Description: It is widely assumed that the ability of an introduced species to acclimate to local environmental conditions determines its invasion success. The sea anemone Diadumene lineata is a cosmopolitan invader and shows extreme physiological tolerances. It was recently discovered in Kiel Fjord (Western Baltic Sea), although the brackish conditions in this area are physiologically challenging for most marine organisms. This study investigated salinity tolerance in D. lineata specimens from Kiel Fjord in order to assess potential geographical range expansion of the species in the Baltic Sea. In laboratory growth assays, we quantified biomass change and asexual reproduction rates under various salinity regimes (34: North Sea, 24: Kattegat, 14: Kiel Fjord, 7: Baltic Proper). Furthermore, we used 1H-NMR-based metabolomics to analyse intracellular osmolyte dynamics. Within four weeks D. lineata exhibited a fivefold population growth through asexual reproduction at high salinities (34 and 24). Biomass increase under these conditions was significantly higher (69 %) than at a salinity of 14. At a salinity of 7, anemones ceased to reproduce asexually, their biomass decreased and metabolic depression was observed. Five main intracellular osmolytes were identified to be regulated in response to salinity change, with osmolyte depletion at a salinity of 7. We postulate that depletion of intracellular osmolytes defines a critical salinity (Scrit) that determines loss of fitness. Our results indicate that D. lineata has the potential to invade the Kattegat and Skagerrak regions with salinity 〉10. However, salinities of the Baltic Proper (salinity 〈8) currently seem to constitute a physiological limit for the species.

Description: Nature Neuroscience 20, 176 (2017). doi:10.1038/nn.4462 Authors: Roman A Romanov, Amit Zeisel, Joanne Bakker, Fatima Girach, Arash Hellysaz, Raju Tomer, Alán Alpár, Jan Mulder, Frédéric Clotman, Erik Keimpema, Brian Hsueh, Ailey K Crow, Henrik Martens, Christian Schwindling, Daniela Calvigioni, Jaideep S Bains, Zoltán Máté, Gábor Szabó, Yuchio Yanagawa, Ming-Dong Zhang, Andre Rendeiro, Matthias Farlik, Mathias Uhlén, Peer Wulff, Christoph Bock, Christian Broberger, Karl Deisseroth, Tomas Hökfelt, Sten Linnarsson, Tamas L Horvath & Tibor Harkany

Description: Ocean acidification causes an accumulation of CO2 in marine organisms and leads to shifts in acid-base parameters. Acid-base regulation in gill breathers involves a net increase of internal bicarbonate levels through transmembrane ion exchange with the surrounding water. Successful maintenance of body fluid pH depends on the functional capacity of ion-exchange mechanisms and associated energy budget. For a detailed understanding of the dependence of acid-base regulation on water parameters, we investigated the physiological responses of the shore crab Carcinus maenas to 4 weeks of ocean acidification [OA, P(CO2)w = 1800 µatm], at variable water bicarbonate levels, paralleled by changes in water pH. Cardiovascular performance was determined together with extra-(pHe) and intracellular pH (pHi), oxygen consumption, haemolymph CO2 parameters, and ion composition. High water P(CO2) caused haemolymph P(CO2) to rise, but pHe and pHi remained constant due to increased haemolymph and cellular [HCO3-]. This process was effective even under reduced seawater pH and bicarbonate concentrations. While extracellular cation concentrations increased throughout, anion levels remained constant or decreased. Despite similar levels of haemolymph pH and ion concentrations under OA, metabolic rates, and haemolymph flow were significantly depressed by 40 and 30%, respectively, when OA was combined with reduced seawater [HCO3-] and pH. Our findings suggest an influence of water bicarbonate levels on metabolic rates as well as on correlations between blood flow and pHe. This previously unknown phenomenon should direct attention to pathways of acid-base regulation and their potential feedback on whole-animal energy demand, in relation with changing seawater carbonate parameters.

Description: Data derived from a study aimed to detect differences in thermal tolerance by investigating the underlying metabolic responses in the green abalone (Haliotis fulgens) under conditions of hypoxia and hypercapnia. Juvenile abalones were exposed to a temperature ramp (+3 °C day−1) under hypoxia (50% air saturation) and hypercapnia (~1000 μatm pCO2), both individually and in combination. Impacts on energy metabolism were assessed by analyzing whole animal respiration rates and metabolic profiles of gills and hepatopancreas via 1H NMR spectroscopy. The experiments are depicted as warming (warming ramp under normoxic normocapnia), hypoxia (warming ramp under hypoxic normocapnia), hypercapnia (warming ramp under normoxic hypercapnia), and combined (warming ramp under hypoxic hypercapnia). Each experiment was accompanied by a Control group, which was exposed to the same water PO2 and PCO2 but at a stable temperature (18 °C).

Description: Understanding mechanisms of intraspecific variation in resilience to environmental drivers is key to predict species' adaptive potential. Recent studies show a higher CO2 resilience of Sydney rock oysters selectively bred for increased growth and disease resistance ('selected oysters') compared to the wild population. We tested whether the higher resilience of selected oysters correlates with an increased ability to compensate for CO2-induced acid-base disturbances. After 7 weeks of exposure to elevated seawater PCO2 (1100 µatm), wild oysters had a lower extracellular pH (pHe = 7.54 ± 0.02 (control) vs. 7.40 ± 0.03 (elevated PCO2)) and increased hemolymph PCO2 whereas extracellular acid-base status of selected oysters remained unaffected. However, differing pHe values between oyster types were not linked to altered metabolic costs of major ion regulators (Na+/K+-ATPase, H+-ATPase and Na+/H+-exchanger) in gill and mantle tissues. Our findings suggest that selected oysters possess an increased systemic capacity to eliminate metabolic CO2, possibly through higher and energetically more efficient filtration rates and associated gas exchange. Thus, effective filtration and CO2 resilience might be positively correlated traits in oysters.

Description: Ocean acidification causes an accumulation of CO2 in marine organisms and leads to shifts in acid-base parameters. Acid-base regulation in gill breathers involves a net increase of internal bicarbonate levels through transmembrane ion exchange with the surrounding water. Successful maintenance of body fluid pH depends on the functional capacity of ion-exchange mechanisms and associated energy budget. For a detailed understanding of the dependence of acid-base regulation on water parameters, we investigated the physiological responses of the shore crab Carcinus maenas to 4 weeks of ocean acidification [OA, P(CO2)w = 1800 µatm], at variable water bicarbonate levels, paralleled by changes in water pH. Cardiovascular performance was determined together with extra-(pHe) and intracellular pH (pHi), oxygen consumption, haemolymph CO2 parameters, and ion composition. High water P(CO2) caused haemolymph P(CO2) to rise, but pHe and pHi remained constant due to increased haemolymph and cellular [HCO3-]. This process was effective even under reduced seawater pH and bicarbonate concentrations. While extracellular cation concentrations increased throughout, anion levels remained constant or decreased. Despite similar levels of haemolymph pH and ion concentrations under OA, metabolic rates, and haemolymph flow were significantly depressed by 40 and 30%, respectively, when OA was combined with reduced seawater [HCO3-] and pH. Our findings suggest an influence of water bicarbonate levels on metabolic rates as well as on correlations between blood flow and pHe. This previously unknown phenomenon should direct attention to pathways of acid-base regulation and their potential feedback on whole-animal energy demand, in relation with changing seawater carbonate parameters.

Description: Objectives: Temperature dependent chemical shifts of important brain metabolites measured by localised 1H MRS were investigated to test how the use of incorrect prior knowledge on chemical shifts impairs the quantification of metabolite concentrations. Materials and methods: Phantom measurements on solutions containing 11 metabolites were performed on a 7 T scanner between 1 and 43 °C. The temperature dependence of the chemical shift differences was fitted by a linear model. Spectra were simulated for different temperatures and analysed by the AQSES program (jMRUI 5.2) using model functions with chemical shift values for 37 °C. Results: Large differences in the temperature dependence of the chemical shift differences were determined with a maximum slope of about ±7.5 × 10-4 ppm/K. For 32-40 °C, only minor quantification errors resulted from using incorrect chemical shifts, with the exception of Cr and PCr. For 1-10 °C considerable quantification errors occurred if the temperature dependence of the chemical shifts was neglected. Conclusion: If 1H MRS measurements are not performed at 37°C, for which the published chemical shift values have been determined, the temperature dependence of chemical shifts should be considered to avoid systematic quantification errors, particularly for measurements on animal models at lower temperatures.

Description: Antarctic marine ectothermal animals may be affected more than temperate species by rising ocean water temperatures due to ongoing climate change. Their specialisation on stable cold temperatures make them vulnerable to even small degrees of warming. Thus, addressing the impacts of warming on Antarctic organisms and identifying their potentially limited capacities to respond is of particular interest. The objective of the study was to determine changes in metabolite profiles related to temperature exposure and acclimation. In a long-term experiment adult fish of two Antarctic sister species Notothenia rossii and Notothenia coriiceps were acclimated to 0 °C and 5 °C for three months. Impacts and indicators of acclimation at the cellular level were determined from metabolite profiles quantified in gill tissue extracts by using nuclear magnetic resonance (NMR) spectroscopy. Furthermore, the metabolite profiles of the two con-generic species were compared. NMR spectroscopy identified over 40 metabolites that were present in each sample, but varied in their absolute concentration between species and between treatments. Variations in the concentration of phospholipid compounds, amino acids and osmolytes suggested that warming caused changes in the cellular membrane structure. It also increased the catabolism of amino acids and initiated shifts in osmoregulation. Some differences in the metabolite profile between the two notothenioid species were related to their divergent lifestyles, especially their different rates of motor activity. Increased levels of the Krebs cycle intermediate succinate and falling amino acid levels in warm-acclimated N. rossii suggested that N. rossii is more sensitive to warming than N. coriiceps. Data are obtained from dried polar gill extracts, which were re-suspended in deuterated water (D2O) to a final concentration of 1 g frozen gill tissue/ml solvent. The D2O contained 0.05 wt.% of 3-(trimethylsilyl) propionic-2,2,3,3-d4 acid, sodium salt (TSP) (Sigma Aldrich, St. Louis, USA). TSP was used as chemical shift and quantification standard. For each sample 50 µl of the resuspended gill extracts were analysed.

Description: MRI of living edible crabs Cancer pagurus submerged in seawater were recorded at 9.4 T. The dataset contains the DICOM files for the respective figures. Anatomical images of the heart were recorded using gradient-echo sequences (FLASH). The structure of the cardiovascular system in vivo was investigated using time-of-flight angiography scans. Haemlymph flow in various vessels was quantified over time with phase-contrast angiography. Self-gated IntraGate CINE MRI could reveal the extent of the heart contraction. FLOWMAP measurements of haemolymph velocity in left and right gills are given, averaging three flow velocities for either side at a specific point in time. Signal and noise values were recorded from anatomical MRI. These values were used to calculate the signal-to-noise ratio for different radiofrequency hardware setups: Images were recorded with either the volume resonator in transmit-receive mode or using the volume resonator for signal excitation and a receive-only surface coil (SUC) for signal reception.