The stromatoporoid animal revisited: Building the skeleton

Modern coralline sponges secrete a skeleton by means of a basal pinacoderm, intracellularly, or inside the soft tissue on an organic matrix The examination of terminal growth surfaces of stromatoporoids indicates that soft tissue in laminate and amalgamate forms occupied the upper galleries and that the skeletal elements were secreted within the soft tissue on an organic matrix. The stromatoporellids and clathrodictyids secreted the skeleton in modules that are homologous to the chambers of a sphinctozoan. In stromatoporellids the module was bounded by a floor that formed the upper layer of the tripatite lamina below and a roof that became the lower layer of the next lamina; it further included the intervening pillars. In clathrodictyids the module had only a roof and pillars, and the laminae are single layers. other stromatoporoids may have secreted their skeletons at the base of the soft tissue and had minimal occupation of the skeleton. *** Stromatoporoid, sphinctozoa, sclerospongiae, sponge, paleobiology.     

The relationships between stromatoporoids and heliolitids

The dense fibro-lamellar skeleton of lophiostromatids (Stromatoporoidea) is closely similar to the trabecular skeleton of protaraeids (Heliolitoidea) and, respectively, the cystose skeleton of labechiids is similar to that of proporids. They can be interpreted as different types of basal exoskeleton of colonial coelenterates. The main difference between these ancient stromatoporoids and heliolitids is in the arrangement of zooids in the colony, that in the heliolitids enabled them to participate in skeleton building, which was not possible in the stromatoporoids. The stratigraphical distribution supports the supposition of their cummon origin. Coelenterata, Stromatoporoidea, Heliolitoidea. skeleton formation, morphology .     

Calcite Formation in Soft Coral Sclerites Is Determined by a Single Reactive Extracellular Protein

Calcium carbonate exists in two main forms, calcite and aragonite, in the skeletons of marine organisms. The primary mineralogy of marine carbonates has changed over the history of the earth depending on the magnesium/calcium ratio in seawater during the periods of the so-called “calcite and aragonite seas.” Organisms that prefer certain mineralogy appear to flourish when their preferred mineralogy is favored by seawater chemistry. However, this rule is not without exceptions. For example, some octocorals produce calcite despite living in an aragonite sea. Here, we address the unresolved question of how organisms such as soft corals are able to form calcitic skeletal elements in an aragonite sea. We show that an extracellular protein called ECMP-67 isolated from soft coral sclerites induces calcite formation in vitro even when the composition of the calcifying solution favors aragonite precipitation. Structural details of both the surface and the interior of single crystals generated upon interaction with ECMP-67 were analyzed with an apertureless-type near-field IR microscope with high spatial resolution. The results show that this protein is the main determining factor for driving the production of calcite instead of aragonite in the biocalcification process and that –OH, secondary structures (e.g. α-helices and amides), and other necessary chemical groups are distributed over the center of the calcite crystals. Using an atomic force microscope, we also explored how this extracellular protein significantly affects the molecular-scale kinetics of crystal formation. We anticipate that a more thorough investigation of the proteinaceous skeleton content of different calcite-producing marine organisms will reveal similar components that determine the mineralogy of the organisms. These findings have significant implications for future models of the crystal structure of calcite in nature.     

Short term viability of soft tissue detached from the skeleton of reef-building corals

We have induced soft tissue detachment from the skeleton of two colonial hard corals of the Pocilloporid family, both in vivo and in vitro. A parallel was made between polyp “bail-out”, i.e. field and laboratory-observed detachment of tissue fragments alone from the skeleton, and the dissociation method used for initiation of coral primary cell cultures. The in vitro approach provided insights into the active cellular re-arrangement mechanisms underlying coral tissue detachment. Functional polyps were not regenerated. Viability of tissue isolates detached from coral skeleton was probed for their use as a model for short-term biological assays. Cell viability dropped from 70% to 30% within the first week maintenance in vitro. Short-term isolate cultures limited to 3 days are a compromise allowing attachment of coral cells, yet preserving viability at about 70% of the total coral cell population.     

The relationship of the stromatoporoids to the sclerosponges

Similarities of the extinct strornatoporoids to the sponges of the recently established order Sclerospongia have strengthened arguments that these fossils are closer to the Porifera than to the Coelenterata. Major features favouring the affinity of the stromatoporoids to the sclerosponges include: (1) lack of evidence of colonialism in the strornatoporoids, (2) similarity of gross structure of some stromatoporoids to that of one sclerosponge ( Astrosclera ), (3) fibrous microstruc-ture of sclerosponges, Mesozoic stromatoporoids, and some Paleozoic stromatoporoids, (4) similarity of stromatoporoid astrorhizae to the excurrent canals of sclerosponges. Points of dissimilarity include: (1) the solid aragonitic skeletons of most sclerosponges, (2) the presence of dissepiments, laminae, and latilaminae in stromatoporoids, (3) the absence of siliceous spicules in stromatoporoids.
These comparisons suggest that the stromatoporoids were basically encrusting filter feeders like the sclerosponges but had progressed by loss of spicules and periodic introduction of dissepirnents and laminae toward a secretion of a skeleton of the coelenterate type. They cannot be placed with confidence in either the sclerosponges or the hydrozoans and should be recognized us a separate subphylum of the Porifera.     

Heavy metals distribution in the coral reef ecosystems of the Northern Red Sea

Concentrations of seven heavy metals (Cu, Zn, Pb, Cd, Ni, Co and Fe) were measured in the seawater, sediments, common scleractinian reef-building corals and soft corals (Octocorallia : Alcyonacea) at seven reef sites in the Northern Red Sea: I (Hurghada), II (Ras Za’farana), III (El-Ain Al-Sukhna), IV (El-Tur), V (Sha’b Rashdan), VI (Sharm El-Sheikh) and VII (Dahab). Levels of heavy metals were considerably elevated in seawater, sediments and corals collected from reef sites exposed to increased environmental contamination, as a result of diversified natural and anthropogenic inputs. Soft corals of genera Lithophyton, Sarcophyton and Sinularia showed higher concentrations of Zn, Pb, Cd and Ni than hard coral genera Acropora and Stylophora. Soft coral Sarcophyton trocheliophorum collected from El Ain Al-Suhkna (Gulf of Suez) had greater concentration of Cu, followed by hard corals Acropora pharaonis and Acropora hemprichi. The elevated levels of Zn, Cd and Ni were reported in the dry tissue of soft coral Sinularia spp. On the other hand, the soft coral Lithophyton arboreum displayed the highest concentration of Pb at Sha’b Rashdan (Gulf of Suez) and elevated concentration of Zn at Sharm El-Sheikh. Sediments showed significantly higher concentration of Fe than corals. The higher levels of Fe in hard corals than soft corals reflected the incorporation of Fe into the aragonite and the chelation with the organic matrix of the skeleton. The greater abundance of soft corals in metal-contaminated reef sites and the elevated levels of metals in their tissue suggesting that the soft corals could develop a tolerance mechanism to relatively high concentrations of metals. Although the effects of heavy metals on reef corals were not isolated from the possible effects of other stresses, the percentage cover of dead corals were significantly higher as the concentrations of heavy metals increased.     

Comprehensive characterization of skeletal tissue growth anomalies of the finger coral Porites compressa

The scleractinian finger coral Porites compressa has been documented to develop raised growth anomalies of unknown origin, commonly referred to as “tumors”. These skeletal tissue anomalies (STAs) are circumscribed nodule-like areas of enlarged skeleton and tissue with fewer polyps and zooxanthellae than adjacent tissue. A field survey of the STA prevalence in Oahu, Kaneohe Bay, Hawaii, was complemented by laboratory analysis to reveal biochemical, histological and skeletal differences between anomalous and reference tissue. MutY, Hsp90a1, GRP75 and metallothionein, proteins known to be up-regulated in hyperplastic tissues, were over expressed in the STAs compared to adjacent normal-appearing and reference tissues. Histological analysis was further accompanied by elemental and micro-structural analyses of skeleton. Anomalous skeleton was of similar aragonite composition to adjacent skeleton but more porous as evidenced by an increased rate of vertical extension without thickening. Polyp structure was retained throughout the lesion, but abnormal polyps were hypertrophied, with increased mass of aboral tissue lining the skeleton, and thickened areas of skeletogenic calicoblastic epithelium along the basal floor. The latter were highly metabolically active and infiltrated with chromophore cells. These observations qualify the STAs as hyperplasia and are the first report in poritid corals of chromophore infiltration processes in active calicoblastic epithelium areas.     

Skeletal development inAcropora cervicornis

Scanning electron microscopy, field studies using dyes which become incorporated into the skeleton of living corals as time markers, and petrographic and mineralogic techniques were used to describe the diel pattern of calcium carbonate accretion in the extending axial corallite ofAcropora cervicornis. The axial corallite extends by the formation of randomly oriented fusiform crystals at the distal tip of the branch. Morphological and mineralogical characteristics suggest that these might be calcite crystals. They form a framework upon which needle-like aragonite crystals (initially small tufts) begin to grow. As the needles elongate, groups of them form well defined bundles, fasciculi, which compose the primary skeletal elements. There is a diel pattern in the deposition of the skeleton. At night (1800–0600 hours) the distal spines are pointed and composed primarily of fusiform crystals. During the day (0600–1800 hours) mineral accretion occurs on all surfaces of the skeleton, apparently by epitaxial growth on the aragonite needles of the fasciculi.     

Organisation de la phase minérale chez Vaceletia crypta (Vacelet)Démosponge,Sphinctozoaire actuelle. Comparaison avec des formes aragonitiques du Trias de Turquie

The fundamental microstructural and ultrastructuralcaracteristics of a non fibrous carbonate tissue has been revealed by the study of the only living Sphinctozoa: Vaceletia crypta (Vacelet), Demospongia.These observations yield important data for interpretation of homogeneous carbonate structure in the skeleton of some fossil sponges. Effectively, we notice that two triassic forms, morphologically very different (Sphinctozoa and Inozoa) show remarkable microstructural analogies with Vaceletia crypta. These considerations should not be leaved out to establish an only classification of Sponges, joining both living and fossil forms.Moreover, the elementary skeletal constituants ofthe two forms show dimensions which indicate a growth in size in comparison with the living species. This increase has probably a diagenetic origin (adjunction of aragonite). So it appears that the present aspect of the mineral components cannot result from a reduction in size (micritization), as has been sometimes asserted.     

The Novel Mechanical Property of Tongue of a Woodpecker

Biomaterials such as bone,teeth,nacre and silk are known to have superior mechanical properties due to their specificnanocomposite structures.Here we report that the woodpecker’s tongue exhibits a novel strength and flexibility due to its specialcomposite micro/nanostructure.The tongue consists of a flexible cartilage-and-bone skeleton covered with a thin layer tissue ofhigh strength and elasticity.At the interface between the cartilage-and-bone skeleton and the tissue layer,there is a hierarchicalfiber-typed connection.It is this special design of the tongue that makes the woodpeckers efficient in catching the insects insidetrees.The special micro/nanostructures of the woodpecker’s tongue show us a potential method to enhance the interfacialconnection between soft and hard material layers for bio-inspired composite system designs.     

Biomechanical analysis of passive flow of stromatoporoids — morphologic, paleoecologic, and systematic implications

Boyajian, George E. & LaBarbera, Michael 1987 07 15: Biomechanical analysis of passive flow of stromatoporoids - morphologic, paleoecologic, and systematic implications.
Investigation of the functional significance of astrorhizae (surficial canals) in some stromatoporoids is necessary to understand the structure and evolutionary affinities of these organisms. To this end, scale models of stromatoporoids with mamelons and astrorhizae were subjected to laminar flow conditions within a flow tank. Flow patterns were traced using dye streams. Dye was observed to enter the distal ends of the astrorhizae and flow to the top of the mamelon (mounds from which astrorhizae radiate) where it entered the overlying current and was removed. Similar flow patterns were observed in Living sclerosponges which display astrorhizal and mamelon structures. Excurrent (dyed) water was not refiltered by the model, or Living organism, thus demonstrating the ability of astrorhizae to function efficiently as excurrent canals. In the model viscous entrainment may aid the flow, but pressure differentials due to the velocity gradient above the mamelons account for most of the flow. In living sclerosponges, active pumping by the living organism accounts for most of its flow; passive mechanisms aid to an unknown degree. If stromatoporoid morphology is plastic and dependent on local environmental influences, local paleocurrent velocities may be deduced by examining the height and spacing of mamelons in fossil stromatoporoids; consequently, mamelons should not be. used as criteria in stromatoporoid systematics. These findings are consistent with Steam's reconstruction of the stromatoporoid animal and his proposed function of astrorhizae.     

Live tissue imaging shows reef corals elevate pH under their calcifying tissue relative to seawater

The threat posed to coral reefs by changes in seawater pH and carbonate chemistry (ocean acidification) raises the need for a better mechanistic understanding of physiological processes linked to coral calcification. Current models of coral calcification argue that corals elevate extracellular pH under their calcifying tissue relative to seawater to promote skeleton formation, but pH measurements taken from the calcifying tissue of living, intact corals have not been achieved to date. We performed live tissue imaging of the reef coral Stylophora pistillata to determine extracellular pH under the calcifying tissue and intracellular pH in calicoblastic cells. We worked with actively calcifying corals under flowing seawater and show that extracellular pH (pHe) under the calicoblastic epithelium is elevated by ～0.5 and ～0.2 pH units relative to the surrounding seawater in light and dark conditions respectively. By contrast, the intracellular pH (pHi) of the calicoblastic epithelium remains stable in the light and dark. Estimates of aragonite saturation states derived from our data indicate the elevation in subcalicoblastic pHe favour calcification and may thus be a critical step in the calcification process. However, the observed close association of the calicoblastic epithelium with the underlying crystals suggests that the calicoblastic cells influence the growth of the coral skeleton by other processes in addition to pHe modification. The procedure used in the current study provides a novel, tangible approach for future investigations into these processes and the impact of environmental change on the cellular mechanisms underpinning coral calcification.     

Indigenous demosponge spicules in a Late Devonian stromatoporoid basal skeleton from the Frasnian of Belgium

This paper records the first example of a demosponge spicule framework in a single specimen of a Devonian stromatoporoid from the Frasnian of southern Belgium. The small sample (2.5 × 2 cm) is a component in a brecciated carbonate from a carbonate mound in La Boverie Quarry 30 km east of Dinant. Because of the small size of the sample, generic identification is not confirmed, but the stromatoporoid basal skeleton is similar to the genus Stromatopora. The spicules are arranged in the calcified skeleton, but not in the gallery space, and are recrystallized as multi‐crystalline calcite. The spicules fall into two size ranges: 10–20 μm diameter and 500–2000 μm long for the large ones and between 5–15 μm diameter and 50–100 μm length for the small ones. In tangential section, the spicules are circular, they have a simple structure, and no axial canal has been preserved. The large spicules are always monaxons, straight or slightly curved styles or strongyles. The spicules most closely resemble halichondrid/axinellid demosponge spicules and are important rare evidence of the existence of spicules in Palaeozoic stromatoporoids, reinforcing the interpretation that stromatoporoids were sponges. The basal skeleton may have had an aragonitic spherulitic mineralogy. Furthermore, the spicules indicate that this stromatoporoid sample is a demosponge.     

Soft anatomy and the affinities of conodonts

Recent claims that conodonts are members of the Craniata or Vertebrata are based in part upon soft tissue features that have been preserved in a small number of specimens. These features include what appear to be radials in the caudal fin and paired structures that have been identified as eye remnants. The evidence for radials is limited, but credible. However, the anatomy of extant cyclostomes suggests that the paired structures are more reasonably interpreted as otic capsules than the remnants of sclerotic eye capsules. Moreover, even if these structures are the remnants of eyes, conodonts might equally well be a sister group to the craniates as a member of that group. Aside from these paired structures, conodont fossils exhibit no features that are suggestive of a cartilaginous skeleton. Given that cyclostome fossils sometimes show evidence of the cartilages of the head, the apparent absence of a similar skeleton in conodont animals calls into question the claim that they are craniates. The simple single chevron shape of conodont myomeres also suggests that they lie outside of the Craniata. All living craniates have double-chevron myomeres as adults, whereas simple myomeres of the conodont type are found in the non-craniate cephalochordates. Thus the available soft tissue evidence suggests that conodonts are best regarded as the sister group of the craniates.     

The biological reconstruction of Tetradium Dana, 1846

The Ordovician fossil Tetradium   Dana, 1846 typically had aragonite tubes with millimetre-size subsquare cross-sections, fourfold symmetry and an inward-projecting septum along the midline of each wall. It increased by axial quadripartite division into four subequal parts when the septa grew together in the centre of the tube. Tetradium is usually classified as a chaetetid sponge or a tabulate coral. However, it is shown that in animals, fourfold symmetry occurs only as a secondary adaptation in medusae, and axial quadripartite division into four subequal parts is unknown. In contrast, both of these characteristics are common in algae. Tetradium is classified here as a rhodophyte, a calcified corticated uniaxial florideophyte. The anatomy of Recent rhodophytes is used to model the living Tetradium , and their branching is used to model growth by axial quadripartite division. The reconstructed microanatomy of the living Tetradium has (1) an uncalcified axial filament of elongated cells, (2) whorls of four lateral axes, rarely calcified and therefore rarely preserved as tabulae, that radiated from each cell of the central filament, and (3) a weakly calcified cortex that formed the subsquare tube and extended into the inward-projecting septa. Aragonite precipitation within the cortex was probably entirely intercellular, and produced a lightly calcified skeleton. Each reconstructed skeletal tube extended distally into a somewhat flexible, photosynthesizing and nutrient-absorbing part of the alga. Holdfasts were weak. This study shows that reconstructing the anatomy of an enigmatic fossil, instead of just comparing hard parts, significantly improves the reliability of its taxonomic identification.     

MT1-MMP-deficient mice develop dwarfism, osteopenia, arthritis, and connective tissue disease due to inadequate collagen turnover.

MT1-MMP is a membrane-bound matrix metalloproteinase (MT-MMP) capable of mediating pericellular proteolysis of extracellular matrix components. MT1-MMP is therefore thought to be an important molecular tool for cellular remodeling of the surrounding matrix. To establish the biological role of this membrane proteinase we generated MT1-MMP-deficient mice by gene targeting. MT1-MMP deficiency causes craniofacial dysmorphism, arthritis, osteopenia, dwarfism, and fibrosis of soft tissues due to ablation of a collagenolytic activity that is essential for modeling of skeletal and extraskeletal connective tissues. Our findings demonstrate the pivotal function of MT1-MMP in connective tissue metabolism, and illustrate that modeling of the soft connective tissue matrix by resident cells is essential for the development and maintenance of the hard tissues of the skeleton.     

Biology Of The Famennian Heterocoral Oligophylloides Pachythecus

Studies on the taxonomy and morphology of the Famennian heterocoral Oligophylloides have placed great emphasis on the character of the soft tissue, coloniality and distal development of the skeleton with regard to the construction of the wall. Here, the existence of soft tissue covering the entire skeleton of the colony is proposed. Thirty-eight branching specimens have been found in addition to the predominant single fragments of corallites; these should be regarded as colonial with a well-developed branching form. It is here proposed that the external wall grew not only at the distal end, and that its thickening did not result from the overlapping of tabulae, but was built independently of tabulae by the soft tissue covering the whole skeleton of the colony. The following new characteristics of Oligophylloides are described: a change in the position of septa, so-called 'septal shifting', a rearrangement of the septal apparatus; the occurrence of aulos-like structures; a groove ornamentation on the external wall; and the granular microstructure of the axial part of septa. A detailed study of Late Devonian Oligophylloides corals shows that O. tenuicinctus Róz˙kowska and O. pachythecus pentagonus Róz˙kowska are synonymous with O. pachythecus Róz˙kowska.     

Establishment and development of patch reefs in the intracratonic Ordovician sequence near Chicoutimi, Quebec

Patch reefs occur near the top of the transgressive sequence of Ordovician Trenton Group limestones in the Chicoutimi area of Quebec, eastern Canada. Despite their small sue, these reefs comprise diverse assemblages dominated by bryozoans, corals, stromatoporoids and receptaculitid algae. Pelmatozoans and gastropods are also conspicuous. The reefs were initiated and grew in a fully marine, open shelf setting. Available substrates varied from loose skeletal lenses to soft, firm or hardened bioturbated wackestones, and the earliest stages of reef growth reflect this heterogeneity. Loose or less firm substrates were colonised by bryozoans and pelmatozoans and/or by receptaculitids, which, together with accessory organisms, stabilised the sediments and provided the basis for further reef development. The resultant firmer, slightly elevated substrates provided sites for attachment of stromatoporoids and colonial corals which spread over earlier reef organisms and sediments and dominated the later stages of reef growth. On hardened areas of sediment, stromatoporoids and corals colonised the surface directly and the early stabilising stage of reef growth is absent. The compositions and developmental stages of these Trenton Group reefs are comparable with those seen in broadly contemporaneous and often larger reefs elsewhere, and are among the earliest in which corals played an important role.     

Muscle tuning during running: implications of an un-tuned landing

BACKGROUND: The impact force in heel-toe running is an input signal into the body that initiates vibrations of the soft tissue compartments of the leg. These vibrations are heavily damped and the paradigm of muscle tuning suggests the body adapts to different input signals to minimize these vibrations. The objectives of the present study were to investigate the implications of not tuning a muscle properly for a landing with a frequency close to the resonance frequency of a soft tissue compartment and to look at the effect of an unexpected surface change on the subsequent step of running. METHOD: Thirteen male runners were recruited and performed heel-toe running over two surface conditions. The peak accelerations and biodynamic responses of the soft tissue compartments of the leg along with the EMG activity of related muscles were determined for expected soft, unexpected hard and expected hard landings. RESULTS AND CONCLUSIONS: For the unexpected hard landing there was a change in the input frequency of the impact force, shifting it closer to the resonance frequency of the soft tissue compartments. For the unexpected landing there was no muscle adaptation, as subjects did not know the running surface was going to change. In support of the muscle-tuning concept an increase in the soft tissue acceleration did occur. This increase was greater when the proximity of the input signal frequency was closer to the resonance frequency of the soft tissue compartment. Following the unexpected change in the input signal a change in pre-contact muscle activity to minimize soft tissue compartment vibrations was not found. This suggests if muscle tuning does occur it is not a continuous feedback response that occurs with every small change in the landing surface properties. In previous studies with significant adaptation periods to new input signals significant correlations between the changes in the input signal frequency and the EMG intensity have been shown, however, changes in soft tissue accelerations have not been found. The results of the present study showed that changes in these soft tissue accelerations can occur in response to a resonance frequency input signal when a muscle reaction has not happened.