MICROMORPHOLOGY OF THE PERIPLAST OF CHROOMONAS SP. (CRYPTOPHYCEAE)1,2

An ultrastructural examination of the periplast of Chroomonas sp. revealed a surface pattern composed of rows of plate areas. The plate areas are delineated by a series of ridges, which emanate from a common line at the posterior cell end, and lateral grooves which intersect the anterior-posterior ridges. Small ejectosomes (trichocysts) are generally located at the intersection of the lateral grooves and the ridges. Size of the plate areas varies, being smallest at the posterior and anterior ends and largest in the midregion of the cell. The average plate area is 1 μ in length and 0.7 μ in width. In section the periplast is seen to consist of 3 intimately attached layers of which the middle (plasma membrane) layer is continuous with the gullet region, flagella, and ejectosome chambers. Trypsin digestion resulted in the disappearance of the inner and outer layers, and in the loss of periplast stiffness.     

A gentle method for the preparation of hard parts (trophi) of the mastax of rotifers and scanning electron microscopy of the trophi ofBrachionus plicatilis (Rotifera)

Summary Trophi of the rotiferBrachionus plicatilis were prepared by dissolving rotifer tissues and lorica with sodium dodecyl sulfate (SDS) and dithiothreitol (DTT) and were examined by scanning electron microscopy in order to obtain information on the functional morphology of these structures. The trophi are not composed of distinct parts but form a continuous structure of rigid pieces and connecting membranous regions. The membranous components allow movements of the rigid parts against each other and/or restrict the extent of such movements. The main hinge for the movement of the trophi is the membranous connection between the two rami; movements of rami and unci occur together since these parts are tightly connected by two narrow membranes in the subuncus region. The subunci seem to constitute masticating devices which act against grooved ridges of the rami and might make it feasible to disintegrate nutrient particles to as small as 1 m. Crushing of coarser nutrients might be performed by the opposite surfaces of the two rami.Abbreviations br bulla rami - c crest along the ventral surface of the manubrium - cd distal part of the manubrium (cauda) - cv proximal part of the manubrium (clava) - d1 entrance from the bowl-shaped recess at the dorsal side of the manubrium into one of the (three) cavities within the proximal part of the manubrium - d2 second dorsal entrance into one of the (three) cavities within the proximal part of the manubrium - eu edge at the distal end of the uncus which fits into a notch at the proximal end of the manubrium - gr small, oblong grooves at the distal surface of the reinforced projecting ridges of the rami - f fulcrum - h hinge between the two rami - l ligaments extending from the central membranes to the dorsal surfaces of the unci - m central membranous structures - ma manubrium - p partition between the cavities within the ramus - ps large, proximal surfaces of the rami - r ramus - rd reinforced ridge on the anterio/dorsal part of the ramus - rv ventral, triangular surface of the ramus - su subuncus - sur root-like structures connecting the subuncus with the uncus plate - t teeth-like proximal endings of the uncus ridges - u uncus - um membranous connection between uncus and manubrium - ur membranous connection between uncus and ramus in the subuncus region - uvr ridges on the ventral side of the uncus - ve ventral entrance into one of the (three) cavities within the proximal part of manubrium     

Carboniferous Psammichnites: Systematic Re-Evaluation,Taphonomy and Autecology

The ichnogenus Psammichnites Torell 1870 includes a wide variety of predominantly horizontal, sinuous to looped, backfilled traces, characterized by a distinctive median dorsal structure. Though commonly preserved in full relief on upper bedding surfaces, some ichnospecies of Psammichnites may be preserved in negative hyporelief. Psammichnites records the feeding activities of a subsurface animal using a siphon-like device. Several ichnogenera reflect this general behavioral pattern, including Plagiogmus Roedel 1929 and the Carboniferous ichnogenera Olivellites Fenton and Fenton 1937a and Aulichnites Fenton and Fenton 1937b. Based on analysis of specimens from the United States, Spain, and the United Kingdom, three Carboniferous ichnospecies of Psammichnites are reviewed in this paper: P. plummeri (Fenton and Fenton, 1937a), P. grumula (Romano and Meléndez 1979), and P. implexus (Rindsberg 1994). Psammichnites plummeri is the most common Carboniferous ichnospecies and is characterized by a relatively straight, continuous dorsal ridge/groove, fine transverse ridges, larger size range, and non-looping geometric pattern. It represents a grazing trace of deposit feeders. Psammichnites grumula differs from the other ichnospecies of Psammichnites by having median dorsal holes or protruding mounds. The presence of mounds or holes in P. grumula suggests a siphon that was regularly connected to the sediment-water interface. This ichnospecies is interpreted as produced by a deposit feeder using the siphon for respiration or as a device for a chemosymbiotic strategy. Psammichnites implexus is characterized by its consistently smaller size range, subtle backfill structure, and tendency to scribble. Although displaying similarities with Dictyodora scotica, P. implexus is a very shallow-tier, grazing trace. Changes in behavioral pattern, preservational style, and bedform morphology suggest a complex interplay of ecological and taphonomic controls in Carboniferous tidal-flat Psammichnites. A first distributional pattern consists of guided meandering specimens preserved in ripple troughs, probably reflecting food-searching of buried organic matter concentrated in troughs. A second is recorded by concentration of Psammichnites on ripple crests and slopes. In some cases, the course is almost straight to slightly sinuous and closely follows topographic highs, suggesting a direct control of bedform morphology on trace pattern. Occurrences of Carboniferous Psammichnites most likely represent an opportunistic strategy in marginal-marine settings. Analysis of Carboniferous Psammichnites indicates the presence of a siphon-like device in the producer and reestablishes the possibility of a molluscan tracemaker.     

Food access in captive Ammotragus: the role played by hierarchy and mother–infant interactions

An analysis of individuals' behavior when accessing a restricted food source (troughs) was carried out in a captive population of aoudad (Ammotragus lervia). Access to the troughs followed a strict hierarchical order, as higher‐ranking individuals fed before lower‐ranking ones. Unweaned male and female calves made use of the troughs from the ages of 2 and 3 months, respectively. Both fed from the troughs more frequently and for longer periods when their mother was present, which allowed them to make use of the troughs while skipping the hierarchical order. Calves received fewer threats when in proximity to their mothers, particularly in high‐ranking families. Mothers defended their calves from other herdmates more frequently when at the feeding area than in other areas of the herd. However, only sated mothers let their calves feed freely from the troughs; unsated mothers showed an aggressive behavior even toward their calves. I conclude that a maternal presence is necessary for aoudad calves to successfully feed from troughs, and that families of higher social rank benefit by getting access to this food source earlier in the day and are disturbed less than low‐ranking families. Zoo Biol 21:597–605, 2002. © 2002 Wiley‐Liss, Inc.     

Microridges in Cyprinus carpio scale epidermis

Actin‐based microridges were evaluated in koi scale epidermis in situ. The fingerprint‐patterned microridges covered the dorsal face of superficial layer cells and were overall similar to that described in many fishes. Several other microridge patterns were observed, however, ranging from loose or tightly packed ridges, fragmented ridges, a honeycomb ridge pattern and the presence of actin‐rich puncta. Individual F‐actin‐stained microridges varied greatly in length, from a few to 30 μm or more, with a few single ridges extending the entire perimeter of a cell. Branched microridges, comprised of single ridges that appeared continuous with each other, extended to over 150 μm in some cases. The actin‐binding proteins α‐actinin and cortactin were distributed in a dot‐like pattern along the length of individual ridges, consistent with bundled actin cores described in earlier studies. Antiphosphotyrosine antibody failed to detect this signal transduction‐related amino acid modification in microridges unless tyrosine phosphatases were first inhibited, after which bright phosphotyrosine‐rich dots were detected along the microridges.     

Endoscopy of gastropods: A novel view of the mantle cavities and gills of the keyhole limpet Diodora aspera and the abalone Haliotis rufescens

The gills, or ctenidia, of marine gastropods serve as the sites for respiratory gas exchange. Cilia on the surface provide the pump that moves water through the mantle cavity and enhance diffusion. Because the gills are housed inside the shell, it is difficult to view them while they are functioning. Published images of gills show contracted, fragile structures that are distorted by the processes of dissection and preservation. Members of the families Fissurellidae (keyhole limpets) and Haliotidae (abalone) have openings in their shells through which water enters and/or exits. I inserted an endoscope connected to a video camera into the openings of the shells of living, non‐anaesthetized individuals of the fissurellid Diodora aspera and the haliotid Haliotis rufescens. In both species, the dorsal afferent branchial vessel of the afferent gill axis appeared large and inflated, as did the leaflets that extended from either side of the axis. In D. aspera, the leaflets appeared to fill the mantle cavity and responded to touch, particles, and dye in the water by contracting quickly and slowly re‐extending. In contrast, the gills of H. rufescens did not noticeably respond to disturbance. On the other hand, these gills showed a regular pattern of pleats that had not been described in the extensive anatomical literature of these common and economically significant animals. These results provide a novel view of the gastropod mantle cavity as a dynamic space filled by the gills, which divide the mantle cavity into distinct incurrent and excurrent chambers and produce a laminar flow of water through the cavity. J. Morphol. 276:787–796, 2015. © 2015 Wiley Periodicals, Inc.     

The presence and location of small cardioactive‐like peptides in larvae of Crassostrea virginica

We examined the presence and location of small cardioactive peptide (SCP)‐like neuropeptides in both the central and peripheral nervous systems of D‐hinge, newly eyed, and pediveliger larvae of Crassostrea virginica. Results indicate that SCP‐like substances are present early in development (D‐hinge larvae), and that presence in the central and peripheral nervous systems increases as the larva develops toward metamorphic competence (pediveliger larvae). In addition, in newly eyed and pediveliger larvae, SCP‐like labeling is found in a varying number of neurons within all central ganglia, with the possible exception of the accessory ganglia. Varicose labeling of axons is also documented within the ganglia, commissures, and connectives, as well as in peripheral nerves. Peripheral tissues innervated by axons exhibiting SCP‐like immunoreactivity include the velum, foot, esophagus, mantle, and various musculatures. As indicated by the location of SCP‐like labeling in various organs and tissues, it is likely that these neuropeptides modulate muscle contraction or ciliary beating in molluscan larvae such as those of C. virginica.     

STRUCTURE OF THE PERIPLAST OF CRYPTOMONAS OVATA VAR. PALUSTRIS1,2

The periplast of Cryptomonas ovata var. palustris is composed of polygonal plates which are delineated by shallow ridges. A small ejectosome is located at each corner of the plate area. The plate areas vary in size; they are smallest at the anterior and posterior ends and are largest in the middle of the cell with an average length of 0.5 μ and of width 0.4 μ. In cross section a plate area is composed of 2 distinct layers, an outer plasma membrane layer with a fine particulate, appearance, and an inner layer consisting of two sheets. The sheets of the inner layer have a striated lattice pattern with a periodicity of about 20 nm. In negatively stained preparations one lattice appears to underlie another at certain angles. Protease digestion removed polygonal shaped inner layer.     

A soft-bodied lophophorate from the Silurian of England

Soft-bodied taxa comprise an important component of the extant lophophorate fauna, but convincing fossils of soft-bodied lophophorates are extremely rare. A small fossil lophophorate, attached to a brachiopod dorsal valve, is described from the Silurian (Wenlock Series) Herefordshire Lagerstätte of England. This unmineralized organism was bilaterally symmetrical and comprised a subconical body attached basally to the host and partially enclosed by a broad ‘hood’; the body bore a small, coiled lophophore. Where the hood attached laterally, there is a series of transverse ridges and furrows. The affinities of this organism probably lie with Brachiopoda; the hood is interpreted as the homologue of a dorsal valve/mantle lobe, and the attachment as the homologue of the ventral valve and/or pedicle. The ridges are arranged in a manner that suggests constructional serial repetition, indicating that they are unlikely to represent mantle canals. Extant brachiopods are not serially structured, but morphological and molecular evidence suggests that their ancestors were. The new organism may belong to the brachiopod stem group, and might also represent a significant element of the Palaeozoic lophophorate fauna.     

Coordinated development in the fly foot: Sequential cuticle secretion

Development of the adult fly foot falls into clearly defined phases of cell division, growth, cuticle secretion and cell death. The pulvillus is composed dorsally of two giant cells and ventrally of thousands of minute tenent cells; the former produce the dorsal footpad cuticle and the latter the thousands of tenent hairs. Cell divisions are still occurring in future tenent cells when increase in size of the cells and in polyteny of the chromosomes is already occurring in the two dorsal cells. Also cell death occurs considerably earlier in the tenent cells, yet the sequential secretion of some six cuticular layers takes place at comparable times in dorsal and ventral cuticles. The cuticular layers formed are, in their order of secretion: ecdysial membrane, cuticulin of the epicuticle, dense exocuticle, homogeneous exocuticle, an intermediate layer, wax of the epicuticle, and an extensive mass of endocuticle. The ecdysial membrane seems to perform an important mechanical role in maintaining the shape of the delicate cytoplasmic projections of the tenent cells, before and during cuticle secretion, and in establishing the cuticular pattern of ridges in the dorsal cuticle. Comparisons are made with trichogen cell cuticle development and with tracheal cuticle. Tracheal, trichogen and dorsal footpad cuticle patterns are compared. Details of giant cell activity provide a working basis for studies of nuclear-cytoplasmic interactions, and the whole system raises many unsolved problems in the general field of cell differentiation and pattern formation.     

Suttonema delta n. g., n. sp. (Nematoda: Trichostrongylina: Heligmosomoidea) from Oxymycterus rufus (Rodentia: Sigmodontinae) in Argentina

A new nippostrongyline, Suttonema delta n. g., n. sp., is described from the intestine of Oxymycterus rufus (Rodentia: Sigmodontinae) from Argentina, in a host from which trichostrongylid nematodes were hitherto unknown. The new genus is very similar to Stilestrongylus Freitas, Lent & Almeida, 1937 and Malvinema Digiani, Sutton & Durette-Desset, 2003, both parasites of Neotropical sigmodontines, in the features of the caudal bursa (with a pattern of type 1-4, asymmetrical with hypertophied right lobe) and the presence of cephalic structures resembling cuticular cordons. The larval synlophe is also identical to that of Stilestrongylus freitasi Durette-Desset, 1968. The new genus is differentiated by an adult synlophe with few ridges (9-12 at mid-body) of two different types: small, rounded ridges without cuticular support on the dorsal side, and pointed ridges of unequal size on the ventral side and in lateral fields. It is also characterised by the presence of comaretes on the left ventral and ventral fields of the synlophe.     

Exceptional preservation of a novel gill grade in large Cretaceous inoceramids: systematic and palaeobiological implications

Organised mineralised structures observed in large inoceramids (valves on a metre scale) from the Late Albian, Toolebuc Formation, Australia (Inoceramus sutherlandi McCoy, 1865), and the Santonian, Niobrara Formation, USA (Platyceramus sp.), were investigated using variable pressure scanning electron microscope (SEM) with energy‐dispersive X‐ray spectroscopy (EDX), X‐ray microcomputed tomography (micro‐CT) and X‐ray diffraction (XRD) analyses. These indicate that the structures comprised a phosphate framework of aligned tubes and shallow troughs overlain perpendicularly by evenly spaced structures. In the Toolebuc Inoceramus, these are U‐shaped cross‐structures, whilst in the Niobrara Platyceramus, they comprise bundled fibre elements. Comparison with modern bivalves indicates that the observed phosphatised structures represent soft‐tissue preservation of the gills, as suggested in earlier publications. The tubes and troughs are remnants of a filamental support framework comprising ordinary and primary filaments, whilst the U‐shaped cross‐structures (I. sutherlandi) and fibrous bands (Platyceramus) represent preserved longitudinal gill musculature. Internal perforate and strand‐like fabric observed on the internal surface of some Platyceramus tubular structures suggests that the framework comprised collagen. The presence of primary and ordinary filaments in numerous unusually large plicae, in at least two lamellae, indicates that the gill structures were heterorhabdic. Each plica has at least 40 ordinary filaments, an exceptional number when compared with the maximum of 20 present in modern heterorhabdic gills. The absence of incontrovertible interfilament junctions makes it difficult to say whether inoceramids were filibranch, pseudolamellibranch or eulamellibranch. However, structures that are best attributed to intraplical junctions between filaments suggest the Inoceramidae had gills akin to those of pseudolamellibranch bivalves, although their unusually large number of filaments per plica is more reminiscent of homorhabdic eulamellibranch gills. The general form of the gill is similar to that described in some other pteriomorphs, most specifically Pteria. However, it has more complex junctions and interconnections, although these are not as intricate or pervasive as those observed in the pseudolamellibranch Ostreidae. The connections and well‐developed filament framework allowed the gill to reach its unusually large size, supporting the large size of these inoceramid species. The unusually large size of the gill and its components indicate that the organism fed on the larger suspended organic particles in the water column. It would also have been capable of processing large volumes of water quickly, leading to greater potential for food accumulation and with likely implications for respiratory efficiency. This may help explain the common association of inoceramids with oxygen‐deficient palaeoenvironments, particularly as the general structure of the inoceramid gill is very different to that observed in the commonest extant chemosymbiotic bivalves.     

SEX‐SPECIFIC CELL SURFACE STRUCTURE OF ANISOGAMETES: MORPHOLOGICAL CHANGES DURING FERTILIZATION OF BRYOPSIS MAXIMA (ULVOPHYCEAE,CHLOROPHYTA) REVEALED BY ULTRA–HIGH‐RESOLUTION FIELD EMISSION SEM1

Cell surfaces of biflagellate gametes and their morphological changes during fertilization of Bryopsis maxima Okamura were observed using a high‐resolution field emission scanning electron microscope. Male gametes have broad and narrow faces, which are divided into at least five morphologically distinct regions: 1) the apical plate is a plate‐like structure that is approximately 380–530 nm long and approximately 190 nm wide, in the center of the papilla and slightly protruded from the plasma membrane; 2) strips are smooth materials on ridges that originate from the basal part of the papilla and extend downward; 3) the lateral belt is a belt‐shaped structure on the center of the narrower faces; 4) the flagellar surface; and 5) the other region of the cell body has a fine‐grained appearance. In contrast, the entire female gamete surface is rough because of many granular or amorphous cell coats on the plasma membrane. When both gametes were mixed together, the initial fusion proceeded between the broader face of the male gamete and the anterior side of the female one near the basal bodies. Morphology of the male gamete's cell surface changed gradually as fusion proceeded and was covered by the granular materials; that surface closely resembled those of female gametes except for the apical plate. It was present until the planozygote attached itself to the substrate by the papilla. It finally disappeared after settlement. Therefore, these results indicate that gametes of B. maxima have sex‐specific surface structures that change their morphology during fertilization and settlement.     

The surface structure of the completely and incompletely orthokeratinized oral epithelium in the rat: a light, scanning and transmission electron microscope study.

Mucosa from the hard and soft palates, molar gingiva, cheek and dorsal surface of the tongue of the rat was examined in the light microscope, following Mallory's triple connective tissue stain, and in the scanning and transmission electron microscopes. The epithelium covering the hard palate, gingiva, the smooth band of mucosa at the junction of the hard and soft palates, intermediate zones of the soft palate, fungiform papilla-like structures in the central zone of the soft palate, the fungiform papillae, and the more superficial part and posterior surfaces of the filiform papillae of the tongue all exhibited complete orthokeratinization. The oral surfaces of the epithelial cells in all these areas had a honeycomb pattern of interconnecting ridges surrounding depressions. Imprints of the overlying cells that had been desquamated were apparent, and the lateral boundaries between the cells were formed by two raised ridges separated by a gap. The epithelium covering the cheek, central zone of the soft palate apart from the fungiform papilla-like structures, lateral zones of the soft palate, gingival crevice, and the mucosa between the fungiform and filiform papillae of the tongue all exhibited incomplete orthokeratinization. The oral surfaces of the epithelial cells in all these areas were relatively smooth and did not exhibit a honeycomb pattern of interconnecting ridges. Imprints of the overlying cells that had been desquamated and the lateral boundaries between the cells were only very occasionally found. In the transmission electron microscope the outlines of the cells were compatible with the surface patterns seen in the scanning electron microscope. The possible relationships between the degree of orthokeratinization and ultrastructure of the various epithelia are discussed.     

Domain motion and interdomain hot spots in a multidomain enzyme

The aim of this article is to analyze conformational changes by comparing 10 different structures of Pseudomonas aeruginosa phosphomannomutase/phosphoglucomutase (PMM/PGM), a four‐domain enzyme in which both substrate binding and catalysis require substantial movement of the C‐terminal domain. We focus on changes in interdomain and active site crevices using a method called computational solvent mapping rather than superimposing the structures. The method places molecular probes (i.e., small organic molecules containing various functional groups) around the protein to find hot spots. One of the most important hot spots is in the active site, consistent with the ability of the enzyme to bind both glucose and mannose phosphosugar substrates. The protein has eight additional hot spots at domain‐domain interfaces and hinge regions. The locations and nature of six of these hot spots vary between the open, half‐open, and closed conformers of the enzyme, in good agreement with the ligand‐induced conformational changes. In the closed structures the number of probe clusters at the hinge region significantly depends on the position of the phosphorylated oxygen in the substrate (e.g., glucose 1‐phosphate versus glucose 6‐phosphate), but the protein remains almost unchanged in terms of the overall RMSD, indicating that computational solvent mapping is a more sensitive approach to detect changes in binding sites and interdomain crevices. Focusing on multidomain proteins we show that the subresolution conformational differences revealed by the mapping are in fact significant, and present a general statistical method of analysis to determine the significance of rigid body domain movements in X‐ray structures.     

Comparative morphology of changeable skin papillae in octopus and cuttlefish

A major component of cephalopod adaptive camouflage behavior has rarely been studied: their ability to change the three‐dimensionality of their skin by morphing their malleable dermal papillae. Recent work has established that simple, conical papillae in cuttlefish (Sepia officinalis) function as muscular hydrostats; that is, the muscles that extend a papilla also provide its structural support. We used brightfield and scanning electron microscopy to investigate and compare the functional morphology of nine types of papillae of different shapes, sizes and complexity in six species: S. officinalis small dorsal papillae, Octopus vulgaris small dorsal and ventral eye papillae, Macrotritopus defilippi dorsal eye papillae, Abdopus aculeatus major mantle papillae, O. bimaculoides arm, minor mantle, and dorsal eye papillae, and S. apama face ridge papillae. Most papillae have two sets of muscles responsible for extension: circular dermal erector muscles arranged in a concentric pattern to lift the papilla away from the body surface and horizontal dermal erector muscles to pull the papilla's perimeter toward its core and determine shape. A third set of muscles, retractors, appears to be responsible for pulling a papilla's apex down toward the body surface while stretching out its base. Connective tissue infiltrated with mucopolysaccharides assists with structural support. S. apama face ridge papillae are different: the contraction of erector muscles perpendicular to the ridge causes overlying tissues to buckle. In this case, mucopolysaccharide‐rich connective tissue provides structural support. These six species possess changeable papillae that are diverse in size and shape, yet with one exception they share somewhat similar functional morphologies. Future research on papilla morphology, biomechanics and neural control in the many unexamined species of octopus and cuttlefish may uncover new principles of actuation in soft, flexible tissue. J. Morphol. 275:371–390, 2014. © 2013 Wiley Periodicals, Inc.     

Ontogenetic variation in the plumage colour of female European Pied Flycatchers Ficedula hypoleuca

Although variation in the dorsal plumage colour of male European Pied Flycatchers Ficedula hypoleuca has received a great deal of attention, females of the species have been usually considered to be nearly uniformly monochromatic brown. Using reflectance spectrophotometry, we explore the age‐dependent variation of plumage colour in females. We disentangle the within‐ and between‐individual effects of this pattern and show a within‐individual darkening of the mantle colour with age, whereas differences between individuals in structural colour expression may underlie the trend for a more reflective white in the females' breast plumage with advancing age. The darkening of the dorsal plumage as females age reflects the most common pattern of age‐related variation in males in most European populations of the species.