VALVE AND BAND MORPHOLOGY OF SOME FRESHWATER DIATOMS. III. PRE- AND POST-AUXOSPORE FRUSTULES AND THE INITIAL CELL OF MELOSIRA ROESEANA1

Frustules of a clonal culture of Melosira roeseana Rabenh. were examined with light and scanning electron microscopy. Vegetative valves in the post-auxospore (full size) stage exhibit a larger width/length ratio than those in the pre-auxospore (size-reduced) stage. Cells form chains by linking spines of adjacent valves which occur at the periphery of the valve face-mantle junction. Three or jour large pores occur at the center of the valve face, with the diameter of each pore tapering from the inner to the outer valve surface; these pores are often occluded by siliceous processes. Features of M. roeseana, not shown previously for Melosira, include a “stepped” mantle, on only one of the two valves resulting from the same cell division, flattened processes attached to short siliceous stalks on the valve face, disk-like processes on the mantle, and an open girdle band with up to eight antiligulae. Siliceous scales on the surface of the initial cell are remnants of the auxospore wall. The epivalve of the initial cell is larger in diameter than the hypovalve, and both valves lack linking spines and a step on the valve surface. The initial, cell epicingulum consists of only two bands; the hypocingulum has up to seven. Initial cells with four or more hypocingular bands divide to form new post-auxospore filaments. Melosira roeseana should not be included in the genus Melosira as it is presently defined by the type species, M. nurnmuloides C. Ag. Major differences include irregular linking spines, a closed pseudoloculate valve construction, and labiate processes on the valve face and mantle of M. nummuloides, compared with well-defined linking spines, a valve constructed of a basal siliceous layer perforated by poroid areolae, and labiate processes lacking on the valve of M. roeseana.     

Altered versican cleavage in ADAMTS5 deficient mice; a novel etiology of myxomatous valve disease

In fetal valve maturation the mechanisms by which the relatively homogeneous proteoglycan-rich extracellular matrix (ECM) of endocardial cushions is replaced by a specialized and stratified ECM found in mature valves are not understood. Therefore, we reasoned that uncovering proteases critical for ‘remodeling’ the proteoglycan rich (extracellular matrix) ECM may elucidate novel mechanisms of valve development. We have determined that mice deficient in ADAMTS5, (A Disintegrin-like And Metalloprotease domain with ThromboSpondin-type 1 motifs) which we demonstrated is expressed predominantly by valvular endocardium during cardiac valve maturation, exhibited enlarged valves. ADAMTS5 deficient valves displayed a reduction in cleavage of its substrate versican, a critical cardiac proteoglycan. In vivo reduction of versican, in Adamts5^−/− mice, achieved through Vcan heterozygosity, substantially rescued the valve anomalies. An increase in BMP2 immunolocalization, Sox9 expression and mesenchymal cell proliferation were observed in Adamts5^−/− valve mesenchyme and correlated with expansion of the spongiosa (proteoglycan-rich) region in Adamts5^−/− valve cusps. Furthermore, these data suggest that ECM remodeling via ADAMTS5 is required for endocardial to mesenchymal signaling in late fetal valve development. Although adult Adamts5^−/− mice are viable they do not recover from developmental valve anomalies and have myxomatous cardiac valves with 100% penetrance. Since the accumulation of proteoglycans is a hallmark of myxomatous valve disease, based on these data we hypothesize that a lack of versican cleavage during fetal valve development may be a potential etiology of adult myxomatous valve disease.     

Mechanical strength of shells of selected extant articulate brachiopods: Implications for paleozoic morphologic trends

Dried shells of Terebratalia transversa, Laqueus californianus, Hemithyris psittacea, and T. unguicula and alcohol‐soaked, tissue‐lined shells of Terebratulina retusa, Dallina septigera, Cryphus vitreus, and Liothyrella uva were crushed in an apparatus that facilitated measurement of the force (newtons) against the valves at the instant of fracture. The results revealed that the costate shells of T. transversa and T. retusa were the strongest. Force is correlated with valve thickness, but not with size (length). When normalized for valve thickness, the force required to fracture shells is correlated with shell biconvexity (height/length) among pooled species of dried specimens. Geniculate specimens of T. retusa were not stronger than the intraspecific variants with a constant radius of curvature to their valves.

The percent‐frequency of plicate, spinose, lamellose and rugate genera increase significantly in the successive stages, Caradocian (Late Ordovician) through Famennian (Late Devonian) at the expense of smooth to costellate genera. The percent‐frequency of rectimarginate (central fold lacking) genera also decreases appreciably in this time frame. These morphologic trends, in combination with the experimental crushing data, support the hypothesis that selection favored species with such anti‐predatory adaptations during a time of escalation of shell‐crushing predators.     

Description of the male of Sclerocypris tuberculata (Methuen, 1910) (Crustacea,Ostracoda, Megalocypridinae)

The male of Sclerocypris tuberculata (Methuen), thus far unknown, is here described. Relying on the morphology of the copulatory appendages and of the prehensile palps, it appears that this taxon belongs to a separate species group, together with S. zelaznyi and perhaps also S. sarsi. There are some interesting sexual dimorphic characters in the valve morphology: males have shorter valves with a dorsal margin which runs nearly parallel to the ventral one (more elongated valves with sloping dorsal margin in females) and there is lobe-like projection of the valve margin on the ventro-caudal corner of the LV in females which is lacking in the male. Furthermore, the female genital region has a very aberrant morphology, and all specimens from the present collection possess the tuberculated and noded valves.     

PUNCTICULATA VERSIFORMIS SP. NOV. AND CYCLOTELLA KATHMANDUENSIS SP. NOV. (BACILLARIOPHYTA), NEW FOSSIL SPECIES FROM MIDDLE PLEISTOCENE LACUSTRINE SEDIMENTS,KATHMANDU, NEPAL HIMALAYA1

New fossil species, Puncticulata versiformis sp. nov. and Cyclotella kathmanduensis sp. nov., are described from lacustrine sediments in the Kathmandu Basin on the southern slope of the Nepal Himalaya. They were dominant in the Middle Pleistocene. Both LM and SEM observations reveal their unique morphological features. Puncticulata versiformis is characterized by (1) various valve outlines (circular, elliptical, or oval), (2) a tangentially undulate central area, (3) a complex alveolar structure composed of three kinds of costae (thick costae, thin costae, and thin and short costae), (4) well‐developed spines (Y‐shaped and tapering) located on one side of the valve face/mantle area junction, and (5) a valvocopula with an extremely undulate margin. The species‐specific feature of C. kathmanduensis is the presence of two kinds of alveolate zones in a single valve: type‐1 zone composed only of normal costae, and type‐2 zone composed of both normal costae and recessed costae bearing fultoportulae. Changes in valve ornamentation occur in these two species from initial valves to vegetative valves. In P. versiformis, the arrangement of areolae with internal domed cribra and fultoportulae in the central area changes from radial rows in the initial valve to groups in the vegetative valve. In the initial valve of C. kathmanduensis, the type‐1 alveolate zone is generally absent.     

PERIZONIUM AND INITIAL VALVE FORMATION IN THE DIATOM NAVICULA CUSPIDATA (BACILLARIOPHYCEAE)1

This paper describes the perizonium and initial valve formation in Navicula cuspidata Kütz., based on light microscope (LM) and scanning electron microscope (SEM) observations. The perizonium consists of concentric over-lapping bands, laid down sequentially at the tips of the expanding biconical auxospore during its elongation. The central perizonial band has fimbriate edges and is considerably more rigid than the more distal bands. During auxospore elongation and the band secretion, the chloroplasts continuously oscillate between the two ends of the cell; this oscillation ceases once the elongation is complete. The initial valves, formed within the perizonium, are molded into the basically biconical shape of the perizonium except for a central flattening of each valve face. In contrast to the raphes in gametangial and vegetative valves which are surrounded by a smooth axial area, the raphes in initial valves lie within a raised ridge running along the apical axis of the valve. The regular pattern of apically oriented ridges on the outer surface of vegetative valves is also lacking on initial valves. Comparison of pore–pore spacing within striae of gametangial valves, initial values and post-initial valves (first division and vegetative cells) reveals that the pore–pore distance within striae is conserved at all sexual stages. However, the distance between striae is considerably larger in initial valves than in gametangial and post-initial valves. Vegetative interstriae spacing as well as the planar morphology of the valve face is regained at the first division of the initial cell. This suggests that the spacing between striae is dependent on the sexual stage of the cell during valve formation (i.e. not directly dependent on the cell size) and can be altered independently of the pore–pore spacing.     

FURTHER OBSERVATIONS AND SOME COMMENTS ON THE FINE STRUCTURE OF THE CENTRIC DIATOM AULACOSEIRA ISLANDICA (BACILLARIOPHYCEAE)1

Using light and electron microscopy, the diatom species Aulacoseira islandica (O. Müll.) Sim. was examined with special emphasis on the following characteristics: structure of the valve areolae, heterovalvy, and distribution of the rimoportulae. The mantle and valve face areolae were pores containing volate occlusions. However, observations only using transmission electron microscopy may result in an incomplete interpretation because of the fragility of the dissected system of volae. Relief valves with a stepped mantle and intaglio valves with a plain mantle occurred. Another form of heterovalvy resulted from the formation of separation valves. Linking valves had spatulate spines while separation valves bore tapering spines. In Aulacoseira, the rimoportulae usually occurred near the “Ringleiste.” The presence of several rimoportulae on the mantle was one of the most striking features in Aulacoseira islandica.     

Interactions between Chlamydia pneumoniae and trace elements: a possible link to aortic valve sclerosis

An association between Chlamydia pneumoniae and atherosclerotic cardiovascular diseases has been suggested. However, other factors may interact in the pathogenesis of valve sclerosis. Therefore, trace elements important for C. pneumoniae growth and host defense and markers of C. pneumoniae infection were studied in sclerotic valves and serum. Forty-six patients undergoing surgical valve replacement due to advanced aortic sclerosis were prospectively studied. Valves from 15 forensic cases with no heart valve disease and plasma from 46 healthy volunteers served as controls. C. pneumoniae was detected in 16/46 (34.8 %) sclerotic valves and in 0/15 forensic controls. IgG and IgA antibodies to C. pneumoniae were present in 54.3% and 26.1 % patients, respectively. In the patients’ valves, iron, magnesium, and zinc each correlated to calcium, a marker of the histopathological severity of disease. Patients showed 10- to 70-fold increases of these trace elements in valves and an increased copper/zinc ratio in serum. In a majority of aortic sclerosis patients, one of several markers of C. pneumoniae infection were detected and all patients had a disturbed trace element balance in valves and serum suggestive of active immune process and infection. The pattern of trace element changes was essentially similar regardless of positive makers of C. pneumoniae, suggesting a similar etiopathogenesis in both subgroups. The 20-fold increase in iron, essential for C. pneumoniae growth, in sclerotic valves suggests a new possible link to this infection in aortic sclerosis.     

Internal valves in populations of Meridion circulare from the A’er Mountain region of northeastern China: Implications for taxonomy and systematics

Abstract A population of Meridion circulare var. circulare (Greville) C.A. Agardh from Inner Mongolia was found to produce Innenschalen or internal spores. Examination of this population with light and scanning electron microscopy showed morphological differentiation between vegetative and spore morphologies. Vegetative valves typically bear costae and one rimoportula at the headpole. Spores lack costae and have two rimoportulae, one at the headpole and the other at the footpole. There is plasticity in the production of valve morphologies, and a variety of vegetative valve and spore combinations are evident. This population of M. circulare var. circulare has initial valves of over 90 μm in length, and all of the initial cells encountered are acostate and bear two rimoportulae. These observations suggest that either spores are the product of sexual reproduction, or that initial valves may be produced parthenogenetically in Meridion. Spores as products of the sexual process have not been reported in diatoms previously, and parthenogenesis in Meridion was reported previously but discounted in other published reports. The plasticity of valve morphologies expressed in M. circulare var. ciculare, between vegetative valves and spores (and back) across a short temporal period suggests that diatoms can alter their cell wall structure dramatically and quickly in response to external variables.     

Speciation,phenotypic plasticity,or ontogeny,the case of the genus Galkinius (Pyrgomatidae,Cirripedia, Crustacea)

Barnacles of the genus Galkinius occupy a large spectrum of host corals, making it one of the least host‐specific genera within the Pyrgomatidae. Molecular analyses show that within the genus Galkinius there are highly supported clades, suggesting that the genus Galkinius is a complex of evolutionarily significant units (ESUs). The morphology of the opercular valves has been used as the basis for the separation of species of Galkinius. In this study, morphological variability was found both between specimens within ESUs extracted from different host species and between specimens extracted from the same colony. Identifications based on the opercular valves cannot therefore be assigned to different species despite being genetically distinguishable. It is proposed that in many cases the differences between valve morphology of different species of Galkinius are the outcome of ontogeny. Allometric growth of the valves has resulted in differences in the proportions of the parts of the valve. © 2015 The Linnean Society of London     

Morphological investigations of the frustule, perizonium and initial valves of the freshwater diatom Achnanthes crenulata Grunow (Bacillariophyceae)

The present study clarifies the fine structure of the vegetative frustules, initial valves and perizonium of Achnanthes crenulata Grunow. The valves of the vegetative cell are distinctly linear‐lanceolate with an undulate margin. The valve face is quite flat and in girdle view is smoothly curved as in species of Gephyria (Bacillariophyceae). However, the valve face of the initial cells is slightly rounded and does not have an undulate margin. Furthermore, the rapheless sternum is centrally positioned along the apical axis of the araphid initial valve. As this taxon develops from auxospore to initial valve, it forms only longitudinal perizonial bands; no transverse bands arise. The perizonium consists of three silicified bands: one large, central longitudinal plate and two bands that underlie this plate; these two bands are either open or closed. This taxon has several conspicuous structures compared to other marine species of Achnanthes, but the structure of the perizonium supports the position of A. crenulata within Achnanthes sensu stricto.     

Numerical Models for the Simulation of Flexible Artificial Heart Valves: Part I - Computational Methods

Abstract

A numerical model of the coupled motion of a flexing surface in a high Reynolds number flow is presented for the simulation of flexible polyurethane heart valves in the aortic position. This is achieved by matching a Lagrangian dynamic leaflet model with a panel method based flow solver. The two models are coupled via the time-dependent pressure field using the unsteady Bernoulli equation.

Incorporation of sub-cycling in the dynamic model equations and fast pre conditioning techniques in the panel method solver yields efficient convergence and near real-time simulations of valve motion. The generality of dynamic model allows different material properties and/or geometries to be studied easily and interactively. This interactivity is realized by embedding the models within a design environment created using the software IRIS Explorer ^TM.

Two flow domains are developed, an infinite domain and an internal domain using conformal mapping theory. In addition bending stress on the valve is computed using a simple stress model based on spline and circle equation techniques.     

Trace element changes in sclerotic heart valves from patients undergoing aortic valve surgery

Several trace elements are essential nutrients for an optimal functioning of organs and tissues, including the immune system and the heart. The pathogenesis of some heart diseases has been associated with changes in the balance of certain trace elements. The etiology of nonrheumatic aortic valve sclerosis is unknown, however. A prospective study was performed on trace element changes in the sclerotic valves of 46 patients undergoing surgical aortic valve replacement because of aortic stenosis. Valves from 15 individual forensic cases without known cardiac disease served as controls. The contents of 15 trace elements (Al, As, Cd, Ca, Co, Cu, Fe, Pb, Mg, Mn, Hg, Se, Ag, V, and Zn) were measured by inductively coupled plasma — mass spectrometry (ICP-MS) of aortic valve tissue from both patients and forensic autopsy controls. Some trace elements showed similar concentrations in sclerotic and control valves (Al, Ag, Hg, Mn), whereas a few were moderately changed in the sclerotic as compared with the control valves, including an increase in Cd by 52% (p<0.05) and decreases in Se by 14% (p<0.05), in V by 42% (p<0,001), and in Cu by 45% (p<0.001). However, there were pronounced increases (p<0.001) in the concentrations of As (5-fold), Ca (70-fold), Co(10-fold), Fe (20-fold), Pb (8-fold), Mg (20-fold), and Zn (10-fold) in the sclerotic valves. Thus, sclerotic aortic valve disease is associated with a pronounced imbalance in several trace elements of well-known importance for cardiovascular and immune function as well as in trace elements with hitherto unknown significance.     

Biology and functional morphology of a new species of endolithic Bryopa (Bivalvia: Anomalodesmata: Clavagelloidea) from Japan and a comparison with fossil species of Stirpulina and other Clavagellidae

Abstract. A new species of Clavagellidae, Bryopa aligamenta, from Okinawa, Japan, is described. The species is endolithic in living corals, with the left valve cemented to the crypt wall, as in all clavagellids. The free right valve exhibits an unusual growth pattern, with commarginal lines seemingly arising from the posterior valve margin and extending towards the anterior. This results from: (i) progressive anterior erosion of the umbones, probably as a consequence of the boring process; (ii) the apparent migration posteriorly, as the umbones are eroded, of the dorso‐ventral growth axis of the shell; and (iii) enhanced posterior inter‐commarginal growth. Unlike other clavagellid genera and species, however, there is no discernible primary ligament, at least in the adult. It is possible, however, that if a juvenile ligament were present (as in B. lata), it too would be lost as a consequence of antero‐dorsal erosion during boring. To retain valve alignment in the absence of a primary ligament, and possibly upon reaching an adult size, the mantle lays down alternating layers of calcium carbonate and proteinaceous periostracum onto the interior surface of the shell to thicken it, most noticeably marginally and, especially, posteriorly. The two valves are united dorsally, therefore, by thin layers of periostracum that probably exert a minimal opening force. B. aligamenta is, however, further characterised by large adductor, pallial, and siphonal retractor muscles so that the entire animal is encased tightly within an internally strengthened shell within a crypt. Movement must be minimal, blood being pumped into pallial haemocoels to push open the valves and extend the siphons. Despite a suggestion to the contrary, Bryopa is retained in the Clavagellidae, its unusual growth processes resulting from an endolithic life style within living corals. The fossil clavagellid Stirpulina bacillus, from the Pliocene/Pleistocene of Palermo, Sicily, Italy, was, unlike Bryopa aligamenta and other clavagellids, endobenthic, with a long adventitious tube and anterior watering pot superficially similar to species of Penicillidae, another family of the Clavagelloidea. Furthermore, as in all clavagellids only the left valve is fused into the fabric of the tube, the right being free within it. In all penicillids, both valves are fused into the fabric of their tubes. The watering pots of the fossil S. coronata, S. vicentina, and S. bacillus, moreover, are formed in a different manner to that of penicillids, by progressive encasement of the right valve inside the tube. In penicillids, the tube is secreted in a single event from the general mantle surface and the incorporation of both valves into its fabric. The constituent genera of the Clavagellidae thus constitute an example of parallel evolution with members of the Penicillidae.     

Silique valves as sails in anemochory of Lunaria (Brassicaceae)

• The generally held opinion that seeds of Lunaria remain at the replum after detachment of the two valves and then wind causes a shaking or rattling of the replum with its diaphragm, thus launching the seeds, is challenged. In a sparse forest in the Swabian Alb, the first author noticed flying valves of Lunaria rediviva to which the narrow‐winged flat seeds are attached.
• Investigations with SEM and histology have shown that the valves secrete a glue only at those sites where the seeds rest on the valves before valve tissues die. Further analysis has shown (using the periodic acid‐Schiff reaction) that the glue consists of polysaccharides. After detachment and dispersal of the valves, the adhesive strength continuously decreases.
• This is the first report for a sticky valve exudate in the Brassicaceae. Because of the adhesion of Lunaria seeds to their valves for some time, the 1st order diaspore is a mericarp, in a broad sense, and can be interpreted as an adaptation to long‐distance dispersal by stronger winds. In this context, the ‘flying carpets’ of Lunaria are more effective and transport more than one seed.
• Molecular studies assigned Lunaria to the tribe Biscutelleae, which now contains the angustiseptate genera Biscutella and Megadenia as well as the latiseptate genera Lunaria and Ricotia. The valves in Ricotia can easily be detached (studied in herbarium material and a living plant), but, in contrast to Lunaria, the ripe seeds remain at the replum and its diaphragm, respectively.

     

Differentiation of species of Terebratella (Brachiopoda: Terebratellinae)

Abstract

Terebratella sanguinea and T. incollSpicua have been differentiabed on foramen position and ornament. Further comparison shows that the valves of T. sanguinea are more strongly curved than those of T. inconspicua, a condition resulting in a longer pedicile, a larger beak, and hinge plates with greater elevation. The relationship between hinge plate ccndition and shell curvature is evident in other terebratellid genera.     

Morphometric variation of Seminavis pusilla (Bacillariophyceae) and its relationship to salinity in inter‐dune lakes of the Badain Jaran Desert,Inner Mongolia,China

We used light and scanning electron microscope analyses to quantify morphometric features (valve length, width, stria density, lineola density and valve curvature) from the observation of valves representing Seminavis pusilla. Cluster analysis based on Gaussian mixture models and the expectation‐maximization algorithm was used for delineating two species, Seminavis pusilla sensu stricto and Seminavis lata (Krammer) Rioual comb. et stat. nov. By comparison with S. pusilla, S. lata is characterized by wider valves and lower stria density. The two species have also markedly different ecology. S. pusilla is most abundant in the most saline lakes of the dataset, while S. lata is most abundant in the less saline lakes. Our results indicate that combining the two species into S. pusilla sensu lato would lead to a loss of ecological information and a decrease of the performance of transfer functions developed for quantitative reconstruction of past salinity from fossil diatom assemblages in sediment cores.     

Raman spectroscopy for the non‐contact and non‐destructive monitoring of collagen damage within tissues

The non‐destructive and label‐free monitoring of extracellular matrix (ECM) remodeling and degradation processes is a great challenge. Raman spectroscopy is a non‐contact method that offers the possibility to analyze ECM in situ without the need for tissue processing. Here, we employed Raman spectroscopy for the detection of heart valve ECM, focusing on collagen fibers. We screened the leaflets of porcine aortic valves either directly after dissection or after treatment with collagenase. By comparing the fingerprint region of the Raman spectra of control and treated tissues (400–1800 cm^–1), we detected no significant differences based on Raman shifts; however, we found that increasing collagen degradation translated into decreasing Raman signal intensities. After these proof‐of‐principal experiments, we compared Raman spectra of native and cryopreserved valve tissues and revealed that the signal intensities of the frozen samples were significantly lower compared to those of native tissues, similar to the data seen in the enzymatically‐degraded tissues. In conclusion, our data demonstrate that Raman microscopy is a promising, non‐destructive and non‐contact tool to probe ECM state in situ. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Aberrant valve formation in a centric diatom,Ditylum brightwellii

Summary Interphase cells of the centric diatom,Ditylum brightwellii (West) Grunow, were treated with a microtubule-inhibitor (amiprophosmethyl, 6×10^–7 M); the cells could proceed to divide, but the spindle apparatus in about 25% of the cells was displaced and their two sibling cells has either two nuclei or none. The cells with two nuclei formed a new valve with two labiate processes, instead of one as in normal cells. Most of the cells lacking a nucleus were unable to form a new valve, and of the 2% that did form new valves, all did so without dividing. The valves with two labiate processes were originally formed in two separate silica deposition vesicles (SDVs) and the two embryonic siliceous valves fused when these two expanding SDVs met. Accordingly, both the pattern of perforations and the shape of the marginal ridges on the new valve vary with the distance between the two initiation sites of the two SDVs. Implications of these observations in the evolution of valves in diatoms are discussed and a hypothesis on multiple origins of the valves is proposed.