Morphological and ultrastructural characterization of the alimentary canal in Japanese wax scale (Ceroplastes japonicus Green)

The morphology and ultrastructure of the alimentary canal in the adult female of the Japanese wax scale, Ceroplastes japonicus Green (Hemiptera: Coccoidea: Coccidae), was investigated using light microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that the foregut was subdivided into a sclerotized pharynx and an oesophagus. A pair of salivary glands attached in the middle of the foregut. The loop-shaped midgut was narrow and longer than the foregut and its inner wall lined with a thick layer of epithelia. The hindgut was divided into a narrower ileum and a broader rectum, with the well-developed filter chamber enclosed in the anterior rectum. Malpighian tubules consisted of two brownish-yellow moniliform tubules with pores, approximately 1 μm in diameter, scattered on the outer surface and many spherical crystals inside the tubules.     

Ultrastructural analysis of Wuchereria bancrofti (Nematoda: Filarioidea) body wall

Bancroftian filariasis constitutes the principal mosquito-borne nematode infection of humans and the surface of adult of Wuchereria bancrofti seems to be especially important in the intricate interplay between host and parasite. The study of the parasite's surface structure might help to understand the localization and function of various organelles. W. bancrofti adult worms were recovered from untreated patients during hydrocele repair surgery and studied by transmission electron microscopy. The body wall of adult parasite is composed of cuticle, hypodermis and muscular layer. Cuticle is the external layer and shows transverse cuticular striation. It is composed by an epicuticle, cortical layers, median layer, fibrous layers and basal layer. The epicuticle is the most external cuticular layer and appears as a single laminar electron-dense layer. The cortical external region is more electron-dense and granular in appearance than the inner cortical layer. Electron-dense structures, called bosses are randomly distributed filling the cuticular striation. The median layer is formed by an electron-dense and continuous thick line. The fibrous layer is subdivided in inner and external layers connected by projections. The basal layer includes a large quantity of membranous projections directed toward the hypodermis. The hypodermis is a syncytium where some cellular organelles are observed. The somatic musculature is meromyarian. The muscle fibers consist of contractile and non-contractile regions and the contractile region is composed of myofilaments separated by dense body. This is the first study of W. bancrofti adult worms obtained from untreated patients and studied by transmission electron microscopy.     

Morphology and histology of the digestive system of the vector leafhopper Psammotettix striatus (L.) (Hemiptera: Cicadellidae)

The vector leafhopper Psammotettix striatus (L.) (Hemiptera: Cicadellidae) is an important economic pest that is a serious threat to wheat in Northwest China, causing great losses to agricultural production by transmitting wheat blue dwarf (WBD) in a persistent circulative manner. Studies on morphology and ultrastructure of the digestive system were made using light, scanning and transmission electron microscopy. The gross morphology of the alimentary canal consists of esophagus (foregut), midgut, hindgut, and special filter chamber. The esophagus, a narrow and slender tube, runs through the whole thorax extending into the filter chamber and connecting with the anterior midgut. The midgut consists of three major regions, anterior, middle and posterior midgut. The anterior midgut is composed of exceptionally thick epithelial cells surrounding a large lumen. Numerous well-developed microvilli occur at the basal region of the epithelium. A large number of electron-lucent and lipid-like vesicles are observed under the microvilli. The posterior midgut is smaller than the anterior midgut in diameter. Numerous different concentric circular bodies are characteristic of the posterior midgut. The hindgut arises from the posterior midgut at the boundary of the filter chamber. It extends downward toward the anus where the hindgut enlarges to form the rectum. The rectum is formed by various cells typical of epithelium, whose nuclei are relatively smaller than those of the midgut. Relatively large muscle cells are present at the well-defined and thick basement membrane. There are two pairs of Malpighian tubules. Numerous mitochondria and lamellar rough endoplasmic reticulum in the cells of the anterior segment of the Malpighian tubules; the sub-anterior segment of the tubules resemble the distal segment which are wave-like, amount vesicles in the cells; numerous tightly packed large vesicles contain two types of brochosomes in the inflated segment of the Malpighian tubules. The salivary system of P. striatus contains one pair of salivary glands, which are made up of the principal and accessory gland. The principal glands are divided into anterior, mid- and posterior lobes. About nineteen acini are observed in the principal glands of P. striatus, and vary in structure and colour. Five cellular types are found in the principal glands by transmission electron microscopy, which are rich in secretory granules, modified in size, electron-dense and shape. Rough endoplasmic reticulum in the shape of vesicular and lamellar, mitochondria and Golgi complexes are observed. The accessory gland has only an oval or a rod-shaped acinus.     

The Sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae) digestive tract: histology, ultrastructure and its physiological significance

The Sunn pest, Eurygaster integriceps Put. (Hemiptera: Scutelleridae), is a key pest of wheat in the Middle East and some other areas which causes severe qualitative and quantitative damage. The objective of the current work is to describe the morphology of the midgut of E. integriceps adult. Microscopic studies revealed that foregut consists of oral cavity, pharynx and oesophagus likely other phytophagous Hemiptera. In the Midgut, four anatomical regions could be identified: the first ventriculus (V1), the second ventriculus (V2), the third ventriculs (V3), and the fourth ventriculus (V4). The microvilli and perimicrovillar membrane (PMM) were found in V1-V3 regions with columnar cells characterized by presence of mitochondria, rough endoplasmic reticulum and basal infoldings in the basal portion. However, V2 and V3 showed less developed basal plasma membrane infoldings. Three cell types: columnar, endocrine and regenerative cells were found in V1-V3. The V4 region showed different histological features from the other three midgut regions by showing a vacuolated epithelium with crypts storing symbiotic bacteria. The hindgut had a short ileum followed by a well-developed rectum with an epithelial cell layer and a thin cuticular intima. The current results suggest V1-V3 midgut regions play a role in enzyme and absorption, whereas V4 seems to have no function in digestion.     

Microstructure,crystallography and diagenetic alteration in fossil ostrich eggshells from Upper Palaeolithic sites of Indian peninsular region

Biominerals studies are of importance as they provide an understanding of natural evolutionary processes. In this study we have investigated the fossil ostrich eggshells using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Electron Backscatter Diffraction (EBSD). SEM studies demonstrated the ultrastructure of fossil eggshells and formation of calcified cuticular layer. The presence of calcified cuticle layer in eggshell is the basis for ancient DNA studies as it contains preserved biomolecules.EBSD accentuates the crystallographic structure of the ostrich eggshells with sub-micrometer resolution. It is a non-destructive tool for evaluating the extent of diagenesis in a biomineral. EBSD analysis revealed the presence of dolomite in the eggshells. This research resulted in the complete recognition of the structure of ostrich eggshells as well as the nature and extent of diagenesis in these eggshells which is vital for genetic and paleoenvironmental studies.     

Morphology of the sternal gland in workers of Coptotermes gestroi (Isoptera, Rhinotermitidae)

The sternal gland is considered the only source of trail pheromones in termites. The morphology of the sternal gland was investigated in workers of Coptotermes gestroi using transmission and scanning electron microscopy. The results showed a small bilobed gland at the anterior part of the fifth abdominal sternite. The cuticular surface of the sternal gland showed a V-shaped structure with two peg sensilla in elevated socket and various campaniform sensilla. Pores and cuticular scale-like protuberances also occur in the glandular area. The ultrastructure showed a gland composed of class 1 cells and two different types of class 3 cells distinguished by location, different size and electron-density of secretory vesicles. Small class 3 cells (type 1) of the anterior lobe are inserted among class 1 cells and have weakly electron-dense vesicles associated with mitochondria, glycogen and smooth endoplasmic reticulum. The class 3 cells (type 2) of posterior lobe showed many round electron-lucent vesicles of secretion, abundant free ribosomes and a well-developed Golgi apparatus. Each class 3 cell is connected to the cuticle by a cuticular duct constituted by the receiving canal and the conducting canal. The secretion of class 1 cells is stored in an inner subcuticular reservoir that is delimited by the microvilli of these cells. This inner reservoir is large and crossed by the campaniform sensilla and ducts of two types of class 3 cells that open outside of the insect body. An exterior reservoir also is present between the fourth and fifth sternite. The complex structure of the sternal gland suggests multicomponents for the trail pheromone in the worker of C. gestroi.     

Ultrastructure of antennal and posterior abdominal sensilla in Chlorophorus caragana females

Chlorophorus caragana Xie & Wang is a destructive wood-boring beetle that damages Caragana spp. bushes and is distributed in desert areas in north-west China. Using scanning electron microscopy and transmission electron microscopy, we observed the morphology and ultrastructure of antennal and posterior abdominal sensilla in C. caragana females, to discuss the putative functions of these sensilla in host location and oviposition behaviors.In total, seven types (24 subtypes) of sensilla were located on the antenna and posterior abdomen. On the antenna, there were Böhm's bristles (BB.); four subtypes of sensilla chaetica (Ch.1–Ch.4) characterized by non-porous surfaces and sensillum-lymph cavities without dendrites; two subtypes of sensilla trichodea (Tr.1 and Tr.2) with a tip pore and dendrites surrounded by dendritic sheaths; dome-shaped sensilla (Dom.) emerging from a deep cavity with one tip pore; four subtypes of sensilla basiconica (Ba.1–Ba.4) and one type of sensilla auricillica (Au.) with a porous cuticular surface and dendrites in the sensillum-lymph cavity; and one type of sensilla styloconica (Sty.) with grooves on the cuticular wall. On the posterior abdomen, there were four subtypes of sensilla chaetica (Ch.5–Ch.8); three subtypes of sensilla trichodea (Tr.3–Tr.5); and three subtypes of sensilla basiconica (Ba.5–Ba.7; Ba.5 had no groove in the cuticular wall, Ba.6 had one tip pore, and Ba.7 was located in a cuticular cavity). The antennal sensilla were believed to be mechanosensitive, chemosensitive, and sensitive to humidity and temperature, and to play roles in mating, host location and oviposition. The abdominal sensilla are believed to be related to oviposition behaviors.     

A new strategy of endosymbiont midgut bacteria in ant (Ponerinae)

The location and ultrastructure of bacteria associated with microvilli in the midgut of Odontomachus bauri were examined by transmission electron microscopy. These filamentous type bacteria are the second morphotype described in the midgut of this ant. They colonizes only the ectoperitrophic space, more specifically attaching along microvilli. A thick capsule attaches bacteria to microvilli and protect them from acidic pH and digestive enzymes. Details of the location and association with microvilli are discussed.     

Symbiotic bacteria and the structural specializations in the ileum of Cephalotes ants

Light, scanning, and transmission electron microscopy were used to examine the ultramorphology and ultrastructure of the ileum of Cephalotes atratus, Cephalotes clypeatus, and Cephalotes pusillus. Sections along the ileum revealed differences among the three main regions: proximal (or pylorus), medial, and distal. The structural specializations present in the ileum of these three ants have implications especially to the symbiotic bacteria harbored in this region of the digestive tract. The structural similarities are conspicuous for the three species examined, suggesting that this is the pattern adopted by the genus Cephalotes.     

Maple syrup urine disease hair reveals the importance of 18-methyleicosanoic acid in cuticular delamination

18-Methyleicosanoic acid (18-MEA) is thought to be covalently bound to the outer surface of human hair and is a major component of the outer beta-layer of the cuticular cell membrane complex (CCMC). Cuticular delamination, whether this occurs between the outer beta- and delta-layers or within the plane of the beta-layer, results in a fresh layer of 18-MEA being exposed at the newly-revealed surface. Hair from patients with Maple Syrup Urine Disease (MSUD), however, does not contain 18-MEA and here, we report on the importance this unusual fatty acid in cuticular delamination. Hair fibres were collected from 10 patients with classic (type 1A) MSUD from a Mennonite community in Pennsylvania, USA. Included amongst these were hairs from dizygotic twins (A1 and A2), one of whom had MSUD, and the other did not; it was unknown at the beginning of the study which twin had MSUD. The outer surfaces were examined using atomic force microscopy (AFM) and transverse sections imaged using transmission electron microscopy (TEM). The newly revealed intercellular surface regions from twin A2 were found to be significantly rougher than those from twin A1. TEM studies showed the trilamellar CCMC to be continuous for twin A1, but possessed discontinuities of variable length (100-1000 nm) for twin A2. In contrast with other work, TEM showed no specific defects in the outer beta-layer. The outer cuticular surfaces for most MSUD patients showed a great abundance of residual endocuticle, although in other cases this was less pronounced. These differences may be explained by some residual activity of the branched-chain alpha-ketoacid (BCKD) dehydrogenase. Cuticular delamination in MSUD-hair probably still occurs within the general plane of the CCMC, although fracture through discontinuities of this layer results in zones of endocuticle being exposed at the new surface.     

UV photodetector behavior of 2D ZnO plates prepared by electrochemical deposition

Zinc oxide (ZnO) with 2D hexagonal structure was successfully prepared using electrochemical deposition (ECD) method on a quartz substrate pre-coated with indium-doped ZnO layer. The X-ray diffraction of the prepared sample confirmed that the hexagonal structure had a dominant c-axis orientation. The scanning electron microscopy revealed the 2D hexagonal structure of the prepared ZnO.     

Flagellar sensilla of Quadraspidiotus perniciosus Comstock (Rhynchota: Diaspididae) male

The flagellar sensory structures of Quadraspidiotus perniciosus Comstock (Rhynchota: Diaspididae) male have been investigated, using scanning and transmission electron microscopy. Five categories of sensilla have been identified: three types of sensilla trichodea, a sensillum coeloconicum and a sensillum basiconicum. The possible function of sensilla is discussed, considering their location, morphology and ultrastructure. No gustatory sensilla have been detected. All the setae (sensilla trichodea) present on the flagellomeres, except for the three 'knobbed' ones that are mechanosensilla, are cuticular components of olfactory structures. These olfactory sensilla are of two distinct types, having fluted or smooth hairs; furthermore, the fluted ones present different typologies for a varied number of dendrites. They are conceivably used for perceiving female sexual pheromone. It might be that each of the different components of the female sexual pheromone is perceived by a specific sensillum. Two types of supposed thermo-hygroreceptors have been found, one sensillum coeloconicum and two sensilla basiconica.     

Ultramorphology of the proventriculus in Panorpidae and Bittacidae (Mecoptera)

The proventriculus is a specialized part of the foregut in the alimentary canal in some insects, varying greatly in its structure across different insect groups. The ultramorphology of the proventriculus in Mecoptera was investigated in eight species of Panorpidae and one of the Bittacidae using light microscopy and scanning electron microscopy. The proventriculus consists of the outer circular muscles, the inner longitudinal muscles, an epithelium, and a sclerotized intima with dense acanthae. The proventricular acanthae could be divided into three categories: the anterior acanthae (AA), the main acanthae (MA), and the posterior acanthae (PA). In Panorpidae the AA are rounded in cross section and could be subdivided into two subtypes, the long AA with a polytomy apiculus and the short AA with a V-shaped or spine-like apiculus. The MA, covering the majority of the proventricular inner surface, are dense, uniform, and hollow rectangular structures in cross section with forked apiculi. Each hollow base of the MA was first found to be inserted with a cone-shaped process of the corresponding epithelial cell. The PA are very thin, with a spine-like apiculus. In Bittacidae the proventriculus is specialized by a ring of cuticular thickening within its anterior orifice, and the AA are shaped like a ring of thin spines. Six cardiac valves were observed in Panorpidae and ten in Bittacidae. The functions of the various types of acanthae in digestion and extra-oral digestion and their significance in insect systematics are briefly discussed.     

Microscopical methods promote the understanding of the integument biology of Rhinella ornata

In Rhinella ornata, the integument of different body regions was investigated using low-vacuum scanning electron and light microscopy through histochemical and immunohistochemical methods, and revealed the basic structure found in other anurans. Keratinocytes formed the keratinized squamous stratified epithelium, and flask cells occurred among the epidermal superficial layer. Just below the epidermis, the dermis was subdivided into a spongious dermis and a compact dermis. Mixed and granular glands were located in the spongious dermis, and myoepithelial cells surrounded their secretory portions. The Eberth-Katschenko (EK) layer occurred as basophilic areas between the spongious and compact dermis and throughout the spongious dermis. A series of alternating layers of bundles of collagenous fibers characterized the compact dermis, being firmly attached to a thin hypodermis. Regarding the morphological features, each integument region revealed distinct structural aspects. The dorsal integument was rougher than ventral, having conical tubercles and spines upon the verrucae. In the ventral and subgular regions, the slightly elevations are visualized, tubercles were absent but some spines occurred. The pelvic integument had a non-keratinized epidermis with an irregular profile and small poorly developed elevations. In addition, the EK layer was absent, and the presence of numerous blood vessels suggests its participation in water absorption and distribution. In the parotoid gland, the epidermis was similar to the dorsal integument; except that the reticular dermis was present, and contained three exocrine glandular types. Expression of cytokeratin was evident in the basal and intermediary layer, but absent in the cornified layer. Flask cells showed strong cytokeratin labeling. Consequently, the integument had the basic morphology, but exhibits regional characteristics, which may be related to the physiology of each surface.     

Low-Dimensional Systems and Surface Physics

Transmission electron microscopy is used to study the structure of the surface layer of an Al-7 wt % Si alloy subjected to laser alloying. The base volume is found to be occupied by an aluminum matrix having a braidlike structure. New phases have been revealed, and their composition, shape, and spatial distribution have been determined.     

Structural Transformation of the Surface of an Aluminum Alloy after Hydroabrasive Action

The results of investigating an Al–Mg alloy (5.8–6.8 wt % Mg) subjected to hydroabrasive action are presented. It is revealed that the cut surface is contaminated with fragments of particles of the abrasive. The cut-surface relief is studied with the help of scanning electron microscopy. The cut-surface microhardness and the cold-hardened layer depth are determined. The structural transformation near the surface is investigated via X-ray diffraction analysis and transmission electron microscopy. The structural state of the alloy near the surface is demonstrated to be extremely inhomogeneous. Plastic deformation leads to the formation of an ultrafine-grained structure with a heightened level of stresses.     

TEM preparation methods and influence of radiation damage on the beam sensitive CaCO3 shell of Emiliania huxleyi

The ultrastructure of biologically formed calcium carbonate crystals like the shell of Emiliania huxleyi depends on the environmental conditions such as pH value, temperature and salinity. Therefore, they can be used as indicator for climate changes. However, for this a detailed understanding of their crystal structure and chemical composition is required. High resolution methods like transmission electron microscopy can provide those information on the nanoscale, given that sufficiently thin samples can be prepared. In our study, we developed sample preparation techniques for cross-section and plan-view investigations and studied the sample stability under electron bombardment. In addition to the biological material (Emiliania huxleyi) we also prepared mineralogical samples (Iceland spar) for comparison. High resolution transmission electron microscopy imaging, electron diffraction and electron energy-loss spectroscopy studies revealed that all prepared samples are relatively stable under electron bombardment at an acceleration voltage of 300 kV when using a parallel illumination. Above an accumulated dose of ∼10⁵ e/nm² the material – independent whether its origin is biological or geological – transformed to poly-crystalline calcium oxide.     

Analysis of polished polycrystalline diamond using dual beam focused ion beam microscopy

This paper presents a study on polycrystalline diamond (PCD) polished by dynamic friction polishing (DFP) with the aid of advanced dual beam FIB (focused ion beam) microscopy. After disclosing a variety of wear tracks by DFP using electron imaging in combination with the ion channelling effect, a dual beam FIB was successfully employed at wear track sites to specifically create both the large cross-sectional specimen for microanalysis and thin foil for nanoanalysis. The study concluded that the polished PCD subsurface was free from microscale cracking. However, the attached debris layer on the top surface contained metal oxides and non-diamond carbon phase with inhomogeneous distributions of C, Fe, Cr, Ni, Si and O across the layer. An attached layer directly above a diamond grain was composed of essentially amorphous carbon, suggesting that a direct phase transformation from diamond crystalline to amorphous occurred during DFP.     

Structure and surface layers of Mg-C nanocomposites produced by ball milling

X-ray diffractometry (XRD), X-ray photoelectron spectrometry (XPS), Auger electron spectrometry (AES) and transmission electron microscopy (TEM) were used to investigate the structure and surface layers properties of nanocomposites produced by the mechanical activation (ball milling) of elemental magnesium with carbon materials (amorphous carbon and graphite). Amorphous carbon was synthesized by electric discharge treatment in kerosene. It was shown that ball milling, the allotropic form of carbon materials, and features of hydrogenation have a considerable effect on the structure, surface layer properties, and hydrogen adsorption of a formed composition. XPS and Auger spectroscopy revealed the surface layer of the composite particles to be enriched with carbon. In addition, there were oxide layers on their surfaces due to the particles’ interaction with the environment.     

Field emission studies of silver nanoparticles synthesized by electron cyclotron resonance plasma

Field emission has been studied for silver nanoparticles (25-200 nm), deposited within a cylindrical silver target in an electron cyclotron resonance (ECR) plasma. Particle size distribution was controlled by optimum biasing voltages between the chamber and the target. Presence of non-oxidized silver was confirmed from the X-Ray diffraction analysis; however, thin protective layer of oxide was identified from the selective area electron diffraction pattern obtained with transmission electron microscopy. The silver nanoparticles were seen to exhibit hilly pointed like structures when viewed under the atomic force microscopy (AFM). The emissive properties of these particles were investigated by field emission microscopy. It is found that this technique of deposition is ideal for formation of nanoparticles films on different substrate geometries with size controllability as well as its application to emission devices.