Amino acid δ13C and δ15N from sclerotized beaks: a new tool to investigate the foraging ecology of cephalopods, including giant and colossal squids

International audienceCombining the use of predators as biological samplers together with measurements of the stable isotopic ratios (d13CBulk and d15NBulk) of their sclerotized beaks help investigate foraging ecology of poorly known oceanic cephalopods. However, high chitin content (an amino-sugar macromolecule) lowers beak d15NBulk values, thus precluding direct isotopic comparison with other tissues and organisms. To overcome the chitin effect, compound-specific isotopic analysis of amino acids (CSIA-AA) was performed on squid beaks. The method was applied on beaks and muscle, and the resulting d13CAA and d15NAA values compared between tissues. The usefulness of CSIA was tested by defining the habitat and trophic position (TPCSIA) of squids using their d13CAA and d15NAA values. Beak d13CAA values were reliably measured on 12 AA that included 5 essential and 7 non-essential AA, and d15NAA values were quantified on at least 7 AA that included 2 source and 4 trophic AA. Importantly, d13CAA and d15NAA varied little between muscle and lower and upper beaks, and TPCSIA estimates were identical regardless of the tissue considered. Tissue d13CAA values of both essential and non-essential AA reflected the latitudinal baseline d13C gradient that occurs in the Southern Indian Ocean, while beak d15NAA from source and trophic AA allowed the disentangling of the baseline effect from the trophic effect, and thus better calculations of squid TP estimates than from d15NBulk values. Beak d13CAA and d15NAA defined isotopic niches of colossal and giant squids, the 2 largest living invertebrates. In subantarctic waters, they segregate by having species-specific foraging habitats (using d13CGly or d15NPhe) and TPCSIA (using d15NGlx and d15NPhe). TPCSIA is higher in colossal (4.7) than giant (4.3) squids, and both values compare well with those of myctophid-eaters, suggesting very large squids prey primarily upon small zoo planktivorous fishes. As expected, CSIA-AA overcomes the chitin effect on beaks and it is a powerful tool to investigate trophic interactions of cephalopods. The method has a great potential with arthropods, because chitin is a main component of their exoskeleton but the deleterious effect of chitin is overlooked in isotopic studies focusing on crustaceans and insects

Diseases, parasites, and contaminants

Cap. 3 - Biology and ecology of cephalopod species commercially exploited in Europe Cap. 3.4. - Diseases, parasites, and contaminant

Progressive ontogenetic niche shift over the prolonged immaturity period of wandering albatrosses

International audienceVery little is known about trophic ontogenetic changes over the prolonged immaturity period of long-lived, wide-ranging seabirds. By using blood and feather trophic tracers (δ13C and δ15N, and mercury, Hg), we studied age-related changes in feeding ecology during the immature phase of wandering albatrosses Diomedea exulans when they gradually change from a pure oceanic life to visits to their future breeding grounds. Immatures fed in subtropical waters at high trophic positions during moult. Between- and within-individual variations in isotopic niche were very high, irrespective of age, highlighting wide-ranging exploratory behaviours. In summer, while acting as central-place foragers from their future breeding colony, individuals progressively relied on lower trophic level prey and/or southern latitudes as they aged, until occupying a similar isotopic niche to that of adults. Immatures had exceptionally high Hg burdens, with males having lower Hg concentrations than females, suggesting that they foraged more in subantarctic waters. Our findings suggest a progressive ontogenetic niche shift during central-place foraging of this long-lived species

Stable isotopes document the winter foraging ecology of king penguins and highlight connectivity between subantarctic and Antarctic ecosystems

International audienceThe poorly known winter foraging ecology of the king penguin, a major Southern Ocean consumer, was investigated at the subantarctic Crozet Islands where the largest global population breeds. Blood δ13C and δ15N values were used as proxies of the birds’ foraging habitat and diet, respectively, and circulating prolactin levels helped in determining the birds’ reproductive status. Plasma prolactin concentrations showed that king penguin adults of unknown breeding status (n = 52) that were present at the colony in winter were in fact breeders and failed breeders, but were not non -breeders. Circulating prolactin was neither related to δ13C nor δ15N values, thus suggesting that both breeders and failed breeders used the same foraging habitats and fed on the same prey. Plasma and blood cell isotopic values depicted four new relevant biological features on the feeding strategies of king penguins during the critical winter period: (1) 42% of the birds foraged in the distant Antarctic Zone, but 58% fed primarily in subantarctic waters (δ13C), (2) they preyed upon myctophids in both zones (δ15N), (3) individuals were consistent in their foraging strategies over the winter months (δ13C and δ15N), and (4) a higher proportion of females (77%–80%) than males (27%–31%) favored feeding in distant Antarctic waters (δ13C). This study highlights trophic connectivity between subantarctic and Antarctic ecosystems and hence the key role of energy export from Antarctic waters to sustain breeding populations of subantarctic predators, including during the Austral winter

Growth and metal uptake of microalgae produced using salt groundwaters from the Bay of Bourgneuf

International audienceThe Bay of Bourgneuf, France, is a main site of shellfish production. In the marshes along the bay, oyster intensive rearing and fattening need the mass production of microalgae. Salt groundwaters, available in this region, support a large part of this production for aquaculture. Studies carried out by local authorities have brought to the fore the accumulation of lead (Pb) in several samples of algal pastes derived from cultures using salt groundwater. The aim of this study was to compare growth, nutritional value and metal (Cd, Cu, Pb and Zn) uptake of four microalgae grown in two salt groundwaters or in enriched coastal seawater. Cultures of microalgae used in aquaculture (Haslea ostrearia, Phaeodactylum tricornutum, Skeletonema costatum and Tetraselmis suecica) were realised at the laboratory under controlled experimental conditions. Results indicated that salt groundwaters provided cultures with, at least, an equal biomass and a nutritional value similar to cultures grown in enriched seawater. There was no difference regarding metal accumulation whatever the culture medium, except when S. costatum was grown in one of the salt groundwater in which case its cadmium levels were higher and could be above the French guideline level. These observations questioned on the bioavailability of metals in salt groundwaters. It also underlines the specificity of metal uptake and accumulation by microalgae

Do population parameters influence the role of seabird colonies as secondary pollutants source? A case study for Antarctic ecosystems

International audiencePollutants in Antarctic ecosystems are largely attributed to long range atmospheric transport. However, previous studies confirmed seabird colonies as relevant secondary sources of organic and inorganic pollutants. When comparing these data, higher trophic level seabird colonies, small and sparse, did not influence results as strongly as lower trophic level birds large dense colonies. Thus, we cross examined results of stable isotopes and pollutants from lichens, moss and soil samples from Antarctic seabird colonies with their data for population parameters to understand how these variables influence each other. Results showed colonies clearly supplying As, Cd, Hg, Se, Zn, HCB and PCBs and corroborated other local sources. Penguin colonies were the most important pollutants sources hereby studied due to their sheer size and also their recent relative growth. Finally, results suggest climate change should likely increase the concentration of contaminants and the overall burden trapped in Antarctic terrestrial ecosystems

Impacts of land use on an insectivorous tropical bat: The importance of mercury, physio-immunology and trophic position

International audienceDeforestation, agricultural intensification, and habitat homogenization are critical threats to biodiversity in Southeast Asia. Limited information is available on the trophic and physiological responses of tropical animals to these environmental changes. The wrinkle-lipped free-tailed bat Chaerephon plicatus is a cave roosting species that is experiencing population declines across Southeast Asia, where landscapes have been drastically modified. In our study site in central Thailand, we tested the hypothesis that wrinkle-lipped free-tailed bats living in landscapes that contrast in heterogeneity and land-use differed in mercury contamination, trophic position and physio-immunological status. Bats from less heterogeneous landscapes (dominated by rice crops, absence of large forest patches) occupied a lower trophic position than conspecifics from more heterogeneous landscapes (including large forest patches). Additionally, bats from these habitats had lower concentrations of mercury in erythrocytes, lower body mass, higher antioxidant superoxide dismutase (SOD), lower antioxidant glutathione peroxidase (GPx) and lower values of the GPx/SOD ratio than bats from more heterogeneous landscapes. Individual bat mercury concentrations were positively correlated with body mass and two immune markers (lysozyme and immunoglobulin) but were negatively correlated with plasma non-enzymatic antioxidant capacity. Our results suggest various links between landscape heterogeneity, mercury accumulation/exposure, and health status of wildlife in Southeast Asian countries

Persistent Organic Pollutants in a marine bivalve on the Marennes-Oléron Bay and the Gironde Estuary (French Atlantic coast) -Part 2: Potential biological effects

International audienceContaminant effects on defence responses of ecologically and economically important organisms, such as the Pacific oyster Crassostrea gigas, are likely to influence their ability to resist infectious diseases, particularly at the young stages. The aim of this study was to explore the potential relationships between organic contaminants accumulated in the soft tissues of juvenile oysters, defence responses and physiological condition. Oysters were transplanted during summer and winter periods in different sites in the Marennes-Oléron Bay, the first area of oyster production in France, and in the Gironde Estuary, the biggest estuary in Occidental Europe. Among the battery of biochemical and physiological biomarkers applied in the present work (superoxide dismutase -SOD-, catalase, glutathione peroxidase -GPx-, malondyaldehyde -MDA-, catecholase, laccase and lysozyme in gills, digestive gland, mantle and haemolymph, glycogen, proteins and lipids in the digestive gland and the condition index at the whole organism level), MDA and lysozyme in the digestive gland and SOD, GPx and laccase in plasma contibuted to significantly discriminate sites in which oysters bioaccumulated different levels of heavy polycyclic aromatic hydrocarbons (HPAHs), polychlorobiphenyls (PCBs), polybromodiphenylethers (PBDEs), dichlorodiphenyltrichloroethanes (DDTs) and lindane. These results strengthen the hypothesis that it is possible to differentiate sites depending on their contamination levels and biological effects by carrying out studies with transplanted juvenile oysters. In addition, correlations between antioxidant and immune defence responses and PAH and DDT body burdens in the first area of oyster production in France, the Marennes-Oléron Bay, and where massive oyster mortalities have been reported, suggest that the presence of organic chemical contaminants in the Marennes-Oléron Bay may influence defence responses in juveniles of C. gigas, and, therefore, could influence their ability to resist infectious diseases

Metal influence on metallothionein synthesis in the hydrothermal vent mussel Bathymodiolus thermophilus

International audienceThe present study reports on the metallothionein expression in the hydrothermal vent mussel Bathymodiolus thermophilus. Metallothioneins (MT) are proteins involved in intracellular metal regulation and conserved throughout the animal kingdom. The hydrothermal vent environment presents peculiarities (high levels of sulfides and metals, low pH, anoxia) that may have driven associated species to develop original evolutionary ways to face these extreme living conditions. Mussels were exposed to different metal solutions at the atmospheric pressure. The MT mRNA levels and MT contents were measured in gills and mantles of each exposed mussel. The intracellular metal distribution was estimated in fractions obtained after the centrifugation of tissue homogenates. A few of the tested metals (Ag, Cu, Cd, Hg and Zn) were able to significantly induce MT mRNA levels. Silver was the only one that produced a significant increase of the MT protein level in both mantle and gills. The gills always presented higher MT protein levels than the mantle did, while their MT mRNA levels were similar. Our data show that MT mRNA and MT protein levels do not follow a clear relationship in the gills and mantle of B. thermophilus and we assume that a post-transcriptional control occurs in these mussels

Toxicity assessment of water-accommodated fractions from two different oils using a zebrafish (Danio rerio) embryo-larval bioassay with a multilevel approach

International audiencePetroleum compounds from chronic discharges and oil spills represent an important source of environmental pollution. To better understand the deleterious effects of these compounds, the toxicity of water-accommodated fractions (WAF) from two different oils (brut Arabian Light and Erika heavy fuel oils) were used in this study. Zebrafish embryos (Danio rerio) were exposed during 96 hours at three WAF concentrations (1, 10 and 100% for Arabian Light and 10, 50 and 100% for Erika) in order to cover a wide range of polycyclic aromatic hydrocarbon (PAH) concentrations, representative of the levels found after environmental oil spills. Several endpoints were recorded at different levels of biological organization, including lethal endpoints, morphological abnormalities, photomotor behavioral responses, cardiac activity, DNA damage and exposure level measurements (EROD activity, cyp1a and PAH metabolites). Neither morphological nor behavioral or physiological alterations were observed after exposure to Arabian Light fractions. In contrast, the Erika fractions led a high degree of toxicity in early life stages of zebrafish. Despite of defense mechanisms induced by oil, acute toxic effects have been recorded including mortality, delayed hatching, high rates of developmental abnormalities, disrupted locomotor activity and cardiac failures at the highest PAH concentrations (Σ TPAHs=257029 ± 47231 ng.L-1). Such differences in toxicity are likely related to the oil composition. The use of developing zebrafish is a good tool to identify wide range of detrimental effects and elucidate their underlying foundations. Our work highlights once more, the cardiotoxic action (and potentially neurotoxic) of petroleum-related PAHs