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[This corrects the article DOI: 10.1186/s12983-017-0227-8.].

Background: Fluorochrome staining is among the most widely used techniques to study growth dynamics of echinoderms. However, it fails to detect fine-scale increments because produced marks are commonly diffusely distributed within the skeleton. In this paper we investigated the potential of trace element (manganese) labeling and subsequent cathodoluminescence (CL) imaging in fine-scale growth studies of echinoderms., Results: Three species of sea urchins ( Paracentrotus lividus , Echinometra sp. and Prionocidaris baculosa ) were incubated for different periods of time in seawater enriched in different Mn 2+ concentrations (1 mg/L; 3 mg/L; 61.6 mg/L). Labeling with low Mn 2+ concentrations (at 1 mg/L and 3 mg/L) had no effect on behavior, growth and survival of sea urchins in contrast to the high Mn 2+ dosage (at 61.6 mg/L) that resulted in lack of skeleton growth. Under CL, manganese produced clearly visible luminescent growth fronts in these specimens (observed in sectioned skeletal parts), which allowed for a determination of the average extension rates and provided direct insights into the morphogenesis of different types of ossicles. The three species tend to follow the same patterns of growth. Spine growth starts with the formation of microspines which are simultaneously becoming reinforced by addition of thickening layers. Spine septa develop via deposition of porous stereom that is rapidly (within less than 2 days) filled by secondary calcite. Development of the inner cortex in cidaroids begins with the formation of microspines which grow at ~3.5 μm/day. Later on, deposition of the outer polycrystalline cortex with spinules and protuberances proceeds at ~12 μm/day. The growth of tooth can be rapid (up to ~1.8 mm/day) and starts with the formation of primary plates (pp) in plumula. Later on, during the further growth of pp in aboral and lateral directions, secondary extensions develop inside (in chronological order: lamellae, needles, secondary plate, prisms and carinar processes), which are increasingly being solidified towards the incisal end. Interradial growth in the ambital interambulacral test plates exceeds meridional growth and inner thickening., Conclusions: Mn 2+ labeling coupled with CL imaging is a promising, low-cost and easily applicable method to study growth dynamics of echinoderms at the micro-length scale. The method allowed us to evaluate and refine models of echinoid skeleton morphogenesis.

Roughly 240 million years ago (Ma), scleractinian corals rapidly expanded and diversified across shallow marine environments. The main driver behind this evolution is uncertain, but the ecological success of modern reef-building corals is attributed to their nutritional symbiosis with photosynthesizing dinoflagellate algae. We show that a suite of exceptionally preserved Late Triassic (ca. 212 Ma) coral skeletons from Antalya (Turkey) have microstructures, carbonate 13 C/ 12 C and 18 O/ 16 O, and intracrystalline skeletal organic matter 15 N/ 14 N all indicating symbiosis. This includes species with growth forms conventionally considered asymbiotic. The nitrogen isotopes further suggest that their Tethys Sea habitat was a nutrient-poor, low-productivity marine environment in which photosymbiosis would be highly advantageous. Thus, coral-dinoflagellate symbiosis was likely a key driver in the evolution and expansion of shallow-water scleractinians.

Today coral reefs are threatened by changes to seawater conditions associated with rapid anthropogenic global climate change. Yet, since the Cenozoic, these organisms have experienced major fluctuations in atmospheric CO2 levels (from greenhouse conditions of high pCO2 in the Eocene to low pCO2 ice-house conditions in the Oligocene-Miocene) and a dramatically changing ocean Mg/Ca ratio. Here we show that the most diverse, widespread, and abundant reef-building coral genus Acropora (20 morphological groups and 150 living species) has not only survived these environmental changes, but has maintained its distinct skeletal biomineralization pattern for at least 40 My: Well-preserved fossil Acropora skeletons from the Eocene, Oligocene, and Miocene show ultra-structures indistinguishable from those of extant representatives of the genus and their aragonitic skeleton Mg/Ca ratios trace the inferred ocean Mg/Ca ratio precisely since the Eocene. Therefore, among marine biogenic carbonate fossils, well-preserved acroporid skeletons represent material with very high potential for reconstruction of ancient ocean chemistry.

Background: In recent years, several types of molecular markers and new microscale skeletal characters have shown potential as powerful tools for phylogenetic reconstructions and higher-level taxonomy of scleractinian corals. Nonetheless, discrimination of closely related taxa is still highly controversial in scleractinian coral research. Here we used newly sequenced complete mitochondrial genomes and 30 microsatellites to define the genetic divergence between two closely related azooxanthellate taxa of the family Caryophylliidae: solitary Desmophyllum dianthus and colonial Lophelia pertusa., Results: In the mitochondrial control region, an astonishing 99.8 % of nucleotides between L. pertusa and D. dianthus were identical. Variability of the mitochondrial genomes of the two species is represented by only 12 non-synonymous out of 19 total nucleotide substitutions. Microsatellite sequence (37 loci) analysis of L. pertusa and D. dianthus showed genetic similarity is about 97 %. Our results also indicated that L. pertusa and D. dianthus show high skeletal plasticity in corallum shape and similarity in skeletal ontogeny, micromorphological (septal and wall granulations) and microstructural characters (arrangement of rapid accretion deposits, thickening deposits)., Conclusions: Molecularly and morphologically, the solitary Desmophyllum and the dendroid Lophelia appear to be significantly more similar to each other than other unambiguous coral genera analysed to date. This consequently leads to ascribe both taxa under the generic name Desmophyllum (priority by date of publication). Findings of this study demonstrate that coloniality may not be a robust taxonomic character in scleractinian corals.

Reef-building scleractinian (stony) corals are among the most efficient bio-mineralizing organisms in nature. The calcification rate of scleractinian corals oscillates under ambient light conditions, with a cyclic, diurnal pattern. A fundamental question is whether this cyclic pattern is controlled by exogenous signals or by an endogenous 'biological-clock' mechanism, or both. To address this problem, we have studied calcification patterns of the Red Sea scleractinian coral Acropora eurystoma with frequent measurements of total alkalinity (AT) under different light conditions. Additionally, skeletal extension and ultra-structure of newly deposited calcium carbonate were elucidated with (86)Sr isotope labeling analysis, combined with NanoSIMS ion microprobe and scanning electron microscope imaging. Our results show that the calcification process persists with its cyclic pattern under constant light conditions while dissolution takes place within one day of constant dark conditions, indicating that an intrinsic, light-entrained mechanism may be involved in controlling the calcification process in photosymbiotic corals.

Understanding the evolution of scleractinian corals on geological timescales is key to predict how modern reef ecosystems will react to changing environmental conditions in the future. Important to such efforts has been the development of several skeleton-based criteria to distinguish between the two major ecological groups of scleractinians: zooxanthellates, which live in symbiosis with dinoflagellate algae, and azooxanthellates, which lack endosymbiotic dinoflagellates. Existing criteria are based on overall skeletal morphology and bio/geo-chemical indicators-none of them being particularly robust. Here we explore another skeletal feature, namely fine-scale growth banding, which differs between these two groups of corals. Using various ultra-structural imaging techniques (e.g., TEM, SEM, and NanoSIMS) we have characterized skeletal growth increments, composed of doublets of optically light and dark bands, in a broad selection of extant symbiotic and asymbiotic corals. Skeletons of zooxanthellate corals are characterized by regular growth banding, whereas in skeletons of azooxanthellate corals the growth banding is irregular. Importantly, the regularity of growth bands can be easily quantified with a coefficient of variation obtained by measuring bandwidths on SEM images of polished and etched skeletal surfaces of septa and/or walls. We find that this coefficient of variation (lower values indicate higher regularity) ranges from ~40 to ~90% in azooxanthellate corals and from ~5 to ~15% in symbiotic species. With more than 90% (28 out of 31) of the studied corals conforming to this microstructural criterion, it represents an easy and robust method to discriminate between zooxanthellate and azooxanthellate corals. This microstructural criterion has been applied to the exceptionally preserved skeleton of the Triassic (Norian, ca. 215 Ma) scleractinian Volzeia sp., which contains the first example of regular, fine-scale banding of thickening deposits in a fossil coral of this age. The regularity of its growth banding strongly suggests that the coral was symbiotic with zooxanthellates.

Scleractinian corals begin their biomineralization process shortly after larval settlement with the formation of calcium carbonate (CaCO(3)) structures at the interface between the larval tissues and the substrate. The newly settled larvae exert variable degrees of control over this skeleton formation, providing an opportunity to study a range of biocarbonate structures, some of which are transient and not observed in adult coral skeletons. Here we present a morphological, structural, crystallographic, and chemical comparison between two types of aragonite deposits observed during the skeletal development of 2-days old recruits of Pocillopora damicornis: (1) Primary septum and (2) Abundant, dumbbell-like structures, quasi-randomly distributed between initial deposits of the basal plate and not present in adult corals-At the mesoscale level, initial septa structures are formed by superimposed fan-shaped fasciculi consisting of bundles of fibers, as also observed in adult corals. This organization is not observed in the dumbbell-like structures. However, at the ultrastructural level there is great similarity between septa and dumbbell components. Both are composed of <100 nm granular units arranged into larger single-crystal domains.Chemically, a small difference is observed between the septae with an average Mg/Ca ratio around 11 mmol/mol and the dumbbell-like structures with ca. 7 mmol/mol; Sr/Ca ratios are similar in the two structures at around 8 mmol/mol-Overall, the observed differences in distribution, morphology, and chemistry between septa, which are highly conserved structures fundamental to the architecture of the skeleton, and the transient, dumbbell-like structures, suggest that the latter might be formed through less controlled biomineralization processes. Our observations emphasize the inherent difficulties involved in distinguishing different biomineralization pathways based on ultrastructural and crystallographical observations., (© 2015 Wiley Periodicals, Inc.)

Calcium carbonate biomineralization of scleractinian coral recruits is fundamental to the construction of reefs and their survival under stress from global and local environmental change. Establishing a baseline for how normal, healthy coral recruits initiate skeletal formation is, therefore, warranted. Here, we present a thorough, multiscale, microscopic and spectroscopic investigation of skeletal elements deposited by Pocillopora damicornis recruits, from 12 h to 22 days after settlement in aquarium on a flat substrate. Six growth stages are defined, primarily based on appearance and morphology of successively deposited skeletal structures, with the following average formation time-scales: A (<24 h), B (24-36 h), C (36-48 h), D (48-72 h), E (72-96 h), and F (>10 days). Raman and energy dispersive X-ray spectroscopy indicate the presence of calcite among the earliest components of the basal plate, which consist of micrometer-sized, rod-shaped crystals with rhomboidal habit. All later CaCO3 skeletal structures are composed exclusively of aragonite. High-resolution scanning electron microscopy reveals that, externally, all CaCO3 deposits consist of <100 nm granular units. Fusiform, dumbbell-like, and semispherulitic structures, 25-35 µm in longest dimension, occur only during the earliest stages (Stages A-C), with morphologies similar to structures formed abiotically or induced by organics in in vitro carbonate crystallization experiments. All other skeletal structures of the basal plate are composed of vertically extending lamellar bundles of granules. From Stage D, straight fibrils, 40-45 nm in width and presumably of organic composition, form bridges between these aragonitic bundles emerging from the growing front of fusing skeletal structures. Our results show a clear evolution in the coral polyp biomineralization process as the carbonate structures develop toward those characterizing the adult skeleton., (© 2014 Wiley Periodicals, Inc.)

Growth dynamics of the primary spine of the cidaroid sea urchin Phyllacanthus imperialis was assessed for the first time using pulsed (26) Mg-labeling and NanoSIMS isotopic imaging. The sea urchin was incubated twice (for 48 h) in artificial seawater with elevated level of (26) Mg. After each labeling event, the sea urchin was returned for 72 h to seawater with natural isotopic abundance of (26) Mg. NanoSIMS ion microprobe was subsequently used to visualize the labeled regions of the spine with submicrometer lateral resolution. The growth of the new skeleton was restricted to the distalmost and peripheral portions of the spine. Skeletogenesis involved mostly the deposition of continuous thickening layers and lateral growth involving bridges between previously formed trabeculae. The timescale of formation of individual thickening layers (ca. 1 µm in width) on the stereom trabeculae was on the order of 1 day. Longitudinal growth occurred mainly at the periphery in the form of small portions of the thickening deposits or more massive microspines that appeared to branch and fuse with those above and below. These microspines were found to grow at about 10 µm/day. These results reveal that the skeletal growth of a juvenile cidaroid spine is complex and highly heterogeneous, with different extension rates depending on the stage of the stereom development and/or direction of the growth fronts. The growth pattern observed here at the submicrometer scale provides direct evidence supporting the earlier suggestions that the lamellar structure of echinoderm stereom is formed by periodic deposition of continuous mineral layers., (© 2014 Wiley Periodicals, Inc.)

Many phosphorylated nucleoside derivatives have therapeutic potential, but their application is limited by problems with membrane permeability and with intracellular delivery. Here, we prepared polypyrrole microvessel structures modified with superparamagnetic nanoparticles for use as potential carriers of nucleotides. The microvessels were prepared via the photochemical polymerization of the monomer onto the surface of aqueous ferrofluidic droplets. A complementary physicochemical analysis revealed that a fraction of the nanoparticles was embedded in the microvessel walls, while the other nanoparticles were in the core of the vessel. SQUID (superconducting quantum interference device) measurements indicated that the incorporated nanoparticles retained their superparamagnetic properties; thus, the resulting nanoparticle-modified microvessels can be directed by an external magnetic field. As a result of these features, these microvessels may be useful as drug carriers in biomedical applications. To demonstrate the encapsulation of drug molecules, two labeled mRNA cap analogues, nucleotide-derived potential anticancer agents, were used. It was shown that the cap analogues are located in the aqueous core of the microvessels and can be released to the external solution by spontaneous permeation through the polymer walls. Mass spectrometry analysis confirmed that the cap analogues were preserved during encapsulation, storage, and release. This finding provides a foundation for the future development of anticancer therapies and for the delivery of nucleotide-based therapeutics.

The skeletal ontogeny of the Micrabaciidae, one of two modern basal scleractinian lineages, is herein reconstructed based on serial micro-computed tomography sections and scanning electron micrographs. Similar to other scleractinians, skeletal growth of micrabaciids starts from the simultaneous formation of six primary septa. New septa of consecutive cycles arise between septa of the preceding cycles from unique wedge-shaped invaginations of the wall. The invagination of wall and formation of septa are accompanied by development of costae alternating in position with septa. During corallite growth, deepening invagination of the wall results in elevation of septa above the level of a horizontal base. The corallite wall is regularly perforated thus invaginated regions consist of pillars inclined downwardly and outwardly from the lower septal margins. Shortly after formation of septa (S2 and higher cycles) their upper margins bend and fuse with the neighboring members of a previous cycle, resulting in a unique septal pattern, formerly misinterpreted as "septal bifurcation." Septa as in other Scleractinia are hexamerally arranged in cycles. However, starting from the quaternaries, septa within single cycles do not appear simultaneously but are inserted in pairs and successively flank the members of a preceding cycle, invariably starting from those in the outermost parts of the septal system. In each pair, the septum adjacent to older septa arises first (e.g., the quinaries between S2 and S4 before quinaries between S3 and S4). Unique features of micrabaciid skeletal ontogeny are congruent with their basal position in scleractinian phylogeny, which was previously supported by microstructural and molecular data., (Copyright © 2012 Wiley Periodicals, Inc.)

We report on the preparation of water-filled polymer microvessels through the photopolymerization of pyrrole in a water/chloroform emulsion. The resulting structures were characterized by complementary spectroscopic and microscopic techniques, including Raman spectroscopy, XPS, SEM, and TEM. The encapsulation of fluorescent, magnetic, and ionic species within the microvessels has been demonstrated. Confocal microscopy and fluorescence anisotropy measurements revealed that the encapsulated chromophore (Rhodamine 6G) resides within voids in the capsules; however, strong interaction of the dye with polypyrrole results in a measurable decrease in its rotational dynamics. Microvessels loaded with ferrofluid exhibit magnetic properties, and their structures can be directed with an external magnetic field. TEM measurements allowed imaging of individual nanoparticles entrapped within the vessels. The application of Cu(2+)-loaded microvessels as a transducer layer in all-solid-state ion-selective electrodes was also demonstrated., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The encapsulation of guest molecules within polymeric hollow nano- or microscale structures is a rapidly developing field of interdisciplinary research due to a variety of applications ranging from drug delivery and sensor fabrication to nanoscale synthesis and bioinspired mineralization. We report on the encapsulation of pyrene within three-dimensional polypyrrole microvessels synthesized by precipitation polymerization of pyrrole onto toluene droplets that contain pyrene. Steady state and time-resolved fluorescence measurements show that the optical response and dynamics of encapsulated pyrene is significantly different from that in the free solution, likely due to interactions with oligomeric species generated during the polymerization process that partition into the organic core of the microvessel. Our results indicate that the encapsulation process can have a significant influence on the local environment of encapsulated species, an issue that is critical from the perspective of potential synthetic or medical applications., (© 2011 American Chemical Society)

This paper reports the results of the first dynamic labeling experiment with regenerating spines of sea urchins Paracentrotus lividus using the stable isotope ²⁶Mg and NanoSIMS high-resolution isotopic imaging, which provide a direct information about the growth process. Growing spines were labeled twice (for 72 and 24 h, respectively) by increasing the abundance of ²⁶Mg in seawater. The incorporation of ²⁶Mg into the growing spines was subsequently imaged with the NanoSIMS ion microprobe. Stereom trabeculae initially grow as conical micro-spines, which form within less than 1 day. These micro-spines fuse together by lateral outgrowths and form a thin, open meshwork (inner stereom), which is subsequently reinforced by addition of layered thickening deposits (outer stereom). The (longitudinal) growth rate of the inner stereom is ca. 125 μm/day. A single (ca. 1 μm) thickening layer in the stereom trabeculae is deposited during 24h. The thickening process is contemporaneous with the formation micro-spines and involves both longitudinal trabeculae and transverse bridges to a similar degree. Furthermore, the skeleton-forming cells remain active in the previously formed open stereom for at least 10 days, and do not migrate upwards until the end of the thickening process. The experimental capability presented here provides a new way to obtain detailed information about the skeleton formation of a multitude of marine, calcite producing organisms., (Copyright © 2011 Elsevier Inc. All rights reserved.)

We have investigated the nanotexture and crystallographic orientation of aragonite in a coral skeleton using synchrotron-based scanning transmission X-ray microscopy (STXM) and transmission electron microscopy (TEM). Polarization-dependent STXM imaging at 40-nm spatial resolution was used to obtain an orientation map of the c-axis of aragonite on a focused ion beam milled ultrathin section of a Porites coral. This imaging showed that one of the basic units of coral skeletons, referred to as the center of calcification (COC), consists of a cluster of 100-nm aragonite globules crystallographically aligned over several micrometers with a fan-like distribution and with the properties of single crystals at the mesoscale. The remainder of the skeleton consists of aragonite single-crystal fibers in crystallographic continuity with the nanoglobules comprising the COC. Our observation provides information on the nm-scale processes that led to biomineral formation in this sample. Importantly, the present study illustrates how the methodology described here, which combines HRTEM and polarization-dependent synchrotron-based STXM imaging, offers an interesting new approach for investigating biomineralizing systems at the nm-scale., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Micrabaciids are solitary, exclusively azooxanthellate deep-sea corals belonging to one of the deepest-living (up to 5,000 m) scleractinian representatives. All modern micrabaciid taxa (genera: Letepsammia, Rhombopsammia, Stephanophyllia, Leptopenus) have a porous and often very fragile skeleton consisting of two main microstructural components known also from other scleractinians: rapid accretion deposits and thickening deposits. However, at the microstructural level, the skeletal organization of the micrabaciids is distinctly different from that of other scleractinians. Rapid accretion deposits consist of alternations of superimposed "microcrystalline" (micrometer-sized aggregates of nodular nanodomains) and fibrous zones. In contrast to all shallow-water and sympatric deep-water corals so far described, the thickening deposits of micrabaciids are composed of irregular meshwork of short (1-2 μm) and extremely thin (ca. 100-300 nm) fibers organized into small, chip-like bundles (ca. 1-2 μm thick). Longer axes of fiber bundles are usually subparallel to the skeletal surfaces and oriented variably in this plane. The unique microstructural organization of the micrabaciid skeleton is consistent with their monophyletic status based on macromorphological and molecular data, and points to a diversity of organic matrix-mediated biomineralization strategies in Scleractinia., (Copyright © 2010 Wiley-Liss, Inc.)

In contrast to siliceous sponge spicules, the biomineralization in calcareous sponges is poorly understood. In particular, the existence of a differentiated central core in calcareous spicules is still controversial. Here we combine high-spatial resolution analyses, including NanoSIMS, Raman, SXM, AFM, SEM and TEM to investigate the composition, mineralogy and ultrastructure of the giant tetractines of Leuconia johnstoniCarter, 1871 (Baeriidae, Calcaronea) and the organization of surrounding cells. A compositionally distinct core is present in these spicule types. The core measures 3.5-10 μm in diameter and is significantly depleted in Mg and lightly enriched in S compared with the adjacent outer layer in the spicule. Measured Mg/Ca ratios in the core range from 70 to 90 mmol/mol compared to 125-130 mmol/mol in the adjacent calcite envelope. However, this heterogeneous distribution of Mg and S is not reflected in the mineralogy and the microstructure. Raman spectroscopy demonstrates a purely calcitic mineralogy. SEM examination of slightly etched spicules indicates an ultrastructure organized hierarchically in a concentric pattern, with layers less than 250 nm in width inside layers averaging 535 ± 260 nm. No change in structural pattern corresponds to the Mg/Ca variation observed. AFM and TEM observations show a nanogranular organization of the spicules with a network of intraspicular organic material intercalated between nanograins 60-130 nm in diameter. Observations of sclerocyte cells in the process of spiculogenesis suggest that the compositionally distinct core is produced by a sub-apical sclerocyte "founder cell" that controls axial growth, while the envelope is secreted by lateral sclerocytes "thickener cells", which control radial growth., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Recent molecular phylogenies conflict with traditional scleractinian classification at ranks ranging from suborder to genus, challenging morphologists to discover new characters that better agree with molecular data. Such characters are essential for including fossils in analyses and tracing evolutionary patterns through geologic time. We examine the skeletal morphology of 36 species belonging to the traditional families Faviidae, Merulinidae, Pectiniidae, and Trachyphylliidae (3 Atlantic, 14 Indo-Pacific, 2 cosmopolitan genera) at the macromorphological, micromorphological, and microstructural levels. Molecular analyses indicate that the families are not monophyletic groups, but consist of six family-level clades, four of which are examined [clade XV = Diploastrea heliopora; clade XVI = Montastraea cavernosa; clade XVII ("Pacific faviids") = Pacific faviids (part) + merulinids (part) + pectiniids (part) + M. annularis complex; clade XXI ("Atlantic faviids") = Atlantic faviids (part) + Atlantic mussids]. Comparisons among molecular clades indicate that micromorphological and microstructural characters (singly and in combination) are clade diagnostic, but with two exceptions, macromorphologic characters are not. The septal teeth of "Atlantic faviids" are paddle-shaped (strong secondary calcification axes) or blocky, whereas the septal teeth of "Pacific faviids" are spine-shaped or multidirectional. Corallite walls in "Atlantic faviids" are usually septothecal, with occasional trabeculothecal elements; whereas corallite walls in "Pacific faviids" are usually trabeculothecal or parathecal or they contain abortive septa. Exceptions include subclades of "Pacific faviids" consisting of a) Caulastraea and Oulophyllia (strong secondary axes) and b) Cyphastrea (septothecal walls). Diploastrea has a diagnostic synapticulothecal wall and thick triangular teeth; Montastraea cavernosa is also distinct, possessing both "Pacific faviid" (abortive septa) and "Atlantic faviid" (paddle-shaped teeth) attributes. The development of secondary axes is similar in traditional Atlantic faviids and mussids, supporting molecular results placing them in the same clade. Subclades of "Pacific faviids" reveal differences in wall structure and the arrangement and distinctiveness of centers of rapid accretion., (Copyright © 2010 Wiley-Liss, Inc.)

Solid-supported and free-standing polypyrrole microcapsules were synthesized by deposition of the polymer onto toluene droplets. The polymer forms an encapsulating thin layer on the droplet surface. The encapsulation of the solvent was verified by FTIR measurements. Entrapment of other guest molecules can be achieved by using a solution of the guest molecules to prepare the droplets. This was demonstrated with perylene, a hydrophobic fluorescent molecule with well established spectroscopic properties. The encapsulation of perylene was probed with fluorescence spectroscopic techniques and optical microscopy. Time-resolved measurements allowed determination of relaxation dynamics of the fluorophore trapped in the capsules. It was shown that the rotational diffusion of perylene in toluene droplets is best described as a prolate rotor. The reorientation data suggest an increased solvent viscosity within the capsule.

Background: Classical morphological taxonomy places the approximately 1400 recognized species of Scleractinia (hard corals) into 27 families, but many aspects of coral evolution remain unclear despite the application of molecular phylogenetic methods. In part, this may be a consequence of such studies focusing on the reef-building (shallow water and zooxanthellate) Scleractinia, and largely ignoring the large number of deep-sea species. To better understand broad patterns of coral evolution, we generated molecular data for a broad and representative range of deep sea scleractinians collected off New Caledonia and Australia during the last decade, and conducted the most comprehensive molecular phylogenetic analysis to date of the order Scleractinia., Methodology: Partial (595 bp) sequences of the mitochondrial cytochrome oxidase subunit 1 (CO1) gene were determined for 65 deep-sea (azooxanthellate) scleractinians and 11 shallow-water species. These new data were aligned with 158 published sequences, generating a 234 taxon dataset representing 25 of the 27 currently recognized scleractinian families., Principal Findings/conclusions: There was a striking discrepancy between the taxonomic validity of coral families consisting predominantly of deep-sea or shallow-water species. Most families composed predominantly of deep-sea azooxanthellate species were monophyletic in both maximum likelihood and Bayesian analyses but, by contrast (and consistent with previous studies), most families composed predominantly of shallow-water zooxanthellate taxa were polyphyletic, although Acroporidae, Poritidae, Pocilloporidae, and Fungiidae were exceptions to this general pattern. One factor contributing to this inconsistency may be the greater environmental stability of deep-sea environments, effectively removing taxonomic "noise" contributed by phenotypic plasticity. Our phylogenetic analyses imply that the most basal extant scleractinians are azooxanthellate solitary corals from deep-water, their divergence predating that of the robust and complex corals. Deep-sea corals are likely to be critical to understanding anthozoan evolution and the origins of the Scleractinia.

Microscopic (AFM and FESEM) observations show that scleractinian coral biomineral fibers in extant Desmophyllum and Favia, and fossil Jurassic Isastrea are composed of nanocrystalline grains of about 30-100 nm in size. In contrast to these findings, SR diffraction data on the same coral materials exhibit narrow Bragg peaks suggesting much larger crystallite size. These seemingly contradicting results of microscopic and diffraction studies are reconciled within a new, minute-scale model of scleractinian biomineral fibers. In this model, nanocrystalline aragonite units are interconnected by mineral bridges and form aggregates usually larger than 200 nm. Most likely, the size of the aggregates is resulting from physiological biomineralization cycles that control cellular secretion of ions and biopolymeric species. Intercalation of biopolymers into crystal lattice may influence consistently several structural parameters of the scleractinian coral bio-aragonite in all studied samples: (i) the lattice parameters and internal strains of the bio-aragonite are larger than in mineral aragonite, (ii) lattice parameter elongations and internal strains reveal directional anisotropy with respect to crystallographic axes.

It has been generally thought that scleractinian corals form purely aragonitic skeletons. We show that a well-preserved fossil coral, Coelosmilia sp. from the Upper Cretaceous (about 70 million years ago), has preserved skeletal structural features identical to those observed in present-day scleractinians. However, the skeleton of Coelosmilia sp. is entirely calcitic. Its fine-scale structure and chemistry indicate that the calcite is primary and did not form from the diagenetic alteration of aragonite. This result implies that corals, like other groups of marine, calcium carbonate-producing organisms, can form skeletons of different carbonate polymorphs.