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.     

Design of the labial cuticle in Cenocorixa bifida Hung. (Hemiptera: Corixidae) with reference to ionic transport

The surface topography and ultrastructure of the labial cuticle of Cenocorixa bifida were examined by scanning and transmission electron microscopy. The dorsal wall of the labium consists of seven sclerotized transverse bars each displaying two rows of semicircular grooves and pores. The cuticle is about 20 microm thick and is composed of epicuticle and lamellate exocuticle and endocuticle, the latter separated from the underlying epidermis by subcuticle containing amorphous material. The epicuticle is subdivided into an electron-dense very thin outer epicuticle and a homogenous thick inner epicuticle, which is penetrated by grooves. The exocuticle is filled with electron-dense blocks of material, which may provide mechanical support to the labial wall. The elongate epidermal cells display extensive infoldings of the apical plasma membrane (facing the cuticle) and contain abundant mitochondria in the cytoplasm. The presence of deep epicuticular grooves and pores in the thin labial cuticle and extensive apical membrane infolding and abundant mitochondria in the epidermal cells suggest that the labium in C. bifida is the site of osmoregulatory ionic uptake.     

Modelling genetic regulation of growth and form in a branching sponge

We present a mathematical model of the genetic regulation controlling skeletogenesis and the influence of the physical environment on a branching sponge with accretive growth (e.g. Haliclona oculata or Lubomirskia baikalensis). From previous work, it is known that high concentrations of silicate induce spicule formation and upregulate the silicatein gene. The upregulation of this gene activates locally the production of spicules in the sponge and the deposition of the skeleton. Furthermore, it is known that the expression of the gene Iroquois induces the formation of an aquiferous system, consisting of exhalant and inhalant pores. We propose a model of the regulatory network controlling the separation in time and space of the skeletogenesis and the formation of the aquiferous system. The regulatory network is closely linked with environmental influences. In building a skeleton, silicate is absorbed from the environment. In our model, silicate is transported by diffusion through the environment and absorbed at the surface of a geometric model of the sponge, resulting in silicate gradients emerging in the neighbourhood of the sponge. Our model simulations predict sponge morphology and the positioning of the exhalant pores over the surface of the sponge.     

Investigating the effects of wettability and gaseous nanobubbles on roughened wall–fluid interface using molecular dynamics simulation

This paper reports on the use of molecular dynamics (MD) simulation to investigate the coupling effects of wettability, surface roughness and interfacial nanobubbles (INBs) on wall–fluid interfaces. The fluid properties close to the wall–fluid interface, such as potential energy, density, diffusion coefficients of fluid molecules and effective slip length are simulated. In the cases without surface nanobubbles, regions with lower potential energy have a higher probability of hosting water molecules. The local translational and rotational diffusion coefficients of water within the cavities are strongly influenced by wettability but largely unaffected by hydrodynamic effects. In cases where INBs exist, variations in wettability result in distinctly different argon morphologies. Argon nanobubbles form a convex shape on Wenzel-like interfaces but a shallow concave shape on Cassie-like interfaces. The phenomenon of water molecules invading grooves tends to occur on Wenzel-like interfaces; however, this depends largely on the morphology of the grooves. The high mobility and high density of argon molecules indicate that the state of the argon molecules within the grooves may require further investigation. Our results also show that the effective slip length is significantly influenced by wall–fluid wettability as well as the morphology of INBs.     

瓶筐类(Calathids)化石几个疑难问题的讨论

根据采自扬子区和新疆塔里木盆地的大量calathids化石的研究,对其硬体构造,生物体定向和生活方式及分类归属问题进行了讨论,并描述了Calathium (Calathella) yangtziensis,Calathium bachuensis,Calathiumelongates 等3个新种。认为此类生物具有多孔的双层体壁,孔道系统与中腔构成清楚的水流循环体系,与海绵类或古杯类类似,应属低级的底栖滤食性动物。在分类学上应与receptaculitids(托盘类)解除隶属关系,不应再将其视为一种托盘藻类,而应归属多孔动物(广义的)门的Soanitidae科。     

Wall ingrowth formation in transfer cells: novel examples of localized wall deposition in plant cells

The formation of wall ingrowths increases plasma membrane surface areas of transfer cells involved in membrane transport of nutrients in plants. Construction of these ingrowths provides intriguing and diverse examples of localized wall deposition. Flange wall ingrowths resemble secondary wall thickenings of tracheary elements in morphology and probable mechanisms of deposition. By contrast, reticulate wall ingrowths, deposited as discrete papillate projections, branch and fuse to create a fenestrated wall labyrinth representing a novel form of localized wall deposition. Papillate wall ingrowths are initiated as patches of disorganized cellulosic material and are compositionally similar to primary walls, except for a surrounding layer of callose and enhanced levels of arabinogalactan proteins at the ingrowth/membrane interface. How this unusual form of localized wall deposition is constructed is unknown but may involve constraining cellulose-synthesizing rosette complexes at their growing tips.     

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.     

Further electron microscope studies of the conidium of Alternaria brassicicola

Summary The freeze-etching technique, aldehyde fixation and heavy metal shadowing of wall material were used in an electron microscope study of the maturing spores of Alternaria brassicicola (Schw.) Wiltshire. The walls are composed of fibres, probably of chitin. The plasmalemma has rectangular grooves in its outer surface and corresponding ridges on the inner one; both surfaces bear particles of two distinct sizes. Endoplasmic reticulum may be lamellated or vesicular and its involvement in wall formation is confirmed; vesicles produced by the endoplasmic reticulum fuse with the plasmalemma. The structure of nuclei, mitochondria and vacuoles is also demonstrated.     

Cuticular sensory receptors on the antenna and maxillary palp of a fly larva, Nephrotoma suturalis (Diptera: Tipulidae)

Abstract. The apex of the larval antenna of the crane fly Nephrotoma suturalis has 6 cuticular sensilla that stained intensely black with silver nitrate, which indicates their porosity. The large sensory cone is innervated by 14 neurons and the 3 small, smooth surfaced, conical pegs have 4 neurons each. The small and large cylindrical sensilla with their smooth walls and pleated apices are innervated by 4 and 6 nerve cells, respectively. The 15 sensilla on the apex of the maxillary palp are all stained by silver nitrate. These sensilla are of five types: 7 type A sensilla with a smooth surface, a distinct apical pore, and 3 or 4 neurons; 2 type B sensilla with a smooth surface, many pores, and 5 neurons; 1 type C sensillum with a grooved surface, a large apical pore, smaller pores in the grooves, and 6 neurons; 3 type D sensilla with a smooth surface, a grooved apex that is elongated into a projection, and 4 neurons; 2 type E sensilla with many pores covering the surface, leaf-like appearance, and 4 neurons. The number and types of sensilla are similar to those in other nematocerous larvae, but in the many different forms of sensilla and the structure of the sensory cone, these tipulid larvae differ greatly from other larvae of lower Diptera.     

Cortical morphogenesis during the cell division cycle in Euplotes: An integrated study using light optical,scanning electron and transnlission electron microscopy

Hypotrichs are among the most complex ciliates in terms of morphology and development. To study the fine structure of cortical morphogenesis associated with cell division in Euplotes eurystomus, three different methods of observation were employed: light microscopy of protargol-stained specimens, scanning electron microscopy of cells prepared by critical point drying, and transmission electron microscopy of sectioned material. Observations on the stages of morphogenesis give much new information about cortical development, particularly about proliferation and aggregation of kinetosomes (basal bodies), ciliary outgrowth, the topography of morphogenesis, cirrus resorption, and growth of the pellicle. During the formation of new cirrus the process of kinetosome proliferation is atypical, i.e., groups of prokinetosomes are seen oriented at random and, in some cases, prokinetosomes apparently are formed at a distance from nearby young kinetosomes. That the new cirri develop in surface grooves, the grooves elongate into “tracks,” and (in some cases) grooves are partitioned into separate tracks suggests that the grooves play a role in the orderly migration of the new cirri on the cell surface. Conspicuous morphogcnctic changes in the cell surface involve local growth of the pellicle. The process of pellicle growth apparently involves two basic steps: (a) growth of the outer cell membrane to form “bare regions,” and (b) formation of alveoli in the bare regions. Alveolar sheets are formed by fusion of alveolus precursor particles. Cirrus resorption is sequential over several stages of development, and old cirri are resorbed as the new cirri impinge on them. As the old cirri regress, both in situ resorption and retraction of axonemes into the cytoplasm occur.     

Fan-shaped ejections of regularly arranged murosomes involved in penicillin-induced death of staphylococci.

Electron microscopic research into the murosomes of staphylococci has shown that the number of murosomes involved in penicillin-induced death varies depending on the experimental conditions employed. With 0.1 micrograms of penicillin G per ml, only 1 of a total of about 20 murosomes, the "killing murosome," completely perforated the pressure-stabilized peripheral cell wall during a three-step process. This strictly localized event was mainly attributed to a mechanical effect being comparable to the process of aneurysm formation. Wall perforation was also considered to mark the very moment of penicillin-induced death ("nonlytic killing event"), while bacteriolysis started only postmortem. By varying the osmolarity of the growth medium, the number of murosomes involved in penicillin-induced killing increased considerably, which resulted in the ejection of a fan-shaped row of murosomes at the second division plane. These data are compatible with the finding that, in untreated or chloramphenicol-treated staphylococci, the activation of the murosomes resulted in (i) the formation of regularly arranged "blebs" on the cell surface, containing traces of disintegrated wall material, and (ii) the subsequent liberation of the murosomes lying underneath, leaving behind their former sites in the peripheral wall as a row of regularly arranged "pores" in every division plane. The number, distribution, and positioning of these blebs corresponded with those of the pores and the original murosomes. The significance of wall autolysins liberated from the first division plane for penicillin-induced wall perforation at the second division plane is discussed.     

STRUCTURE AND DEVELOPMENT OF HYPHAL SEPTA IN ALLOMYCES

Development of hyphal septa (pseudosepta) in Allomyces macrogynus begins with the formation of five or more discontinuous pieces of wall material that project inward from the hyphal wall. Lateral fusion of these projections leaves a central pore in the septum that is later filled in by centripetal deposition of wall material. However, lateral fusion of the projections is not complete; peripheral pores remain in the rim of the mature septum. The position of cytoplasmic microtubules corresponds to the position of actively moving cellular particles and organelles. Allomyces reticulatus and A. arbuscula have similar septa.     

Nine new species of Dichogaster (Oligochaeta, Megascolecidae) from Guadeloupe (French West Indies)

Nine species belonging to two distinct groups within the genus Dichogaster Beddard, 1888 are described from material collected on the volcanic section of the island of Guadeloupe. The species Dichogaster arborea, D. caesitifusca, D. callaina, D. girija and D. basseterrensis all inhabit the leaf tanks of bromeliads and share the following anatomical characteristics: spermathecal pores on the trailing edges of segments, spermathecal axis differentiated into ampulla, internally fluted central chamber and duct, penial setae long and slender, testes and funnels free, prostomium undivided or divided by two grooves, simple single typhlosole and a pair of dorsal caeca on the mid-intestine. Dichogaster athena also inhabits bromeliads, but lacks the above characteristics and male reproductive organs, and is more similar to the remaining species. The three remaining species, D. guadeloupensis, D. matoubensis and D. musciphila , with lateral typhlosoles, no intestinal caeca, simpler spermathecal structure, prostomiums divided by a single groove and short penial setae, all inhabit soils of montane forests. The division of Dichogaster based on muscularity of the proventriculus wall is shown to be unsupportable, since thickness of the wall is size-related.     

First evidence of the presence of chitin in skeletons of marine sponges. Part II. Glass sponges (Hexactinellida: Porifera)

Sponges (Porifera) are presently gaining increased scientific attention because of their secondary metabolites and specific skeleton structures. In contrast to demosponges, whose skeletons are formed from biopolymer spongin, glass sponges (hexactinellids) possess silica-organic composites as the main natural material for their skeletal fibres. Chitin has a crystalline structure and it constitutes a network of organized fibres. This structure confers rigidity and resistance to organisms that contain it, including monocellular (yeast, amoeba, diatoms) and multicellular (higher fungi, arthropods, nematodes, molluscs) organisms. In contrast to different marine invertebrates whose exoskeletons are built of chitin, this polysaccharide has not been found previously as an endogenous biopolymer within glass sponges (Hexactinellida). We hypothesized that glass sponges, which are considered to be the most basal lineage of multicellular animals, must possess chitin. Here, we present a detailed study of the structural and physico-chemical properties of skeletal fragments of the glass sponge Farrea occa. We show that these fibres have a layered design with specific compositional variations in the chitin/silica composite. We applied an effective approach for the demineralization of glass sponge skeletal formations based on an etching procedure using alkali solutions. The results show unambiguously that alpha-chitin is an essential component of the skeletal structures of Hexactinellida. This is the first report of a silica-chitin's composite biomaterial found in nature. From this perspective, the view that silica-chitin scaffolds may be key templates for skeleton formation also in ancestral unicellular organisms, rather than silica-protein composites, emerges as a viable alternative hypothesis.     

Comparative scanning electron-microscopic study of the lingual papillae in two species of domestic mammals (Equus caballus and Bos taurus). 1. Gustatory Papillae

The morphological characteristics of bovine and equine gustatory lingual papillae are compared by scanning electron microscopy. The fungiform papillae in the cow have a shape that corresponds to their name, while in the horse, they almost do not emerge from the surface of the tongue. These papillae show taste pores in both species. The vallate papillae, four times larger in the horse than in the cow, show a complex organization of papillae and secondary grooves in the horse. In the cow, they occur single and are surrounded by a thick annular pad of lingual mucosa. Taste pores have been observed in the vallate papillae of both species, whereas in the foliate papillae, they are present only in the horse. A characteristic distribution of stratified scales and channeled tracts is observed on the surface of all gustatory papillae in both species. The possible functional importance of each type of gustatory papilla is discussed on the basis of their morphostructural features.     

Study of supramolecular structures released from the cell wall of Candida albicans by ethylenediamine treatment

Candida albicans cell wall components were analyzed by ethylenediamine (EDA) treatment. Based on their different solubility properties, the cell wall components produced three fractions (A, B, and C). Fractions B (EDA-soluble, water-insoluble) and C (EDA-insoluble) contained glucan, chitin, and protein in different proportions. After zymolyase (mainly a β-glucanase complex) or chitinase treatment of fractions B and C, more polysaccharides and proteins were solubilized by a second EDA treatment, suggesting that the solubility of the polymers in EDA depends on the degree of polymer interactions. Western blot analysis using two monoclonal antibodies (1B12 and 4C12) revealed electrophoretic patterns that were similar in mycelial and yeast morphologies, except that in material obtained from mycelial walls, an additional band was detected with MAb 1B12. Fluorescence microscopy of cell wall fractions treated with FITC-labeled Con-A, Calcofluor white, and FITC-labeled agglutinin showed that glucan and mannoproteins are uniformly distributed in fractions B and C, while chitin is restricted to distinct patches. Transmission electron microscopy demonstrated that fraction C maintained the original shape of the cells, with an irregular thickness generally wider than the walls. When fraction C was treated with chitinase, the morphology was still present and was maintained by an external glucan layer, with an internal expanded fibrillar material covering the entire cellular lumen. Degradation of the glucan skeleton of fraction C with zymolyase resulted in the loss of the morphology. Received: 1 April 1996 / Accepted: 2 September 1996     

Functional morphology of Tethya species (Porifera): 2. Three-dimensional morphometrics on spicules and skeleton superstructures of T. minuta

The biomechanics of body contraction in Porifera is almost unknown, although sponge contraction has been observed already in ancient times. Some members of the genus Tethya represent the most contractile poriferan species. All of them show a highly ordered skeleton layout. Based on three main spicule types, functional units are assembled, termed skeleton superstructures here. Using synchrotron radiation based x-ray microtomography and quantitative image analysis with specially developed particle and structure recognition algorithms allowed us to perform spatial allocation and 3D-morphometric characterizations of single spicules and skeleton superstructures in T. minuta. We found and analyzed three skeleton superstructures in the investigated specimen: (1) 85 megasclere bundles, (2) a megaster sphere, composed by 16,646 oxyasters and (3) a pinacoderm–tylaster layer composed by micrasters. All three skeleton superstructures represent composite materials of siliceous spicules and extracellular matrix. From structure recognition we developed an abstracted mathematical model of the bundles and the sphere. In addition, we analyzed the megaster network interrelation topology and found a baso-apical linear symmetry axis for the megaster density inside the sphere. Based on our results, we propose a hypothetical biomechanical contraction model for T. minuta and T. wilhelma, in which the skeleton superstructures restrain physical stress generated by contraction in the tissue. While skeletal structures within the genus Tethya have been explained using R. Buckminster Fullers principle of tensegrity by other authors, we prefer material science based biomechanical approaches, to understand skeletal superstructures by referring to their composite material properties.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

Ultrastructural localization of spicule matrix proteins in normal and metalloproteinase inhibitor-treated sea urchin primary mesenchyme cells

Studies of the sea urchin larval skeleton have contributed greatly to our understanding of the process of biomineralization. In this study we have undertaken an investigation of the morphology of skeleton formation and the localization of proteins involved in the process of spicule formation at the electron microscope level. Sea urchin primary mesenchyme cells undergo a number of morphological changes as they synthesize the larval skeleton. They form a large spicule compartment that surrounds the growing spicule and, as spicule formation comes to an end, the density of the cytoplasm decreases. Inhibition of spicule formation by specific matrix metalloproteinase inhibitors or serum deprivation has some subtle effects on the morphology of cells and causes the accumulation of specific classes of vesicles. We have localized proteins of the organic matrix of the spicule and found that one protein, SM30, is localized to the Golgi apparatus and transport vesicles in the cytoplasm as well as throughout the occluded protein matrix of the spicule itself. This localization suggests that SM30 is an important structural protein in the spicule. Another spicule matrix protein, SM50, has a similar cytoplasmic localization, but in the spicule much of it is localized at the periphery of the spicule compartment, and consequently it may play a role in the assembly of new material onto the growing spicule or in the maintenance of the integrity of the matrix surrounding the spicule.     

A NEW BASIDIOMYCETOUS SEPTAL TYPE: THE MULTIPERFORATE SEPTUM IN KRIEGERIA ERIOPHORI

Septa from metabasidia and clamp connections of the heterobasidiomycetous sedge parasite Kriegeria eriophori were studied with light and electron microscopy. Septa from clamp connections subtending probasidia were reconstructed from serial sections. Septa at clamp connections are perforated by multiple, simple pores, while metabasidial septa possess single, central swellings which probably represent pores occluded by wall material. The occurrence of multiperforate septa in the fungi is reviewed. The septal morphology of K. eriophori is compared to that of simple-septate heterobasidiomycetes, and the systematic and functional implications are discussed.