Locust Wing Research Articles

Development and formation of wing cuticle based on transcriptomic analysis in Locusta migratoria during metamorphosis

Wings are an important flight organ of insects. Wing development is a complex process controlled by a series of genes. The flightless wing pad transforms into a mature wing with the function of migratory flight during the nymph-to-adult metamorphosis. However, the mechanism of wing morphogenesis in locusts is still unclear. This study analyzed the microstructures of the locust wing pads at pre-eclosion and the wings after eclosion and performed the comparative transcriptome analysis. RNA-seq identified 25,334 unigenes and 3,430 differentially expressed genes (DEGs) (1,907 up-regulated and 1,523 down-regulated). The DEGs mainly included cuticle development (LmACPs), chitin metabolism (LmIdgf4), lipid metabolism-related genes, cell adhesion (Integrin), zinc finger transcription factors (LmSalm, LmZF593 and LmZF521), and others. Functional analysis based on RNA interference and hematoxylin and eosin (H&E) staining showed that the three genes encoded zinc finger transcription factors are essential for forming wing cuticle and maintaining morphology in Locusta migratoria. Finally, the study found that the LmSalm regulates the expression of LmACPs in the wing pads at pre-eclosion, and LmZF593 and LmZF521 regulate the expression of LmIntegrin/LmIdgf4/LmHMT420 in the wings after eclosion. This study revealed that the molecular regulatory axis controls wing morphology in nymphal and adult stages of locusts, offering a theoretical basis for the study of wing development mechanisms in hemimetabolous insects.

Aerodynamic Analysis and Optimization of Gliding Locust Wing Using Nash Genetic Algorithm

Natural fliers glide and minimize wing articulation to conserve energy for endured and long-range flights. Elucidating the underlying physiology of such a capability could potentially address numerous challenging problems in flight engineering. This study investigates the aerodynamic characteristics of an insect species called desert locust (Schistocerca gregaria) with extraordinary gliding skills at low Reynolds numbers. Here, locust tandem wings are subjected to a computational fluid dynamics (CFD) simulation using two-dimensional and three-dimensional (3-D) Navier–Stokes equations, revealing fore–hindwing interactions and the influence of their corrugations on aerodynamic performance. Furthermore, the obtained CFD results are mathematically parameterized using the PARSEC method and optimized based on a novel fusion of genetic algorithms and Nash game theory to achieve Nash equilibrium. It was concluded that the lift–drag (gliding) ratio of the optimized profiles were improved by at least 77% and 150% compared to the original wing and the published literature, respectively. Ultimately, the profiles are integrated and analyzed using 3-D CFD simulations that demonstrated a 14% performance improvement, validating the proposed wing models for further fabrication and rapid prototyping presented in a future study.

Towards locust-inspired gliding wing prototypes for micro aerial vehicle applications.

In aviation, gliding is the most economical mode of flight explicitly appreciated by natural fliers. They achieve it by high-performance wing structures evolved over millions of years in nature. Among other prehistoric beings, locust is a perfect example of such natural glider capable of endured transatlantic flights that could inspire a practical solution to achieve similar capabilities on micro aerial vehicles. An investigation in this study demonstrates the effects of haemolymph on the flexibility of several flying insect wings proving that many species exist with further simplistic yet well-designed wing structures. However, biomimicry of such aerodynamic and structural properties is hindered by the limitations of modern as well as conventional fabrication technologies in terms of availability and precision, respectively. Therefore, here we adopt finite-element analysis to investigate the manufacturing-worthiness of a three-dimensional digitally reconstructed locust wing, and propose novel combinations of economical and readily available manufacturing methods to develop the model into prototypes that are structurally similar to their counterparts in nature while maintaining the optimum gliding ratio previously obtained in the aerodynamic simulations. The former is assessed here via an experimental analysis of the flexural stiffness and maximum deformation rate as EIs = 1.34 × 10−4 Nm2, EIc = 5.67 × 10−6 Nm2 and greater than 148.2%, respectively. Ultimately, a comparative study of the mechanical properties reveals the feasibility of each prototype for gliding micro aerial vehicle applications.

Spalt is functionally conserved in Locusta and Drosophila to promote wing growth

Locusta has strong fly wings to ensure its long distance migration, but the molecular mechanism that regulates the Locusta wing development is poorly understood. To address the developmental mechanism of the Locusta flying wing, we cloned the Dpp target gene spalt (sal) and analyzed its function in wing growth in the Locusta. The Locusta wing size is apparently reduced with vein defects when sal is interfered by injection of dsRNA, indicating that sal is required for locust wing growth and vein formation. This function is conserved during the Drosophila wing development. To better understand sal’s function in wing growth, we then used Drosophila wing disc as a model for further study. We found that sal promotes cell proliferation in the whole wing disc via positive regulation of a microRNA bantam. Our results firstly unravel sal’s function in the Locusta wing growth and confirm a highly conserved function of sal in Locusta and Drosophila.

Aerodynamic Performance of the Locust Wing in Gliding Mode at Low Reynolds Number

Gliding is an important flight mode for insects because it saves energy during long distance flight without wing flapping. In this study, we investigated the influence of locust wing corrugation on the aerodynamic performance in gliding mode at low Reynolds number. Numerical simulations using two-dimensional Navier-Stokes equations are applied to study the gliding flight, which reveals the interaction between forewing and hindwing. The lift of the corrugated airfoil in a locust wing decreases from the wing root to the tip. Simulation results show that the pressure drags on the forewing and hindwing increase with an increase in wing thickness; while the lift-drag ratio of the airfoil is marginally affected by the corrugation on the airfoil. Geometric parameters analysis of the locust wing is also carried out, which includes the corrugation height, the corrugation placement and the shapes of leading and trailing edges.

Biomimetic fabrication of polymer film with high adhesive superhydrophobicity by duplicating locust wing surface

Locust is a common flying insect. Locust wings were used as biomimetic templates to fabricate multi-functional polymer(polydimethylsiloxane, PDMS) films by soft lithography. The microstructure and wettability of the natural and artificial locust wing surfaces were investigated by means of a scanning electron microscope(SEM) and a video-based contact angle meter. The natural locust wing surface exhibits complicated hierarchical structures and high adhesive superhydrophobicity(contact angle 152°). The prepared polymer film faithfully reproduces the surface microstructures of the bio-template, and displays a good hydrophobicity and high adhesion(contact angle 144°). The complex wettability of the natural and artificial locust wing surfaces ascribes to the cooperative effect of hydrophobic composition and multi-dimensional rough microstructures. This work not only promotes our understanding of the wetting mechanism on bio-surfaces, but offers an inexpensive and effective approach for biomimetic fabrication of multi-functional interfacial materials.

A Comparison of the Complex Wettability between Locust and Moth Wing

The microstructure, hydrophobicity and chemical composition of the locust and moth wing surfaces were investigated by a scanning electron microscope (SEM), a contact angle meter and a Fourier transform infrared spectrometer (FT-IR). The hydrophobicity models were established on the basis of the Cassie-Baxter equation. The locust and moth wing surfaces are composed of naturally hydrophobic materials, but exhibit different complex wettability. The locust wing surface is of extremely high adhesion (sliding angle>180°) and superhydrophobicity (contact angle 151.5~157.3°), while the moth wing surface is of low adhesion (sliding angle 1~3°) and superhydrophobicity (contact angle 150.5~155.6°). The complex wettability of the wing surfaces ascribes to the cooperative effect of material element and structural element. The locust and moth wings can be potentially used as biomimetic templates for design and preparation of novel functional interface and no-loss microfluidic transport channels.

High Adhesive Superhydrophobicity and Wetting Mechanism of Locust Wing Surface

The complex wettability, chemical composition and microstructure of locust wing surface were investigated by a video-based contact angle (CA) meter, a Fourier transform infrared spectrometer (FT-IR) and a scanning electron microscope (SEM). A model for hydrophobicity of wing surface was established on the basis of Cassie equation. The wetting mechanism was discussed from the perspective of biological coupling. The wing surface is a waxy layer composed mainly of long chain hydrocarbon, tallate and fatty-acid alcohol, possesses multiple-dimensional rough microstructures including primary structure (wing vein grids), secondary structure (regularly arraying micrometric pillar gibbosities), and tertiary structure (nanocorrugations). The diameter, height, and spacing of pillar gibbosity are 3.0~10.2 μm, 3.4~9.2 μm, and 7.5~18.5 μm, respectively. Locust wing surface is of high adhesive superhydrophobicity (CA 150.1~157.3°). The complex wettability of the wing surface ascribes to coupling effect of material element (waxy crystal) and structural element (hierarchical rough microstructure). Locust wing can be potentially used as a biomimetic template for design of special functional surface. This work may bring insights for preparation of micro-controllable superhydrophobic surface and no-loss microfluidic channels.

A Comparative Study on the Wettability between Butterfly and Locust Wing Surface

The microstructure, hydrophobicity and chemical composition of the butterfly and locust wing surfaces were investigated by a scanning electron microscope (SEM), a contact angle meter and a Fourier transform infrared spectrometer (FT-IR). The hydrophobicity models were established on the basis of the Cassie equation. The wetting mechanism was comparatively discussed from the perspective of biological coupling. The butterfly and the locust wing surfaces are composed of naturally hydrophobic materials, but exhibit different complex wettability. The butterfly wing surface is of low adhesion (sliding angle 1~3°) and superhydrophobicity (contact angle 151.6~156.9°), while the locust wing surface is of extremely high adhesion (sliding angle>180°) and superhydrophobicity (contact angle 155.8~157.3°). The complex wettability of the wing surfaces ascribes to the coupling effect of hydrophobic material and rough structure. The butterfly and locust wings can be used as bio-templates for design and preparation of biomimetic functional surface, intelligent interfacial material and no-loss microfluidic transport channels.

Locust wing stretch receptor adaptation and recovery from adaptation

Adaptation of action potential frequency is a common feature of neurons from various parts of the nervous system. Adaptation is thought to contribute to information coding, integration, input filtering and saving of metabolic resources. Despite inten sive investigation, the kinetics of adaptation and recovery from adaptation are not fully described. The locust forewing stretch receptor (fSR) was used to investigate the kinetics of adaptation and recovery from adaptation in response to wing elevation. We have found that adaptation can be well described by a sum of two exponential decays with time constants 5.04 ± 0.6 s and 24.86 ± 2.45 s. The dependence of recovery on adaptation time was biphasic in 70% of the fSRs investigated. In these fSRs, the break point (10.54 ± 1.09 s) separates the initial linear phase from the following exponential one. These findings suggest that at least two mechanisms with different kinetics are involved in the adaptation of locust wing stretch receptor.

Details of Insect Wing Design and Deformation Enhance Aerodynamic Function and Flight Efficiency

Insect wings are complex structures that deform dramatically in flight. We analyzed the aerodynamic consequences of wing deformation in locusts using a three-dimensional computational fluid dynamics simulation based on detailed wing kinematics. We validated the simulation against smoke visualizations and digital particle image velocimetry on real locusts. We then used the validated model to explore the effects of wing topography and deformation, first by removing camber while keeping the same time-varying twist distribution, and second by removing camber and spanwise twist. The full-fidelity model achieved greater power economy than the uncambered model, which performed better than the untwisted model, showing that the details of insect wing topography and deformation are important aerodynamically. Such details are likely to be important in engineering applications of flapping flight.

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Skėrio sparno vyrio tempimo receptoriaus atsako adaptacija esant dinaminiam režimui

* Corresponding author: E-mail: osvaldas.ruksenas@gf.vu.lt Locust wing stretch receptor is known to exhibit fi ring frequency adaptation when the forewing is lift ed to a constant position. However, during fl ight, the wing periodically moves and the receptor’s response properties are in this dynamic mode unknown. We recorded extracellularly the response from the Locusta migratoria forewing stretch receptor while the wing was periodically lift ed and found that the adaptation of the stretch receptor is expressed in a dynamic mode as well; however, this adaptation is weaker than in the static mode.

Identification of the neurotransmitters involved in modulation of transmitter release from the central terminals of the locust wing hinge stretch receptor

The flight motor system of the locust represents a model preparation for the investigation of neuromodulation. At the wing hinges are stretch receptors important in generating and controlling the flight motor pattern. The forewing stretch receptor (fSR) makes direct cholinergic synapses with depressor motor neurons (MN) controlling that wing, including the first basalar MN (BA1). The fSR/BA1 synapse is modulated by muscarinic cholinergic receptors located on gamma-aminobutyric acid (GABA)-ergic interneurons (Judge and Leitch [1999a] J. Comp. Neurol. 407:103-114; Judge and Leitch [1999b] J. Neurobiol. 40:420-431). However, electrophysiology has shown that fSR/BA is also modulated by biogenic amines (Leitch et al. [2003] J. Comp. Neurol. 462:55-70). We have used electron microscopic immunocytochemistry (ICC) to identify the neurotransmitters in neurons presynaptic to the fSR and to determine the relative proportion of these different classes of modulatory inputs. Approximately 55% of all inputs to the fSR are glutamate-IR, indicating that glutamatergic neurons may also play an important role in presynaptically modulating the fSR terminals. Anti-GABA ICC confirmed that over 40% of inputs to the fSR are GABA-IR (Judge and Leitch [1999a] J. Comp. Neurol. 407:103-114). Labelling sections with an antioctopamine antibody revealed neurons containing distinctive large, electron-dense granules, which could reliably be used to identify them. Aminergic neurons that modulate the synapse may have very few morphologically recognizable synaptic outputs. Although putative octopaminergic processes were found in close contact to horseradish peroxidase-filled fSR profiles, no morphologically recognizable synaptic inputs to the fSR were evident. Collectively, these data suggest that most inputs to the fSR are from either glutamatergic or GABAergic neurons.

The contribution of surface waxes to pre-penetration growth of an entomopathogenic fungus on host cuticle

A locust wing bioassay, that allowed an entomopathogenic fungus to be removed from host cuticle before penetration, was used to investigate the role of surface lipids and waxes in pre-penetration growth of the specific locust pathogen Metarhizium anisopliae var. acridum. SEM and atomic force electron microscopy showed the impact of the fungus on the architecture of the cuticle surface. Although the fungus can germinate on authentic alkanes as the sole carbon source, only low levels of germination occurred on crude, non-polar wing cuticle extracts, containing a mixture of long-chain n-alkanes and other waxes (identified in particular by gas chromatography and mass spectroscopy). The fungus removed a large proportion of non-polar and polar components during pre-penetration growth on the wing. Polar crude extracts from Schistocerca gregaria hindwings, which contained fatty acids, fatty acid esters, glucose, amino acids and peptides, were strong promoters of germination, and poor germination was observed on a locust hindwing from which the extract had been taken. Thus simple polar compounds, also present on the surface, may be required to stimulate germination before the fungus can make use of a complex mixture of non-polar lipids.

The locust tegula: kinematic parameters and activity pattern during the wing stroke.

The tegula is a complex, knob-shaped sense organ associated with the base of the locust wing. Despite a detailed knowledge of its role in flight motor control, little is known about the relationship between the stroke parameters of the wing, movement of the tegula organ and the pattern of tegula activity. In this study, therefore, the kinematic parameters of the fore- and hindwings were investigated with respect to the tegula activity pattern during tethered flight. The following results were obtained. (i) The tegula moves through a complex three-dimensional trajectory during the wing stroke, involving inclination and rotation about its longitudinal axis. (ii) The kinematic parameters of tegula movement are phase-locked to the wing stroke and vary in conjunction with wing stroke parameters such as amplitude and cycle period. (iii) In accordance with these phase-locked kinematics, both the onset of tegula activity with respect to the downstroke (latency) and the discharge of the organ (burst duration and amplitude) vary in conjunction with downstroke movement and cycle period, resulting in an (almost) constant phase of tegula activation during the stroke cycle. (iv) The pattern of tegula activity during flight is largely independent of stroke amplitude. (v) The latency, burst duration and amplitude of tegula activity are strongly related to the angular velocity of the wing during the downstroke, with latency reaching a steady minimum value at higher angular velocities. The data suggest that the tegula encodes the timing and velocity of the downstroke and that it may be involved in the control of the stroke's angular velocity.

GABA immunoreactivity in processes presynaptic to the locust wing stretch receptor neuron

GABA immunoreactivity in processes presynaptic to the locust wing stretch receptor neuron

GABA immunoreactivity in processes presynaptic to the locust wing stretch receptor neuron

Studies on the locust Locusta migratoria (Leitch et al. [1998] Soc. Neurosci. Abstr. 624.10) suggest that gamma-aminobutyric acid (GABA)ergic interneurons, activated via muscarinic receptors, may be involved in modulation of transmitter release at synapses between the forewing stretch receptor (fSR) and wing depressor motoneurons. To help elucidate the role GABAergic interneurons may play in modulation of transmitter release from fSR terminals, the proportion and distribution of GABA-immunoreactive (GABA-IR) inputs to the fSR were analysed using double-labelling (horseradish peroxidase and GABA immunocytochemistry) and electron microscopy. Forty-three percent of synaptic inputs to the fSR were from GABA-IR profiles, the majority of which were located on lateral branches. The highest proportion (57%) of inputs to the fSR, however, were from non-IR processes containing either clear spherical vesicles or mixed clear and dense-cored vesicles. Outputs from the fSR to GABA-IR profiles were also found, although their number was relatively low (7%). Networks were identified in which both the fSR and its non-IR postsynaptic partner received input from the same GABA-IR neuron. Such an arrangement would allow both pre- and postsynaptic inhibition of fSR afferent outputs, for example at fSR/motoneuron synapses. These observations demonstrate that the fSR does receive presynaptic inputs from GABA-IR neurons, thus providing morphological support for pharmacological and electrophysiological findings that GABAergic neurons are involved in the presynaptic modulation of the fSR. Nevertheless, modulation at this synapse may be more intricate and involve other, as yet unidentified, neurotransmitters released from non GABA-IR presynaptic processes and also muscarinic receptors located on the fSR itself.

Role of Cuticle-Degrading Proteases in the Virulence ofMetarhiziumspp. for the Desert Locust,Schistocerca gregaria

The production of the subtilisin proteinase, PR1, and the trypsin-like enzyme, PR2, in liquid cultures of 19 isolates ofMetarhiziumspp. was investigated. PR1 activity was generally observed 72 h after inoculation whilst PR2 activity was detected in most strains 48 h after inoculation. PR1 was partially purified from each isolate ofMetarhiziumspp. The ability of this enzyme from each isolate to degrade different types of insect cuticle was investigated. The cuticle types used wereManduca sextapupal cuticle, adult desert locust (Schistocerca gregaria) wing cuticle, abdominal cuticle, and pharate adult locust abdominal cuticle. These cuticle types differ in their protein composition and degree of sclerotization. PR1 hydrolyzed the locust cuticle to different degrees. The data suggest a hierarchy for the susceptibility to hydrolysis in the order pharate adult abdominal > adult abdominal > wing. There was no significant correlation between the ability of the enzymes to degrade any of the cuticle types and median lethal time of the isolates against the desert locust. However, a correlation was found between the ability of enzymes to hydrolyze different locust cuticles. Such correlations were not apparent to the same extent betweenM. sextacuticle and the locust cuticles. These results are discussed in terms of a possible contribution of PR1 to host specificity.

Modulation of transmitter release from the terminals of the locust wing stretch receptor neuron by muscarinic antagonists

The forewing stretch receptor (SR) neuron makes monosynaptic connections with wing depressor motoneurons; in this article the pharmacology of its output onto the first basalar motoneuron (BA1) has been investigated. The SR, like other insect afferents that have been studied so far, appears to be cholinergic; transmission was suppressed reversibly by the nicotinic antagonist gallamine (10(-4) M) and irreversibly by alpha-bungarotoxin (10(-6) M). The choline reuptake blocker hemicholinium-3 (10(-4) M) also caused a reversible reduction in the amplitude of SR excitatory postsynaptic potentials (EPSPs) recorded in BA1. The receptor subtype nonselective muscarinic antagonists atropine (10(-4) M), scopolamine (10(-4) M), and quinuclidinyl benzilate (10(-5) M), unlike nicotinic antagonists, caused an augmentation in EPSP amplitude. This effect does not appear to be caused by an increase in sensitivity of the motoneuron to acetylcholine (ACh), since atropine produced a marked reduction rather than an increase in the amplitude of responses to ACh pressure applied to the soma of BA1. Scopolamine only caused a modest reduction in the amplitude of ACh somatic responses. The simplest explanation for these observations is that muscarinic antagonists bring about an increase in EPSP amplitude by blockade of presynaptic autoreceptors that normally down-regulate the release of ACh from SR terminals. The effects of muscarinic receptor subtype-selective antagonists indicate that presynaptic receptors in this preparation may have a pharmacological profile more similar to that of vertebrate M2 receptors than to that of M1 or M3 subtypes. The functional significance of autoreceptors in this preparation are discussed.