Centers Of Calcification Research Articles

Live imaging of center of calcification formation during septum development in primary polyps of Acropora digitifera

Recent studies have revealed that stony corals create their extracellular skeletons via biologically controlled calcification, in which amorphous calcium carbonate (ACC), regarded as precursors of aragonite crystals, have been observed at nanoscale using electron microscopy. However, the exact mechanism by which ACC is generated, and how it contributes to skeletal growth in coral calcifying tissue, remains enigmatic. The septal skeleton of an individual polyp is composed of radially aligned plates extending upward from the aboral calcifying tissue. This structure includes microstructure known as the centers of calcification (CoC). However, despite its importance, direct in vivo observation of septal growth has not been reported. Observations under transmitted illumination using polarized light microscopy on calcifying tissue of young Acropora digitifera revealed small crystals, a few micrometers in size, that accompany subtle movements and that emerge exclusively on the inner wall of the pocket in extracellular calcifying fluid (ECF). Crystal growth initiated from small, scattered crystals on a glass plate resembles this phenomenon observed in coral skeletons. Time-lapse photographs of 12 individuals in early primary polyp settlement revealed this process in three individuals, documenting 13 of these crystal events. This phenomenon occurred solely at the bases of subsequently formed septa. These crystals differ notably from fusiform crystals and from dumbbell-like or rod-like crystals growing individually. Upright two-photon microscopy captured movement of sub-micron-sized fluorescent calcein-accumulating particles, emphasizing their presence on the surface of the growing fronts of septa. Methodological advances that facilitate comprehensive in vivo observation of sub-micron-sized structures, calcein-accumulating particles to the skeleton, are needed to develop a more detailed understanding of coral skeletal growth.

Correlative geochemical imaging of Desmophyllum dianthus reveals biomineralisation strategy as a key coral vital effect

The chemical and isotopic composition of stony coral skeletons form an important archive of past climate. However, these reconstructions are largely based on empirical relationships often complicated by “vital effects” arising from uncertain physiological processes of the coral holobiont. The skeletons of deep-sea corals, such as Desmophyllum dianthus, are characterised by micron-scale or larger geochemical heterogeneity associated with: (1) centres of calcification (COCs) where nucleation of new skeleton begins, and (2) fibres that thicken the skeleton. These features are difficult to sample cleanly using traditional techniques, resulting in uncertainty surrounding both the causes of geochemical differences and their influence on environmental signals. Here we combine optical, and in-situ chemical and isotopic, imaging tools across a range of spatial resolutions (~ 100 nm to 10 s of μm) in a correlative multimodal imaging (CMI) approach to isolate the microstructural geochemistry of each component. This reveals COCs are characterised by higher organic content, Mg, Li and Sr and lower U, B and δ11B compared to fibres, reflecting the contrasting biomineralisation mechanisms employed to construct each feature. CMI is rarely applied in Environmental/Earth Sciences, but here we illustrate the power of this approach to unpick the “vital effects” in D. dianthus, and by extension, other scleractinian corals.

Forensic age diagnosis by assessment of sternum ossification processes

To study the sternum ossification processes that take place over time as well as the possibilities of sternum X-rays application to evaluate the age on the modern Russian population in forensic terms. Sternum X-rays with fragments of ribs' chondral parts were obtained from 369 male and female corpses aged 12-96 years without pathological and traumatic changes. The X-rays were done in frontal projection. The set of examined parameters included: complete and partial synostosis of manubrium and body, induration along the synostosis (or on the articulated edges of manubrium and body), complete and partial synostosis of body segments, traces of body segments union, complete and partial synostosis of body and xiphoid process, induration along the synostosis (or on the articulated edges of manubrium and body), form of costal notches, induration of articular edges of body, presence of calcification foci in sternal edge of II-VII ribs' cartilages, depth of sternum notches, overgrowths on articular edges of body, presence of union between body's costal notches and calcification centers of ribs' cartilages. Mean values, standard deviation and correlation coefficient were determined. The maximal correlation with age was found in such parameters such: overgrowths on articular edges of body (r=0.6), presence of calcification foci in sternal edge of II-VII ribs (r=0.6), induration of body's articular edges (r=0.5), presence of union between costal notches and calcification centers of ribs cartilages (r=0.5), synostosis of body and xiphoid process (r=0.4). A subsequent construction of linear model for age diagnosis has its details when comparing the predicted age with the real.

Evaluation of the skeletal ossification of sheep fetuses at different gestational ages (20–95 days) using radiography and whole-mount skeletal staining

The emergence of ossification centers is a useful tool for estimating prenatal fetal age, evaluating the process of fetal bone maturity, and diagnosing of some fetal abnormalities. In this study, the sheep fetal skeleton at different gestational ages was evaluated using radiography and whole-mount skeletal staining. The sheep's pregnant uteri were prepared from the slaughterhouse at different gestational ages, with fetal age estimated using ultrasonography. Five fetuses were aligned in each age range of 30–40 days, 40–50 days, 50–60 days, 60–70 days and 70–95 days. The fetus was removed from the uterus and laterally placed on the radiographic cassette. Whole-mount skeletal staining was then performed, with data recorded including the overall shape of the fetal skeleton and the time and area of presence of bone calcification centers at different ages of pregnancy. The results show that the emergence and expansion of ossification centers began from the bones near the midline of the body on the back surface at about 45–55 days of pregnancy. The ossification of the fetal skeleton was completed at the age of 80–95 days of pregnancy in the toes, tooth, and near the abdominal midline. Whole-mount skeletal staining revealed ossification centers from day 23. Therefore, radiography can be used to depict the time of emergence of bone centers and to examine the evolution of the fetus during sheep pregnancy. Opacity of embryonic and fetal fluids did not change during this period, preventing observation of the fetus in fetal membranes and uterus before ossification of the fetal skeleton.

Coherent tracer correlations in deep-sea corals and implications for biomineralization mechanisms underlying vital effects

Deep-sea corals are a useful archive of thermocline, intermediate, and deep waters in past oceans. However, application of traditional oceanographic tracers to deep-sea corals remains a challenge due to our insufficient understanding of their “vital effects”. Deep-sea corals are ideal test organisms to study the mechanism underlying vital effects generally, due to the large tracer gradients in individual corals living under relatively constant environmental conditions. Lessons learned from these corals might apply to other scleractinia and to marine calcifiers more generally. Here we present stable isotope, minor and trace metal (Me/Ca ratios) data in a suite of modern Desmophyllum dianthus specimens, collected over multiple spatial scales in individual corals (bulk, micromill, SIMS, NanoSIMS), with multi-proxy analyses made on the same material whenever possible. Spatially coherent Me/Ca correlations are observed in the fibrous aragonite of individual corals, including positive correlations between Mg/Ca, Li/Ca and B/Ca, as well as negative correlations between Mg/Ca and Sr/Ca, consistent with previous studies. We also for the first time document strong correlations between the isotopic (δ18O and δ13C) and elemental compositions of the skeletons, most notably a negative correlation between δ18O and Mg/Ca. The centers of calcification (COCs) in the coral skeletons show distinct tracer correlations from the aragonite fibers that possibly reflect a more complicated formation mechanism. We interpret the spatially coherent tracer correlations in deep-sea corals with a numerical model of coral calcification previously developed for stable isotopes that considers the role of the enzyme carbonic anhydrase in the calcification processs. With the carbonate chemistry in the model constrained by the stable isotope data, we are able to explain the observed Me/Ca correlations as well as their range of variability, as a result of internal pH elevation in the extracellular calcifying fluid (ECF) of the corals with limited Ca-pumping through the calicoblastic membrane. In particular, the positive Mg/Ca–B/Ca correlation in the fibrous aragonite suggests a borate (B(OH)4–) substitution for carbonate ion (CO32–) incorporation mechanism in biogenic aragonite. We also suggest the growth rate dependence of the incorporation of minor and trace elements based conceptually on an ion-by-ion growth model may help explain the absolute Me/Ca values in biogenic aragonites. Finally, we generally find more limited tracer variability in corals from undersaturated seawater compared to their counterparts from supersaturated conditions, suggesting a limit to their internal pH elevation in response to this environmental stress. Understanding the biomineralization mechanisms underlying the vital effects is important for better use of these tracers for paleoceanographic applications, and may shed light on the response of marine calcification to future ocean acidification.

Crystal orientation mapping and microindentation reveal anisotropy in Porites skeletons

Structures made by scleractinian corals support diverse ocean ecosystems. Despite the importance of coral skeletons and their predicted vulnerability to climate change, few studies have examined the mechanical and crystallographic properties of coral skeletons at the micro- and nano-scales. Here, we investigated the interplay of crystallographic and microarchitectural organization with mechanical anisotropy within Porites skeletons by measuring Young’s modulus and hardness along surfaces transverse and longitudinal to the primary coral growth direction. We observed micro-scale anisotropy, where the transverse surface had greater Young’s modulus and hardness by ∼ 6 GPa and 0.2 GPa, respectively. Electron backscatter diffraction (EBSD) revealed that this surface also had a higher percentage of crystals oriented with the a-axis between ± 30–60∘, relative to the longitudinal surface, and a broader grain size distribution. Within a region containing a sharp microscale gradient in Young’s modulus, nanoscale indentation mapping, energy dispersive spectroscopy (EDS), EBSD, and Raman crystallography were performed. A correlative trend showed higher Young’s modulus and hardness in regions with individual crystal bases (c-axis) facing upward, and in crystal fibers relative to centers of calcification. These relationships highlight the difference in mechanical properties between scales (i.e. crystals, crystal bundles, grains). Observations of crystal orientation and mechanical properties suggest that anisotropy is driven by microscale organization and crystal packing rather than intrinsic crystal anisotropy. In comparison with previous observations of nanoscale isotropy in corals, our results illustrate the role of hierarchical architecture in coral skeletons and the influence of biotic and abiotic factors on mechanical properties at different scales. Statement of significanceCoral biomineralization and the ability of corals’ skeletal structure to withstand biotic and abiotic forces underpins the success of reef ecosystems. At the microscale, we show increased skeletal stiffness and hardness perpendicular to the coral growth direction. By comparing nano- and micro-scale indentation results, we also reveal an effect of hierarchical architecture on the mechanical properties of coral skeletons and hypothesize that crystal packing and orientation result in microscale anisotropy. In contrast to previous findings, we demonstrate that mechanical and crystallographic properties of coral skeletons can vary between surface planes, within surface planes, and at different analytical scales. These results improve our understanding of biomineralization and the effects of scale and direction on how biomineral structures respond to environmental stimuli.

Microstructural characteristics of the stony coral genus Acropora useful to coral reef paleoecology and modern conservation.

Identification of fossil corals is often limited due to poor preservation of external skeleton morphology, especially in the genus Acropora which is widespread across the Indo‐Pacific. Based on skeleton characteristics from thin section, we here develop a link between the internal skeleton structure and external morphology. Ten characteristics were summarized to distinguish Acropora and five related genera, including the type and differentiation of corallites, the skeleton nature of corallites (septa, columellae, dissepiments, wall), and calcification centers within septa. Acropora is distinctive for its dimorphic corallites: axial and radial. Isopora is similar to Acropora but possess more than a single axial corallites. Montipora and Astreopora (family Acroporidae) have monomorphic corallites and a synapticular ring wall, with clustered calcification center in the former and medial lines in the latter. Pocillopora and Porties are classified by distinctive dissepiments, columellae and septa. These microstructural skeleton characteristics were effective in the genus identification of fossil corals from drilled cores in the South China Sea. Eighteen detailed characteristics (ten of axial corallites, four of radial corallites, and four of coenosteum) were used in the Acropora species classification. The axial corallites size and structure (including corallite diameter, synapticular rings, and septa), the septa of radial corallites, and the arrangement of coenosteum were critical indicators for species identification. This identification guide can help paleoenvironmental and paleoecological analyses and modern coral reef conservation and restoration.

Temperature control on high-resolution SIMS oxygen isotopic compositions in Porites coral skeletons

Oxygen isotope composition (δ18O) in Porites coral skeletons at the micrometer scale has been proposed to be uninfluenced by temperature in previous studies. Considering that temperature is the main controlling factor of coral δ18O at the macro scale, the effect of temperature on the δ18O variations at the micrometer scale should be evaluated carefully. To better understand the climatic and biological significance of high-resolution δ18O in coral skeletons, in situ δ18O values were analyzed in three modern Porites corals from the South China Sea and the Great Barrier Reef by a Cameca IMS 1280-HR secondary ion mass spectrometry (SIMS). A twice vacuum impregnation procedure for sample mount preparation and a subsection calibration method based on multiple controlling points for coral matrix effect correction were used for SIMS analysis. The derived SIMS coral δ18O time series exhibit consistent long-term variations with the monthly δ18O (measured by conventional gas isotope ratios mass spectrometry), monthly Sr/Ca, and daily sea surface temperature, first highlighting the dominant temperature control on micrometer-scale coral δ18O. The 1.5‰ fluctuation amplitude of SIMS coral δ18O at the scales of 400–800 μm can be explained by the combined SST effects of ~10-day variation and day–night fluctuation, whereas the effects of seawater δ18O and growth rate on SIMS coral δ18O seem not dominant. Some abnormally negative δ18O values possibly resulted from the primary ion bombardment on indistinguishable centers of calcification.

Crystal nucleation and growth of spherulites demonstrated by coral skeletons and phase-field simulations

Spherulites are radial distributions of acicular crystals, common in biogenic, geologic, and synthetic systems, yet exactly how spherulitic crystals nucleate and grow is still poorly understood. To investigate these processes in more detail, we chose scleractinian corals as a model system, because they are well known to form their skeletons from aragonite (CaCO3) spherulites, and because a comparative study of crystal structures across coral species has not been performed previously. We observed that all 12 diverse coral species analyzed here exhibit plumose spherulites in their skeletons, with well-defined centers of calcification (CoCs), and crystalline fibers radiating from them. In 7 of the 12 species, we observed a skeletal structural motif not observed previously: randomly oriented, equant crystals, which we termed “sprinkles”. In Acropora pharaonis, these sprinkles are localized at the CoCs, while in 6 other species, sprinkles are either layered at the growth front (GF) of the spherulites, or randomly distributed. At the nano- and micro-scale, coral skeletons fill space as much as single crystals of aragonite. Based on these observations, we tentatively propose a spherulite formation mechanism in which growth front nucleation (GFN) of randomly oriented sprinkles, competition for space, and coarsening produce spherulites, rather than the previously assumed slightly misoriented nucleations termed “non-crystallographic branching”. Phase-field simulations support this mechanism, and, using a minimal set of thermodynamic parameters, are able to reproduce all of the microstructural variation observed experimentally in all of the investigated coral skeletons. Beyond coral skeletons, other spherulitic systems, from aspirin to semicrystalline polymers and chocolate, may also form according to the mechanism for spherulite formation proposed here. Statement of SignificanceUnderstanding the fundamental mechanisms of spherulite nucleation and growth has broad ranging applications in the fields of metallurgy, polymers, food science, and pharmaceutical production. Using the skeletons of reef-building corals as a model system for investigating these processes, we propose a new spherulite growth mechanism that can not only explain the micro-structural diversity observed in distantly related coral species, but may point to a universal growth mechanism in a wide range of biologically and technologically relevant spherulitic materials systems.

Mineral formation in the primary polyps of pocilloporoid corals

In reef-building corals, larval settlement and its rapid calcification provides a unique opportunity to study the bio-calcium carbonate formation mechanism involving skeleton morphological changes. Here we investigate the mineral formation of primary polyps, just after settlement, in two species of the pocilloporoid corals: Stylophora pistillata (Esper, 1797) and Pocillopora acuta (Lamarck, 1816). We show that the initial mineral phase is nascent Mg-Calcite, with rod-like morphology in P. acuta, and dumbbell morphology in S. pistillata. These structures constitute the first layer of the basal plate which is comparable to Rapid Accretion Deposits (Centers of Calcification, CoC) in adult coral skeleton. We found also that the rod-like/dumbbell Mg-Calcite structures in subsequent growth step will merge into larger aggregates by deposition of aragonite needles. Our results suggest that a biologically controlled mineralization of initial skeletal deposits occurs in three steps: first, vesicles filled with divalent ions are formed intracellularly. These vesicles are then transferred to the calcification site, forming nascent Mg-Calcite rod/pristine dumbbell structures. During the third step, aragonite crystals develop between these structures forming spherulite-like aggregates. Statement of SignificanceCoral settlement and recruitment periods are highly sensitive to environmental conditions. Successful mineralization during these periods is vital and influences the coral’s chances of survival. Therefore, understanding the exact mechanism underlying carbonate precipitation is highly important. Here, we used in vivo microscopy, spectroscopy and molecular methods to provide new insights into mineral development. We show that the primary polyp’s mineral arsenal consists of two types of minerals: Mg-Calcite and aragonite. In addition, we provide new insights into the ion pathway by showing that divalent ions are concentrated in intracellular vesicles and are eventually deposited at the calcification site.

Boron isotope composition of the cold-water coral Lophelia pertusa along the Norwegian margin: Zooming into a potential pH-proxy by combining bulk and high-resolution approaches

High-latitude cold-water coral reefs are particularly vulnerable to climate change due to enhanced CO2 uptake in these regions. To evaluate their physiological functioning and potential application as pH archives, we retrieved both recent and fossil samples of Lophelia pertusa along the Norwegian margin from Oslofjord (59°N), over to Trondheimsfjord, Sula and Lopphavet (70.6°N). Boron isotope analyses (δ11B) were undertaken using solution-based and laser ablation multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS; LA-ICP-MS), and secondary ion mass spectrometry (SIMS). Epi-fluorescence microscopy was employed to provide a rapid pre-screening routine for structure-specific subsampling in the coral skeleton. This integrated approach enabled us to assess heterogeneities within single specimens, as well as to investigate the role of local environmental influences including recent and past variations. All three mass spectrometry methods show substantial differences in the δ11B of the theca wall (TW) and the centres of calcification (COC's). Micro-bulk subsamples milled from the theca wall of modern specimens originating from different habitats but with comparable seawater pH (8–8.16) gave consistent δ11B values averaging 26.7 (±0.2‰, 2σ, n = 4), while COC subsamples systematically deviated towards lower B/Ca (by ~40%) and depleted δ11B values (minimum 22.7 ± 0.3‰, 2σ), implying a difference of at least 4‰ between TW and COC. SIMS and LA-ICP-MS measurements identified much larger internal heterogeneities with maximum variation of ~10‰ between the distinct skeletal structures; minimal SIMS δ11B values of ~17.3 ± 1.2‰ (2σ) were associated with the pure COC material. Our findings may be interpreted in terms of the occurrence of two main, but likely different, biomineralisation mechanisms in L. pertusa, with the COC's generally exhibiting minimal pH up-regulation, potentially supporting the use of bicarbonate in the early stages of biomineralisation. Furthermore, we highlight the potential utility of L. pertusa for palaeo-proxy studies if targeting the compositionally homogenous TW zones devoid of COC admixtures, which appear to provide highly reproducible measurements.

In vivo studies of novel scaffolds with tannic acid addition

Scaffolds based on chitosan, collagen, and hyaluronic acid supplemented with nano-hydroxyapatite and tannic acid were obtained by using the freeze-drying method. Biocompatibility was studied by the in vivo implantation into proximal tibial bones of rabbits. The bones were drilled and the biomaterial was introduced by filling the pre-drilled space. The histological studies were carried out three months after the implantation.The results showed low stability of the scaffolds based on chitosan, collagen, and hyaluronic acid supplemented with hydroxyapatite and tannic acid. The histological images showed the cetia and calcification centers. Moreover, the presence of thin-walled vessels filled with blood was noticed. Macrophages were observed in the area surrounding the implanted materials. The tissue response to the material implantation confirms that the tissue regeneration was initiated. The results showed satisfactory tissue response to the implanted scaffolds.

Biomineral Reactivity: The Kinetics of the Replacement Reaction of Biological Aragonite to Apatite

We present results of bioaragonite to apatite conversion in bivalve, coral and cuttlebone skeletons, biological hard materials distinguished by specific microstructures, skeletal densities, original porosities and biopolymer contents. The most profound conversion occurs in the cuttlebone of the cephalopod Sepia officinalis, the least effect is observed for the nacreous shell portion of the bivalve Hyriopsis cumingii. The shell of the bivalve Arctica islandica consists of cross-lamellar aragonite, is dense at its innermost and porous at the seaward pointing shell layers. Increased porosity facilitates infiltration of the reaction fluid and renders large surface areas for the dissolution of aragonite and conversion to apatite. Skeletal microstructures of the coral Porites sp. and prismatic H. cumingii allow considerable conversion to apatite. Even though the surface area in Porites sp. is significantly larger in comparison to that of prismatic H. cumingii, the coral skeleton consists of clusters of dense, acicular aragonite. Conversion in the latter is sluggish at first as most apatite precipitates only onto its surface area. However, the process is accelerated when, in addition, fluids enter the hard tissue at centers of calcification. The prismatic shell portion of H. cumingii is readily transformed to apatite as we find here an increased porosity between prisms as well as within the membranes encasing the prisms. In conclusion, we observe distinct differences in bioaragonite to apatite conversion rates and kinetics depending on the feasibility of the reaction fluid to access aragonite crystallites. The latter is dependent on the content of biopolymers within the hard tissue, their feasibility to be decomposed, the extent of newly formed mineral surface area and the specific biogenic ultra- and microstructures.

The Origin and Role of Organic Matrix in Coral Calcification: Insights From Comparing Coral Skeleton and Abiogenic Aragonite

Understanding the mechanisms of coral calcification is critical for accurately projecting coral reef futures under ocean acidification and warming. Recent suggestions that calcification is primarily controlled by organic molecules and the biological activity of the coral polyp imply that ocean acidification may not affect skeletal accretion. The basis for these suggestions relies heavily on correlating the presence of organic matter with the orientation and disorder of aragonite crystals in the skeleton, carrying the assumptions that organic matter observed in the skeleton was produced by the polyp to control calcification. Here we use Raman spectroscopy to test whether there are differences in organic matter content between coral skeleton and abiogenic aragonites precipitated from seawater, both before and after thermal annealing (heating). We measured the background fluorescence and intensity of C-H bonding signals in the Raman spectra, which are commonly attributed to coral polyp-derived skeletal organic matrix (SOM) and have been used to map its distribution. Surprisingly, we found no differences in either fluorescence or C-H bonding between abiogenic aragonite and coral skeleton. Annealing reduced the molecular disorder in coral skeleton, potentially due to removal of organic matter, but the same effect was also observed in the abiogenic aragonites. The presence of organic molecules in the abiogenic aragonites is further supported by measurements of N content and δ15N. Together, our data suggest that some of what has been interpreted in previous studies as polyp-derived SOM may actually be seawater-sourced organic matter or some other signal not unique to biogenic aragonite. Finally, we create a high-resolution Raman map of a Pocillopora skeleton to demonstrate how patterns of fluorescence and elevated calcifying fluid aragonite saturation state along centers of calcification are consistent with both biological and physico-chemical controls. Our aim is to advance discussion on biological mediation of calcification and the implications for coral resilience in a high-CO2 world.

Computed Tomography in the Detection Hepatic Calcification Hemangioma

The purpose: the estimation of a computed tomography(CT) signs of hepatic calcification hemangioma. Material and methods. Retrospectively results of CT with bolus contrast enhancement for examination hepatic calcified lesions of the 36 patients were analyzed. Results. As a basis for the retrospective analysis, the semiotic signs of patients, in which the hemangioma calcification developed during the dynamic CT monitoring, were used. As shown by the analysis, the center of calcification in combination with the cloisonne structures leading the arterial vessel, the decrease in the area of the focal lesion in the portovenous phase due to the vascular structures along the periphery of the focus are the criteria of calcified hemangioma. In 11 of 36 patients, calcified foci in the liver turned out to be hemangiomas.Conclusion. More than 30% calcifications in the liver detected at CT can be calcification hemangioma.

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature's Three-Dimensional Printing.

Coral skeletons were long assumed to have a spherulitic structure, that is, a radial distribution of acicular aragonite (CaCO3) crystals with their c-axes radiating from series of points, termed centers of calcification (CoCs). This assumption was based on morphology alone, not on crystallography. Here we measure the orientation of crystals and nanocrystals and confirm that corals grow their skeletons in bundles of aragonite crystals, with their c-axes and long axes oriented radially and at an angle from the CoCs, thus precisely as expected for feather-like or "plumose" spherulites. Furthermore, we find that in both synthetic and coral aragonite spherulites at the nanoscale adjacent crystals have similar but not identical orientations, thus demonstrating by direct observation that even at nanoscale the mechanism of spherulite formation is non-crystallographic branching (NCB), as predicted by theory. Finally, synthetic aragonite spherulites and coral skeletons have similar angle spreads, and angular distances of adjacent crystals, further confirming that coral skeletons are spherulites. This is important because aragonite grows anisotropically, 10 times faster along the c-axis than along the a-axis direction, and spherulites fill space with crystals growing almost exclusively along the c-axis, thus they can fill space faster than any other aragonite growth geometry, and create isotropic materials from anisotropic crystals. Greater space filling rate and isotropic mechanical behavior are key to the skeleton's supporting function and therefore to its evolutionary success. In this sense, spherulitic growth is Nature's 3D printing.

Primary Life Stage Boron Isotope and Trace Elements Incorporation in Aposymbiotic Acropora millepora Coral under Ocean Acidification and Warming

Early-life stages of reef-building corals are vital to coral existence and reef maintenance. It is therefore crucial to study juvenile coral response to future climate change pressures. Moreover, corals are known to be reliable recorders of environmental conditions in their skeletal materials. Aposymbiotic Acropora millepora larvae were cultured in different seawater temperature (27 and 29oC) and pCO2 (390 and 750 µatm) conditions to understand the impacts of ‘end of century’ ocean acidification (OA) and ocean warming (OW) conditions on skeletal morphology and geochemistry. The experimental conditions impacted primary polyp juvenile coral skeletal morphology and growth resulting in asymmetric translucent appearances with brittle skeleton features. The impact of OA resulted in microstructure differences with decreased precipitation or lengthening of fasciculi and disorganized aragonite crystals that led to more concentrations of centers of calcifications. The coral skeletal δ11B composition measured by laser ablation MC-ICP-MS was significantly affected by pCO2 (p = 0.0024) and water temperature (p = 1.46 x 10-5). Reconstructed pH of the primary polyp skeleton using the δ11B proxy suggests a difference in coral calcification site and seawater pH consistent with previously observed coral pH up-regulation. Similarly, trace element results measured by laser ablation ICP-MS indicate the impact of pCO2. Primary polyp juvenile Sr/Ca ratio indicates a bias in reconstructed sea surface temperature (SST) under higher pCO2 conditions. Coral microstructure content changes (center of calcification and fasciculi) due to OA possibly contributed to the variability in B/Ca ratios. Our results imply that increasing OA and OW may lead to coral acclimation issues and species-specific inaccuracies of the commonly used Sr/Ca-SST proxy.

Low Florida coral calcification rates in the Plio-Pleistocene

Abstract. In geological outcrops and drill cores from reef frameworks, the skeletons of scleractinian corals are usually leached and more or less completely transformed into sparry calcite because the highly porous skeletons formed of metastable aragonite (CaCO3) undergo rapid diagenetic alteration. Upon alteration, ghost structures of the distinct annual growth bands often allow for reconstructions of annual extension ( = growth) rates, but information on skeletal density needed for reconstructions of calcification rates is invariably lost. This report presents the bulk density, extension rates and calcification rates of fossil reef corals which underwent minor diagenetic alteration only. The corals derive from unlithified shallow water carbonates of the Florida platform (south-eastern USA), which formed during four interglacial sea level highstands dated approximately 3.2, 2.9, 1.8, and 1.2 Ma in the mid-Pliocene to early Pleistocene. With regard to the preservation, the coral skeletons display smooth growth surfaces with minor volumes of marine aragonite cement within intra-skeletal porosity. Within the skeletal structures, voids are commonly present along centres of calcification which lack secondary cements. Mean extension rates were 0.44 ± 0.19 cm yr−1 (range 0.16 to 0.86 cm yr−1), mean bulk density was 0.96 ± 0.36 g cm−3 (range 0.55 to 1.83 g cm−3) and calcification rates ranged from 0.18 to 0.82 g cm−2 yr−1 (mean 0.38 ± 0.16 g cm−2 yr−1), values which are 50 % of modern shallow-water reef corals. To understand the possible mechanisms behind these low calcification rates, we compared the fossil calcification rates with those of modern zooxanthellate corals (z corals) from the Western Atlantic (WA) and Indo-Pacific calibrated against sea surface temperature (SST). In the fossil data, we found a widely analogous relationship with SST in z corals from the WA, i.e. density increases and extension rate decreases with increasing SST, but over a significantly larger temperature window during the Plio-Pleistocene. With regard to the environment of coral growth, stable isotope proxy data from the fossil corals and the overall structure of the ancient shallow marine communities are consistent with a well-mixed, open marine environment similar to the present-day Florida Reef Tract, but variably affected by intermittent upwelling. Upwelling along the platform may explain low rates of reef coral calcification and inorganic cementation, but is too localised to account also for low extension rates of Pliocene z corals throughout the tropical WA region. Low aragonite saturation on a more global scale in response to rapid glacial–interglacial CO2 cyclicity is also a potential factor, but Plio-Pleistocene atmospheric pCO2 is generally believed to have been broadly similar to the present day. Heat stress related to globally high interglacial SST only episodically moderated by intermittent upwelling affecting the Florida platform seems to be another likely reason for low calcification rates. From these observations we suggest some present coral reef systems to be endangered from future ocean warming.

Bat Development: Interspecies Differences in Baculum Ossification Patterns

Developmental studies are fundamental to understanding specialized morphologies. The baculum (os penis) is a heterotopic bone in the glans penis, which is probably subject to sexual selection and may play a role in reproductive isolation between closely related species. In this ongoing study, the pre‐ and postnatal development of the reproductive organs will be compared between species of the bat genera Pipistrellus, Eptesicus, and Cynopterus histologically and with 3D X‐ray microtomography (microCT) imaging. We aim to show how bacula with different shapes start to calcify at different ossification centers and to compare soft tissue development of bat reproductive organs.Bat organ system development has mainly been studied using histological methods, dissection, or clearing and staining. The skeletal system has also been studied with x‐ray techniques including microCT. Here, we will use 1% (w/v) elemental iodine in 100% ethanol (I2E) to study the development of reproductive organs in a sample of 14 Cynopterus brachyotis (Chiroptera: Pteropodidae) embryos from the collection of the Museum Zoologicum Bogoriense (Indonesia), and several juvenile and subadult bats of the species Cynopterus sphinx (Indonesia), Pipistrellus pipistrellus (Naturalis Biodiversity Center Leiden, Netherlands), and Eptesicus serotinus (Netherlands and Ukraine). Iodine contrast staining has been used successfully in a number of studies on fetal and adult vertebrates, because soft tissues can thus be differentiated in microCT images.Preliminary results show different patterns of ossification. In Pipistrellus pipistrellus the distal part of the baculum reaches its adult shape before the proximal part. The different states of medullary cavity development found in our samples suggest the medullary cavity first forms from the ventral side of the baculum, where the branches of the base meet the shaft and that it is later replaced by a secondary medullary cavity. The baculum of Eptesicus serotinus calcifies from both lateral sides, while four different calcification centers can be shown in a developing baculum of Cynopterus sphinx.

Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

Geochemical proxies measured in the carbonate skeleton of tropical coral Porites sp. have commonly been used to reconstruct sea surface temperature (SST) and more recently seawater pH. Nevertheless, both reconstructed SST and pH depend on the preservation state of the skeleton, here made of aragonite; i.e., diagenetic processes and its related effects should be limited. In this study, we report on the impact of the presence of intra-skeletal calcite on the skeleton geochemistry of a live-collected Porites sp. The Porites skeleton preservation state was analyzed using X-ray diffraction and scanning electron microscopy. Sr/Ca, Mg/Ca, U/Ca, Ba/Ca, Li/Mg, and B/Ca ratios were measured at a monthly and yearly resolution using quadrupole ICP-MS and multi-collector ICP-MS. The δ11B signatures and the calcite percentages were acquired at a yearly timescale. The coral colony presents two parts, one with less than 3% calcite (referred to as “no-calcite” skeleton), the other one, corresponding to the skeleton formed during the last 4years of growth, with calcite percentages varying from 13% to 32% (referred to as “with calcite” skeleton). This intra-skeletal calcite replaces partly or completely numerous centers of calcification (COCs). All investigated geochemical tracers are significantly impacted by the presence of calcite. The reconstructed SST decreases by about 0.1°C per calcite-percent as inferred from the Sr/Ca ratio. Such impact reaches up to 0.26°C per calcite-percent for temperature deduced from the Li/Mg ratio. So, less than 5% of such intra-skeletal calcite does not prevent SST reconstructions using Sr/Ca ratio, but the percentage and type of calcite have to be determined before fine SST interpretation. Seawater pH reconstruction inferred from boron isotopes drop by about −0.011 pH-unit per calcite-percent. Such sensitivity to calcite presence is particularly dramatic for fine paleo-pH reconstructions. Here we suggest that after being brought to shallow waters following a cyclone, the studied coral was seasonally subjected to rainfall-related water freshening that could have mimicked a vadose environment like can be encountered on raised fossil coral reefs. Nevertheless, the process of calcite precipitation remains to be determined.