Belgium

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.

SEB Conference 2025

The unique muscle architecture of the seahorse tail demystified

bio-inspired robotics

seahorses

evolutionary adaptations

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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.

This study focuses on the wing coloration of long-distance flying seabirds, many of which exhibit a characteristic black-and-white wing pattern, with a notable tendency for black wingtips. Since black surfaces absorb more solar radiation than white surfaces, they tend to heat up, thereby warming the surrounding air. This temperature difference can affect the airflow around the wing and its wake, potentially altering aerodynamic characteristics. In this study, a 3D-printed experimental model based on a NACA airfoil was developed, incorporating an internal heater to investigate the effects of wing surface temperature variation on the surrounding airflow. Wind tunnel experiments and oil flow visualization tests were conducted to analyze how surface heating affects boundary layer properties and flow separation. The experimental setup featured a film heater embedded inside the wing, enabling continuous heating to better simulate the flight conditions of birds. The results showed that the lift-to-drag ratio improved within a specific range of angles of attack. This suggests that surface heating altered boundary layer characteristics and helped suppress flow separation. These findings indicate that optimizing wing coloration and surface heating could contribute to improving the flight efficiency of long-distance flying seabirds, and thus applicable to the development of high efficiency aircraft wings.

Effects of Wing Coloration on Flight Performance of Long-Distance Flying Seabirds

A novel biomimetic approach to understanding the aerodynamic and stabilizing functions of the barn owl’s tail is presented. A full‐size, 3D‐printed replica of a barn owl configured in a natural gliding posture with an actuated, movable tail was designed and manufactured for controlled wind tunnel experiments. Aerodynamic forces—including lift, drag, and pitching moments—were systematically measured over a range of angles of attack and tail pitches, with the results calibrated against established literature. Analysis revealed that although the tail contributes only marginally to overall aerodynamic efficiency, it plays a critical role in generating stabilizing pitching moments, particularly under small perturbations. Wind tunnel tests further assessed the tail’s effectiveness in supplying stabilizing moments, showing that for minor disturbances, tail actuation maintains pitch stability at a low energetic cost. To further elucidate the barn owl’s dynamic behavior in pitch, a simplified differential equations model was developed to simulate its response to gust-induced and other disturbances; the effects of disturbance frequency were also evaluated. Owing to the bird’s low moment of inertia, even minimal tail actuation produced significant stabilizing effects without compromising efficiency. Thus, the study indicates that pairing a low‐moment‐of‐inertia airframe (like the birds' body) with an active stability augmentation system may reduce or eliminate the need for a large horizontal stabilizer, thereby enhancing both aerodynamic agility and structural efficiency. These findings provide novel insights into the aerodynamic control strategies of gliding birds and offer promising design principles for the development of bio-inspired aerial vehicles.

Quantification of the dynamic response (pitch) of a replica barn owl (Tyto Alba) under atmospheric disturbance with an actively controlled tail.

Semi-aquatic mammals have evolved adaptations for aquatic locomotion, an activity which differs greatly from terrestrial locomotion due to the denser and more viscous medium. Furthermore, semi-aquatic species cannot fully specialise since they need to balance their adaptations to fit their needs in both environments. Mustelids provide a valuable model for studying the evolution of such adaptations, as the group encompasses a wide range of aquatic specializations. Previous studies on their skeletal limb anatomy suggest a correlation between increased robustness and the higher biomechanical demands of swimming. To meet the elevated force requirements of swimming, we hypothesize that skeletal changes are accompanied by modifications in muscle architecture, specifically an increase in force-generating potential in distal limb muscles. To investigate this, we conducted manual dissections to measure muscle mass, fascicle length, pennation angle and to calculate the physiological cross-sectional area (PCSA). PCSA and fascicle length serve as indicators of specialization for either high force generation or increased contraction speed, providing a quantitative insight into muscle  performance potential. The next phase is to link these anatomical adaptations to specific functional demands of aquatic (and terrestrial) locomotion. Future steps involve gathering kinematic data of terrestrial and aquatic locomotion in live animals and modelling these locomotor patterns. By integrating anatomical and functional data across a gradient of aquatic specialization in mustelids (fully terrestrial ferrets < infrequently aquatic minks < habitually aquatic otters), this study aims to enhance our understanding of the evolution of aquatic locomotion in mustelids and, more broadly, in mammals.

Comparative muscle architecture in (semi-aquatic) mustelids and subsequent steps to identify musculoskeletal adaptations for aquatic locomotion

Birds rely on their beak as a versatile, multi-functional tool during various behaviours. Depending on a bird’s ecology, a beak may be specialised for producing high bite forces (e.g., to break down hard food items) or fast oscillation rates (e.g., to produce elaborate birdsong). Previous studies indicated that high bite force and fast beak movements oppose one-another, suggesting a force-velocity trade-off. However, the underlying mechanisms contributing to this trade-off in songbirds have not been studied in detail. We hypothesise that the contractile properties of the avian jaw muscles, specifically their normalised rates of force rise during contraction and force decay during relaxation, are a limiting factor for maximal beak oscillation rates. To test our hypothesis, we measured the tetanic, isometric half-contraction and half-relaxation times of beak opener and beak closer muscles in a weak biting (canary) and a hard biting (Java sparrow) songbird in vitro. We observed that, in the harder biting species, both muscle types are slower in contraction and relaxation. Furthermore, within both species, beak closer muscles were slower in contraction and relaxation compared to beak opener muscles. We conclude that muscles which are adapted to high force production need more time to contract and relax compared to muscles producing low maximal forces. These findings suggest that the contractile properties of avian jaw musculature may contribute to the observed force-velocity trade-off in songbird beak movements. Our results further suggest that the muscles involved in forceful biting may contain a greater proportion of slow, fatigue-resistant fibres.

Contractile properties of jaw muscles contribute to force-velocity trade-off in beak movements of songbirds

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.

ABA inhibits rice seed germination under low temperature through its induced biosynthesis and enhanced trehalose accumulation

Holometabolous insects often undergo a metabolic shift as adults due to feeding cessation. In the seed beetle Acanthoscelides obtectus, which enters a post-larval starvation phase, metabolic strategies are key to survival and longevity. This study contrasts two experimental evolution lines with divergent life histories: a short-lived, early-reproducing line (E, ~7 days) and a long-lived, late-reproducing line (L, ~15 days).
Targeted metabolomics revealed significant differences in amino acid metabolism between the two A. obtectus lines. Notably, amino acid concentrations were consistently lower in the long-lived L line than in the E line across all ages, with this distinction evident as early as day 1. This suggests a sustained, higher rate of amino acid catabolism in L beetles, potentially providing an alternative energy source to compensate for reduced complex I activity and the absence of fatty acid oxidation. Furthermore, tricarboxylic acid (TCA) cycle intermediates indicated line-specific mitochondrial adaptations. Higher succinate-to-fumarate ratio observed at day 1 in L beetles suggests increased complex II activity, which could offset the lowered complex I activity. These metabolomic findings strongly corroborate previous respirometry data, supporting metabolic rewiring in L beetles that favours alternative electron entry points into the mitochondrial electron transport system.
Our results highlight that metabolic plasticity, driven by enhanced amino acid catabolism and altered TCA cycle flux, is critical for extending survival in the L line. These adaptations provide insights into bioenergetic mechanisms governing lifespan in insects and highlight how mitochondrial remodelling contributes to the evolution of different ageing patterns.

Amino acid catabolism and mitochondrial shifts support increased longevity in the seed beetle Acanthoscelides obtectus

Parasites can impair host performance through various physiological processes, including alterations to host metabolism. Since mitochondria are responsible for cellular energy production, it is likely that disruptions in host cellular metabolism contribute to changes in metabolism at the organismal level. However, some studies investigating parasite-induced alteration in cellular metabolism have been limited by the presence of parasites in the target tissues. Before analyzing these key tissues, it is critical to confirm that the measured enzyme activities reflect those of the hosts rather than the parasites themselves. Here, we tested a parasite extraction protocol to evaluate the extent to which parasite contamination impacts estimates of cellular enzyme activities in hepatic tissues of wild pumpkinseed sunfish (Lepomis gibbosus) infected with bass tapeworm (Proteocephalus ambloplitis). We tested four treatments: uninfected livers, cleaned infected livers, infected livers (repopulated) and parasites alone. We then compared the activity of key metabolic enzymes among groups. PCR tests were used to assess parasitic contamination after applying the parasite extraction protocol on hepatic tissue. Enzyme activities of cleaned livers and contaminated livers were similar even if PCR tests revealed contamination. The intensity of cestode infection also did not influence enzyme activity, which suggests that parasite presence in the livers does not impact the accuracy of the enzyme activity estimates made. Through this protocol, we show that parasite contamination has no effect on metabolism measurements showing that the study of parasitized organs is possible. We also recommend the use of this protocol to avoid any biases in highly infected individuals.

Mitochondrial enzyme activity in fish livers is not impacted by parasite presence

Pollutants drive adaptive metabolic and evolutionary responses. However, this pollution-driven rapid evolution in invertebrates, particularly its effects on metabolism and mitochondrial oxidative phosphorylation (OXPHOS), remains overlooked. Using the European green crab Carcinus maenas, we investigated: (i) whether historic exposure to cadmium induces adaptive metabolic and mitochondrial responses; and (ii) if pre-exposure to cadmium confers protection from another source of pollution, copper. Crabs were captured from the wild from one site exposed to cadmium pollution but naïve to copper and a second reference site which had no cadmium or copper. After four months of depuration, animals were exposed to either 8.2 nM cadmium, or 20 nM copper-hydrate, or clean seawater. Mitochondrial respiration in heart homogenates was measured using high performance respirometry (Oroboros). Reactive oxygen species production (ROS) and antioxidant content was measured in hemolymph spectrofluorometrically (C-H2 DFFDA) and electrochemically (BRS system), respectively. While all crabs showed similar mitochondrial routine respiration values, the historically polluted crabs had higher OXPHOS respiration, higher electron transport system capacity, and enhanced capacity of complex II (CII), accompanied by increased ROS formation and higher antioxidant defences. Exposure to cadmium or copper did not affect any of the parameters considered in historically polluted crabs. In contrast, reference animals responded with a decreased complex I (CI) and increased CII contribution. This may reduce CI-associated ROS formation while enabling detoxification and (or) other defence mechanisms. Our findings suggest that long-term metal exposure induces mitochondrial adaptations that enhance resilience to pollution, potentially facilitating the invasion success of C. maenas in contaminated environments.

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