Critical Structure for Telescopic Movement of Honey bee (Insecta: Apidae) Abdomen: Folded Intersegmental Membrane

Biomechanical properties of honeybee abdominal muscles during stretch activation

The mechanical properties of the honeybee's abdominal muscles endow its abdomen with movement flexibility to perform various activities. However, the biomechanical properties of abdominal muscles during stretch activation remain unclear. To clarify this issue, we observed the microstructures of the abdominal muscles to obtain structural information. The similarity and symmetry of abdominal muscle distribution contribute to the ability to drive abdominal movement. Combined with the segmented structure characteristics, an experimental device to measure muscle stretch measurement of honeybees was developed to investigate the mechanical properties of the abdominal muscles. During measurement, the muscles were kept in a solution to maintain a physiological environment. The mechanical properties of abdominal muscles included phases: the ascending phase with proportional increase, stable phase with slight fluctuation, and decay phase with parabolic decline. These findings indicate that the nonlinear and rate-sensitive mechanical properties of the abdominal muscles enable them to rapidly adapt to environmental changes. The stretch force and stiffness coefficient reached 0.660 ± 0.139 mN and 14.364 ± 2.961 N/m, respectively. A simplified biomechanical model of the muscle fiber considering the hierarchical microstructure was introduced, in which the mechanical properties were consistent with the experimental data. Further analysis of the effects of the activation probability and the effective range of binding sites on the mechanical properties demonstrated the critical role in force generation, revealing the mechanism of underlying muscle stretch activation in the honeybee abdomen. The findings can provide a new reference for studying the biomechanical properties of the muscles of other arthropod insects.

Physiological Signatures of Changes in Honeybee's Central Complex During Wing Flapping

Many kinds of locomotion abilities of insects-including flight control, spatial orientation memory, position memory, angle information integration, and polarized light guidance are considered to be related to the central complex. However, evidence was still not sufficient to support those conclusions from the aspect of neural basis. For the locomotion form of wing flapping, little is known about the patterns of changes in brain activity of the central complex during movement. Here, we analyze the changes in honeybees' neuronal population firing activity of central complex and optic lobes with the perspectives of energy and nonlinear changes. Although the specific function of the central complex remains unknown, evidence suggests that its neural activities change remarkably during wing flapping and its delta rhythm is dominative. Together, our data reveal that the firing activity of some of the neuronal populations of the optic lobe shows reduction in complexity during wing flapping. Elucidating the brain activity changes during a flapping period of insects promotes our understanding of the neuro-mechanisms of insect locomotor control, thus can inspire the fine control of insect cyborgs.

Skin wrinkles and folds enable asymmetric stretch in the elephant trunk

The elephant's trunk is multifunctional: It must be flexible to wrap around vegetation, but tough to knock down trees and resist attack. How can one appendage satisfy both constraints? In this combined experimental and theoretical study, we challenged African elephants to reach far-away objects with only horizontal extensions of their trunk. Surprisingly, the trunk does not extend uniformly, but instead exhibits a dorsal "joint" that stretches 15% more than the corresponding ventral section. Using material testing with the skin of a deceased elephant, we show that the asymmetry is due in part to patterns of the skin. The dorsal skin is folded and 15% more pliable than the wrinkled ventral skin. Skin folds protect the dorsal section and stretch to facilitate downward wrapping, the most common gripping style when picking up items. The elephant's skin is also sufficiently stiff to influence its mechanics: At the joint, the skin requires 13 times more energy to stretch than the corresponding length of muscle. The use of wrinkles and folds to modulate stiffness may provide a valuable concept for both biology and soft robotics.

A novel bioinspired mechanism to elucidate the movement flexibility of the honeybee abdomen driven by muscles

The abdomen of a honeybee is a blueprint for bioinspired mechanical design because of its movement flexibility and compactness. However, the abdominal muscles closely related to the movement flexibility mechanism have not been fully identified, limiting the potential biological advantage of their use in bionic mechanism design. In this study, we reveal the muscle distribution of the complete muscular driving unit in a honeybee abdomen using stereoscopy and scanning electron microscopy, and the muscle distribution was effectively verified using X-ray tomography. A novel equivalent unit mechanism (EUM) was then proposed and the kinematic analysis indicated that the extension ratio, bending angle, and swing angle of the EUM reached 9.36%, 1.22°, and 4.43°, respectively. The deformation ability of the EUM was consistent with the movement of the abdomen, confirming the movement flexibility. This work may provide a new perspective for distributed bionic mechanism design.

Hairy-Layer Friction Reduction Mechanism in the Honeybee Abdomen

Abdominal sections of honeybees undergo numerous reciprocating motions during their lifetime. However, the overlapped contact areas adjacent to the abdominal sections have a shallow wear extent, a physical mechanism that remains obscure to date. Therefore, this study explored a biofrictional reduction model based on a solid surface texture and the hairy surface of the honeybee abdomen. We collected honeybee samples and observed their abdomens using a camera (Zeiss Stemi 508). Subsequently, we sliced these samples using a microtome and detected their microscopic friction. The exterior surface of the honeybee abdomen was not smooth but was distributed with a dense microvilli structure, which played a vital role in adjusting the friction reduction characteristics between the abdominal sections. When the adjacent abdominal sections moved relatively to each other, their upper and lower surfaces were not in direct rigid contact. Briefly, this study shows that the microscale hair arrays on the surface of the posterior abdominal segment can significantly reduce real contact area and friction, which considerably decreases wear or abrasion. The friction reduction mechanism alleviates the abrasion during the relative bending movement and saves a large amount of energy, which is essential for the honeybees' daily activities. This microtexture compliance friction reduction characteristic could be used to fabricate hierarchical surfaces for long-lasting friction reduction mechanisms, which increase the life of soft devices, including soft actuators and hinges.

Parallel Mechanism Composed of Abdominal Cuticles and Muscles Simulates the Complex and Diverse Movements of Honey Bee (Apis mellifera L.) Abdomen

The abdominal intersegmental structures allow insects, such as honey bees, dragonflies, butterflies, and drosophilae, to complete diverse behavioral movements. In order to reveal how the complex abdominal movements of these insects are produced, we use the honey bee (Apis mellifera L.) as a typical insect to study the relationship between intersegmental structures and abdominal motions. Microstructure observational experiments are performed by using the stereoscope and the scanning electron microscope. We find that a parallel mechanism, composed of abdominal cuticle and muscles between the adjacent segments, produces the complex and diverse movements of the honey bee abdomen. These properties regulate multiple behavioral activities such as waggle dance and flight attitude adjustment. The experimental results demonstrate that it is the joint efforts of the muscles and membranes that connected the adjacent cuticles together. The honey bee abdomen can be waggled, expanded, contracted, and flexed with the actions of the muscles. From the view point of mechanics, a parallel mechanism is evolved from the intersegmental connection structures of the honey bee abdomen. Here, we conduct a kinematic analysis of the parallel mechanism to simulate the intersegmental abdominal motions.

Electroantennogram reveals a strong correlation between the passion of honeybee and the properties of the volatile

INTRODUCTION

Insects use their antennae to detect food, mates, and predators, mainly via olfactory recognition of specific volatile compounds. Honeybees also communicate, learn complex tasks, and show adaptable behavior by recognizing and responding to specific odors. However, the relationship between the electroantennogram and the passion of honeybee has not been determined.

METHODS

We established a four-channel maze system to detect the degree of sensitivity of the honeybee's antenna to different odors. In addition, electroantennography (EAG) signal was recorded from the right antennae of the honeybees in our experiments to explore electrophysiological responses to different volatiles.

RESULTS

The olfactory sensilla on the antennae of honeybees engender distinct electrophysiological responses to different volatiles. The bees were exposed to honey, 1-hexanol and formic acid, and EAG parameters like depolarization time, falling slope, and amplitude were measured. The EAG indicators varied significantly between honey and formic acid, indicating either "happy" or "anxious" moods.

CONCLUSIONS

Honeybee can express its passion by the characteristic changes of EAG parameters. We defined a preference factor (F) to quantify the preference of bees to varying concentrations of different compounds, where greater positive values indicate an increased passion. Our findings provide novel insights into the understanding of odor recognition in insects.

Kinematics of Stewart Platform Explains Three-Dimensional Movement of Honeybee's Abdominal Structure

The Stewart platform is a typical parallel mechanism, used extensively in flight simulators with six degrees of freedom. It is rarely found in animals and has never been reported to regulate and control physiological activities. Now an equivalent Stewart platform structure is found in the honey bee (Hymenoptera: Apidae: Apis mellifera L.) abdomen to explain its three-dimensional movements. The stereoscope and scanning electron microscope are used to observe the internal structures of honeybees' abdomens. Experimental observations show that the muscles and intersegmental membranes connect the terga with the sterna and guarantee the honey bee abdominal movements. From the perspective of mechanics, a Stewart platform is evolved from the lateral connection structure of the honey bee abdomen, and the intrasegmental muscles between the sternum and tergum function as actuators between planes of the Stewart platform. The extraordinary structure provides various advantages for a honey bee to complete a variety of physiological activities. This equivalent Stewart platform structure can also be used to illustrate the flexible abdominal movements of other insects with the segmental abdomen.

Abdominal pumping involvement in the liquid feeding of honeybee

Honeybee drinking is facilitated by a "mop-like" tongue, which helps honeybees suck in the sucrose solution from the environment. However, the liquid-transport mechanism from the pharynx to the crop, especially the natural link between abdominal pumping and dipping behavior on the sucrose solution intake, remains obscure. A significant increase in abdominal pumping frequency is observed when honeybees drink the sucrose solution. Abdominal pumping exhibits a function other than respiration. This second function assists in driving the sucrose solution from the pharynx to the crop. We combine the experimental measurements using high-speed video and X-ray phase contrast imaging with theoretical modeling to investigate the effect of abdominal pumping in liquid feeding of honeybee. Experimental results show that a honeybee performs abdominal pumping in the abdomen at a faster rhythm during sucrose solution feeding than during other physiological activities. In addition, the period of abdominal pumping is in concordance with that of dipping cycles. Theoretical analysis demonstrates that the abdomen, which is comparable with a micro pump, changes its volume rhythmically. Such expansion reduces pressure in the abdomen, which also reduces pressure in the crop and helps propel the sucrose solution from the pharynx to the crop. Abdominal pumping can help honeybees improve their feeding efficiency and save foraging time. This research work reveals a specific feeding mechanism of insects fed on sucrose solution and opens a new way for the design of microfluidic pump.

The Effect of Sodium Fluoride on Cell Apoptosis and the Mechanism of Human Lung BEAS-2B Cells In Vitro

Sodium fluoride (NaF) is a source of fluoride ions used in many applications. Previous studies found that NaF suppressed the proliferation of osteoblast MC3T3 E1 cells and induced the apoptosis of chondrocytes. However, little is known about the effects of NaF on human lung BEAS-2B cells. Therefore, we investigated the mode of cell death induced by NaF and its underlying molecular mechanisms. BEAS-2B cells were treated with NaF at concentrations of 0, 0.25, 0.5, 1.0, 2.0, and 4.0 mmol/L. Cell viability decreased and apoptotic cells significantly increased as concentrations of NaF increased over specific periods of time. The IC₅₀ of NaF was 1.9 and 0.9 mM after 24 and 48 h, respectively. The rates of apoptosis increased from 4.8 to 37.7% after NaF exposure. HE staining, electron microscopy, and single cell gel electrophoresis revealed that morphological changes of apoptosis increased with exposure concentrations. RT-PCR and Western blotting were used to detect the apoptotic pathways. The expressions of bax, caspase-3, caspase-9, p53, and the cytoplasmic CytC of the NaF groups increased, while bcl-2 and mitochondrial CytC decreased compared with that of the control group (P < 0.05). Further, the fluorescence intensities of ROS in the NaF groups were higher than those in the control group, and the membrane potential of mitochondria in the NaF group was significantly lower than that of the control group (P < 0.05). These findings suggested that NaF induced apoptosis in the BEAS-2B cells through mitochondria-mediated signal pathways. Our study provides the theoretical foundation and experimental basis for exploring the mechanisms of human lung epithelial cell damage and cytotoxicity induced by fluorine.