Search

After overexposure to loud music, we experience a decrease in our ability to hear (robustness), which usually recovers (resilience). Here, we exploited the amenable auditory system of the desert locust, Schistocerca gregaria , to measure how robustness and resilience depend on age. We found that gene expression changes are dominated by age as opposed to noise exposure. We measured sound-evoked nerve activity for young and aged locusts directly, after 24 hours and 48 hours after noise exposure. We found that both young and aged locusts recovered their auditory nerve function over 48 hours. We also measured the sound-evoked transduction current in individual auditory neurons, and although the transduction current magnitude recovered in the young locusts after noise exposure, it failed to recover in the aged locusts. A plastic mechanism compensates for the decreased transduction current in aged locusts. We suggest key genes upregulated in young noise-exposed locusts that mediate robustness to noise exposure and find potential candidates responsible for compensatory mechanisms in the auditory neurons of aged noise-exposed locusts. [ABSTRACT FROM AUTHOR]

Insect cuticle can reach a wide range of material properties, which is thought to be the result of adaptations to applied mechanical stresses. Biomechanical mechanisms behind these property variations remain largely unknown. To fill this gap, here we performed a comprehensive study by simultaneous investigation of the microstructure, sclerotization and the elasticity modulus of the specialized cuticle of the femora of desert locusts. We hypothesized that, considering their different roles in jumping, the femora of fore-, mid- and hind legs should be equipped with cuticles that have different mechanical properties. Surprisingly, our results showed that the hind femur, which typically bears higher stresses, has a lower elasticity modulus than the fore and mid femora in the longitudinal direction. This is likely due to the lower sclerotization and different microstructure of the hind femur cuticle. This allows for some deformability in the femur wall and is likely to reduce the risk of mechanical failure. In contrast to both other femora, the hind femur is also equipped with a set of sclerotized ridges that are likely to provide it with the required stiffness to withstand the mechanical loads during walking and jumping. This paper is one of only a few comprehensive studies on insect cuticle, which advances the current understanding of the relationship between the structure, material property and function in this complex biological composite. Insect cuticle is a biological composite with strong anisotropy and wide ranges of material properties. Using an example of the femoral cuticle of desert locusts, we measured the elasticity modulus, microstructure and sclerotization level of the cuticle. Our results show that, although the hind femur withstands most of the stress during locomotion, it has a lower elasticity modulus than the fore and mid femora. This is likely to be a functional adaption to jumping, in order to allow small deformations of the femur wall and reduce the risk of material failure. Our results deepen the current understanding of the structure-material-function relationship in the complex insect cuticle. [Display omitted] [ABSTRACT FROM AUTHOR]

• Locusts are an old concern and swarms need to be controlled but they travel a lot. • A model of desert locust swarm migration was developed based on real observations. • With the possibility of flying upwind, our model better reproduces the migrations. • Food intake must be considered to regulate movement dynamics. To be efficient, locust swarm control must focus on the place where eggs are laid and hopper bands may appear. But swarms travel a lot and among all the places likely to host them, there is a need to predict to which exactly they will fly. It is then essential to consider movement dynamics to anticipate any displacement that may lead to a further reproduction of locust swarms. Swarms mostly fly downwind and sometimes upwind. We designed an agent-based model to explore swarm displacements depending on the direction of the wind and the possibility for the swarms to realise upwind flights. A primary objective was to assess how upwind flights can improve the replication – and prediction – of documented migratory paths. We looked at the effects of using upwind flight on the swarm ratio arriving in expected (i.e. historically known) areas. Our simulations clearly showed that using upwind flight helped for a better replication of Schistocerca gregaria migrations than not using upwind flight. Not using upwind flight reduced swarm dispersion and reduced the range of migrations. Hence, prevailing winds alone cannot explain locust swarm migrations. Food intake must also be considered to regulate movement dynamics and vegetated areas seem to be more attractive to locusts than expected. Our simulations did not perfectly reproduce the general patterns of migrations in some scenarios, but this invites further investigations and the use of other types of field data to calibrate the model. Nonetheless, our results highlighted the importance of upwind flight and showed the major role of wind and temperature on swarm displacement. [ABSTRACT FROM AUTHOR]

A striking characteristic of insect cuticle is the wide range of its material property values, with respect to stiffness, strength and toughness. The elastic modulus of cuticle, for instance, ranges over seven orders of magnitude in different structures and different species. Previous studies suggested that this characteristic is influenced by the microstructure and sclerotization of cuticle. However, the relative role of the two factors in determining the material properties of cuticle is unknown. Here we used a combination of scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and nanoindentation, to investigate the effect of microstructure and sclerotization on the elastic modulus of tibiae of desert locusts. Our results showed that tibial cuticle is an anisotropic material with the highest elastic modulus along the tibial axis. This is likely because majority of the fibers in the cuticle are oriented along this axis. We also found that the hind tibia has a significantly higher elastic modulus, compared with the fore and mid tibiae. This is likely due to the higher sclerotization level of the hind tibia cuticle, and seems to be an adaptation to the locust locomotion by jumping, in which axial loads in the hind tibiae may reach several times the insect body weight. Our results suggest that while sclerotization determines the difference between the elastic moduli of the tibiae, anisotropic properties of each tibia is controlled by the specific fiber orientation. Our study provides one of only a few comprehensive investigations on insect cuticle, and helps to better understand the structure-material-function relationship in this complex biological composite. Insect cuticle is a biological composite with strong anisotropy and wide ranges of material properties. Using an example of the tibial cuticle of desert locusts, we examined the role of two influential factors on the elastic modulus of cuticle: microstructure and sclerotization. Our results suggested the strong influence of sclerotization on the variation of the elastic modulus among fore, mid and hind tibiae, and that of the microstructure on the anisotropy of each tibia. Our results deepens the current understanding of the structure-material-function relationship in complex insect cuticle. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Resilin is an extremely efficient elastic protein found in the moving parts of insects. Despite many years of resilin research, we are still only just starting to understand its diversity, native structures, and functions. Understanding differences in resilin structure and diversity could lead to the development of bioinspired elastic polymers, with broad applications in materials science. Here, to better understand resilin structure, we offer a novel methodology for identifying resilin-rich regions of the insect cuticle using non-invasive Raman spectroscopy in a model species, the desert locust (Schistocerca gregaria). The Raman spectrum of the resilin-rich semilunar process of the hind leg was compared with that of nearby low-resilin cuticle, and reference spectra and peaks assigned for these two regions. The main peaks of resilin include two bands associated with tyrosine at 955–962 and 1141–1203 cm−1 and a strong peak at 1615 cm−1, attributed to the α-Amide I group associated with dityrosine. We also found the chitin skeletal modes at ~485–567 cm−1 to be significant contributors to spectra variance between the groups. Raman spectra were also compared to results obtained by fluorescence spectroscopy, as a control technique. Principal component analysis of these resulting spectra revealed differences in the light-scattering properties of resilin-rich and resilin-poor cuticular regions, which may relate to differences in native protein structure and relative abundance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tympanal displacements at the foot of the styliform body increase immediately after noise-exposure in adult locusts. • Tympanal displacements decrease 24hrs post noise-exposure, before recovering to normal levels after 48hrs. • Tympanal displacements decrease with age between 10 and 34 days post-final moult. • Decreases in displacement with age are not compounded by noise-exposure. Insect cuticle is an evolutionary-malleable exoskeleton that has specialised for various functions. Insects that detect the pressure component of sound bear specialised sound-capturing tympani evolved from cuticular thinning. Whilst the outer layer of insect cuticle is composed of non-living chitin, its mechanical properties change during development and aging. Here, we measured the displacements of the tympanum of the desert Locust, Schistocerca gregaria , to understand biomechanical changes as a function of age and noise-exposure. We found that the stiffness of the tympanum decreases within 12 h of noise-exposure and increases as a function of age, independent of noise-exposure. Noise-induced changes were dynamic with an increased tympanum displacement to sound within 12 h post noise-exposure. Within 24 h, however, the tone-evoked displacement of the tympanum decreased below that of control Locusts. After 48 h, the tone-evoked displacement of the tympanum was not significantly different to Locusts not exposed to noise. Tympanal displacements reduced predictably with age and repeatably noise-exposed Locusts (every three days) did not differ from their non-noise-exposed counterparts. Changes in the biomechanics of the tympanum may explain an age-dependent decrease in auditory detection in tympanal insects. [ABSTRACT FROM AUTHOR]

• MASP-1 accelerated the lysis of whole blood clots assessed by thrombelastometry. • Inhibition of endogenous MASP-1 prolonged plasma clot lysis in a turbidimetric lysis assay. • In other experimental settings antifibrinolytic effects of MASP-1 were observed. • MASP-1 has complex, mostly promoting effects on fibrinolysis with high inter-individual variation. The lectin pathway serine protease mannan-binding lectin-associated serine protease 1 (MASP-1) has been demonstrated to be a major link between complement and coagulation, yet little is known about its interactions with the fibrinolytic system. The aim of this work was to assess the effects of MASP-1 on fibrin clot lysis in different experimental settings. Rotational thrombelastometry was used to evaluate the effect of MASP-1 on the lysis of clots formed in whole blood under static conditions. Whole blood clots were also formed in the presence and absence of MASP-1 under flow conditions in the Chandler loop and their lysis was analysed separately by fluorescence release of incorporated labelled fibrin. Real-time observation by laser scanning confocal microscopy was used to investigate the lysis of plasma clots where MASP-1 was present either during clot formation or lysis. Cleavage of tPA or plasminogen by MASP-1 was analysed by gel electrophoresis. We performed a turbidimetric clot lysis assay in the presence and absence of the MASP-1 inhibitor SGMI-1 (Schistocerca gregaria protease inhibitor (SGPI)-based MASP inhibitor-1) to evaluate the effect of endogenous MASP-1 in normal plasma and plasma samples from sepsis patients. In the thrombelastometric experiments, where MASP-1 was present during the entire clotting and lysis process, MASP-1 had a significant profibrinolytic effect and accelerated clot lysis. When clots were formed in the presence of MASP-1 under flow in the Chandler loop, the effects on fibrinolysis were heterogenous with impaired fibrinolysis in some individuals (n = 5) and no (n = 3) or even the opposite effect (n = 2) in others. In plasma clot lysis observed by confocal microscopy, lysis was prolonged when MASP-1 was added to the lysis solution, yet there was no difference in lysis time when MASP-1 was present during clot formation. When MASP-1 was incubated with tPA or plasminogen, respectively, cleavage of single-chain tPA into two-chain tPA and a slight reduction of plasminogen were observed. SGMI-1 significantly prolonged clot lysis in the turbidimetric clot lysis assay suggesting that MASP-1 accelerated lysis in plasma samples. MASP-1 is able to alter the susceptibility of blood clots to the fibrinolytic system. MASP-1 has complex, mostly promoting effects on fibrinolysis with high inter-individual variation. Interactions of MASP-1 with the fibrinolytic system may be relevant in the development and therapy of cardiovascular and thrombotic diseases. [ABSTRACT FROM AUTHOR]

• Females kept in isolation did not easily change progeny characteristics upon crowding. • No evidence was obtained to show presence of a 4-day period of sensitivity to crowding. • No evidence was obtained to show that the antennae perceived crowding stimuli. • No evidence was obtained to show the importance of light in progeny phase changes. • These results contradicted the conclusions reported in previous studies. The desert locust shows conspicuous phase polyphenism of various traits in response to crowding conditions. Gregarious females lay larger eggs that produce black hatchlings, whereas solitarious females lay smaller eggs that produce green hatchlings. Previous studies have shown that changes in egg size and hatchling body color occurred easily in the laboratory upon exposure of the female parent to crowding or isolation for as few as 2 days. Based on these observations, these studies concluded that female adults perceive crowding stimuli with their antennae and require light for perception of the stimuli, with contact chemicals present on the integument of sexually mature males that are responsible for the crowding effect. We undertook this study to identify the chemical structures of the reported contact substances, which remain unknown to date. However, we could not reproduce the main results reported in the aforementioned studies and found that egg size and hatchling body color did not alter easily, even after crowding or isolation of the female parent for 2 days or longer. We were not able to observe a change in the progeny crowding characteristics by stimulating the antennae of female adults through either physical contact with male adults or using hexane extracts of their body surfaces. Similarly, the importance of light for gregarization or solitarization was also ruled out. These results indicate that some of the conclusions of previous studies should be reconsidered. [ABSTRACT FROM AUTHOR]

Highlights • The subesophageal ganglion (SEG) encompasses some 300 descending interneurons. • In vitro the SEG does not spontaneously induce rhythmic output in leg motor neurons. • The SEG modulates the bilateral coupling among the leg central pattern generators. • The role of the SEG in insect locomotion is discussed. Abstract Higher motor centers and central pattern generators (CPGs) interact in the control of coordinated leg movements during locomotion throughout the animal kingdom. The subesophageal ganglion (SEG) is one of the insect head ganglia reported to have a role in the control of walking behavior. Here we explored the functional relations between the SEG and the thoracic leg CPGs in the desert locust. Backfill staining revealed about 300 SEG descending interneurons (DINs) altogether. Recordings from an in-vitro isolated chain of thoracic ganglia, with intact or severed connections to the SEG, during pharmacological activation were used to determine how the SEG affects the centrally generated motor output to the legs. The SEG was demonstrated to both activate leg CPGs and synchronize their bilateral activity. The role of the SEG in insect locomotion is discussed in light of these findings. [ABSTRACT FROM AUTHOR]

• New information on locust hatching timing and location is produced. • The information can be used to mitigate severe impact of locust plagues in eastern Africa. • A fuzzy logic modeling framework is developed suitable for ecological modeling in data scarce regions. Desert locust (Schistocerca gregaria) plagues threaten agricultural production, food security and the environment across Africa, the Middle East, and Southwest Asia. Control methods targeting adult desert locusts present significant challenges and financial costs. Recognizing this, we developed a ground-breaking fuzzy set Mamdani type inference model that provides an innovative solution for early warning alerts. The model aids in predicting the juvenile stages of locust development, thereby preventing wide-scale locust swarming and mitigating its extensive damages and socioeconomic costs. The novelty of our approach lies in our unique application of environmental variables relevant for locust breeding to estimate the timing and location of desert locust hatching. Additionally, we improved the algorithmic handling of these variables, with localized desert locust bands data used as a proxy for hatching timing with a temporal offset of 35 days. The model's boundary conditions were determined using a training area in Sudan, where comprehensive ground data was available. This rule set was subsequently applied to Turkana County in Kenya, a data-scarce region, demonstrating the model's applicability and success in different contexts. The model's accuracy, assessed by data from the Sudan training site, demonstrated a remarkable score of 82% for true predictions. Furthermore, the model correctly identified the months of highest hatching probabilities in Turkana during 2020, demonstrating its real-world effectiveness and practical value. A correlation analysis affirmed that hatching was associated with increases in chlorophyll levels and precipitation accumulations. Our study marks a significant advancement in predicting the timing of hatching using fuzzy logic in data-scarce environments. By operationalizing more targeted early responses to desert locust infestations, our model facilitates more effective locust control. This study stands as an important contribution to locust management strategies, with substantial implications for agricultural production and food security in affected regions. [ABSTRACT FROM AUTHOR]

Corazonin (Crz) is a neuropeptide that controls phase-dependent body color polyphenism in locusts. The Crz signaling pathway is responsible for the development of gregarious black patterns in nymphs and determination of the morphometric ratio F/C ( F  = hind femur length, C  = maximum head width) in adults. However, little information is available regarding the mediator and effector proteins regulated by Crz. In this study, we identified a novel transcription factor, Loct, which functions downstream of Crz in Schistocerca gregaria and Locusta migratoria . In S. gregaria , we detected a variant of Loct lacking the N-terminal region. Protein–protein interaction assays showed that both the long and short Loct variants formed a complex with themselves. LOCT knockdown in gregarious nymphs reduced the intensity of their black patterning, but did not affect F/C ratios in adults. LOCT was exclusively expressed in the integument of gregarious nymphs, suggesting that Loct is involved in melanin production. In addition, we found that the melanization-associated protein Yellow ( YEL ) and the albino-related takeout protein ( ALTO ) are expressed in the integument and function downstream of Crz. However, Crz injection failed to influence LOCT , YEL , and ALTO expression. Therefore, additional factors probably cooperate with Crz to induce these genes. The gene expression profiles of YEL and ALTO in LOCT -knockdown nymphs suggest that Loct does not directly control the transcription of YEL or ALTO. In summary, we present a working model of the Crz pathway, which is active in crowded S. gregaria nymphs. [ABSTRACT FROM AUTHOR]

Locusts show body color polyphenism that is considered to be an adaptation to various biotic and abiotic environmental changes. In Schistocerca gregaria, wild-type late-instar nymphs growing under crowded conditions (gregarious form) develop yellow and black body coloration, whereas they assume various body colors under isolated conditions (solitarious form). Black and green body colorations are induced by the neuropeptide corazonin (Crz) and juvenile hormone (JH), respectively. To characterize the molecular mechanisms controlling body color polyphenism, we investigated factors influencing body coloration in S. gregaria . We report here that yellow body coloration in the last nymphal instar is caused by the yellow protein of the takeout family (YPT) in this locust. YPT transcription was enhanced under high-temperature conditions during which the nymphs turned bright yellow and had little black patterning. RNAi-mediated YPT knockdown suppressed the appearance of yellow individuals and yellow staining in the exuviae. In albino nymphs, injection of JH induced yellow and green coloration and enhanced the YPT expression levels in both yellow and green individuals. YPT knockdown also suppressed yellow staining in the exuviae but did not prevent the appearance of yellow individuals. Therefore, another factor or pigment may contribute to the observed yellow body color. Injection of Crz into wild-type nymphs caused darkening and suppressed yellowing and YPT expression at high temperatures. Thus, Crz signaling could inhibit yellowing by suppressing YPT expression. Rearing cup substrate color significantly influenced YPT expression in albino nymphs both under isolated and crowded conditions. In contrast, substrate color affected YPT expression in wild-type nymphs only under isolated conditions. From these results, we conclude that YPT is an important factor in the control of body color polyphenism in S. gregaria , and its expression is influenced by temperature, JH, Crz, and substrate color of the growing environment. [ABSTRACT FROM AUTHOR]

Understanding Desert Locust population dynamics is a prerequisite for the implementation of a preventive management strategy against its invasions. The present study aims to describe these dynamics through conducting probability analyses of locust presence in time and space. Historical data from field surveys conducted by management teams in Mauritania and Morocco for the period 1988–2015 were used. Temporal smoothing and spatio-temporal extrapolations were performed on a monthly basis. We established monthly probability maps of locust observation following two scenarios: recession period (mainly solitarious phase) and invasion period (mainly gregarious phase). Also, observation probability maps of hoppers or mature adults allowed the identification of seasonal breeding areas. The methodology highlights the potentially favourable areas to be monitored every year. It also highlights the lack of information in some areas of the two countries. We observed that the seasonal survey process during recession periods follow the seasonal pattern of gregarious invasions. We argue that this is the result of climatic conditions related to the oscillation of the intertropical convergence zone. However, we advise that these similar yearly cycles should not hinder surveys in recession periods to be conducted in places not receiving swarms during invasion periods. Nevertheless, we conclude that these maps should be helpful for planning the preparation of survey teams in the field. This will reduce survey operation costs and decrease invasion risks. [ABSTRACT FROM AUTHOR]

It is important to design insecticides having both low drug resistance and less undesirable toxicity for desert locust control. Specific GPCRs of Schistocerca gregaria , especially β-adrenergic-like octopamine receptor (SgOctβR), can be considered as its potential effective insecticide targets. However, either the unavailability of SgOctβR’s structure or the inadequate capability of its sequence lead the development of insecticide for Schistocerca gregaria meets its plateau. To relax this difficulty, this paper develops a promising progressive structure simulation from SgOctβR’s sequence, to its predicted structure of SgOctβR in vacuum, to its conformation as well as its complex with endogenous ligand octopamine in a solvent-membrane system. The combined approach of multiple sequence alignment, static structural characterization, and dynamic process of conformational change during binding octopamine reveal three important aspects. The first one is the characterization of SgOctβR’s active pocket, including the attending secondary structure elements, its hydrophobic residues and nonpolar surface. The second one is the interaction with octopamine, especially the involved hydrogen bonds and an aromatic stacking of pi–pi interactions. The third one is the potential binding sites, including six highly conserved residues and one highly variable residue for locust insecticide design. This work is definitely helpful for the further structure-based drug design for efficient and eco-friendly insecticides, as well as site-directed mutagenesis biochemical research of SgOctβR. [ABSTRACT FROM AUTHOR]

Albinism is caused by mutations in the genes involved in melanin production. Albino nymphs of Locusta migratoria and Schistocerca gregaria reared under crowded conditions are uniformly creamy-white in color. However, nothing is known about the molecular mechanisms underlying this phenomenon in locusts. The albino strain of L. migratoria is known to lack the dark-color-inducing neuropeptide corazonin (Crz). In this study, we report that this albino strain has a 10-base-pair deletion in the gene LmCRZ , which encodes Crz. This mutation was found to cause a frame-shift, resulting in a null mutation in Crz. On the other hand, the albino strain of S . gregaria is known to have an intact Crz. This strain was found to possess a single-nucleotide substitution in the middle of the Crz receptor-encoding gene, SgCRZR , which caused a nonsense mutation, resulting in a truncated receptor. Silencing of SgCRZR in wild-type S . gregaria nymphs greatly reduced the area and intensity of their black patterning, suggesting that the functional defect of SgCRZR likely causes the albinism. The expression level of SgCRZR in the albino S . gregaria was comparable to that in the wild type. Unlike the wild type, the albino strain of this locust did not show a phase-dependent shift in a morphometric trait controlled by Crz. From these results, we conclude that the mutations in LmCRZ and SgCRZR are responsible for the albinism in L. migratoria and S . gregaria , respectively, indicating that the two types of albinism are caused by different genetic defects in the same Crz signaling pathway. [ABSTRACT FROM AUTHOR]

Chitosan (CS) has received great attention in tissue engineering, especially in wound healing acceleration. In this study, chitin was isolated from desert locust ( Schistocerca gregaria ) and shrimp (Penaeus monodon) then deacetylated to chitosan. Then, chitosan was characterized by degree of deacetylation (DD), molecular weight (M.Wt), swelling index (SI), Fourier transform infrared (FTIR) and X ray diffraction (XRD). The chitosan was then casted into 2D scaffolds and was pictured using scanning electron microscope (SEM). In a comparative study, primary cell cultures of neonatal (1–2 day old) mice skin tissue, supplemented with 10% fetal calf serum, were seeded onto locust chitosan based scaffolds (LCSBS) and shrimp chitosan based scaffold (SCSBS). Their attachment percentage was determined after 1 h. The cell proliferation rate was tested for 5 days on LCSBS and SCSBS. Wound healing activity progress of LCSBS and SCSBS was tested in vivo using histopathology, and results revealed that seeded and unseeded LCSBS accelerated healing in contrast to SCSBS. The data demonstrated that LCSBS shows a high degree of biocompatibility in vivo. These results suggest that LCSBS is a potential substitute for the development of low cost implantable materials to accelerate wound healing. [ABSTRACT FROM AUTHOR]

Chymotrypsin-like elastases (CELAs) are pancreatic serine proteinases that digest dietary proteins. CELAs are typically expressed in multiple isoforms that can vary among different species. The human pancreas does not express CELA1 but secretes two CELA3 isoforms, CELA3A and CELA3B. The reasons for the CELA3 duplication and the substrate preferences of the duplicated isoforms are unclear. Here, we tested whether CELA3A and CELA3B evolved unique substrate specificities to compensate for the loss of CELA1. We constructed a phage library displaying variants of the substrate-like Schistocerca gregaria proteinase inhibitor 2 (SGPI-2) to select reversible high affinity inhibitors of human CELA3A, CELA3B, and porcine CELA1. Based on the reactive loop sequences of the phage display- selected inhibitors, we recombinantly expressed and purified 12 SGPI-2 variants and determined their binding affinities. Wefound that the primary specificity of CELA3A, CELA3B, and CELA1 was similar; all preferred aliphatic side chains at the socalled P1 position, the amino acid residue located directly N-terminal to the scissile peptide bond. P1 Met was an interesting exception that was preferred by CELA1 but weakly recognized by the CELA3 isoforms. The extended substrate specificity of CELA3A and CELA3B was comparable, whereas CELA1 exhibited unique interactions at several subsites. These observations indicated that the CELA1 and CELA3 paralogs have some different but also overlapping specificities and that the duplicated CELA3A and CELA3B isoforms did not evolve distinct substrate preferences. Thus, increased gene dosage rather than specificity divergence of the CELA3 isoforms may compensate for the loss of CELA1 digestive activity in the human pancreas. [ABSTRACT FROM AUTHOR]

The responsiveness towards orally delivered dsRNA and the potency of a subsequent environmental RNA interference (RNAi) response strongly differs between different insect species. While some species are very sensitive to dsRNA delivery through the diet, others are not. The underlying reasons for this may vary, but degradation of dsRNA by nucleases in the gut lumen is believed to play a crucial role. The Colorado potato beetle, Leptinotarsa decemlineata , is a voracious defoliator of potato crops worldwide, and is currently under investigation for novel control methods based on dsRNA treatments. Here we describe the identification and characterization of two nuclease genes exclusively expressed in the gut of this pest species. Removal of nuclease activity in adults increased the sensitivity towards dsRNA and resulted in improved protection of potato plants. A similar strategy in the desert locust, Schistocerca gregaria , for which we show a far more potent nuclease activity in the gut juice, did however not lead to an improvement of the RNAi response. Possible reasons for this are discussed. Taken together, the present data confirm a negative effect of nucleases in the gut on the environmental RNAi response, and further suggest that interfering with this activity is a strategy worth pursuing for improving RNAi efficacy in insect pest control applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crowded desert locusts produce larger eggs than isolated locusts. • Egg developmental rates were similar between small and large eggs. • The initial embryo sizes were similar. • After yolk absorption, large egg embryos became larger than small egg embryos. Phenotypic plasticity in body size is a product of modification of the developmental pathway. Although hatchlings of the desert locust, Schistocerca gregaria , show egg size-dependent plasticity in body size, it remains unclear how embryogenesis during egg development regulates final embryonic body size. To determine the developmental pathway causing body size variation at hatching, we examined egg and embryonic development at the early, middle, and late egg developmental stages in S. gregaria by comparing small and large eggs. Crowd-reared females produced larger eggs than isolated-reared females. The daily egg developmental rate was similar between small and large eggs: eggs dramatically absorbed external water after days 3 to 7 and nearly doubled the initial egg weight at the late stage of day 12. Morphological measurements of eggs and embryos at different days after oviposition revealed that large eggs were longer than small eggs throughout developmental stages. However, embryo length was similar between small and large eggs at the early stage (anatrepsis). Embryos begin to absorb yolk into their bodies after blastokinesis. The size of large-egg embryos increased significantly from the middle stage (katatrepsis) due to absorption of more yolk than small eggs. Egg length and embryo length were conspicuously larger in large eggs than in small eggs on day 12 of late katatrepsis. These results suggest that egg size did not influence the egg developmental rate and initial embryo size. Large eggs had more yolk and space, resulting in larger final embryos than small eggs. The amount of yolk and size of eggshells during katatrepsis could play a key role in determining hatchling body size in S. gregaria. [ABSTRACT FROM AUTHOR]

Most terrestrial animals are constrained by extreme heat conditions such as midday desert environments, while a few terrestrial ectothermic insects are active in such ecological niches. Sexually mature males of the desert locust (Schistocerca gregaria) in the Sahara Desert remain on the open ground, despite the ground temperatures exceeding their lethal limit, to form leks and to mate incoming gravid females during the daytime. Lekking male locusts apparently suffer from extreme heat stress and greatly fluctuating thermal conditions. The present study examined the thermoregulatory strategies of the lekking male S. gregaria. Our field observations showed that lekking males changed their body orientation toward the sun depending on the temperature and time of day. In the relatively cool morning, males basked by orienting perpendicular to the sun's rays, maximizing the area of body surface exposed to the sun's rays. In contrast, around midday, when the ground surface temperature exceeded lethal high temperatures, some males tended to shelter inside the plants or remain in the shade. However, the remainder stayed on the ground, stilted (i.e., extending their legs to raise their bodies off the hot ground) and oriented parallel to the sun's rays, which minimized radiative heating. Measurements of body temperature throughout the hot middle period of the day confirmed that the stilting posture prevented overheating. Their critical lethal body temperature was as high as 54.7 °C. In this lekking system, gravid females enter male leks by flying. These incoming females usually landed on open ground, whereupon nearby males immediately approached, mounted, and mated the female, implying that males with greater heat-tolerance can increase mating chance. These results suggest that behavioral thermoregulation and physiologically high heat tolerance of male desert locusts allows them to endure extreme thermal conditions for lekking. [Display omitted] • Thermoregulatory strategies of the lekking desert locust male were investigated. • Lekking males exhibited behavioral and physiological strategies to tolerate heat. • Stilting posture prevented overheating. • Desert locust males have one of the highest known thermal tolerances of the species of insects. [ABSTRACT FROM AUTHOR]

Identifying chemical odors rapidly and accurately is critical in a variety of fields. Due to the limited human sense of smell, much effort has been dedicated to the development of electronic sensing devices. Despite some recent progress, such devices are still no match for the capabilities of biological (animal) olfactory sensors, which are light, robust, versatile, and sensitive. Consequently, scientists are turning to a new approach: Bio-Hybrid sensors. These sensors combine animal biological sensors with electronic components to achieve maximum detection and classification while conveying a comprehensible signal to the end user. In this work, we created a bio-hybrid odor discriminator utilizing the desert locust's primary olfactory apparatus - its antennae, together with simple electroantennogram technology and artificial intelligence tools for signal analysis. Our discriminator is able to differentiate between at least eight pure odors and two mixtures of different odorants, independently of odorant concentration. With four orders of magnitude higher sensitivity than gas chromatography–mass spectrometry, it is able to detect the presence of less than 1 ng of volatile compounds and, compared to other bio-hybrid sensors available today, it can be easily operated by an unskilled individual. This study thus opens up the future for robust and simple bio-hybrid robotic sensing devices that can be widely deployed. [ABSTRACT FROM AUTHOR]

This paper investigates the consequences of the 2004 locust plague in Mali. We argue that in agricultural economies with a single harvest per year, this type of shock can affect households through two channels: first, a speculative/anticipatory effect that kicks in during the growing season, followed by a local crop failure effect after harvest. We document a substantial impact of the plague on crop price inflation before the harvest. Regarding health setbacks, children subject only to the speculative/anticipatory effect suffered as much as those exposed to the actual crop failure effect. The latter is more severe for children born in isolated areas. [ABSTRACT FROM AUTHOR]

Lysozymes are bacteriolytic peptides that are implicated in the insect nonspecific innate immune responses. In this study, a full-length cDNA encoding a c-type lysozyme from Schistocerca gregaria ( SgLys ) has been cloned and characterized from the fat body of immune-challenged 5 th instar. The deduced mature lysozyme is 119 amino acid residues in length, has a calculated molecular mass of 13.4 kDa and an isoelectric point (Ip) of 9.2. Sg Lys showed high identities with other insect lysozymes, ranging from 41.5% to 93.3% by BLASTp search in NCBI. Eukaryotic in vitro expression of the SgLys ORF (r Sg Lys) with an apparent molecular mass of ∼16 kDa under SDS-PAGE is close to the calculated molecular weight of the full-length protein. r Sg Lys displayed growth inhibitory activity against Gram-negative and Gram-positive bacteria. 3D structure modeling of Sg Lys, based on comparison with that of silkworm lysozyme, and sequence comparison with the helix-loop-helix (α-hairpin) structure of hen egg white lysozyme (HEWL) were employed to interpret the antibacterial potencies. Phylogenetic alignments indicate that Sg Lys aligns well with insect c-type lysozymes that expressed principally in fat body and hemocytes and whose role has been defined as immune-related. Western blot analysis showed that Sg Lys expression was highest at 6–12 h post-bacterial challenge and subsequently decreased with time. Transcriptional profiles of SgLys were determined by semi-quantitative RT-PCR analysis. SgLys transcript was upregulated at the highest level in fat body, hemocytes, salivary gland, thoracic muscles, and epidermal tissue. It was expressed in all developmental stages from egg to adult. These data indicate that Sg Lys is a predominant acute-phase protein that is expressed and upregulated upon immune challenge. [ABSTRACT FROM AUTHOR]

The arthropod-specific hormone family of ecdysteroids plays an important role in regulating diverse physiological processes, such as moulting and metamorphosis, reproduction, diapause and innate immunity. Ecdysteroids mediate their response by binding to a heterodimeric complex of two nuclear receptors, the ecdysone receptor (EcR) and the retinoid-X-receptor/ultraspiracle (RXR/USP). In this study we investigated the role of EcR and RXR in metamorphosis and development of the desert locust, Schistocerca gregaria . The desert locust is a voracious, phytophagous, swarming pest that can ruin crops and harvests in some of the world's poorest countries. A profound knowledge of the ecdysteroid signalling pathway can be used in the development of more target-specific insecticides to combat this harmful plague insect. Here we report an in-depth profiling study of the transcript levels of EcR and RXR , as well as its downstream response genes, in different tissues isolated throughout the last larval stage of a hemimetabolous insect, showing a clear correlation with circulating ecdysteroid titres. Using RNA interference (RNAi), the role of SgEcR/SgRXR in moulting and development was investigated. We have proven the importance of the receptor components for successful moulting of locust nymphs into the adult stage. Some SgEcR / SgRXR knockdown females were arrested in the last larval stage, and 65 % of them initiated vitellogenesis and oocyte maturation, which normally only occurs in adults. Furthermore, our results clearly indicate that at the peak of ecdysteroid synthesis, on day six of the last larval stage, knockdown of SgEcR / SgRXR is affecting the transcript levels of the Halloween genes, Spook , Shadow and Shade . [ABSTRACT FROM AUTHOR]

In insects that lay eggs in large clutches, yolk accumulation in each of the many ovarioles is restricted to the basal (terminal) oocyte, the one closest to the lateral oviduct. All succeeding (subterminal) oocytes remain small until the terminal oocytes finished their development and were ovulated into the oviduct. The major step regulating yolk uptake by terminal oocytes is the formation of gaps between cells of the follicle layer, a process termed patency. In the migratory as well as in the desert locust, patency is induced by a Patency Inducing Factor (PIF) produced by the lateral oviducts. PIF is secreted in all regions of the lateral oviducts and interacts with the basal follicle cells via the pedicel, a fine duct that connects an ovariole with the oviduct. By this mechanism, patency is triggered in the follicle cells of the terminal oocyte only, restricting yolk accumulation to the oocytes next to ovulation. In contrast to the previous hypothesis, juvenile hormone (JH) is not necessary to induce patency, rather JH amplifies the effect of PIF. [ABSTRACT FROM AUTHOR]

Drought and locust plague are disasters that have brought destruction to the Yellow River Basin. Here, we use Chinese historical sources to study a severe prolonged drought and locust plague in the middle of the 10th century. From 942 to 944 AD, an exceptionally severe drought and accompanying locust plague swept through the Yellow River Basin of China. The drought and locust plague began and developed into a great disaster in 942 AD, and worsened in 943 AD, then ended in 944 AD. The drought and locust plague resulted in a great famine, and approximately one tenth of the total population of the Yellow River Basin starved to death. The Later Jin Dynasty (936–947 AD), a state in the region, thus fell into a national crisis. We suggest the prolonged Eldgjá eruption in Iceland as a possible cause of the drought. The eruption began circa 934 AD, and lasted for three to eight years. It was one of the largest volcanic eruptions in the world during the past 2000 years. The whole process of the drought and locust plague was: 1) the Eldgjá eruption resulted in abrupt cooling and drought; 2) drought and a locust plague resulted in great famine; 3) the famine resulted in massive deaths and a national crisis. [ABSTRACT FROM AUTHOR]

Peptides of the short neuropeptide F (sNPF) family modulate feeding behavior in a wide variety of insect species, including the desert locust, Schistocerca gregaria . Likewise, the nutritional state of the animal can strongly affect sNPF expression. Although several studies have been published describing these nutrient-dependent effects, it remains largely unclear how they are achieved. In this study, we describe a series of in vivo experiments which indicate that it is not the act of feeding in se , but rather the consequent availability of nutrients in the insect's hemolymph that gives rise to the postprandial modulation of sNPF expression. Furthermore, by performing a series of RNAi-mediated knockdown experiments, we were able to show that components of the evolutionarily conserved insulin/insulin-related growth factor (IGF) signaling pathway form a functional link between nutrient levels and sNPF transcript levels. [ABSTRACT FROM AUTHOR]

In the early embryonic grasshopper, two pairs of sibling cells near the apex of the antenna pioneer its dorsal and ventral nerve tracts to the brain. En route, the growth cones of these pioneers contact a so-called base pioneer associated with each tract and which acts as a guidepost cell. Both apical and basal pioneers express stereotypic molecular labels allowing them to be uniquely identified. Although their developmental origins are largely understood, the fates of the respective pioneers remain unclear. We therefore employed the established cell death markers acridine orange and TUNEL to determine whether the apical and basal pioneers undergo apoptosis during embryogenesis. Our data reveal that the apical pioneers maintain a consistent molecular profile from their birth up to mid-embryogenesis, at which point the initial antennal nerve tracts to the brain have been established. Shortly after this the apical pioneers undergo apoptosis. Death occurs at a developmental stage similar to that reported elsewhere for pioneers in a leg – an homologous appendage. Base pioneers, by contrast, progressively change their molecular profile and can no longer be unequivocally identified after mid-embryogenesis. At no stage up to then do they exhibit death labels. If they persist, the base pioneers must be assumed to adopt a new role in the developing antennal nervous system. [ABSTRACT FROM AUTHOR]

Chitin was extracted from four different local sources: the shrimp ( Penaeus monodon ), the desert locust ( Schistocerca gregaria ), the honey bee ( Apis mellifera ) and the beetles ( Calosoma rugosa ) . Chitosan was then obtained by deacetylation of chitin and physicochemically characterized using the Fourier transform infrared (FTIR) and X-ray diffraction. The moisture content, water binding capacity, fats binding capacity, ash content were determined and chitosans morphology was visualized using the scanning electron microscope (SEM). The difference between the obtained chitosans from three insect sources and α-chitosan from shrimp in terms of crystallinity, fibrous structure was discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • We hypothesize that attraction to fresh faeces enhance locust hopper band cohesion. • We exposed third instar hoppers of desert locust to faeces odours of different ages. • We observed an attraction of faeces explained by 11 volatile organic compounds. • Latecomers could get back to the band following faeces' odours after 24 h. Collective motion is one of the most impressive common features of gregarious locusts: once formed, bands and swarms get moving for long distances. It was shown that visual perception of neighbours plays a key role in maintaining marching behaviour at a local scale. But at a larger scale, mechanisms underlying band cohesion are less understood. It was shown in several field studies that individuals separated from the band were able to get back to the group, even after being separated since a night. In this context, faeces' odours could be a possible indicator of the recent passage of a group. In this study, we tested if nymphs are attracted by faeces' odours and if this effect is modulated by the age of the faeces. To this end, we conducted individual olfactometric behavioural assays of 3 rd instar hoppers of desert locust, Schistocerca gregaria , exposed to odours of 1 h-old and 24 h-old faeces. We also used Gas Chromatography-Mass Spectrometry (GC–MS) to identify odours' volatile organic compounds from faeces. The results of behavioural assays indicated a strong attractive effect of faeces, with no preference for one of the two faecal age classes. Nymphs spent significantly more time in the side of the olfactometer where the faeces' odours came from, and 72.7% of tested individuals chose this side first. We filtered and annotated 11 volatile organic compounds present in both fresh and old faeces in GC–MS analyses, including guaiacol and phenol, which are known to cause an aggregative effect on desert locusts. As the attractive effect lasted over 24 h, band's faeces could still have an attractive effect when individuals are separated from the band since one day. In this situation, latecomers individuals would be able to get back to the group by following the traces of their predecessors. [ABSTRACT FROM AUTHOR]

This article explores how new technologies – such as drones and satellites – are incorporated into disaster management and questions the implications for power relations between disaster authorities and subjects. This is a critical area of research, as the proliferation of aerial and networked technologies has made their use in disaster management and response more common. Although concerns have been raised about the potential use of aerial and networked technologies in the surveillance and spatial discipline of populations by commercial and government actors, few have considered the implications for disaster management. In response, this article turns to geographical literature on necropower, verticality, and planetary spatialities to analyse technological innovations in responses to desert locust upsurges in Kenya. Drawing from qualitative research carried out between February 2020 and January 2021, we explain how desert locust control operations have shifted from horizontal to vertical to networked and planetary in nature through experimentation with new technologies over the past century. We argue that aerial and networked technologies have led to a volumetric shift in desert locust management and response, giving remote and increasingly automated actors who operate 'above' greater power over the life and death of populations 'below'. In making this argument, we adopt a more-than-human perspective to account for how nonhuman entities and lifeforms shape and are subjected to necropolitical disaster management and responses. We conclude by reflecting on what this analytical approach has to offer the study of vertical and volumetric geographies. • New technologies are increasingly central to disaster management. • These technologies are reorienting disaster action around volumetric, planetary space. • This means new actors and authorities are calculating disaster interventions. • Emerging spatialities of disaster actions have implications for power asymmetries. • The new technologies we focus on are largely aerial, automated, and autonomous. [ABSTRACT FROM AUTHOR]

Pancreatic chymotrypsins (CTRs) are digestive proteases that in humans include CTRB1, CTRB2, CTRC, and CTRL. The highly similar CTRB1 and CTRB2 are the products of gene duplication. A common inversion at the CTRB1-CTRB2 locus reverses the expression ratio of these isoforms in favor of CTRB2. Carriers of the inversion allele are protected against the inflammatory disorder pancreatitis presumably via their increased capacity for CTRB2-mediated degradation of harmful trypsinogen. To reveal the protective molecular determinants of CTRB2, we compared enzymatic properties of CTRB1, CTRB2, and bovine CTRA (bCTRA). By evolving substrate-like Schistocerca gregaria proteinase inhibitor 2 (SGPI-2) inhibitory loop variants against the chymotrypsins, we found that the substrate binding groove of the three enzymes had overlapping specificities. Based on the selected sequences, we produced eight SGPI-2 variants. Remarkably, CTRB2 and bCTRA bound these inhibitors with significantly higher affinity than CTRB1. Moreover, digestion of peptide substrates, beta casein, and human anionic trypsinogen unequivocally confirmed that CTRB2 is a generally better enzyme than CTRB1 while the potency of bCTRA lies between those of the human isoforms. Unexpectedly, mutation D236R alone converted CTRB1 to a CTRB2-like high activity protease. Modeling indicated that in CTRB1 Met210 partially obstructed the substrate binding groove, which was relieved by the D236R mutation. Taken together, we identify CTRB2 Arg236 as a key positive determinant, while CTRB1 Asp236 as a negative determinant for chymotrypsin activity. These findings strongly support the concept that in carriers of the CTRB1-CTRB2 inversion allele, the superior trypsinogen degradation capacity of CTRB2 protects against pancreatitis. • Human chymotrypsin B1 (CTRB1) and CTRB2 are the products of gene duplication. • An inversion at the CTRB1/2 locus reverses their expression ratio in favor of CTRB2. • Higher CTRB2 level in inversion allele carriers protects against pancreatitis. • We map the protecting role of CTRB2 to a single Arg (CTRB2) vs Asp (CTRB1) difference. • Modeling of phage-evolved inhibitor/CTRB complexes provide structural interpretation. [ABSTRACT FROM AUTHOR]

The two plague locusts, Schistocerca gregaria and Locusta migratoria , exhibit density-dependent phase polyphenism. Nymphs occurring at low population densities (solitarious forms) are uniformly colored and match their body color to the background color of their habitat, whereas those occurring at high population densities (gregarious) develop black patterns. An injection of the neuropeptide, corazonin (Crz) has been shown to induce black patterns in locusts and affect the classical morphometric ratio, F/C (F, hind femur length; C, maximum head width). We herein identified and cloned the CRZ genes from S. gregaria ( SgCRZ ) and L. migratoria . A comparative analysis of prepro-Crz sequences among insects showed that the functional peptide was well conserved; its conservation was limited to the peptide region. Silencing of the identified SgCRZ gene in gregarious S. gregaria nymphs markedly lightened their body color and shifted the adult F/C ratio toward the value typical of solitarious forms. In addition, knockdown of the gene in solitarious nymphs strongly inhibited darkening even after a transfer to crowded conditions; however, these individuals developed black patterns after being injected with the Crz as a rescue treatment. SgCRZ was constitutively expressed in the brains of S. gregaria during nymphal development in both phases. This gene was highly expressed not only in the brain in both phases, but also in the corpora allata in the gregarious phase. This conspicuous phase-dependent difference in SgCRZ gene expression may indicate a functional role in the control of phase polyphenism in this locust. [ABSTRACT FROM AUTHOR]

The basal caeliferan family Tetrigidae is investigated to identify neuropeptides belonging to the adipokinetic hormone (AKH) family. The pygmy grasshopper Tetrix subulata contains in its corpus cardiacum two octapeptides as revealed by liquid chromatography coupled to electrospray ionization mass spectrometry. The less abundant peptide is the well-known Schgr-AKH-II (pELNFSTGW amide) which is suggested to be the ancestral AKH of Caelifera and Ensifera. The second peptide, Tetsu-AKH (pEFNFTPGW amide), is novel and quite unusual with its third aromatic residue at position 2. It is thought to be autapomorphic for Caelifera. Tetsu-AKH has hyperlipemic activity in T. subulata and in Schistocerca gregaria . [ABSTRACT FROM AUTHOR]

The present study showed that the eggs of the desert locust, Schistocerca gregaria , and the migratory locust, Locusta migratoria , responded to photoperiod by hatching when placed on sand in the laboratory. S. gregaria mainly hatched during the dark phase and L. migratoria during the light phase. The importance of light as a hatching cue depended on the magnitude of the temperature change during the thermoperiod; photoperiod played a more important role in the control of hatching time in both species when the magnitude of the temperature change was small. In addition, the eggs of the two species that were covered with sand did not respond to photoperiod and hatched during both the light and dark phases, indicating that light did not penetrate through the sand. Because locust eggs are normally laid as egg pods and a foam plug is deposited between the egg mass and the ground surface, we tested a possibility that naturally deposited eggs perceived light through the foam plug. The eggs that were deposited and left undisturbed in the sand hatched during the light and dark phases at similar frequencies. These results suggest that the eggs of both locust species responded to light and controlled their hatching timing accordingly but would not use light as a hatching cue in the field. The evolutionary significance of the ability of eggs to respond to light in these locusts was discussed. [ABSTRACT FROM AUTHOR]

In this article, we identify and characterise the miRNA machinery components Drosha, Dicer-1 and Argonaute-1 of the desert locust. By means of phylogenetic analyses, we reveal important insights in the evolutionary context of these components. Our data illustrate that insect Argonaute-1 proteins form a monophyletic group with ALG-1 and ALG-2 of Caenorhabditis elegans and with the four (non-Piwi) Argonaute proteins present in humans. On the other hand, humans apparently lack clear homologues of the insect Argonaute-2 proteins. In addition, we demonstrate that drosha , dicer-1 and argonaute-1 display wide transcript tissue-distribution in adult desert locusts, and that during locust phase transition and feeding of starved locusts the expression levels of the miRNA pathway are regulated at the transcript level. [ABSTRACT FROM AUTHOR]

This article reports on the chemical analysis of molecular profiles of tarsal secretions of the desert locust Schistocerca gregaria (Forsskål, 1775) by gas chromatography hyphenated with quadrupol mass spectrometry (GC–MS) as well as 1 H-nuclear magnetic resonance ( 1 H NMR) spectroscopy. Special focus of this study was to elaborate on sampling methods which enable selective microscale extraction of insect secretions in a spatially controlled manner, in particular tarsal adhesive secretions and secretions located on cuticle surfaces at the tibia. Various solvent sampling procedures and contact solid-phase microextraction (SPME) methods were compared in terms of comprehensiveness and extraction efficiencies as measured by signal intensities in GC–MS. Solvent sampling with water as extraction solvent gave access to the elucidation of chemical profiles of polar compound classes such as amino acids and carbohydrates, but is extremely tedious. Contact SPME on the other hand can be regarded as a simplified and more elegant alternative, in particular for the lipophilic compound fraction. Many proteinogenic amino acids and ornithine as well as carbohydrate monomers arabinose, xylose, glucose, and galactose were detected in tarsal secretions after acid hydrolysis of aqueous extracts. Qualitatively similar but quantitatively significantly different molecular profiles were found for the lipid fraction which contained mainly n -alkanes and internally branched monomethyl-, dimethyl-, and trimethyl-alkanes in the C23–C49 range as well as long chain fatty acids and aldehydes. Especially, hydrocarbons with >C40 carbon numbers have previously been rarely reported for insect secretions. The results suggest that the investigated insect secretions are complex emulsions which allow the attachment of tarsi on various otherwise incompatible materials of smooth and rough surfaces. The solid consistence of the established alkanes at ambient temperatures might contribute to a semi-solid consistence of the adhesive, amalgamating partly opposing functions such as slip resistance, tarsal release, desiccation resistance, and mechanical compliance. The methods developed can be extended to other similar applications of studying compositions of insect secretions of other species. [ABSTRACT FROM AUTHOR]

This study examined the effects of temperature and phase polyphenism on egg hatching time in the desert locust, Schistocerca gregaria , and the migratory locust, Locusta migratoria . The two species exhibited differences and similarities in hatching behavior when exposed to different temperature conditions. In 12-h thermocycles of various temperatures, the S. gregaria eggs hatched during the cryoperiod (low temperature period), whereas L. migratoria eggs hatched during the thermoperiod (high temperature period). The eggs of both species hatched during the species-specific period of the thermoperiod in response to a temperature difference as small as 1 °C. Furthermore, the locusts adjusted hatching time to a new thermal environment that occurred shortly before the expected hatching time. In both species, the hatching of the eggs was synchronized to a specific time of the day, and two hatching peaks separated by approximately 1 day were observed at a constant temperature after the eggs were transferred from thermocycles 3 days before hatching. Eggs laid by gregarious females hatched earlier than those laid by solitarious females in S. gregaria but this difference was not observed in L. migratoria . [ABSTRACT FROM AUTHOR]

Highlights: [•] Desert Locusts can transform between solitarious and gregarious phases. [•] Stimuli from conspecifics cause rapid behavioural gregarization in just 4h. [•] Gregarization entails synchronous changes in several discrete behaviours. [•] Overall activity and attraction to other locusts change at the same rate. [•] Serotonin causes changes in both attraction and locomotion. [Copyright &y& Elsevier]

Highlights: [•] The sNPF precursor of Schistocerca gregaria was identified and shown to contain both known Schgr-sNPF isoforms. [•] The Schgr-sNPF precursor transcript is present throughout the nervous system. [•] Schgr-sNPF precursor transcript levels in the optic lobes of the brain drop upon starvation. [•] RNAi mediated knockdown of the Schgr-sNPF precursor transcript strongly increases food uptake. [Copyright &y& Elsevier]

Abstract: RNA interference (RNAi) has become a widely used reverse genetics tool in eukaryotes and holds great potential to contribute to the development of novel strategies for insect pest control. While previous studies clearly demonstrated that injection of dsRNA into the body cavity of the desert locust, Schistocerca gregaria, is highly effective to induce gene silencing effects, we observed that the RNAi response is much less sensitive to orally delivered dsRNA. In line with this, we report on the presence of a potent dsRNA degrading activity in the midgut juice. Four different dsRNase sequences that belong to the DNA/RNA Non-specific Nuclease superfamily were retrieved from a transcriptome database of the desert locust. Surprisingly, we have found that, in the publicly available eukaryote nucleotide sequence databases, the presence of this group of enzymes is restricted to insects and crustaceans. Nonetheless, phylogenetic analyses predict a common origin of these enzymes with the Endonuclease G (EndoG) Non-specific Nucleases that display a widespread taxonomic distribution. Moreover, in contrast to the Sg-endoG transcript, the four Sg-dsRNase transcripts appear to be specifically expressed in the gut. Finally, by means of RNAi, we provide evidence for an important contribution of dsRNase2 to the dsRNA degrading activity that is present in the gut lumen of S. gregaria. [Copyright &y& Elsevier]

• Defining the dynamics of behavioural phase change has unified the study of desert locust swarming, • Leading to discovery of key crowding stimuli and neurochemical mechanisms, • Uncovering the importance of local resource distribution and quality, • Explaining the emergence of collective mass movement, • And yielding landscape-scale predictive models for control and management of outbreaks. Behavioural phase change initiates and functionally couples the suite of traits that comprise density-dependent polyphenism in locusts. Here I provide a semi-expurgated account of my 25-year research journey studying behavioural phase transition in the desert locust. The journey spans continents, involves a cast of extraordinary colleagues, and travels across levels of biological organisation from deep within the nervous system of individual locusts to mass migration and the evolution and population dynamics of swarming. [ABSTRACT FROM AUTHOR]

[Display omitted] • In desert locust adults, male accessory glands become fully developed after 9 days. • SgEcR mRNA levels are significantly higher in fat body of sexually mature males. • Knockdown of SgEcR , not SgRXR, increased relative weight of male accessory glands. • Knockdown of SgEcR or SgRXR caused a delay in the onset of mating behavior. • In some cases Sg EcR and Sg RXR might act independently of each other. Locusts have been known as pests of agricultural crops for thousands of years. Recently (2018–2021) the world has faced the largest swarms of desert locusts, Schistocerca gregaria , in decades and food security in large parts of Africa and Asia was under extreme pressure. There is an urgent need for the development of highly specific bio-rational pesticides to combat these pests. However, to do so, fundamental research is needed to better understand the molecular mechanisms behind key physiological processes underpinning swarm formation, such as development and reproduction. The scope of this study is to investigate the possible role(s) of the ecdysteroid receptor in the reproductive physiology of male S. gregaria. Ecdysteroids and juvenile hormones are two important classes of insect hormones and are key regulators of post-embryonic development. Ecdysteroids are best known for their role in moulting and exert their function via a heterodimer consisting of the nuclear receptors ecdysone receptor (EcR) and retinoid-X receptor (RXR). To gain insight into the role of SgEcR and/or SgRXR in the male reproductive physiology of S. gregaria we performed RNAi-induced knockdown experiments. A knockdown of SgEcR , but not SgRXR , resulted in an increased relative weight of the male accessory glands (MAG). Furthermore, the knockdown of these genes, either in combination or separately, caused a significant delay in the onset of mating behavior. Nevertheless, the MAG appeared to mature normally and the fertility of mated males was not affected. The high transcript levels of SgEcR in the fat body, especially towards the end of sexual maturation in both males and females, represent a remarkable finding since as of yet the exact role of SgEcR in this tissue in S. gregaria is unknown. Finally, our data suggest that in some cases SgEcR and SgRXR might act independently of each other. This is supported by the fact that the spatiotemporal expression profiles of SgEcR and SgRXR do not always coincide and that knockdown of SgEcR , but not SgRXR, significantly affected the relative weight of the MAG. [ABSTRACT FROM AUTHOR]

Highlights: [•] The French colonial Empire was in crisis during WWII. [•] Efforts to control Desert Locusts helped resolve this crisis. [•] Responses to locust invasions enabled new modes of government. [•] Resulting field allowed transnational federation of techno-scientific benevolence. [•] Fit or mismatch between institutions and ecological dynamics is unstable, contingent. [Copyright &y& Elsevier]

Highlights: [•] trNPF injections in adult female locusts increase ovarian ecdysteroid titers. [•] trNPF injections positively affect hemolymph ecdysteroid titers in adult females. [•] npf-RNAi reduces ecdysteroid levels in hemolymph and ovaries of adult female locusts. [Copyright &y& Elsevier]

Abstract: The second messengers involved in the signal transduction for Schistocerca gregaria, ion transport peptide (Schgr-ITP) that regulates ion and fluid transport across the ileum of the desert locust S. gregaria, were measured using competitive enzyme-linked immunosorbent assays (ELISAs). Synthetic Schgr-ITP elevates intracellular levels of both cyclic AMP and cyclic GMP, measured over a 15min period in the presence of 3-isobutyl-1-methylxanthine, in a dose-dependent manner. Furthermore, crude corpora cardiaca (CC) extracts elevate intracellular cyclic AMP levels 2-fold greater than Schgr-ITP, suggesting that factors present in the CC, other than Schgr-ITP, also act via this second messenger. These results suggest that the interaction of Schgr-ITP with two separate receptors, most likely a G-protein coupled receptor and a membrane bound guanylate cyclase, elevates intracellular levels of cyclic AMP and cyclic GMP to regulate ion and fluid transport across the locust ileum. Cyclic AMP stimulates Cl−, K+ and Na+ reabsorption, whereas secretion of H+ into the lumen of the ileum is most likely mediated via cyclic GMP. Cyclic GMP also stimulates Cl− uptake in a similar manner to cyclic AMP. The measurement of tissue (central nervous system) levels of Schgr-ITP using an indirect ELISA confirms that the peptide is only present in the locust brain and the CC. The amounts present are greatest in the CC, where the peptide is presumably stored for release into the hemolymph when locusts feed. [Copyright &y& Elsevier]

Abstract: Although Neuropeptide F (NPF) has been identified in different insect species, its function has mainly been studied in the fruit fly, Drosophila melanogaster, where it regulates diverse physiological processes, such as learning, stress responses and male courtship behavior. In locusts, only a truncated form of the “full-length” NPF (the biologically active “trNPF”) has been isolated. This 9 AA peptide stimulates oocyte maturation, food intake and weight increase in adult desert locusts (Schistocerca gregaria [Forskål]). In this study, we investigated whether this peptide is also involved in the regulation of male reproductive physiology in this orthopteran species. Daily injections of trNPF in adult males resulted in proportionally heavier testes and seminal vesicles, while RNAi-mediated knockdown of the Schgr-NPF precursor transcript gave rise to proportionally lighter testes and seminal vesicles. Furthermore, adult males precociously displayed courtship behavior when injected daily with trNPF, while this behavior was inhibited or delayed by RNAi knockdown of the Schgr-NPF precursor transcript. In order to further analyze these effects of trNPF on male reproductive physiology, fertility of males was tested by analyzing progeny numbers following copulation with untreated females. In this way, we showed that daily trNPF injection in adult males resulted in a larger egg pod size and a higher percentage of hatched eggs per egg pod after copulation, while RNAi knockdown caused the opposite effects. Taken together, we provide clear evidence for a role of trNPF in the regulation of reproductive physiology in adult males of the desert locust, S. gregaria. Possible modes of action of trNPF in influencing these reproductive processes in male locusts are discussed. [Copyright &y& Elsevier]

Abstract: Our knowledge on the physiological function of the insect Neuropeptide F (NPF) mostly comes from studies in the fruit fly, Drosophila melanogaster, where NPF was shown to regulate diverse processes, such as feeding, learning and responding to stress. In the desert locust, Schistocerca gregaria, only a truncated form of the “full-length” NPF (the biologically active “trNPF”) has been isolated. In this study, we investigated whether this peptide is involved in the regulation of feeding in this orthopteran species. In the S. gregaria EST-database, an NPF-precursor encoding transcript was found. Alignment with other insect NPF-precursors showed relatively highest sequence conservation within the trNPF region (and the flanking dibasic cleavage site), as compared to other regions of the NPF-precursor. Quantitative real-time RT-PCR revealed that the Schgr-NPF-precursor encoding transcript occurs throughout the central nervous system with relatively high transcript levels in the brain, optic lobes and suboesophageal ganglion. It was also detected at relatively high levels in the midgut, which suggests that the encoded peptide also functions in the digestive system. Moreover, Schgr-NPF-transcript levels were notably higher in starved animals than in animals fed ad libitum, while transcript levels were also shown to be regulated after the consumption of a meal. Injection of locust trNPF in adults stimulated food intake, while RNAi knockdown reduced food intake. Furthermore, injection of trNPF in adults stimulated weight increase, while RNAi knockdown reduced weight gain. This effect of trNPF on body weight gain may result from its stimulatory effect on food intake. Taken together, we provide clear evidence for an important role of trNPF in the regulation of feeding in the desert locust, S. gregaria. [Copyright &y& Elsevier]

Abstract: Schistocerca gregaria exhibits a phase-specific behavior in response to crowding. Nymphs occurring at low population densities (solitarious phase) tend to avoid one another, whereas those occurring at high population densities (gregarious phase) are attracted to one another. This study examined how this attraction/avoidance behavior changed after isolation or crowding. The behavior of the test nymphs was assessed by determining their positioning with respect to a stimulus cup, which contained 12 gregarious nymphs, placed at one end of an elliptical arena and an empty cup placed at the opposite end. Gregarious (crowd-reared) nymphs were most frequently observed close to the stimulus cup, whereas solitarious (isolated-reared) nymphs tended to avoid it. This tendency was easily changed by exposing the nymphs to isolation or crowding. However, contrary to a previously reported conclusion that behavioral gregarization occurs in 4–8h of crowding, the nymphs required at least 3days to achieve a significant change in the attraction/avoidance behavior in either direction, from solitarious to gregarious or the converse. The discrepancies between the present study and previous studies appear to result from the different behaviors observed. The present study focused on the attraction/avoidance behavior that is most likely the most important element in the gregarization and solitarization processes, whereas other studies used a mixture of various activity-related behaviors. No evidence was obtained for a trans-generational accumulation in the attraction/avoidance behaviors. Serotonin, a biogenic amine that is suggested by others to be involved in behavioral phase changes in S. gregaria, had no influence on this behavior or body color when injected into the solitarious nymphs. [Copyright &y& Elsevier]

Abstract: We report on a comprehensive study of the systemic RNAi-response in the desert locust, Schistocerca gregaria. Upon intra-abdominal injection of dsRNA for two housekeeping genes (alpha-tubulin 1a and gapdh) in the range of pg amounts of dsRNA per mg tissue, a potent reduction of their corresponding mRNA was obtained. Moreover, the observed transcript knockdown significantly increased in at least a 10 days period and eventually resulted in high mortality upon silencing of the alpha-tubulin 1a gene. A more moderate RNAi-response was however observed in the reproductive systems. Analysis of the tissue-dependent transcript level profile of several putative RNAi-genes indicated reduced levels of two genes, namely sg-dicer-2 and sg-argonaute-2, in the reproductive systems. By silencing these components, we confirmed their importance in the RNAi-process and suggest that their expression levels are determinant for tissue-dependent differences in the potency of RNAi in the desert locust. [Copyright &y& Elsevier]