Belgium

Flight tests were conducted on Nankeen kestrels (Falco cenchroides) hovering in a wind tunnel to investigate their responses to discrete gusts. Gusts were generated using downstream rotating louvres, which modulated the strength of an updraught in which the birds could hover with wings fixed. Motion capture cameras recorded the kestrels’ kinematic responses during gust encounters. These gust responses were replicated using a robotic morphing kestrel wing and tail with three degrees of freedom: wing extension, tail spread, and tail pitch. The model was pre-programmed with movements imitating the birds’ gust responses, which were actuated in coordination with the gust generator. Measurements of the aerodynamic loads showed that the gust loads were effectively mitigated in the lift axis for both upward and downward step gusts. These findings highlight key degrees of freedom that could inform bioinspired gust mitigation strategies for small UAVs.

SEB Conference 2025

Reproduction of kestrel gust-mitigation kinematics with a robotic morphing wing

wing-tunnel

morphing wing

gust generation

bioinspiration

bird flight

avian flight

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SEB Conference 2024

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Landing precisely is vital for flying animals. However, disturbances in outdoor environments always complicate the process. For bumblebees, dynamic gusts cause both unpredictable flower movements and displacements of foraging bumblebees, which necessitate a rapid compensation of perturbations with their sensory-motor control system. Here, we study how rapid flower movements affect the landing behavior of bumblebees (Bombus terrestris). Using stereoscopic high-speed videography, we track bumblebees landing on an oscillating flower mimic and model their landing kinematics with control theory. The result shows that bumblebees land on moving flower with rapid motor actions controlled using visual perception of the moving target. The proposed visual-motor control model shows that optical perception signals facilitate bumblebees tracking the moving flower and gaze control while landing. The model also suggests a surprisingly low sensory-motor delay (median 57.1 ms). Moreover, by examining in-flight time histories of roll angle and sideway-acceleration, the helicopter model for aerodynamics force production proposed based on fruit flies is proved as valid for bumblebee flights. These results lead to a more thorough understanding of insect flight control system and could facilitate bio-inspired tracking and landing algorithms for flying robots.

How bumblebees land on rapidly-moving flowers: Sensory-motor flight control of landing on sideway moving flowers

Fastening barbules are hook-like microstructures on the surface of a bird’s primary flight feathers which prevent separation of adjacent feathers during wing extension. As a result, they are thought to be important for improving bird flight performance at high angles of attack by helping to maintain a smooth aerodynamic surface. This ability would be very useful for morphing-wing uncrewed aerial vehicles (UAVs) which can adjust the shape of their wing to suit a variety of flight conditions. Some of these UAV wings are comprised of multiple feather-like segments which slide over one another. However, they lack this between-feather fastening. Because of this, they struggle in gusty flight conditions and when flying at high angles of attack; their wing segments flap apart creating gaps that air can pass through which prevents the wings from producing sufficient aerodynamic force to maintain flight. Taking inspiration from fastening barbules, we investigate an electro-adhesive mechanism with the aim to enable controllable fastening between wing segments. Electro-adhesion involves the application of high voltage to electrodes which causes them to adhere together, but as soon as this voltage is removed, adhesion is lost. This study measures maximum adhesion strength between two electrodes in multiple directions. Results from these tests will enable application of this mechanism to future morphing wing UAVs.

A feather-inspired, electro-adhesive mechanism to improve flight capabilities of morphing wing UAVs

Fast motions play a crucial role in many biological processes, allowing organisms to capture elusive prey, escape predators, or navigate challenging environments with remarkable speed and precision. These rapid movements are especially vital in predator-prey interactions, often requiring a performance that exceeds the limits of pure muscle contraction alone, to fulfil the particularly high demands placed on the associated musculature and skeletal system. To overcome these limitations, specialized anatomical structures and biomechanical mechanisms are employed, often involving elastic energy storage, rapidly released through latch-mediated spring actuation (LaMSA) systems combined with optimized musculoskeletal gearing. These biological catapults are widespread in nature, enabling animals to achieve speeds and accelerations far beyond what muscle power alone could produce. Although commonly known for their grasping-like predatory strike, which was until now reported to be purely muscle driven, a small group of mantodeans (praying mantises) reveals strong morphological and behavioural deviations. The highly transformed raptorial forelegs of Haania orlovi are moved in a ballistic high-speed motion (~1,6 ms), utilizing the spear-like reinforced distal spines of the tibia to impale their prey item. The system is mainly based on elastic energy storage in the deformed cuticle of the trochanter, presumably caused by co-activated contraction of the large extensor and flexor muscles of the coxa, with a calculated mechanical power output of more than 100.000 W/kg. It presents a very simple and compact power amplification system. Understanding the principles behind such high-speed movements provides insights into evolutionary adaptations of biological systems and may inspire new technological innovations.

A striking difference: Biomechanics of a specialized predatory strike - the impaling hunting strategy of the moss mantis Haania orlovi (Insecta: Mantodea)

Seahorses possess a unique tail muscle architecture that enables efficient grasping and anchoring onto objects. This prehensile ability is crucial for their survival, as it allows them to resist currents, cling to mates during reproduction, and remain camouflaged to avoid predators. Unlike in any other fish, the muscles of the seahorse tail form long, parallel sheets that can span up to eleven vertebral segments. Our study investigates how this distinctive muscle arrangement influences the mechanics of prehension. Through in-silico simulations validated by a 3D-printed prototype, we reveal the complementary roles of these elongated muscles alongside shorter, intersegmental muscles. Furthermore, we show that muscles spanning more segments allow greater contractile forces and provide more efficient force-to-torque transmissions. Our findings confirm that the elongated muscle-tendon organisation in the seahorse tail provides a functional advantage for grasping, offering insights into the evolutionary adaptations of this unique tail structure.

The unique muscle architecture of the seahorse tail demystified

Animals exhibit escape behaviours as a defence against predators. In this study, we investigated the escape behaviour of mosquitoes when threatened by hosts such as humans and other animals. While previous studies have examined escape behaviours in various animals, most have focused on two-dimensional stimulus-response relationship, overlooking the complexity of three-dimensional behaviours. To address this gap, we developed a mosquito-swatting robot and an experimental arena where both the direction of the stimulus and the mosquitoes’ initial position can be controlled in three-dimensional space. Using this setup, we observed the mosquitoes’ three-dimensional and anisotropic escape strategies. Our results confirmed that the swatting robot effectively induces the mosquito escape behaviour. Detailed observations of their escape manoeuvres revealed the critical role of leg thrust in take off and a mechanism that compensates for their inherent low manoeuvrability. Additionally, we found that the relative direction of the gravity strongly influences the time taken for mosquitoes to escape. In the case where mosquitoes collided with the robot piston during escape, acceleration was 3-4 times higher than normal, suggesting passive escape mechanism by collision. Our methodology provides new insights into mosquito escape behaviour and may contribute to novel physical control strategies for mosquito management.

Three-dimensional and anisotropic escape strategies of mosquito revealed by swatting robot

Female mosquitoes detect host odours using olfactory receptors on the flagellum of their antennae. However, it is unclear how well antenna morphology is adapted to capture odour molecules. In this study, we measured Culex pipiens antenna geometry using microscope images and performed computational fluid dynamic analyses on an idealised three-dimensional model. The flow around the antennae was used to simulate the particle motion of odour molecules, and thereby test the effect of fibrillae length on odour molecule capture rate. Results suggest that the fibrillae hinder the movement of odour molecules toward the olfactory receptors on the flagellum and increase the aerodynamic drag on the antenna. The increase of drag increases the cost of flight but may enhance sensitivity to sounds, which is important for mosquito reproduction. This finding indicates a potential trade-off between olfactory and auditory functions in mosquito antennae.

The effect of mosquito antennal morphology on odour molecule capture.

Resurrection or desiccation tolerant plants are characterized by a remarkable ability to survive extreme desiccation, losing more than 90% of the cellular water in their vegetative tissues, and then recover normal physiological activity after only few hours of rehydration.  Plants release many different Volatile Organic Compounds (VOCs) to cope with environmental stresses. The VOC emission capacity have been investigated only in few resurrection species and most of these studies has shown the leaf emission of isoprene and other VOCs (C6 green leaf volatiles), and oxygenated compounds (acetone, and methanol). In the present study, the leaf emission of VOCs was assessed in the resurrection angiosperm Haberlea rhodopensis Friv. (Gesneriaceae) that belongs to the homoiochlorophyllous type species that are characterized to retain the photosynthetic apparatus and pigments, which allows a quicker recovery following rehydration. However, the high concentration of chlorophyll during desiccation is a source for the production of harmful reactive oxygen specie. Therefore, H. rhodopensis needs better antioxidant protection against free radical attack experienced either during dehydration or immediately upon rehydration. Our study aims to understand the role of leaf VOCs emission in the desiccation tolerance strategy of H. rhodopensis. The temporal dynamic of VOC emission during dehdyration and rehydration was monitored continuously by applying proton transfer reaction – time of flight-mass spectrometry (PTR-MS) and gas chromatography-mass spectrometry (GC-MS). Our study on the VOC emission, together with parallel analysis of the photosynthetic activity and photoprotective mechanisms, provides new insights into the potential role of VOCs for the “drying without dying” ability.

Resurrection plants: the unsolved mystery of Volatile Organic Compounds (VOCs) emissions under extreme physiological desiccation

The final morphology of a plant is determined by the activity of the shoot apical meristem (SAM), a group of pluripotent cells responsible for the generation of above-ground aerial plants’ organs. The identity and differentiation of SAM cells are under a strict hormonal and transcriptional regulatory network, involving epigenetic modifications and different signalling molecules. Among these, Reactive Oxygen Species (ROS) play an important role in cell cycle regulation, thus contributing to plant growth. Overall, plant hormones and ROS create a complex interplay of connections that can be modulated to boost plant development and productivity. Biogenic Volatile Organic Compounds (BVOCs) are a large variety of molecules produced by different plant tissues. There is increasing evidence that BVOCs participate in the regulation of signalling pathways involving ROS production and hormone synthesis. For this reason, application of BVOCs may represent a novel strategy to enhance plant meristematic activity, with a positive impact on plant productivity. Our project investigates the effects of exposure to BVOCs (i.e. isoprenoids) on rice, with the aim of exploring the possibility to increase rice yield through modulation of hormone signalling, gene activation and plant redox state. Experiments are currently ongoing to evaluate changes in cell redox mechanisms, hormones synthesis and gene expression at different plant levels: (i) on undifferentiated and regenerating rice callus, (ii) on rice seedlings exposed to exogenous isoprene. Preliminary results suggest that isoprene is able to modulate the rice redox machinery and positively affects the expression of auxin-responsive genes, possibly impacting plant growth and development.

Biogenic Volatile Organic Compounds (BVOCs) For Plant Growth Promotion: A Preliminary Study On Rice Callus and Seedlings

Global temperatures are rising, putting pressure on our wheat production systems. Predictions indicate that for every 1°C increase in temperature, wheat yields have the potential to decrease by 6%. This represents an approximate one million metric tonne loss in the UK yearly. Furthermore, regions experiencing the largest temperature shifts align with some of the world’s most food-insecure communities. Wild relatives of wheat offer a solution for enhancing yields under elevated temperatures. One such wild relative is Aegilops umbellulata, which can be found in Iran, Iraq, Turkey, and Syria—areas that frequently experience temperatures exceeding 40°C. Consequently, these conditions have influenced the development of Ae. umbellulata to withstand high temperatures compared to bread wheat. We measured chlorophyll fluorescence to determine Tcrit (the temperature at which Fv/Fm shifts from a steady decline in efficiency to a rapid decline, indicating severe damage to photosynthetic apparatus due to high temperatures) in a collection of Ae. umbellulata accessions and Ae. umbellulata/hexaploid wheat addition and substitution lines. Furthermore, we recorded plant yields and assessed seed morphology and elemental composition through imaging, ICP-MS, and carbon-nitrogen analysis. Our findings suggest that chromosome 7U of Ae. umbellulata may possess the ability to enhance the thermotolerance of bread wheat, therefore protecting yields under high-temperature stress.

Aegilops umbellulata: A wheat wild relative giving heat tolerance to hexaploid wheat

Low-temperature (LT) stress poses a serious threat to rice seed germination under direct sowing in rice production. Germination under LT therefore constitutes an important agronomic trait for such rice cultivation system. In this study, we identified a trehalose synthesis pathway gene, trehalose-6-phosphate phosphatase 3 (OsTPP3), involved in the regulation of LT germination in rice, as well as its upstream regulatory factor, the ABA signaling pathway gene OsbZIP23. LT stress induced the accumulation of ABA by upregulating the expression of OsNCED3. Consistently, overexpression of OsNCED3 significantly inhibited seed germination under LT conditions. RT-qPCR experiments found that the expression of OsbZIP23, a key component of ABA signaling pathway, was also significantly induced under LT stress and ABA treatment. Overexpressing OsbZIP23 increased the sensitivity to LT stress, resembling the phenotype of OsNCED3 overexpressing seeds. Furthermore, both LT stress and exogenous ABA treatment increased the trehalose content in WT seeds, by upregulating the expression of OsTPP3. Enhancing the expression of OsTPP3 or application of exogenous trehalose significantly increased the sensitivity to LT stress during seed germination. Transcriptional activation assays demonstrated that OsbZIP23 bound to the promoter of OsTPP3 and activated its expression, which was intensified by LT stress or application of ABA. Our study revealed an ABA-dependent OsbZIP23-OsTPP3 molecular module that responds to LT stress and inhibits seed germination under LT conditions. The regulated trehalose accumulation then balances growth and stress resistance under different temperature conditions.

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How bumblebees land on rapidly-moving flowers: Sensory-motor flight control of landing on sideway moving flowers

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Kestrel kinematics during discrete gust encounters while windhovering in a wind tunnel