Jonathan Flye-Sainte-Marie

Deep sequencing of the mantle transcriptome of the great scallop Pecten maximus.

RNA-Seq transcriptome data were generated from mantle tissue of the great scallop, Pecten maximus. The consensus data were produced from a time course series of animals subjected to a 56-day thermal challenge at 3 different temperatures. A total of 26,064 contigs were assembled de novo, providing a useful resource for both the aquaculture community and researchers with an interest in mollusc shell production.

Towards the Determination of Mytilus edulis Food Preferences Using the Dynamic Energy Budget (DEB) Theory.

The blue mussel, Mytilus edulis, is a commercially important species, with production based on both fisheries and aquaculture. Dynamic Energy Budget (DEB) models have been extensively applied to study its energetics but such applications require a deep understanding of its nutrition, from filtration to assimilation. Being filter feeders, mussels show multiple responses to temporal fluctuations in their food and environment, raising questions that can be investigated by modeling. To provide a better insight into mussel–environment interactions, an experiment was conducted in one of the main French growing zones (Utah Beach, Normandy). Mussel growth was monitored monthly for 18 months, with a large number of environmental descriptors measured in parallel. Food proxies such as chlorophyll a, particulate organic carbon and phytoplankton were also sampled, in addition to non-nutritious particles. High-frequency physical data recording (e.g., water temperature, immersion duration) completed the habitat description. Measures revealed an increase in dry flesh mass during the first year, followed by a high mass loss, which could not be completely explained by the DEB model using raw external signals. We propose two methods that reconstruct food from shell length and dry flesh mass variations. The former depends on the inversion of the growth equation while the latter is based on iterative simulations. Assemblages of food proxies are then related to reconstructed food input, with a special focus on plankton species. A characteristic contribution is attributed to these sources to estimate nutritional values for mussels. M. edulis shows no preference between most plankton life history traits. Selection is based on the size of the ingested particles, which is modified by the volume and social behavior of plankton species. This finding reveals the importance of diet diversity and both passive and active selections, and confirms the need to adjust DEB models to different populations and sites.

Respiratory response to combined heat and hypoxia in the marine bivalves Pecten maximus and Mytilus spp.

Coastal ecosystems are increasingly disturbed by the increase of mean sea surface temperature and expansion of hypoxic areas. The objectives of the present work were to describe and compare the respiratory responses to combined heat and hypoxia in two bivalve species (Pecten maximus and Mytilus spp.) living in two contrasted coastal habitats (subtidal and intertidal, respectively). Results were consistent with the vertical zonation of both species. Mytilus spp. seemed to cope better with a temperature increase than P. maximus, which was found to be outside of its optimal thermal window at 25°C. Concerning respiratory responses to hypoxia at a given temperature, P. maximus displayed greater oxyregulation capacity that was maintained over a larger range of O2 levels, as compared to Mytilus spp. When acclimation temperatures increased, both species showed a decrease in their oxyregulation capacities alongside a reduction in aerobic performance, especially in P. maximus. The comparison between species suggests that subtidal species, such as P. maximus, might be more vulnerable to a combination of heat and hypoxia than intertidal species, such as Mytilus spp. Lastly, this study highlighted the utility of segmented linear models to estimate PcO2 and regulation percentages in marine organisms exposed to hypoxia.

Proteomic responses to hypoxia at different temperatures in the great scallop (Pecten maximus)

Hypoxia and hyperthermia are two connected consequences of the ongoing global change and constitute major threats for coastal marine organisms. In the present study, we used a proteomic approach to characterize the changes induced by hypoxia in the great scallop, Pecten maximus, subjected to three different temperatures (10 °C, 18 °C and 25 °C). We did not observe any significant change induced by hypoxia in animals acclimated at 10 °C. At 18 °C and 25 °C, 16 and 11 protein spots were differentially accumulated between normoxia and hypoxia, respectively. Moreover, biochemical data (octopine dehydrogenase activity and arginine assays) suggest that animals grown at 25 °C switched their metabolism towards anaerobic metabolism when exposed to both normoxia and hypoxia, suggesting that this temperature is out of the scallops’ optimal thermal window. The 11 proteins identified with high confidence by mass spectrometry are involved in protein modifications and signaling (e.g., CK2, TBK1), energy metabolism (e.g., ENO3) or cytoskeleton (GSN), giving insights into the thermal-dependent response of scallops to hypoxia.

Handling enhances the development of brown ring disease signs in Ruditapes philippinarum

ABSTRACT Brown ring disease (BRD) in the Manila clam is characterized by the formation of a brown deposit of conchiolin on the inner surface of the shell that gives the disease its name. The development of the signs of BRD may be favored by the entry of bacteria in the extrapallial compartments via mechanical disruptions of the periostracal lamina and/or chipping of the shell margin. To test this hypothesis, we conducted an experiment simulating clam handling under aquaculture conditions and we checked for prevalence of BRD signs. Our results assess that rough handling of Ruditapes philippinarum in presence of the bacterium Vibrio tapetis significantly increase the prevalence of BRD signs. As a consequence, our results show that minimizing manipulation and transfer of clams during culture is beneficial to avoid the development of BRD signs.

Sources of paralytic shellfish toxin accumulation variability in the Pacific oyster Crassostrea gigas

&NA; This study was designed to assess the contribution of feeding behavior to inter‐individual variability of paralytic shellfish toxin (PST) accumulation in the Pacific oyster Crassostrea gigas. For this purpose 42 oysters were exposed for 2 days to non‐toxic algae and then for 2 other days to the PST producer Alexandrium minutum. Individual clearance rate (CR) of oysters was continuously monitored over the 4 days using an ecophysiological measurement system. Comparison of CR values when exposed to toxic and non toxic algae allowed to estimate a clearance rate inhibition index (CRII). Toxin concentration of oysters was quantified at the end of the experiment. These data allowed to estimate the toxin accumulation efficiency (TAE) as the ratio of toxin accumulated on toxin consumed. Changes of clearance rate during the experiment indicated that all individuals stopped feeding immediately after being exposed to A. minutum for at least 7 h. This fast response likely corresponded to a behavioral mechanism of avoidance rather to a toxin‐induced response. Individuals also showed high inter‐variability in their recovery of filtration after this period. Most of the inter‐individual variability (78%) in PST accumulation in C. gigas could be explained by the consumption of A. minutum cells, thus emphasizing the importance of the feeding behavior in accumulation. Based on the toxin concentration in their tissues, oysters were clustered in 3 groups showing contrasted patterns of PST accumulation: the high accumulation group was characterized by high feeding rates both on non‐toxic and toxic diet and subsequently a low CRII and high TAE. Inversely, the low accumulation group was characterized by low filtration rates, high CRII and low TAE. Both filtration capacity and sensitivity of oysters to toxins may account for the differences in their accumulation. The contribution of TAE in PST accumulation is discussed and might result from differences in assimilation and detoxification abilities among individuals. HighlightsFacing exposure to A. minutum, individual clearance rates of oysters were measured.Algal consumption explains variability in paralytic shellfish toxin accumulation.Three phenotypes were identified on the basis of their accumulation potential.Phenotypes differed in their feeding rates.Phenotypes also differed in their sensitivity to toxins and accumulation efficiency.

Thermal preference and tolerance of Peruvian grunt Anisotremus scapularis juveniles (Pisces: Haemulidae), Preferencia y tolerancia térmica de juveniles de chita Anisotremus scapularis (Pisces: Haemulidae)

Thermal preference and tolerance of juvenile Anisotremus scapularis (Pisces: Haemulidae) at different acclimation temperatures (14, 17 and 22°C) were evaluated in order to estimate the optimum temperature and the thermal tolerance limits of this species. The preference was determined through acute preferred temperature. Maximum critical temperature and mean lethal temperature allowed to estimate thermal tolerance. The results show that acclimation temperatures higher than 14°C increase both thermal preference and tolerance. However, individuals acclimatized to 22°C preferred temperatures lower than their acclimation. In addition, thermal tolerance was identical between individuals acclimatized at 17°C and 22°C. The optimum temperature of juvenile A. scapularis was 18.7 ± 2°C and its upper and lower tolerance limit was 32.6 and 10.1°C, respectively. Based on the results, we concluded that a temperature of 18.7 ± 2°C would optimize the physiological processes in juvenile A. scapularis and that temperature higher than 32.6°C and lower than 10.1°C would cause the immediate death of the organism.

DEBSe@: an e-learning platform to introduce the Dynamic Energy Budget (DEB) theory for marine ecology, fisheries sciences and aquaculture applications

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. DEBSe@: an e-learning platform to introduce the Dynamic Energy Budget (DEB) theory for marine ecology, fisheries sciences and aquaculture applications Yoann Thomas, Fred Jean, Laure Pecquerie, Gonçalo Marques, Sébastien Hervé, Valérie Dantec, Jonathan Flye-Sainte-Marie