Abstract. The shells of two marine bivalve species (Fulvia tenuicostata and Soletellina biradiata) endemic to south Western Australia have been characterised using a combined crystallographic, spectroscopic and geochemical approach. Both species have been described previously as purely aragonitic; however, this study identified the presence of three phases, namely aragonite, calcite and Mg-calcite, using XRD analysis. Data obtained via confocal Raman spectroscopy, electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) show correlations between Mg ∕ S and Mg ∕ P in F. tenuicostata and between Sr ∕ S and S ∕ Ba in S. biradiata. The composition of the organic macromolecules that constitute the shell organic matrix (i.e. the soluble phosphorus-dominated and/or insoluble sulfur-dominated fraction) influences the incorporation of Mg, Sr and Ba into the crystal lattice. Ionic substitution, particularly Ca2+ by Mg2+ in calcite in F. tenuicostata, appears to have been promoted by the combination of both S- and P-dominated organic macromolecules. The elemental composition of these two marine bivalve shells is species specific and influenced by many factors, such as crystallographic structure, organic macromolecule composition and environmental setting. In order to reliably use bivalve shells as proxies for paleoenvironmental reconstructions, both the organic and inorganic crystalline material need to be characterised to account for all influencing factors and accurately describe the vital effect.
Abstract Roger, L. M., Richardson, A. J., McKinnon, A. D., Knott, B., Matear, R., and Scadding, C. 2012. Comparison of the shell structure of two tropical Thecosomata (Creseis acicula and Diacavolinia longirostris) from 1963 to 2009: potential implications of declining aragonite saturation. – ICES Journal of Marine Science, 69: 465–474. Thecosomata (shelled pteropod molluscs) are calcifiers that play an important role in the ocean carbonate cycle. Ocean acidification as a result of the uptake of CO2 affects pteropods by increasing dissolution rates of their aragonite skeletons. Two species of pteropod found in Australian tropical waters were studied, Creseis acicula and Diacavolinia longirostris. To assess the changes in their aragonite shells, shell morphology, growth patterns, structure, size, and porosity are described for both species, from material collected at seven sites between the 1960s and the 2000s. Shell characteristics were used to explore variations over time potentially related to ocean acidification. The aragonite saturation level (Ωarag) of surface waters was hindcast and a decline equivalent to −10% (average of the seven sites) was found. Simultaneously, variations in shell thickness were recorded (C. acicula by −4.43 µm, D. longirostris by −5.37 µm) over the study period along with a significant increase in shell porosity (C. acicula: +1.43%, D. longirostris: +8.69%). The work, although not conclusive, does suggest that pteropods off Northern Australia may have been influenced by the decline in Ωarag over the past few decades. Such adverse effects could ultimately affect thecosome survival and that of their predators.
Human activities threaten coral survival. A better understanding of the coral behaviors in response to environmental changes may lead to a rescue plan but remains challenging. The authors demonstrate quantitative features of coral motion---a key trait of coral polyps---through real-time microscopy on a fluidic platform, and discover the correlated fractional Brownian motion of coral polyps under different light and temperature conditions. Numerical analysis and theoretical modeling are performed to interpret the observed coral dynamics. This work provides systematic techniques to study coral polyp motions and advances our knowledge of their behavior under climate change.
Once thought to be a unique capability of the Langerhans Islands in the pancreas of mammals, insulin production is now recognized as an evolutionarily ancient function going back to prokaryotes, ubiquitously present in unicellular eukaryotes, fungi, worm, Drosophila and of course human. While the functionality of the signaling pathway has been experimentally demonstrated in some of these organisms, it has not yet been exploited for pharmacological applications. To enable such applications, we need to understand the extent to which the structure and function of the insulin-insulin receptor system is conserved. To this end, we analyzed the insulin signaling pathway in corals through remote homology detection and modeling. By docking known insulin receptor ligands to a coral homology structure, we locate ligand binding pockets and demonstrate their conservation suggesting that it may be possible to exploit the structural conservation for pharmacological applications in non-model organisms. We also identified the coral homologues of the over 100 signaling proteins involved in insulin and its related signaling pathways, demonstrating their wide-spread conservation. Notable exceptions are glucagon and somatostatin. It is tempting to speculate that under high light conditions, when the algae synthetize excess sugars, the cnidarian host may experience insulin resistance, and that the cnidarian microbiome may be involved in manipulating the insulin signaling system.
Abstract The application of established cell viability assays such as the commonly used trypan blue staining method to coral cells is not straightforward due to different culture parameters and different cellular features specific to mammalian cells compared to marine invertebrates. Using Pocillopora damicornis as a model, we characterized the autofluorescence and tested different fluorescent dye pair combinations to identify alternative viability indicators. The cytotoxicity of different representative molecules, namely small organic molecule, protein and nanoparticles (NP), was measured after 24 hours of exposure using the fluorescent dye pair Hoechst 33342 and SYTOX® orange. Our results show that this dye pair can be distinctly measured in the presence of fluorescent proteins plus chlorophyll. P. damicornis cells exposed for 24 hours to Triton-X100, insulin or titanium dioxide (TiO2) NPs, respectively, at concentrations ranging from 0.5-100 µg/mL, revealed a LC50 of 0.5 µg/mL for Triton-X100, 20 µg/mL for TiO2 NPs and an average 20% reduction in viability at 100 µg/mL for insulin. The workflow presented here provides a general framework for customizing dye pairs for cell viability assays considering the species- and genotype-specific autofluorescence of scleractinian corals.
Abstract The application of established cell viability assays such as the commonly used trypan blue staining method to coral cells is not straightforward due to different culture parameters and different cellular features specific to mammalian cells compared to marine invertebrates. Using Pocillopora damicornis as a model, we characterized the autofluorescence and tested different fluorescent dye pair combinations to identify alternative viability indicators. The cytotoxicity of different representative molecules, namely small organic molecules, proteins and nanoparticles (NP), was measured after 24 h of exposure using the fluorescent dye pair Hoechst 33342 and SYTOX orange. Our results show that this dye pair can be distinctly measured in the presence of fluorescent proteins plus chlorophyll. P. damicornis cells exposed for 24 h to Triton-X100, insulin or titanium dioxide (TiO 2 ) NPs, respectively, at concentrations ranging from 0.5 to 100 µg/mL, revealed a LC50 of 0.46 µg/mL for Triton-X100, 6.21 µg/mL for TiO 2 NPs and 33.9 µg/mL for insulin. This work presents the approach used to customize dye pairs for membrane integrity-based cell viability assays considering the species- and genotype-specific autofluorescence of scleractinian corals, namely: endogenous fluorescence characterization followed by the selection of dyes that do not overlap with endogenous signals.
Once thought to be a unique capability of the Langerhans islets in the pancreas of mammals, insulin (INS) signaling is now recognized as an evolutionarily ancient function going back to prokaryotes. INS is ubiquitously present not only in humans but also in unicellular eukaryotes, fungi, worms, and Drosophila . Remote homologue identification also supports the presence of INS and INS receptor in corals where the availability of glucose is largely dependent on the photosynthetic activity of the symbiotic algae. The cnidarian animal host of corals operates together with a 20,000-sized microbiome, in direct analogy to the human gut microbiome. In humans, aberrant INS signaling is the hallmark of metabolic disease, and is thought to play a major role in aging, and age-related diseases, such as Alzheimer’s disease. We here would like to argue that a broader view of INS beyond its human homeostasis function may help us understand other organisms, and in turn, studying those non-model organisms may enable a novel view of the human INS signaling system. To this end, we here review INS signaling from a new angle, by drawing analogies between humans and corals at the molecular level.
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