Elemental composition and material properties of radular teeth in the heterobranch snail Gastropteron rubrum (Mollusca, Gastropoda, Cephalaspidea) foraging on hard organisms.

The molluscan feeding structure is the radula, a chitinous membrane with teeth, which are highly adapted to the food and the substrate to which the food is attached. In Polyplacophora and Patellogastropoda, the handling of hard ingesta can be facilitated by high content of chemical compounds containing Fe or Si in the tooth cusps. Other taxa, however, possess teeth that are less mineralized, even though animals have to avoid structural failure or high wear during feeding as well. Here, we investigated the gastropod Gastropteron rubrum, feeding on hard Foraminifera, diatoms and Porifera. Tooth morphologies and wear were documented by scanning electron microscopy and their mechanical properties were tested by nanoindentation. We determined that gradients of hard- and stiffness run along each tooth, decreasing from cusp to basis. We also found that inner lateral teeth were harder and stiffer than the outer ones. These findings allowed us to propose hypotheses about the radula-ingesta interaction. In search for the origins of the gradients, teeth were visualized using confocal laser scanning microscopy, to determine the degree of tanning, and analyzed with energy-dispersive X-ray spectroscopy, to test the elemental composition. We found that the mechanical gradients did not have their origins in the elemental content, as the teeth did not contain high proportions of metals or other minerals. This indicates that their origin might be the degree of tanning. However, in the tooth surfaces that interact with the ingesta high Si and Ca contents were determined, which is likely an adaptation to reduce wear.

A switchable joint in the head of dragonfly larvae (Insecta: Odonata) as key to the multifunctionality of the prehensile labial mask.

Dragonfly and damselfly larvae (Insecta: Odonata) capture prey by rapid protraction of a raptorial mouthpart, based on a modified labium. Yet, in insects with biting-chewing mouthparts, the labium has an essential role in food handling. These two distinct functions -prey capturing and handling-lead to a mechanical problem in Odonata larvae: while the labium is always protracted in a straight line during prey capture, food handling requires more dexterity. In this study, we investigate the role of the labium in the feeding process and analyse the mechanics of the labial joints in the dragonfly larva Anax imperator. Our results show that the labium features a multiaxial joint connecting the basal segment (postmentum) and the head. During feeding, a combination of rotations around different axes is used to handle and orient prey, which is unique among biting-chewing mouthparts. Furthermore, we identified structures at the joint which likely restrict lateral motion during the predatory strike. Our results provide a further understanding of the unique prey-capturing apparatus of odonate larvae capable of controlling a 'switchable' multiaxial to a restricted monoaxial joint. This concept highlights the evolution of a highly modified raptorial mouthpart appendage where the degrees of freedom can be actively restricted to allow for the respectively needed functionality.

A controllable dual-catapult system inspired by the biomechanics of the dragonfly larvae's predatory strike.

The biomechanics underlying the predatory strike of dragonfly larvae is not yet understood. Dragonfly larvae are aquatic ambush predators, capturing their prey with a strongly modified extensible mouthpart. The current theory of hydraulic pressure being the driving force of the predatory strike can be refuted by our manipulation experiments and reinterpretation of former studies. Here, we report evidence for an independently loaded synchronized dual-catapult system. To power the ballistic movement of a single specialized mouthpart, two independently loaded springs simultaneously release and actuate two separate joints in a kinematic chain. Energy for the movement is stored by straining an elastic structure at each joint and, possibly, the surrounding cuticle, which is preloaded by muscle contraction. As a proof of concept, we developed a bioinspired robotic model resembling the morphology and functional principle of the extensible mouthpart. Understanding the biomechanics of the independently loaded synchronized dual-catapult system found in dragonfly larvae can be used to control the extension direction and, thereby, thrust vector of a power-modulated robotic system.

Illuminating nature's beauty: modular, scalable and low-cost LED dome illumination system using 3D-printing technology.

Presenting your research in the proper light can be exceptionally challenging. Meanwhile, dome illumination systems became a standard for micro- and macrophotography in taxonomy, morphology, systematics and especially important in natural history collections. However, proper illumination systems are either expensive and/or laborious to use. Nowadays, 3D-printing technology revolutionizes lab-life and will soon find its way into most people's everyday life. Consequently, fused deposition modelling printers become more and more available, with online services offering personalized printing options. Here, we present a 3D-printed, scalable, low-cost and modular LED illumination dome system for scientific micro- and macrophotography. We provide stereolithography ('.stl') files and print settings, as well as a complete list of necessary components required for the construction of three differently sized domes. Additionally, we included an optional iris diaphragm and a sliding table, to arrange the object of desire inside the dome. The dome can be easily scaled and modified by adding customized parts, allowing you to always present your research object in the best light.

Step by step and frame by frame - Workflow for efficient motion tracking of high-speed movements in animals.

Analysing the motion of animals, especially at high speeds, is often challenging. Motion tracking software needs to deal with a variety of visual contexts, variable lighting conditions, heterogeneous backgrounds and even background movements. Here we present motion tracking via the easy to use and constantly updated Adobe After Effects software - which is often included in software packages most researchers are already using. The provided custom-made Javascript allows for easy exporting of tracking coordinates. Furthermore, some examples for analysing the obtained data in the open source statistical software 'R' will provide reference points, even for an unexperienced user. We present a step-by-step guide of the methodology using high-speed video recordings of locust jumps and additionally validate this method by successful tracking of simulated data under defined subpar filming conditions. This simulated data allows experienced users to compare the tracking software in use with the here presented workflow to weigh the advantages and disadvantages of any motion tracking software on the market.

Traction reinforcement in prehensile feet of harvestmen (Arachnida, Opiliones).

Prehensile and gripping organs are recurring structures in different organisms that enhance friction by the reinforcement and redirection of normal forces. The relationship between organ structure and biomechanical performance is poorly understood, despite a broad relevance for microhabitat choice, movement ecology and biomimetics. Here, we present the first study of the biomechanics of prehensile feet in long-legged harvestmen. These arachnids exhibit the strongest sub-division of legs among arthropods, permitting extreme hyperflexion (i.e. curling up the foot tip). We found that despite the lack of adhesive foot pads, these moderately sized arthropods are able to scale vertical smooth surfaces, if the surface is curved. Comparison of three species of harvestmen differing in leg morphology shows that traction reinforcement by foot wrapping depends on the degree of leg sub-division, not leg length. Differences are explained by adaptation to different microhabitats on trees. The exponential increase of foot section length from distal to proximal introduces a gradient of flexibility that permits adaptation to a wide range of surface curvature while maintaining integrity at strong flexion. A pulley system of the claw depressor tendon ensures the controlled flexion of the high number of adesmatic joints in the harvestman foot. These results contribute to the general understanding of foot function in arthropods and showcase an interesting model for the biomimetic engineering of novel transportation systems and surgical probes.