The degree of plant silicification is classically proxied by organ-scale silicon concentration, [Si], which ignores where Si is allocated at the cellular scale. Bridging this scale gap is crucial to elucidate the physiological and ecological roles of silicification in high-Si taxa and its influence on biogeochemical cycles. We used high-resolution X-ray microtomography and cellular-scale element mapping to study silica allocation and silicification patterns in 15 species from the second most-abundant Si-accumulating family worldwide, namely Cyperaceae (sedges). Despite considerable variation in deposition sites and cellular [Si] between species and anatomical areas, we show that at least 78±17% of silica is localized in the epidermis, mostly as a silica layer in the outer tangential cell wall (OTW). Both the thickness and cellular-scale [Si] of this continuous layer, which is up to 18 µm thick, were highly correlated to organ-scale [Si] among species. Our findings demonstrate that bulk silica content is largely governed by deposition in the OTW in sedges, rather than by deposition in cell lumina. These findings open new perspectives for Si-related plant physiological and biogeochemical processes and pave the way for the use of X-ray microtomography not only to visualize, but also to quantify biogenic silica allocation in plants.

Anthropogenic greenhouse gas emissions increase sea surface temperature and acidification, inhibiting calcification of reef-building corals. While ocean acidification is known to hinder skeletal development of newly settled coral recruits, little is known of its effects on older purebred or interspecific hybrid recruits, or its combined effects with temperature. Using 3D X-ray microscopy, we found that predicted mid-century ocean warming and acidification conditions (28 °C, 685 ppm pCO2) negatively affected the skeletal development of 7-month-old Acropora purebreds and hybrids in one direction (Acropora cf. kenti mother x Acropora loripes father). Conversely, the skeletal parameters of reciprocal hybrids (A. loripes mother x A. cf. kenti father) remained unaffected. Skeletal measurements taken from 3D data revealed patterns overlooked by previous 2D measurements, leading support to the likelihood of hybrid vigour in hybrids of A. loripes (mother) and A. cf. kenti (father) and the potential of interspecific hybridization as a reef restoration tool to enhance coral resilience.

Oxygen fugacity (fO2) controls the speciation of COH fluids in Earth's mantle; a major question is whether the sublithospheric mantle is metal-saturated, maintaining fO2 near the Iron-Wustite (IW) buffer reaction. If so, then COH fluids from this source will be dominated by CH4 + H2, rather than the more oxidized CO2-H2O fluids commonly considered in petrological studies. A key to this question is found in rare but widespread examples of natural mineral assemblages that require unusually low fO2. We summarize an investigation of super-reduced mineral assemblages in corundum xenocrysts from Late Cretaceous alkali-basalt volcanoes on Mt Carmel, northern Israel and related Plio-Pleistocene alluvial deposits. P-T estimates indicate that the corundum xenocrysts crystallized in the uppermost mantle. The well-documented geological controls on the origin of these deposits, and radiometric dating of the super-reduced phases, ensure the "naturalness" of the controversial assemblages and make these mineral par-ageneses a benchmark for evaluation of related occurrences worldwide.The tuffs contain a "basalt-megacryst" mineral suite (zircon, sapphire, ilmenite, spinel). The megacryst chemistry and the geochronology of the zircons indicate that the megacrysts crystallized from broadly syenitic melts that differentiated at subcrustal levels (P ca 1 GPa) within a thick gabbroic underplate built up from Permian through Pliocene time and perhaps into the Pleistocene. Reaction of mantle-derived CH4-H2 fluids with these syenitic melts led to the separation of immiscible Fe0 and Fe-Ti oxide melts near fO2 = IW. Trace-element distributions suggest the syenitic melts then separated into immiscible Si-Al-Na-K-rich and FeO-rich oxide melts; the latter were enriched in HFSE, REE, P and Zr as in other natural and synthetic examples of melt-melt immiscibility.In a model magma chamber the FeO-rich melts would sink, leaving the Si-Al-Na-K melts in an upper zone, both still fluxed by CH4-H2 fluids. At fO2 of DIW-6 to-7 the removal of immiscible Fe-Ti-Si-C silicide melts from the FeO-rich melt would leave a desilicated Ca-Al-Si oxide melt that crystallized high-Ti corundum hibonite cumulates with inclusions requiring fO2 from DIW + 2 to DIW-9, while the less-reduced conjugate silicate melts in the upper levels crystallized low-Ti corundum. Aggregates of skeletal, strongly Ti-zoned corundum crystals. reflect rapid crystallization from very reduced melt-fluid mixtures, probably in fluid-escape channels. Explosive eruptions sampled individual magma chambers at different depths and with different initial compositions, fluid mixtures and fluid dynamics to produce Mt Carmel's mineralogical diversity.A review of similar occurrences worldwide suggests that the Mt Carmel assemblages reflect a fundamental process - the rise of CH4-H2 fluids into the upper mantle --that accompanies mantle-derived magmatism in many tectonic settings. The interaction of these fluids with lithospheric mantle rocks

Calcareous sands of biogenic origin are widely spread throughout the world’s seabed. They are the foundation soils for many offshore geotechnical structures, and, in addition, onshore uses of this material are becoming more significant with the growing demand of backfill material for transport infrastructure. These sands comprise the remains of marine organisms such as shells and tests, and the grains can vary from platy to hollow thin-walled forms with highly angular features. Geotechnical design on calcareous sands is challenging owing to the many uncertainties related to their microscale properties. This study uses non-invasive X-ray micro-computed tomography (μCT) and advanced three-dimensional (3D) image analysis techniques to quantify the morphology of bioclastic calcareous sands from São Tomé & Príncipe. The statistics of particle shape parameters of the São Tomé sand are compared to that of the previously studied Ledge Point sand. In spite of an order of magnitude difference in particle size, São Tomé and Ledge Point sands are markedly similar and, as seen in other calcareous sand, São Tomé shows a strong correlation in 3D sphericity and convexity. The results presented here help to better understand the mechanisms of grain interlocking, and the role of intra-granular void ratio on the mechanical behaviour of calcareous sands from different parts of the world.

The sponge-like biomineralised calcite materials found in echinoderm skeletons are of interest in terms of both structure formation and biological function. Despite their crystalline atomic structure, they exhibit curved interfaces that have been related to known triply-periodic minimal surfaces. Here, we investigate the endoskeleton of the sea urchin Cidaris rugosa that has long been known to form a microstructure related to the Primitive surface. Using X-ray tomography, we find that the endoskeleton is organised as a composite material consisting of domains of bicontinuous microstructures with different structural properties. We describe, for the first time, the co-occurrence of ordered Primitive and Diamond structures and of a disordered structure within a single skeletal plate. We show that these structures can be distinguished by structural properties including solid volume fraction, trabeculae width, and to a lesser extent, interface area and mean curvature. In doing so, we present a robust method that extracts interface areas and curvature integrals from voxelized datasets using the Steiner polynomial for parallel body volumes. We discuss these very large scale bicontinuous structures in the context of their function, formation, and evolution.

In recent years, the detection of numerous negative correlations between silicon (Si) and carbon (C)-based compounds in plants has suggested trade-offs between different stress resistance and/or mechanical support strategies. However, nearly all studies have involved whole-leaf analysis, and it is unclear how the trade-off operates mechanistically, at the cellular level. Here we combined leaf trait measurements and microscopic analyses (electron microscopy with elemental X-ray mapping and X-ray microtomography) of 17 species from a high-Si family: Cyperaceae. Accumulation of Si was strongly negatively correlated with C-based compounds, particularly tannins. Our microscopical investigations showed that the accumulation of phenolics and deposition of silica were mutually exclusive in the outer epidermal cell walls. This trade-off was independent of that between the construction of tough, sclerenchyma-rich leaves and growth potential (the leaf economics spectrum). We also identified a strong negative correlation between Si and accumulation of epicuticular waxes. Previous whole leaf analyses were, in effect, hiding the locations of the trade-off between Si and C-based compounds in plants. The epidermal location of this trade-off and the specific involvement of tannins and waxes suggest the existence of different strategies to resist environmental stresses. Our study provides key insights into plant Si utilization and highlights the multidimensionality of plant stress resistance strategies.

Among marsupials, the endangered numbat (Myrmecobius fasciatus) is the only obligate myrmecophage with a diet comprised strictly of termites. Like many other specialised myrmecophagous mammals, numbats have a gracile and highly specialised skull morphology with an elongated rostrum and small braincase. Myrmecobiidae is one of four taxonomic families within the Australasian marsupial order Dasyuromorphia, and to date, the muscular anatomy of any member of this group is relatively poorly known. We utilised microdissection and contrast-enhanced microcomputed tomography scanning to provide the first comprehensive qualitative and quantitative descriptions of jaw muscle anatomy in numbats and quolls (Dasuyrus species). The arrangement of the jaw muscles across these species was conservative, both in gross anatomy and muscle proportions, corresponding to a 'generalised' mammalian pattern. In contrast to Dasyurus, the jaw muscles of the numbat were greatly reduced. Many aspects of the muscle anatomy of the numbat were similar to patterns reported in other myrmecophagous species, particularly a greatly reduced temporalis muscle. Unusually, the digastric muscle in the numbat was comprised of a single, large anterior belly while the posterior belly was absent. We propose that the enlarged anterior belly of the digastric may be linked to jaw stabilisation and coordination of tongue movements during feeding. The lateral insertion and fascial connection of the digastric to the tongue in numbats may also aid in distributing stress evenly across the jaw and minimise muscle fatigue. The muscle descriptions and three-dimensional models provided in this study will facilitate further analysis of musculoskeletal adaptation and evolution within the Dasyuromorphia.

Frutexites-like microstructures are described from the exhumed Late Devonian reef complexes of the northern Canning Basin, Western Australia. Several high-resolution imaging techniques, including X-ray microcomputerised tomography, scanning electron microscopy and X-ray fluorescence microscopy, were used to investigate morphology and composition in two samples. Three types of Frutexites-like microstructures (Types I-III) have been identified. Type I, found lining an early marine cement-filled cavity in fore-reef grainstone facies, consists of dendritic structures formed primarily of coccoid bacteria with filamentous bacteria embedded in sheets of amorphous extracellular polymeric substances (EPS). These ferromanganiferous dendrites have laminated to spheroidal textures. Types II and III are from a toe-of-slope hardground. Type II grew in a crypt between two corals, is also dendritic and composed of bacilliform and filamentous bacteria embedded in an amorphous EPS sheet. The opaqueness of these ferriferous dendrites precludes more detailed description of textures. Type III grew as branching columnar microstromatolites and is composed of entwined filaments of Girvanella, Rothpletzella and Wetheredella with Fe-enriched outer walls that generate Frutexites-like microstructures. Types I and II resemble Frutexites sensu stricto as defined by Maslov (Stromatolites, Trudy Instituta geologicheskikh nauk Akademiya nauk SSR, 1960) and are the result of the consecutive growth and permineralisation of biofilms composed of mixed bacterial communities growing in cryptic habitats. Type III superficially resembles Frutexites sensu stricto based on macroscopic field observations, however, detailed microscopic analysis reveals that it is composed of Fe-enriched tubular walls surrounded by Mn-enriched calcite.

Roads affect ecological functioning at local to landscape scales, but little is known about the indirect effects on hydrology and vegetation outside road corridors. These impacts are of particular concern in arid landscapes such as the southwestern US, where road networks have rapidly expanded in recent decades. This study quantified impacts to vegetation where roads eliminated downslope sheetflow runon and identified how road and landscape characteristics affect the probability of sheetflow disruptions at Organ Pipe Cactus National Monument, in the Sonoran Desert of southern Arizona, USA. The abundance of perennial grasses, drought-deciduous subshrubs, and trees were significantly reduced in downslope plant communities where entrenched graded roads and above-grade paved roads diverted or impounded sheetflow. The remaining vegetation was dominated by annual herbaceous plants and the drought -resistant evergreen shrub creosotebush (Larrea tridentata [de Candolle] Coville), resulting in lower species and functional group richness. Sheetflow runon reductions also significantly decreased the growth, vigor, and sur-vival of woody plants, particularly for the winter-deciduous tree velvet mesquite (Prosopis velutina Wooten). Hydrologic alterations affected the density and extent of nearby vegetation at 25% of 484 locations where roadways intersected sheetflow paths. Primitive roads such as off-highway vehicle routes produced the smallest topographic changes and were the least likely to disrupt runon, while graded roads had a 48% cumulative probability of ecohydrological impacts due to their tendency to become entrenched below ground. Paved roads were most likely to alter hydrologic connectivity due to embankments and roadside ditches and berms. Geologic substrate and soil type affected the probability of sheetflow impacts, which were most frequent on Quaternary alluvium and young soils lacking restrictive horizons. These results were used to map landscape sensitivity to sheetflow path disruption by roadways throughout Organ Pipe Cactus National Monument and to provide rec-ommendations for sustainable management of existing and future roads.

Aggregates of corundum crystals with skeletal to hopper morphology occur in pyroclastic rocks erupted from Cretaceous basaltic volcanoes on Mt Carmel, N. Israel. The rapid growth of the crystals trapped volumes of the parental Al 2 O 3 -supersaturated melt; phenocrysts of tistarite (Ti 2 O 3 ) in the trapped melts indicate crystallization at oxygen fugacities 6–7 log units below the Iron-Wüstite buffer ( f O 2 = ΔIW − 6 to − 7), induced by fluxes of mantle-derived CH 4 -H 2 fluids. Cathodoluminescence images reveal growth zoning within the individual crystals of the aggregates, related to the substitution of Ti 3+ in the corundum structure. Ti contents are < 0.3 wt% initially, then increase first linearly, then exponentially, toward adjacent melt pockets to reach values > 2 wt%. Numerical modelling indicates that the first skeletal crystals grew in an open system, from a moving magma. The subsequent linear increase in Ti reflects growth in a partially closed system, with decreasing porosity; the exponential increase in Ti close to melt pockets reflects closed-system growth, leading to dramatic increases in incompatible-element concentrations in the residual melts. We suggest that the corundum aggregates grew in melt/fluid conduits; diffusion modelling implies timescales of days to years before crystallization was terminated by explosive eruption. These processes probably operate in explosive volcanic systems in several tectonic settings.

Cognettia sphagnetorum (Vejdovský, 1878), a common inhabitant of forest soils and bogs in northern Europe, is a model organism in soil biology. We report the first documented occurrence of C. sphagnetorum in North America, based on DNA sequencing from a Sphagnum bog in western Washington, USA. Sequences were identical to that of worms from Sweden and the Czech Republic.

Background: The etiology of Meniere's disease (MD) and endolymphatic hydrops believed to underlie its symptoms remain unknown. One reason may be the exceptional complexity of the human inner ear, its vulnerability, and surrounding hard bone. The vestibular organ contains an endolymphatic duct system (EDS) bridging the different fluid reservoirs. It may be essential for monitoring hydraulic equilibrium, and a dysregulation may result in distension of the fluid spaces or endolymphatic hydrops.Material and Methods: We studied the EDS using high-resolution synchrotron phase contrast non-invasive imaging (SR-PCI), and micro-computed tomography (micro-CT). Ten fresh human temporal bones underwent SR-PCI. One bone underwent micro-CT after fixation and staining with Lugol's iodine solution (I2KI) to increase tissue resolution. Data were processed using volume-rendering software to create 3D reconstructions allowing orthogonal sectioning, cropping, and tissue segmentation.Results: Combined imaging techniques with segmentation and tissue modeling demonstrated the 3D anatomy of the human saccule, utricle, endolymphatic duct, and sac together with connecting pathways. The utricular duct (UD) and utriculo-endolymphatic valve (UEV or Bast's valve) were demonstrated three-dimensionally for the first time. The reunion duct was displayed with micro-CT. It may serve as a safety valve to maintain cochlear endolymph homeostasis under certain conditions.Discussion: The thin reunion duct seems to play a minor role in the exchange of endolymph between the cochlea and vestibule under normal conditions. The saccule wall appears highly flexible, which may explain occult hydrops occasionally preceding symptoms in MD on magnetic resonance imaging (MRI). The design of the UEV and connecting ducts suggests that there is a reciprocal exchange of fluid among the utricle, semicircular canals, and the EDS. Based on the anatomic framework and previous experimental data, we speculate that precipitous vestibular symptoms in MD arise from a sudden increase in endolymph pressure caused by an uncontrolled endolymphatic sac secretion. A rapid rise in UD pressure, mediated along the fairly wide UEV, may underlie the acute vertigo attack, refuting the rupture/K+-intoxication theory.

Background: Reports vary on the incidence of vestibular dysfunction and dizziness in patients following cochlear implantation (CI). Disequilibrium may be caused by surgery at the cochlear base, leading to functional disturbances of the vestibular receptors and endolymphatic duct system (EDS) which are located nearby. Here, we analyzed the three-dimensional (3D) anatomy of this region, aiming to optimize surgical approaches to limit damage to the vestibular organ.Material and Methods: A total of 22 fresh-frozen human temporal bones underwent synchrotron radiation phase-contrast imaging (SR-PCI). One temporal bone underwent micro-computed tomography (micro-CT) after fixation and staining with Lugol's iodine solution (I2KI) to increase tissue contrast. We used volume-rendering software to create 3D reconstructions and tissue segmentation that allowed precise assessment of anatomical relationships and topography. Macerated human ears belonging to the Uppsala collection were also used. Drilling and insertion of CI electrodes was performed with metric analyses of different trajectories.Results and Conclusions: SR-PCI and micro-CT imaging demonstrated the complex 3D anatomy of the basal region of the human cochlea, vestibular apparatus, and EDS. Drilling of a cochleostomy may disturb vestibular organ function by injuring the endolymphatic space and disrupting fluid barriers. The saccule is at particular risk due to its proximity to the surgical area and may explain immediate and long-term post-operative vertigo. Round window insertion may be less traumatic to the inner ear, however it may affect the vestibular receptors.

By the 1930’s vast areas of the western US were severely degraded by overgrazing and erosion. In response, Congress authorized conservation work including the construction of erosion control and water storage, distribution, and conveyance structures. Thousands of structures such as check dams, water spreaders, and contour berms were built during the 1930s and 40s to control water and sediment in an attempt to restore degraded rangelands. However, across most of the western US, these soil and water conservation measures were implemented without the benefit of local hydrologic data or technical design guidance. Many of the established conservation practices had been developed for humid regions and were untested for use in semiarid areas that are characterized by highly variable rainfall and flash floods. As a result, many structures proved ineffective and were subsequently abandoned. Even in cases where structures were effective, many never received maintenance after their initial construction. Although structurally compromised, abandoned and unmaintained structures continue to alter surface runoff patterns and can greatly exacerbate erosion. Four sites in Arizona, USA were selected to characterize the multi-decadal impacts of conservation structures. Breaches have formed in 100% of contour berms (n = 67) while 96% of water spreader berms (n = 26) were compromised. Localized failures in these structures has created concentrated flow paths that reorganized routing of runoff and sediment thus transforming sheetflow regimes to concentrated flow regimes. This study emphasizes the unintended legacy impacts of soil and water conservation structures and highlights their role as a potential constraint on contemporary resource management.

Sexually antagonistic coevolution can drive the evolution of male traits that harm females, and female resistance to those traits. While males have been found to vary their harmfulness to females in response to social cues, plasticity in female resistance traits remains to be examined. Here, we ask whether female seed beetles Callosobruchus maculatus are capable of adjusting their resistance to male harm in response to the social environment. Among seed beetles, male genital spines harm females during copulation and females might resist male harm via thickening of the reproductive tract walls. We develop a novel micro computed tomography imaging technique to quantify female reproductive tract thickness in three-dimensional space, and compared the reproductive tracts of females from populations that had evolved under high and low levels of sexual conflict, and for females reared under a social environment that predicted either high or low levels of sexual conflict. We find little evidence to suggest that females can adjust the thickness of their reproductive tracts in response to the social environment. Neither did evolutionary history affect reproductive tract thickness. Nevertheless, our novel methodology was capable of quantifying fine-scale differences in the internal reproductive tracts of individual females, and will allow future investigations into the internal organs of insects and other animals.

The size (volume or mass) of the olfactory bulbs in relation to the whole brain has been used as a neuroanatomical proxy for olfactory capability in a range of vertebrates, including fishes. Here, we use diffusible iodine-based contrast-enhanced computed tomography (diceCT) to test the value of this novel bioimaging technique for generating accurate measurements of the relative volume of the main olfactory brain areas (olfactory bulbs, peduncles, and telencephalon) and to describe the morphological organisation of the ascending olfactory pathway in model fish species from two taxa, the brownbanded bamboo shark Chiloscyllium punctatum and the common goldfish Carassius auratus. We also describe the arrangement of primary projections to the olfactory bulb and secondary projections to the telencephalon in both species. Our results identified substantially larger olfactory bulbs and telencephalon in C. punctatum compared to C. auratus (comprising approximately 5.2% vs. 1.8%, and 51.8% vs. 11.8% of the total brain volume, respectively), reflecting differences between taxa, but also possibly in the role of olfaction in the sensory ecology of these species. We identified segregated primary projections to the bulbs, associated with a compartmentalised olfactory bulb in C. punctatum, which supports previous findings in elasmobranch fishes. DiceCT imaging has been crucial for visualising differences in the morphological organisation of the olfactory system of both model species. We consider comparative neuroanatomical studies between representative species of both elasmobranch and teleost fish groups are fundamental to further our understanding of the evolution of the olfactory system in early vertebrates and the neural basis of olfactory abilities.

There is currently a limited understanding of the morphological and functional organization of the olfactory system in cartilaginous fishes, particularly when compared to bony fishes and terrestrial vertebrates. In this fish group, there is a clear paucity of information on the characterization, density, and distribution of olfactory receptor neurons (ORNs) within the sensory olfactory epithelium lining the paired olfactory rosettes, and their functional implications with respect to the hydrodynamics of incurrent water flow into the nares. This imaging study examines the brownbanded bamboo shark Chiloscyllium punctatum (Elasmobranchii) and combines immunohistochemical labeling using antisera raised against five G-protein α-subunits (Gαs/olf, Gαq/11/14, Gαi–1/2/3, Gαi–3, Gαo) with light and electron microscopy, to characterize the morphological ORN types present. Three main ORNs (“long”, “microvillous” and “crypt-like”) are confirmed and up to three additional microvilli-bearing types are also described; “Kappe-like” (potential or homologous “Kappe” as in teleosts), “pear-shaped” and “teardrop-shaped” cells. These morphotypes will need to be confirmed molecularly in the future. Using X-ray diffusible iodine-based contrast-enhanced computed tomography (diceCT), high-resolution scans of the olfactory rosettes, olfactory bulbs (OBs), peduncles, and telencephalon reveal a lateral segregation of primary olfactory inputs within the OBs, with distinct medial and lateral clusters of glomeruli, suggesting a potential somatotopic organization. However, most ORN morphotypes are found to be ubiquitously distributed within the medial and lateral regions of the olfactory rosette, with at least three microvilli-bearing ORNs labeled with anti-Gαo found in significantly higher densities in lateral lamellae [in lateral lamellae] and on the anterior portion of lamellae (facing the olfactory cavity). These microvilli-bearing ORN morphotypes (microvillous, “Kappe-like,” “pear-shaped,” and “teardrop-shaped”) are the most abundant across the olfactory rosette of this species, while ciliated ORNs are less common and crypt cells are rare. Spatial simulations of the fluid dynamics of the incurrent water flow into the nares and within the olfactory cavities indicate that the high densities of microvilli-bearing ORNs located within the lateral region of the rosette are important for sampling incoming odorants during swimming and may determine subsequent tracking behavior.

This article discusses particle size distribution (PSD) by sieving as it relates to variable granular density soils such as hemipelagic calcareous sediment and pyroclastic pumice. These soils tend to have low-density porous sand-sized particles and high-density solid silt and clay-sized particles. When mass fraction passing each sieve is used to create the gravimetric PSD, the quantity of sand-sized particles in these soils can be underestimated, because of their low density. This article presents the volumetric PSD as a new method to account for granular density variation in these unique sediments.

Coarse-grained xenoliths of hibonite + grossite + Mg-Al-V spinel from Cretaceous pyroclastic rocks on Mt. Carmel, N. Israel, and from Sierra de Comechingones, Argentina, include spherules, rods and dense branching structures of native vanadium and V-Al alloys. Microstructures suggest that vanadium melts became immiscible with the host Ca-Al-Mg-Si-O melt, and nucleated as droplets on the surfaces of the oxide phases, principally hibonite. Many extended outward as rods or branching structures as the host oxide crystal grew. The stability of V-0 implies oxygen fugacities >= 9 log units below the Iron-Wustite buffer, suggesting a hydrogendominated atmosphere. This is supported by wt%-levels of hydrogen in gasses released by crushing, by Raman spectroscopy, and by the presence of VH2 among the vanadium balls. The oxide assemblage formed at 1400-1200 degrees C; the solution of hydrogen in the metal could lower the melting point of vanadium to these temperatures. These assemblages probably resulted from reaction between differentiated mafic melts and mantle-derived CH4 + H-2 fluids near the crust-mantle boundary, and they record the most reducing magmatic conditions yet documented on Earth. (C) 2020 Elsevier B.V. All rights reserved.

Contrast-enhanced X-ray imaging provides a non-destructive and flexible approach to optimizing contrast in soft tissues, especially when incorporated with Lugol's solution (aqueous I2KI), a technique currently referred to as diffusible iodine-based contrast-enhanced computed tomography (diceCT). This stain exhibits high rates of penetration and results in excellent contrast between and within soft tissues, including the central nervous system. Here, we present a staining method for optimizing contrast in the brain of a cartilaginous fish, the brownbanded bamboo shark, Chiloscyllium punctatum, and a bony fish, the common goldfish, Carassius auratus, using diceCT. The aim of this optimization procedure is to provide suitable contrast between neural tissue and background tissue(s) of the head, thereby facilitating digital segmentation and volumetric analysis of the central nervous system. Both species were scanned before staining and were rescanned at time (T) intervals, either every 48 h (C. punctatum) or every 24 h (C. auratus), to assess stain penetration and contrast enhancement. To compare stain intensities, raw X-ray CT data were reconstructed using air and water calibration phantoms that were scanned under identical conditions to the samples. Optimal contrast across the brain was achieved at T = 240 h for C. punctatum and T = 96 h for C. auratus. Higher resolution scans of the whole brain were obtained at the two optimized staining times for all the corresponding specimens. The use of diceCT provides a new and valuable tool for visualizing differences in the anatomic organization of both the central and peripheral nervous systems of fish.