The biomechanics of sensory organs

Studies of mechanosensory systems have largely focused on the filter characteristics of their neural components in relation to their ultimate function. Less attention has focused on the role of the physical structure of the sensory organ which also acts as a mechanical filter of the sensory input. This biomechanical filtering is readily apparent in the case of several mechanosensory systems that transduce information about the deformations of the sensory organs in response to external forces. Because these deformations critically depend on the geometry and material properties of the mechanosensory organs, it is necessary to conduct focused studies on the biomechanical characteristics of these organs when studying the encoding properties of the mechanosensory system. Modern experimental tools such as Laser Doppler Vibrometry and computational tools such as Computational Fluid Dynamics and Finite Element Analysis provide the means for determining the sensory pre-filtering properties of small-scale mechanosensory structures. In all the cases covered in this review, the physical properties of the sensory organs play a central role in determining the signals received by the nervous system

Bio-inspired Antennal Tactile Sensing

Vision dominates perception research in robotics and biology, but for many animals, it is not the dominant sensory system. Indeed, arthropods often rely on sensory cues sampled via a pair of passive head-mounted antennae to achieve navigation and control. These mechanosensory structures support multimodal receptors—tactile, hygrometric, thermal, olfactory—enabling a wide range of sensorimotor behaviors. One model biological system, Periplaneta americana cockroach, performs a remarkably robust escape behavior by using its long, slender, flexible antennae to facilitate rapid closed-loop course control. The antenna is a passive, hyper-redundant kinematic linkage that acts as a distributed tactile sensory structure to mediate mechanical interactions with the environment at very high rates. This thesis demonstrates that the antennal mechanics are tuned to enable high-speed, high-bandwidth locomotor control even in total darkness. Despite the extraordinary success of antennal sensing in nature, there are few effective bio-inspired antennae. To incorporate similar antennal sensing capability in agile mobile robots, I developed a tunable bio-inspired modular robotic research antenna and experimentation platform. I also synthesized numerical models to approximate antenna mechanics under relevant boundary conditions, which I verified against my physical model. Both numerical simulations and physical experiments were conducted to isolate fundamental parameters that underly the stability and performance I observed in the biological model. Using a combination of numerical and robotic experiments, in concert with biological experiments conducted by my collaborators, I discovered that several behaviorally relevant characteristics of an antennae are predominantly governed by a combination of (1) the stiffness profile of the antenna and (2) the interaction of hairlike mechano-structures along the length of the antenna. I found that the “right” combination of these features improves the postural stability and the steady state spatial acuity of tactile interaction with the environment. Specifically, antennae with an exponentially decreasing stiffness profile accompanied by distally pointing anisotropic mechano-hairs are ideal for navigation tasks, and greatly facilitate stable high-speed wall following

Functional properties of insect olfactory receptors: ionotropic receptors and odorant receptors

The majority of insect olfactory receptors belong to two distinct protein families, the ionotropic receptors (IRs), which are related to the ionotropic glutamate receptor family, and the odorant receptors (ORs), which evolved from the gustatory receptor family. Both receptor types assemble to heteromeric ligand-gated cation channels composed of odor-specific receptor proteins and co-receptor proteins. We here present in short the current view on evolution, function, and regulation of IRs and ORs. Special attention is given on how their functional properties can meet the environmental and ecological challenges an insect has to face

The damping and structural properties of dragonfly and damselfly wings during dynamic movement

For flying insects, stability is essential to maintain the orientation and direction of motion in flight. Flight instability is caused by a variety of factors, such as intended abrupt flight manoeuvres and unwanted environmental disturbances. Although wings play a key role in insect flight stability, little is known about their oscillatory behaviour. Here we present the first systematic study of insect wing damping. We show that different wing regions have almost identical damping properties. The mean damping ratio of fresh wings is noticeably higher than that previously thought. Flight muscles and hemolymph have almost no ‘direct’ influence on the wing damping. In contrast, the involvement of the wing hinge can significantly increase damping. We also show that although desiccation reduces the wing damping ratio, rehydration leads to full recovery of damping properties after desiccation. Hence, we expect hemolymph to influence the wing damping indirectly, by continuously hydrating the wing system

Investigation of visual pathways in honeybees (Apis mellifera) and desert locusts (Schistocerca gregaria): anatomical, ultrastructural, and physiological approaches

Many insect species demonstrate sophisticated abilities regarding spatial orientation and navigation, despite their small brain size. The behaviors that are based on spatial orientation differ dramatically between individual insect species according to their lifestyle and habitat. Central place foragers like bees and ants, for example, orient themselves in their surrounding and navigate back to the nest after foraging for food or water. Insects like some locust and butterfly species, on the other hand, use spatial orientation during migratory phases to keep a stable heading into a certain direction over a long period of time. In both scenarios, homing and long-distance migration, vision is the primary source for orientation cues even though additional features like wind direction, the earth’s magnetic field, and olfactory cues can be taken into account as well. Visual cues that are used for orientational purposes range from landmarks and the panorama to celestial cues. The latter consists in diurnal insects of the position of the sun itself, the sun-based polarization pattern and intensity and spectral gradient, and is summarized as sky-compass system. For a reliable sky-compass orientation, the animal needs, in addition to the perception of celestial cues, to compensate for the daily movement of the sun across the sky. It is likely that a connection from the circadian pacemaker system to the sky-compass network could provide the necessary circuitry for this time compensation. The present thesis focuses on the sky-compass system of honeybees and locusts. There is a large body of work on the navigational abilities of honeybees from a behavioral perspective but the underlying neuronal anatomy and physiology has received less attention so far. Therefore, the first two chapters of this thesis reveals a large part of the anatomy of the anterior sky-compass pathway in the bee brain. To this end, dye injections, immunohistochemical stainings, and ultrastructural examinations were conducted. The third chapter describes a novel methodical protocol for physiological investigations of neurons involved in the sky-compass system using calcium imaging in behaving animals. The fourth chapter of this thesis deals with the anatomical basis of time compensation in the sky-compass system of locusts. Therefore, the ultrastructure of synaptic connections in a brain region of the desert locust where the contact of both systems could be feasible has been investigated

It’s Not a Bug, It’s a Feature: Functional Materials in Insects

Over the course of their wildly successful proliferation across the earth, the insects as a taxon have evolved enviable adaptations to their diverse habitats, which include adhesives, locomotor systems, hydrophobic surfaces, and sensors and actuators that transduce mechanical, acoustic, optical, thermal, and chemical signals. Insect‐inspired designs currently appear in a range of contexts, including antireflective coatings, optical displays, and computing algorithms. However, as over one million distinct and highly specialized species of insects have colonized nearly all habitable regions on the planet, they still provide a largely untapped pool of unique problem‐solving strategies. With the intent of providing materials scientists and engineers with a muse for the next generation of bioinspired materials, here, a selection of some of the most spectacular adaptations that insects have evolved is assembled and organized by function. The insects presented display dazzling optical properties as a result of natural photonic crystals, precise hierarchical patterns that span length scales from nanometers to millimeters, and formidable defense mechanisms that deploy an arsenal of chemical weaponry. Successful mimicry of these adaptations may facilitate technological solutions to as wide a range of problems as they solve in the insects that originated them.Insects have evolved manifold optimized solutions to everyday problems. The diversity and precision of their hierarchical material adaptations often outsmart and outperform current man‐made approaches. These materials hence provide an excellent basis for the inspiration of new technological approaches by taking design cues from nature’s solutions.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143760/1/adma201705322.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143760/2/adma201705322_am.pd

Coatings preventing insect adhesion: An overview

Insect pests cause considerable damage worldwide to plants, buildings and human health. This review explores how controlling insect adhesion to coatings might mitigate these problems. We summarise the current knowledge of the mechanisms of insect adhesion on natural and synthetic surfaces and natural examples of non-adhesive and slippery surfaces. Biomimetic, multi-scaled rough and particle-transferring surfaces provide an efficient method to reduce adhesion of crawling insects.</p

Integrating perspectives in actinomycete research: an ActinoBase review of 2020-21

Last year ActinoBase, a Wiki-style initiative supported by the UK Microbiology Society, published a review highlighting the research of particular interest to the actinomycete community. Here, we present the second ActinoBase review showcasing selected reports published in 2020 and early 2021, integrating perspectives in the actinomycete field. Actinomycetes are well-known for their unsurpassed ability to produce specialised metabolites, of which many are used as therapeutic agents with antibacterial, antifungal, or immunosuppressive activities. Much research is carried out to understand the purpose of these metabolites in the environment, either within communities or in host interactions. Moreover, many efforts have been placed in developing computational tools to handle big data, simplify experimental design, and find new biosynthetic gene cluster prioritisation strategies. Alongside, synthetic biology has provided advances in tools to elucidate the biosynthesis of these metabolites. Additionally, there are still mysteries to be uncovered in understanding the fundamentals of filamentous actinomycetes' developmental cycle and regulation of their metabolism. This review focuses on research using integrative methodologies and approaches to understand the bigger picture of actinomycete biology, covering four research areas: i) technology and methodology; ii) specialised metabolites; iii) development and regulation; and iv) ecology and host interactions