Supermicrovascular anastomosis training using chicken wings and colored water.

Plastic surgeons require experience in supermicroscopic vascular anastomosis. Herein, we report a simple, rapid, and cost-effective training method using chicken wings and colored water. The avian ventral metacarpal artery was selected for dissection and anastomosis to mimic supermicrosurgery. Over 14 weeks (one anastomosis per day), the ulnar artery in 100 chicken wings was exposed by dissection, cut proximally, and injected with blue food dye-colored water by an inexperienced surgeon. After ligating the artery branches, it was cut and subjected to end-to-end anastomosis. Next, colored water was injected into the ulnar artery to check for suture sufficiency. The vessel was re-dissected to inspect the lumen and sutures qualitatively. Of the 100 wings, the first and last 20 wings' ventral metacarpal artery dissection, anastomosis times, and leakage frequency were compared. Avian ventral metacarpal artery diameter was recorded, and the cumulative anastomosis time where individual anastomosis times started decreasing was determined. Leakage rates before and after this point were compared. The avian ventral metacarpal artery diameter was 0.7-0.8 mm. The last 20 wings had significantly shorter median dissection times (12:27 vs. 17:45 min), anastomosis times (9:02 vs. 12:29 min), and leakage rates (15% vs. 70%); more even stitching and parallel ligature points; and less vessel layer inversion than the first 20 wings. After a cumulative anastomosis time of 10 h 26 min, individual times sharply decreased, and the leakage rate decreased significantly (58.3% vs. 23.8%). The proposed method significantly improved supermicrosurgical anastomosis. Thus, we believe that this method will help surgeons improve their supermicrosurgical skills.

Golden ratio in venation patterns of dragonfly wings.

The vein pattern in insect wings allows this lightweight structure to carry multiple biological functions. Here, an investigation of the angular distribution of the vein struts in dragonfly wings revealed that the golden angle or golden ratio dominates the venation patterns. We find that the golden angle dominates the intervein angles in regions where thin veins and membranes demand strength reinforcement. A golden ratio partition method has thus been developed that explains a set of preferred intervein angles in distorted polygon-shaped venation cells throughout the venation pattern in dragonfly wings. These observations provide new evidence that the wing structure is spatially optimized, by the golden rule in nature, for supporting biomechanical functions of dragonfly wings.

A multi-gene phylogenetic analysis of the leafhopper subfamily Typhlocybinae (Hemiptera: Cicadellidae) challenges the traditional view of the evolution of wing venation.

Genera of the diverse leafhopper subfamily Typhlocybinae have traditionally been classified into tribes primarily based on characters of the wing venation and an intuitive phylogeny of this group was previously proposed based on the hypothetical pattern of wing vein evolution. Some recent authors suggested that wing vein characters are not always reliable but few attempts have been made to examine the status and relationships of typhlocybine tribes using rigorous phylogenetic analyses. Phylogenetic analysis of a dataset comprising DNA sequences from five gene regions (H3, H2A, 28S rDNA D2, 16S rDNA, and COI with a total length of 2413 bps) and 61 species representing six previously recognized tribes of Typhlocybinae provides strong support for the monophyly of the subfamily and five of the previously recognized tribes. Most branches received moderate to strong maximum likelihood bootstrap support. The following intertribal relationships were recovered: (Alebrini + Empoascini) + ((Dikraneurini + Erythroneurini) + Typhlocybini). Maximum likelihood analysis recovered Zyginellini (treated as a separate tribe by some authors) as sister to Typhlocybini with low branch support, but the former tribe was derived from within the latter in Bayesian analysis of the same dataset and relationships within Typhlocybini (sensu lato) were generally poorly resolved in both analyses. The relationship of Typhlocybini to other tribes is also unstable, suggesting that more data are needed to resolve the position of this tribe with confidence. Parts of the phylogeny receiving strong support in both analyses contradict the traditional view that Alebrini, the only tribe retaining an appendix in the forewing, is the earliest diverging lineage and possibly gave rise to the other tribes. Ancestral state reconstructions indicate that characters of the wing venation traditionally used for diagnosing typhlocybine tribes are generally conservative but exhibit some homoplasy and may not, by themselves, be reliable for recognizing monophyletic groups within this subfamily.

Molecular mechanisms underlying simplification of venation patterns in holometabolous insects.

How mechanisms of pattern formation evolve has remained a central research theme in the field of evolutionary and developmental biology. The mechanism of wing vein differentiation in Drosophila is a classic text-book example of pattern formation using a system of positional information, yet very little is known about how species with a different number of veins pattern their wings, and how insect venation patterns evolved. Here, we examine the expression pattern of genes previously implicated in vein differentiation in Drosophila in two butterfly species with more complex venation Bicyclus anynana and Pieris canidia We also test the function of some of these genes in B. anynana We identify both conserved as well as new domains of decapentaplegic, engrailed, invected, spalt, optix, wingless, armadillo, blistered and rhomboid gene expression in butterflies, and propose how the simplified venation in Drosophila might have evolved via loss of decapentaplegic, spalt and optix gene expression domains, via silencing of vein-inducing programs at Spalt-expression boundaries, and via changes in expression of vein maintenance genes.

Circulation in Insect Wings.

Insect wings are living, flexible structures composed of tubular veins and thin wing membrane. Wing veins can contain hemolymph (insect blood), tracheae, and nerves. Continuous flow of hemolymph within insect wings ensures that sensory hairs, structural elements such as resilin, and other living tissue within the wings remain functional. While it is well known that hemolymph circulates through insect wings, the extent of wing circulation (e.g., whether flow is present in every vein, and whether it is confined to the veins alone) is not well understood, especially for wings with complex wing venation. Over the last 100 years, scientists have developed experimental methods including microscopy, fluorescence, and thermography to observe flow in the wings. Recognizing and evaluating the importance of hemolymph movement in insect wings is critical in evaluating how the wings function both as flight appendages, as active sensors, and as thermoregulatory organs. In this review, we discuss the history of circulation in wings, past and present experimental techniques for measuring hemolymph, and broad implications for the field of hemodynamics in insect wings.

Structure and tensile properties of the forewing costal vein of the honeybee Apis mellifera.

In this study, we investigated the morphological features and tensile properties of the forewing costal vein of the honeybee (Apis mellifera) under fresh, dry and in vitro-time varied conditions. The costal vein is composed of an outer sub-vein and an inner vein starting from the wing base to nearly 50% of the wing span and then they are fused into one vein extending to the wing tip. Confocal laser scanning microscopy revealed that the outer sub-vein with red autofluorescence is stiffer than the inner one with green autofluorescence, and the membrane in the gap between the sub-veins exhibited a long blue-autofluorescence resilin stripe. Considering the irregular cross-sectional shape of the costal vein, cross-sections of the tested specimens after tensile failure were analysed using scanning electron microscopy, to precisely calculate their cross-sectional areas by a customized MATLAB program. The Young's modulus and tensile strength of fresh specimens were ∼4.78 GPa and ∼119.84 MPa, which are lower than those of dry specimens (∼9.08 GPa and ∼154.45 MPa). However, the tensile strain had the opposite relationship (fresh: ∼0.031, dry: ∼0.018). Thus, specimen desiccation results in increasing stiffness and brittleness. The morphological features and material properties of the costal vein taken together represent a tradeoff between both deformability and stiffness. Our study provides guidance for material selection and bionic design of the technical wings of flapping micro aerial vehicles.

Structural characteristics analysis of the hind wings in a bamboo weevil (Cyrtotrachelus buqueti).

The finite element method is a powerful tool for evaluating the experimental results. It can help to study the flight mechanism of insects and the structural characteristics of flying wings. Therefore, the research object based on the hind wings of Cyrtotrachelus buqueti (C. buqueti) was completed here. A finite element model with a length of 45 mm in the spanwise direction and a 16 mm width in the chordwise direction were established. We used a three-dimensional (3D) scanner to scan a real hind wing to obtain point cloud images. The physical model of the hind wing was carried out by using both the software Imageware and Unigraphics NX. To quantify the quality of the finite element model of the hind wing, the material properties of the wing membranes and veins were conducted by the tensile testing machine. The structural static properties of the hind wing, including static characteristics analysis and natural vibration modal analysis, were analysed by ANSYS; the stress and deflection under uniformly distributed load, bending moment, and torque were, respectively, shown. It was found that the model only had a small deformation, which shows that the hind wings of C. buqueti have excellent structural properties.

Investigation of the morphological cell structures and their optical significances of Aeshna cyanea.

The transparent wing of the dragonfly Aeshna cyanea has been investigated using scanning electron microscopy (SEM), optical microscopy (OPM), energy-dispersive X-ray spectroscopy (EDS) and reflectance spectroscopy. Four cells (D1-D4) were studied and classified according to their general morphology. The OPM depicted the vein-joint characterised by the distribution of resilin. EDS technique showed common elements such as carbon, oxygen, and chlorine. SEM analysis revealed thin membranes reinforced with a network of hallow veins. Spikes and round shape of microstructures were identified. The roughness of the pruinosity was estimated, which indicates the shape and curvature of the microstructures that essentially play a significant role in the optical response observed. The study can be essential to design and improve micro-air vehicles.

The extracellular protease AdamTS-B inhibits vein formation in the Drosophila wing.

Vein patterning in the Drosophila wing provides a powerful tool to study regulation of various signaling pathways. Here we show that the ADAMTS extracellular protease AdamTS-B (CG4096) is expressed in the embryonic wing imaginal disc precursor cells and the wing imaginal disc, and functions to inhibit wing vein formation. Knock-down of AdamTS-B displayed posterior crossveins (PCVs) with either extra branches or deltas, or wider PCVs, and a wandering distal tip of the L5 longitudinal vein. Conversely, over-expression of AdamTS-B resulted in a complete absence of the PCV, an incomplete anterior crossvein, and missing distal end of the L5 longitudinal vein. We conclude that AdamTS-B inhibits wing vein formation through negative regulation of signaling pathways, possibly BMP as well as Egfr, displaying the complexity of roles for this family of extracellular proteases.

Influence of hydrodynamic pressure and vein strength on the super-elasticity of honeybee wings.

The wings of honeybees (Apis mellifera L.) usually produce bending and torsional deformations during flapping wing movement. These deformations endow honeybees with perfect aerodynamic control to escape predators and exploit scattered resources. However, the mechanisms by which honeybee wings recover from large deformations are unclear. This study demonstrates that honeybee wings are super-elastic that they can recover rapidly from one extreme contorted state to their original position. A comparative experiment is conducted to evaluate the difference in super-elastic recovery between attached and detached wings. Results show that the structural stiffness of wings is affected by the reticulate vein and the haemolymph pressure generated by the blood circulation. Further analysis indicates that the haemolymph pressure can increase the stiffness of honeybee wings, especially that of the subcostal veins. This phenomenon shortens the recovery time of wing deflection behaviour.

Drosophila immune cells extravasate from vessels to wounds using Tre1 GPCR and Rho signaling.

Inflammation is pivotal to fight infection, clear debris, and orchestrate repair of injured tissues. Although Drosophila melanogaster have proven invaluable for studying extravascular recruitment of innate immune cells (hemocytes) to wounds, they have been somewhat neglected as viable models to investigate a key rate-limiting component of inflammation-that of immune cell extravasation across vessel walls-due to their open circulation. We have now identified a period during pupal development when wing hearts pulse hemolymph, including circulating hemocytes, through developing wing veins. Wounding near these vessels triggers local immune cell extravasation, enabling live imaging and correlative light-electron microscopy of these events in vivo. We show that RNAi knockdown of immune cell integrin blocks diapedesis, just as in vertebrates, and we uncover a novel role for Rho-like signaling through the GPCR Tre1, a gene previously implicated in the trans-epithelial migration of germ cells. We believe this new Drosophila model complements current murine models and provides new mechanistic insight into immune cell extravasation.

Morphology of hindwing veins in the shield bug Graphosoma italicum (Heteroptera: Pentatomidae).

Light, fluorescence, and electron microscopy were applied to cross sections and -breakage and whole-mount preparations of the anterior hindwing vein of the shield bug Graphosoma italicum. These analyses were complemented by investigations of the basal part of the forewing Corium and Clavus. The integration of structural, histological, and fluorescence data revealed a complex arrangement of both rigid and elastic structures in the wall of wing veins and provided insights into the constitution of transition zones between rigid and elastic regions. Beneath the exocuticular layers, which are continuous with the dorsal and ventral cuticle of the wing membrane, the lumen of the veins is encompassed by a mesocuticular layer, an internal circular exocuticular layer, and an internal longitudinal endocuticular layer. Separate parallel lumina within the anterior longitudinal vein of the hindwing, arranged side-by-side rostro-caudally, suggest that several veins have fused in the phylogenetic context of vein reduction in the pentatomid hindwing. Gradual structural transition zones and resilin enrichment between sclerotized layers of the vein wall and along the edges of the claval furrow are interpreted as mechanical adaptations to enhance the reliability and durability of the mechanically stressed wing veins.

Morphological and mechanical properties of flexible resilin joints on damselfly wings (Rhinocypha spp.).

Resilin functions as an elastic spring that demonstrates extraordinary extensibility and elasticity. Here we use combined techniques, laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM) to illuminate the structure and study the function of wing flexibility in damselflies, focusing on the genus Rhinocypha. Morphological studies using LSCM and SEM revealed that resilin patches and cuticular spikes were widespread along the longitudinal veins on both dorsal and ventral wing surfaces. Nanoindentation was performed by using atomic force microscopy (AFM), where the wing samples were divided into three sections (membrane of the wing, mobile and immobile joints). The resulting topographic images revealed the presence of various sizes of nanostructures for all sample sections. The elasticity range values were: membrane (0.04 to 0.16 GPa), mobile joint (1.1 to 2.0 GPa) and immobile joint (1.8 to 6.0 GPa). The elastomeric and glycine-rich biopolymer, resilin was shown to be an important protein responsible for the elasticity and wing flexibility.

Effects of hypo-O-GlcNAcylation on Drosophila development.

Post-translational modification of serine/threonine residues in nucleocytoplasmic proteins with GlcNAc (O-GlcNAcylation) is an essential regulatory mechanism in many cellular processes. In Drosophila, null mutants of the Polycomb gene O-GlcNAc transferase (OGT; also known as super sex combs (sxc)) display homeotic phenotypes. To dissect the requirement for O-GlcNAc signaling in Drosophila development, we used CRISPR/Cas9 gene editing to generate rationally designed sxc catalytically hypomorphic or null point mutants. Of the fertile males derived from embryos injected with the CRISPR/Cas9 reagents, 25% produced progeny carrying precise point mutations with no detectable off-target effects. One of these mutants, the catalytically inactive sxcK872M , was recessive lethal, whereas a second mutant, the hypomorphic sxcH537A , was homozygous viable. We observed that reduced total protein O-GlcNAcylation in the sxcH537A mutant is associated with a wing vein phenotype and temperature-dependent lethality. Genetic interaction between sxcH537A and a null allele of Drosophila host cell factor (dHcf), encoding an extensively O-GlcNAcylated transcriptional coactivator, resulted in abnormal scutellar bristle numbers. A similar phenotype was also observed in sxcH537A flies lacking a copy of skuld (skd), a Mediator complex gene known to affect scutellar bristle formation. Interestingly, this phenotype was independent of OGT Polycomb function or dHcf downstream targets. In conclusion, the generation of the endogenous OGT hypomorphic mutant sxcH537A enabled us to identify pleiotropic effects of globally reduced protein O-GlcNAc during Drosophila development. The mutants generated and phenotypes observed in this study provide a platform for discovery of OGT substrates that are critical for Drosophila development.

New insights on basivenal sclerites using 3D tools and homology of wing veins in Odonatoptera (Insecta).

Being implied in flight, mimetism, communication, and protection, the insect wings were crucial organs for the mega diversification of this clade. Despite several attempts, the problem of wing evolution remains unresolved because the basal parts of the veins essential for vein identification are hidden in the basivenal sclerites. The homologies between wing characters thus cannot be accurately verified, while they are of primary importance to solve long-standing problems, such as the monophyly of the Palaeoptera, viz. Odonatoptera, Panephemeroptera, and Palaeozoic Palaeodictyopterida mainly known by their wings. Hitherto the tools to homologize venation were suffering several cases of exceptions, rendering them unreliable. Here we reconstruct the odonatopteran venation using fossils and a new 3D imaging tool, resulting congruent with the concept of Riek and Kukalová-Peck, with important novelties, viz. median anterior vein fused to radius and radius posterior nearly as convex as radius anterior (putative synapomorphies of Odonatoptera); subcostal anterior (ScA) fused to costal vein and most basal primary antenodal crossvein being a modified posterior branch of ScA (putative synapomorphies of Palaeoptera). These findings may reveal critical for future analyses of the relationships between fossil and extant Palaeoptera, helping to solve the evolutionary history of the insects as a whole.

Role of wing color and seasonal changes in ambient temperature and solar irradiation on predicted flight efficiency of the Albatross.

Drag reduction of the wings of migrating birds is crucial to their flight efficiency. Wing color impacts absorption of solar irradiation which may affect drag but there is little known in this area. To this end, the drag reduction induced by the thermal effect of the wing color of migrating birds with unpowered flight modes is presented in this study. Considering this natural phenomenon in the albatross as an example of migrating birds, and applying an energy balance for this biological system, a thermal analysis is performed on the wings during the summer and winter to obtain different ranges of air density, viscosity, and wing surface temperature brought about from a range of ambient temperatures and climatic conditions seen in different seasons and to study their effects. The exact shape of the albatross wing is used and nine different wing colors are considered in order to gain a better understanding of the effect different colors' absorptivities make on the change in aerodynamic performances. The thermal effect is found to be more important during the summer than during the winter due to the higher values of solar irradiation and a maximum drag reduction of 7.8% is found in summer changing the wing color from light white to dark black. The obtained results show that albatrosses with darker colored wings are more efficient (constant lift to drag ratio and drag reduction) and have better endurance due to this drag reduction.

Wing cross veins: an efficient biomechanical strategy to mitigate fatigue failure of insect cuticle.

Locust wings are able to sustain millions of cycles of mechanical loading during the lifetime of the insect. Previous studies have shown that cross veins play an important role in delaying crack propagation in the wings. Do cross veins thus also influence the fatigue behaviour of the wings? Since many important fatigue parameters are not experimentally accessible in a small biological sample, here we use the finite element (FE) method to address this question numerically. Our FE model combines a linear elastic material model, a direct cyclic approach and the Paris law and shows results which are in very good agreement with previously reported experimental data. The obtained results of our study show that cross veins indeed enhance the durability of the wings by temporarily stopping cracks. The cross veins further distribute the stress over a larger area and therefore minimize stress concentrations. In addition, our work indicates that locust hind wings have an endurance limit of about 40% of the ultimate tensile strength of the wing material, which is comparable to many engineering materials. The comparison of the results of the computational study with predictions of two most commonly used fatigue failure criteria further indicates that the Goodman criterion can be used to roughly predict the failure of the insect wing. The methodological framework presented in our study could provide a basis for future research on fatigue of insect cuticle and other biological composite structures.

Resilin microjoints: a smart design strategy to avoid failure in dragonfly wings.

Dragonflies are fast and manoeuvrable fliers and this ability is reflected in their unique wing morphology. Due to the specific lightweight structure, with the crossing veins joined by rubber-like resilin patches, wings possess strong deformability but can resist high forces and large deformations during aerial collisions. The computational results demonstrate the strong influence of resilin-containing vein joints on the stress distribution within the wing. The presence of flexible resilin in the contact region of the veins prevents excessive bending of the cross veins and significantly reduces the stress concentration in the joint.

Color Pattern on the Forewing of Micropterix (Lepidoptera: Micropterigidae): Insights into the Evolution of Wing Pattern and Wing Venation in Moths.

Wing patterns are key taxonomic characters that have long been used in descriptions of Lepidoptera; however, wing pattern homologies are not understood among different moth lineages. Here, we examine the relationship between wing venation and wing pattern in the genus Micropterix, among the most basal extant Lepidoptera, in order to evaluate the two existing predictive models that have the potential to establish wing pattern element homologies for the order. The location of wing pattern elements along the costal margin of the wing in Micropterix is consistent with the predictions of the model proposed for Tortricidae by Brown and Powell in 1991, later modified by Baixeras in 2002. The predictive power of this model for such distantly related taxa suggests that the model may hold across various superfamilies within Lepidoptera, and supports the long-held notion that fasciae, not spots, are the most likely primitive wing pattern elements for the order. In addition, the location of wing pattern elements suggests that the wing vein commonly termed Sc1 may in fact be a different vein, which Comstock identified in Trichoptera and referred to as "a."