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As an arboreal animal, tree frogs face diverse challenges when landing on perches, including variations in substrate shape, diameter, flexibility, and angular distribution, with potentially significant consequences for failed landings. Research on tree frog landing behavior on perches, especially concerning landing on vertical substrates, remains limited. This study investigated the landing strategies (forelimb, abdomen, and hindlimb) of tree frogs on vertical perches, considering perch diameter. Although all three strategies were observed across perches of different diameters, their frequencies differed. Forelimb landing was most common across all perch diameters, with its frequency increasing with perch diameter, while abdomen and hindlimb landing strategies were more prevalent on smaller diameter perches. During the process from take‐off to landing, the body axis underwent some deviation owing to the asymmetric movement of the left and right limbs; however, these deviations did not significantly differ among landing strategies. Additionally, different landing strategies led to variations in the landing forces, with abdominal landings generating significantly higher impact forces than the other two strategies. These findings provide insights into the biomechanics and biological adaptations of tree frogs when landing on challenging substrates, such as leaves or branches. [ABSTRACT FROM AUTHOR]

Morphological adaptation is crucial for animals and robots in navigating unstructured environments. In this article, a quadruped robot with a reconfigurable sprawl posture and posture transformation strategy is proposed, which can transform between different sprawl postures to cope with complex environments and adapt to a dorsal downward fall posture through reverse sprawling. First, the function and structure of the robot are described, including an analysis of the Hawken mechanism's endpoint trajectories and a regional examination of the robot leg's fundamental components, establishing a relationship between the trajectory characteristics and linkage length. Second, the robot posture transformation strategy is analysed, obtaining the geometric dimensional constraints and feasibility regions of the posture transformation. The posture transformation process is quantified, and the robot transformation gait and drive functions are designed. The robot gait and velocity regulation are implemented based on a neural control architecture. Finally, the robot's locomotion and posture transformation are tested using four high‐speed cameras. The results show that the robot can crawl on an inclined surface and continue crawling in a dorsal downward posture post‐fall. Additionally, the robot effectively navigates obstacles and narrow spaces after posture transformation. [ABSTRACT FROM AUTHOR]

A precise measurement of animal behavior and reaction forces from their surroundings can help elucidate the fundamental principle of animal locomotion, such as landing and takeoff. Compared with stiff substrates, compliant substrates, like leaves, readily yield to loads, presenting grand challenges in measuring the reaction forces on the substrates involving compliance. To gain insight into the kinematic mechanisms and structural–functional evolution associated with arboreal animal locomotion, this study introduces an innovative device that facilitates the quantification of the reaction forces on compliant substrates, like leaves. By utilizing the stiffness–damping characteristics of servomotors and the adjustable length of a cantilever structure, the substrate compliance of the device can be accurately controlled. The substrate was further connected to a force sensor and an acceleration sensor. With the cooperation of these sensors, the measured interaction force between the animal and the compliant substrate prevented the effects of inertial force coupling. The device was calibrated under preset conditions, and its force measurement accuracy was validated, with the error between the actual measured and theoretical values being no greater than 10%. Force curves were measured, and frictional adhesion coefficients were calculated from comparative experiments on the landing/takeoff of adherent animals (tree frogs and geckos) on this device. Analysis revealed that the adhesion force limits were significantly lower than previously reported values (0.2~0.4 times those estimated in previous research). This apparatus provides mechanical evidence for elucidating structural–functional relationships exhibited by animals during locomotion and can serve as an experimental platform for optimizing the locomotion of bioinspired robots on compliant substrates. [ABSTRACT FROM AUTHOR]

Small vertebrates, such as geckos, often use their tails to regulate their posture after take-off and suppress abnormal rotations in mid-air (such as sliding and falling). However, research on tail function before take-off remains scarce, particularly when animals overcome gravity to jump upward. This study examined tailed and tailless geckos' ability to jump over obstacles. The tails swung up and reached their upper limits during take-off, corresponding to a continuous increase in their trunk elevation angle. Compared to tailless geckos, geckos with intact tails had lower body and tail angular velocities. In addition, tailed geckos achieved larger take-off angles and higher jumps; moreover, their take-off angles were consistent with their velocity angles. Theoretical analyses demonstrated that the tail and its upward swing before take-off could benefit lifting the forelimb and hindlimbs off the ground, expanding the stability area of their centre of mass (COM). A robot prototype verified the effect of the tail and its swing on trunk elevation before take-off. Other parameters, such as the posture of the hindlimbs (support length and angle) and initial angle of the trunk, affect posture regulation. This study significantly extends our knowledge in animal locomotion and provides indispensable information for improving robot jumping ability. [ABSTRACT FROM AUTHOR]

Myasthenia gravis (MG) is an antibody‐mediated autoimmune disorder characterized by fluctuation of fatigue and weakness of muscle. Due to the heterogeneity of the course of MG, available biomarkers for prognostic prediction are urgently needed. Ceramide (Cer) was reported to participate in immune regulation and many autoimmune diseases, but its effects on MG remain undefined. This study aimed to investigate the ceramides expression levels in MG patients and their potential as novel biomarkers of disease severity. Levels of plasma ceramides were determined by ultra performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS). Severity of disease was assessed by quantitative MG scores (QMGs), MG‐specific activities of daily living scale (MG‐ADLs) and 15‐item MG quality of Life (MG‐QOL15). The concentrations of serum interleukin‐1β (IL‐1β), IL‐6, IL‐17A, and IL‐21 were determined by enzyme‐linked immunosorbent assay (ELISA), and the proportions of circulating memory B cells and plasmablasts were detected by flow‐cytometry assay. Four plasma ceramides levels we studied were detected higher in MG patients. And three of them (C16:0‐Cer, C18:0‐Cer, and C24:0‐Cer) were positively associated with QMGs. In addition, receiver operating characteristic (ROC) analysis suggested that plasma ceramides have a good ability of differentiating MG from HCs. Importantly, only C18:0‐Cer was shown to be positively associated with the concentration of serum IL and circulating memory B cells, and the decrease in plasma C18:0‐Cer paralleled the clinical improvement of patients with MG. All together, our data suggest that ceramides may play an important role in the immunopathological mechanism of MG, and C18:0‐Cer has the potential to be a novel biomarker for disease severity in MG. [ABSTRACT FROM AUTHOR]