en Landunvez, France.

The response of Crassostrea gigas to prolonged hypoxia was investigated for the first time by analyzing the metabolic branch point formed by pyruvate kinase (PK) and hosphoenolpyruvate carboxykinase (PEPCK). PK and PEPCK cDNAs were cloned and sequenced. The main functional domains of the PK sequence, such as the binding sites for ADP/ATP and phosphoenolpyruvate (PEP), were identified whereas the PEPCK sequence showed the specific domain to bind PEP in addition to the kinase-1 and kinase-2 motifs to bind guanosine triphosphate (GTP) and Mg(2+), specific for all PEPCKs. A C-terminal extension was detected for the first time in eukaryota PK. Separation of mitochondrial and cytosolic fraction showed that more than 92% of the PEPCK enzyme activity was cytosolic in gills, digestive gland, mantle and muscle. PK and PEPCK mRNAs and enzyme activities have been measured in muscle during prolonged hypoxia for 20 days. Adaptation of PK in hypoxic muscle at transcriptional level occurred lately by decreasing significantly the PK mRNA level at day 20 while PK enzyme activity was inhibited by the high content of alanine. The PEPCK mRNA ratio in hypoxic muscle significantly increased at day 10 simultaneously to the PEPCK enzyme activity. Succinate accumulation observed at day 10 and day 20 confirmed the anaerobic pathway of muscle metabolism in oyster subjected to hypoxia. Regulation of C. gigas PEPCK in muscle occurred at gene transcription level while PK was first regulated at enzyme level with alanine as allosteric inhibitor, and then at molecular level under a fast effect of hypoxia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jez.390DOI Listing
July 2007