Search results for "Spicule"
showing 10 items of 73 documents
Probing the Multiple Structures of Vaterite through Combined Computational and Experimental Raman Spectroscopy.
2014
First-principles Raman spectra have been computed for several new vaterite structural models that have been recently proposed, and compared with spectra recorded on a set of biogenic, geological and synthetic samples. This set includes new measurements collected on Herdamania momus spicules (Great Barrier Reef, Queensland, Australia), which are known to have purity and crystallinity that are higher than for other biogenic samples. Overall, due to the close structural connection between the various models, the computed Raman spectra are found to be broadly similar. However, the spectra obtained for the two most stable models (monoclinic C2 and trigonal P3221, corresponding to two different p…
Siliceous spicules in marine demosponges (example Suberites domuncula)
2005
All metazoan animals comprise a body plan of different complexity. Since-especially based on molecular and cell biological data-it is well established that all metazoan phyla, including the Porifera (sponges), evolved from a common ancestor the search for common, basic principles of pattern formation (body plan) in all phyla began. Common to all metazoan body plans is the formation of at least one axis that runs from the apical to the basal region; examples for this type of organization are the Porifera and the Cnidaria (diploblastic animals). It seems conceivable that the basis for the formation of the Bauplan in sponges is the construction of their skeleton by spicules. In Demospongiae (w…
Self-healing, an intrinsic property of biomineralization processes
2013
The sponge siliceous spicules are formed enzymatically via silicatein, in contrast to other siliceous biominerals. Originally, silicatein had been described as a major structural protein of the spicules that has the property to allow a specific deposition of silica onto their surface. More recently, it had been unequivocally demonstrated that silicatein displays a genuine enzyme activity, initiating and maintaining silica biopolycondensation at low precursor concentrations (<2 mM). Even more, as silicatein becomes embedded into the biosilica polymer, formed by the enzyme, it retains its functionality to enable a controlled biosilica deposition. The protection of silicatein through the biosi…
Regional and modular expression of morphogenetic factors in the demosponge Lubomirskia baicalensis
2008
Some sponges [phylum Porifera], e.g. the demosponges Lubomirskia baicalensis or Axinella polypoides, show an arborescent growth form. In the freshwater sponge L. baicalensis this morphotype is seen mostly in depths below 4 m while in more shallow regions it grows as a crust. The different growth forms are determined in nature very likely by water current and/or light. The branches of this species are composed of modules, arranged along the apical-basal axis. The modules are delimited by a precise architecture of the spicule bundles; longitudinal bundles originate from the apex of the earlier module, while at the basis of each module these bundles are cross-linked by traverse bundles under f…
Bio-sintering processes in hexactinellid sponges: Fusion of bio-silica in giant basal spicules from Monorhaphis chuni☆
2009
The two sponge classes, Hexactinellida and Demospongiae, comprise a skeleton that is composed of siliceous skeletal elements (spicules). Spicule growth proceeds by appositional layering of lamellae that consist of silica nanoparticles, which are synthesized via the sponge-specific enzyme silicatein. While in demosponges during maturation the lamellae consolidate to a solid rod, the lamellar organization of hexactinellid spicules largely persists. However, the innermost lamellae, near the spicule core, can also fuse to a solid axial cylinder. Similar to the fusion of siliceous nanoparticles and lamella, in several hexactinellid species individual spicules unify during sintering-like processe…
Analysis of the axial filament in spicules of the demosponge Geodia cydonium: different silicatein composition in microscleres (asters) and megascler…
2007
The skeleton of the siliceous sponges (Porifera: Hexactinellida and Demospongiae) is supported by spicules composed of bio-silica. In the axial canals of megascleres, harboring the axial filaments, three isoforms of the enzyme silicatein (-alpha, -beta and -gamma) have been identified until now, using the demosponges Tethya aurantium and Suberites domuncula. Here we describe the composition of the proteinaceous components of the axial filament from small spicules, the microscleres, in the demosponge Geodia cydonium that possesses megascleres and microscleres. The morphology of the different spicule types is described. Also in G. cydonium the synthesis of the spicules starts intracellularly …
Histochemical and electron microscopic analysis of spiculogenesis in the demosponge Suberites domuncula.
2006
The skeleton of demosponges is built of spicules consisting of biosilica. Using the primmorph system from Suberites domuncula, we demonstrate that silicatein, the biosilica-synthesizing enzyme, and silicase, the catabolic enzyme, are colocalized at the surface of growing spicules as well as in the axial filament located in the axial canal. It is assumed that these two enzymes are responsible for the deposition of biosilica. In search of additional potential structural molecules that might guide the mineralization process during spiculogenesis to species-specific spicules, electron microscopic studies with antibodies against galectin and silicatein were performed. These studies showed that …
Enzyme-based biosilica and biocalcite: biomaterials for the future in regenerative medicine
2013
The oldest animals on Earth, sponges, form both the calcareous and the siliceous matrices of their spicules enzymatically. Until recently, it has been neglected that enzymes play crucial roles during formation of these biominerals. This paradigm shift occurred after the discovery that the enzyme silicatein, which catalyzes the polycondensation of silica, and the enzyme carbonic anhydrase (CA), which catalyzes the formation of bicarbonate (HCO3(-)/CaCO3), produce solid amorphous bioglass or biocalcite. This suggests that in mammals, biosilica and biocalcite can act anabolically during hydroxyapatite (HA) synthesis and bone formation. Biosilica and biocalcite are thus promising candidates for…
Biocalcite, a multifunctional inorganic polymer: Building block for calcareous sponge spicules and bioseed for the synthesis of calcium phosphate-bas…
2014
Calcium carbonate is the material that builds up the spicules of the calcareous sponges. Recent results revealed that the calcium carbonate/biocalcite-based spicular skeleton of these animals is formed through an enzymatic mechanism, such as the skeleton of the siliceous sponges, evolutionarily the oldest animals that consist of biosilica. The enzyme that mediates the calcium carbonate deposition has been identified as a carbonic anhydrase (CA) and has been cloned from the calcareous sponge species Sycon raphanus. Calcium carbonate deposits are also found in vertebrate bones besides the main constituent, calcium phosphate/hydroxyapatite (HA). Evidence has been presented that during the init…
A new cystidicolid nematode from Mullus surmuletus (Perciformes: Mullidae) from the western Mediterranean.
2005
Ascarophis valentina n. sp. is described from Mullus surmuletus off the Valencian coast of Spain on the basis of both light and scanning electron microscopy. It can be distinguished from the other members of the genus by the length of the left (long) spicule of the males and by egg morphology. An updated grouping of the species of Ascarophis considered valid is provided with respect to these characters. The new species resembles Ascarophis capelanus, belonging to the group of species possessing eggs with a single polar knob with filaments, but is distinguished by the size of the body, the length of the esophagus (especially in relation to body length), the position of the vulva, and the siz…