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Tran D.,CNRS Laboratory of Oceanic Environments and Paleo-environments (EPOC) | Ciutat A.,CNRS Laboratory of Oceanic Environments and Paleo-environments (EPOC) | Mat A.,CNRS Laboratory of Oceanic Environments and Paleo-environments (EPOC) | Massabuau J.-C.,CNRS Laboratory of Oceanic Environments and Paleo-environments (EPOC) | And 4 more authors.
Aquatic Toxicology | Year: 2015

The objective of the present work was to study the effect of the harmful alga Alexandrium minutum on the daily rhythm of the oyster Crassostrea gigas. Many metabolic and physiological functions are rhythmic in living animals. Their cycles are modeled in accordance with environmental cycles such as the day/night cycle, which are fundamental to increase the fitness of an organism in its environment. A disruption of rhythmic activities is known to possibly impact the health of an animal. This study focused in C. gigas, on a gene known to be involved in circadian rhythmicity, cryptochrome gene (CgCry), on putative clock-controlled genes involved in metabolic and physiological functions, on the length cycle of the style, a structure involved in digestion, and on the rhythmicity of valve activity involved in behavior. The results indicate that daily activity is synchronized at the gene level by light:dark cycles in C. gigas. A daily rhythm of valve activity and a difference in crystalline style length between scotophase and photophase were also demonstrated. Additionally, A. minutum exposure was shown to alter cyclic activities: in exposed oysters, gene transcription remained at a constant low level throughout a daily cycle, valve opening duration remained maximal and crystalline style length variation disappeared. The results show that a realistic bloom of A. minutum clearly can disrupt numerous and diverse molecular, physiological and behavioral functions via a loss of rhythmicity. © 2014 Elsevier B.V.


Da Costa F.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Robert R.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Robert R.,French Research Institute for Exploitation of the Sea | Quere C.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | And 2 more authors.
Lipids | Year: 2015

Essential fatty acids (EFA) are important for bivalve larval survival and growth. The purpose of this study was to quantitatively assess for the first time through a mass-balance approach dietary EFA incorporation and synthesis within Crassostrea gigas larvae. A first experiment was carried out using two microalgae, Tisochrysis lutea (T) and Chaetoceros neogracile (Cg), as mono- and bi-specific diets. A second experiment using a similar design was performed to confirm and extend the results obtained in the first. Flow-through larval rearing was used for accurate control of food supply and measurement of ingestion. Non-methylene-interrupted fatty acids were synthetized from precursors supplied in the diet: 16:1n-7 and 18:1n-9, mediated by Δ5 desaturase. Moreover, this Δ5 desaturase presumably allowed larvae to convert 20:3n-6 and 20:4n-3 to 20:4n-6 and 20:5n-3, respectively, when the product EFA were poorly or not supplied in the diet, as when larvae were fed T exclusively. Under our experimental conditions, none of the diets induced 22:6n-3 synthesis; however, 22:6n-3 incorporation into larval tissues occurred selectively under non-limiting dietary supply to maintain optimal levels in the larvae. This combination of flow-through larval rearing and biochemical analysis of FA levels could be applied to additional dietary experiments to precisely define optimal levels of EFA supply. © 2015 AOCS.


Da Costa F.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Petton B.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Mingant C.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Bougaran G.,Ifremer Laboratoire Physiologie et Biotechnologies des Algues Nantes Cedex 3 France | And 5 more authors.
Aquaculture Nutrition | Year: 2015

Effects of a remarkably high overall lipid Tisochrysis lutea strain (T+) upon gross biochemical composition, fatty acid (FA), sterol and lipid class composition of Crassostrea gigas larvae were evaluated and compared with a normal strain of Tisochrysis lutea (T) and the diatom Chaetoceros neogracile (Cg). In a first experiment, the influence of different single diets (T, T+ and Cg) and a bispecific diet (TCg) was studied, whereas, effects of monospecific diets (T and T+) and bispecific diets (TCg and T+Cg) were evaluated in a second experiment. The strain T+ was very rich in triglycerides (TAG: 93-95% of total neutral lipids), saturated FA (45%), monounsaturated FA (31-33%) and total fatty acids (4.0-4.7 pg cell-1). Larval oyster survival and growth rate were positively correlated with 18:1n-7 and 20:1n-7, in storage lipids (SL), and negatively related to 14:0, 18:1n-9, 20:1n-9, 20:4n-6 and trans-22-dehydrocholesterol in membrane lipids (ML). Surprisingly, only the essential fatty acid 20:5n-3 in SL was correlated positively with larval survival. Correlations suggest that physiological disruption by overabundance of TAG, FFA and certain fatty acids in larvae fed T+ was largely responsible for the poor performance of these larvae. 'High-lipid' strains of microalgae, without regard to qualitative lipid composition, do not always improve bivalve larval performance. © 2015 John Wiley & Sons Ltd.


PubMed | CNRS Laboratory of Oceanic Environments and Paleo-environments (EPOC) and Laboratoire Des Science Of Lenvironnement Marin Umr 6539
Type: | Journal: Aquatic toxicology (Amsterdam, Netherlands) | Year: 2014

The objective of the present work was to study the effect of the harmful alga Alexandrium minutum on the daily rhythm of the oyster Crassostrea gigas. Many metabolic and physiological functions are rhythmic in living animals. Their cycles are modeled in accordance with environmental cycles such as the day/night cycle, which are fundamental to increase the fitness of an organism in its environment. A disruption of rhythmic activities is known to possibly impact the health of an animal. This study focused in C. gigas, on a gene known to be involved in circadian rhythmicity, cryptochrome gene (CgCry), on putative clock-controlled genes involved in metabolic and physiological functions, on the length cycle of the style, a structure involved in digestion, and on the rhythmicity of valve activity involved in behavior. The results indicate that daily activity is synchronized at the gene level by light:dark cycles in C. gigas. A daily rhythm of valve activity and a difference in crystalline style length between scotophase and photophase were also demonstrated. Additionally, A. minutum exposure was shown to alter cyclic activities: in exposed oysters, gene transcription remained at a constant low level throughout a daily cycle, valve opening duration remained maximal and crystalline style length variation disappeared. The results show that a realistic bloom of A. minutum clearly can disrupt numerous and diverse molecular, physiological and behavioral functions via a loss of rhythmicity.

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