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Synopsis Structures specialized for adherence, such as suction cups, toe pads, barbs, and hooks, are abundant in nature. Many of these structures function well passively and are reversible, making them potent inspiration for biomimetic technology. However, the biological aspect of how these structures are used by animals in nature is often ignored or abstracted, even though active input by the animal often improves the structure’s adhesive performance. The northern clingfish, Gobiesox maeandricus, is a common animal model for bio-inspired suction cups because it performs well where standard cups cannot, such as dry, rough, and fouled surfaces. Here, we investigated whether suction performance is actively modulated in response to increasing flow speeds using a dynamic experimental design. We compared maximum suction pressures, maximum suction forces, and detachment speeds between live and euthanized clingfish. We found that both living and euthanized individuals increase suction in response to faster flows, but that live animals increased their suction to a greater extent, suggesting both behavioral and morphological components contribute to suction performance. Our results indicate that active modulation improves aspects of suction performance, making them important to consider for advancing bio-inspired design applications. 

Synopsis Biological segmented armors integrate mineralized tiles with soft tissues, forming a structure that is both puncture resistant and flexible. In the 9-banded armadillo Dasypus novemcinctus, scapular and pelvic buckler osteoderm tiles are hexagonally shaped, tapering from the superficial face down to the deep face. Each osteoderm is embedded in the dermis and adjacent osteoderms are connected to one another via connective Sharpey’s fibers. Our study hierarchically investigated the relationship between armor geometry, connective fibers, and soft supporting layers during flexion. We used micro-CT scans to inform the design of simplified 3D-printed buckler osteoderm models with 3 taper angles, 2 types of connective layers of different compliances (elastic and rigid), and one soft silicone rubber layer. Resistance to bending for 18 model combinations were tested using a 3-point bend test. We found that tapered tiles form a “sweet spot” between flexibility and rigidity. Tapered geometry decreased the stiffness of the system, while models without tapers greatly increased the stiffness via increased tile interactions. The stiff fabric set a limit for bending, regardless of taper type, and there was no additive effect when combining stiff and elastic fabrics. The silicone rubber increased the flexural stiffness of the model and helped to redistribute forces. This study further demonstrates that armadillo armor is complex and relies on hard-soft interfaces to resist bending and to translocate damaging forces. When creating bio-inspired models, it is imperative to take biological complexity into account, yet test the system hierarchically to better predict the role of the geometry as well as the material (hard and soft elements). 

Frugivorous vertebrates engage in a mutualism with fruiting plants: the former receive a nutrient subsidy, and the latter benefit by having their seeds dispersed far from parent plants. Vertebrate frugivores like primates and bats have particular morphologies suited for gripping fruit and then pulverizing fruit soft tissues; however, variation among frugivores and fruits has made the identification of common frugivore phenotypes difficult. Here, we evaluated the performance of frugivorous fish (pacu and piranha; Serrasalmidae) dentitions when puncturing fruits and seeds and compared specialist frugivorous species to facultative frugivorous and non-herbivorous relatives. We also explored how fruit characteristics affect puncture performance and how the indentation of fruit differs mechanically from harder foods like nuts. Based on expectations from studies on frugivorous bats and primates, we expected that frugivore dentitions would exhibit low force and then high work when engaging fruit tissues. Aligning with our expectation, the specialized frugivorous pacu,Colossoma, had dental performance that matched this low force, high work prediction. We also document how frugivory in omnivorous piranhas may be driven more by seed predation than a focus on softer fruit tissues like pulp. Overall, this study demonstrates remarkable similarity in the form and function of frugivore dentitions across vertebrates. 

Synopsis Biological armors have evolved across taxa as structural adaptations that provide protection from external forces while balancing mobility, metabolic cost, and functional trade-offs. These systems, from arthropod exoskeletons to vertebrate osteoderms, illustrate how natural selection shapes materials and morphology to optimize defense without compromising essential movement and physiological processes. The evolution of armor is constrained by biomechanical limits, as seen in the structural rigidity of heavily plated organisms and the flexible composites that integrate protective and dynamic properties. Methods used to study these systems—CT scanning, histology, finite element analysis, and mechanical testing—directly influence how the biological principles of armor are defined and understood. These approaches reveal the material properties and functional constraints of armored structures that can be translated into engineered applications through bioinspiration. Bioinspired designs informed by natural armor have led to innovations in impact-resistant materials, flexible ceramics, and modular protective systems. By integrating biomechanics, materials science, and evolutionary biology, this manuscript examines how armor evolves, functions, and informs bioinspired design. 

Synopsis Armor is a multipurpose set of structures that has evolved independently at least 30 times in fishes. In addition to providing protection, armor can manipulate flow, increase camouflage, and be sexually dimorphic. There are potential tradeoffs in armor function: increased impact resistance may come at the cost of maneuvering ability; and ornate armor may offer visual or protective advantages, but could incur excess drag. Pacific spiny lumpsuckers (Eumicrotremus orbis) are covered in rows of odontic, cone-shaped armor whorls, protecting the fish from wave driven impacts and the threat of predation. We are interested in measuring the effects of lumpsucker armor on the hydrodynamic forces on the fish. Bigger lumpsuckers have larger and more complex armor, which may incur a greater hydrodynamic cost. In addition to their protective armor, lumpsuckers have evolved a ventral adhesive disc, allowing them to remain stationary in their environment. We hypothesize a tradeoff between the armor and adhesion: little fish prioritize suction, while big fish prioritize protection. Using micro-CT, we compared armor volume to disc area over lumpsucker development and built 3D models to measure changes in drag over ontogeny. We found that drag and drag coefficients decrease with greater armor coverage and vary consistently with orientation. Adhesive disc area is isometric but safety factor increases with size, allowing larger fish to remain attached in higher flows than smaller fish. 

MONOLITh is a bioinspired, untethered crawling soft robot. The body is made from a lightweight reticulated foam that provides passive shape restoration and supports the internally embedded components (motors, battery, wireless controller). DC motors pull tendons attached to an external fabric that distributes forces, and novel differential friction elements enable forward locomotion. This robot is capable of traveling at a maximum speed of 0.1 body lengths/sec, lifting 100% its body weight, while remaining 95% soft materials by volume. We expect that the design principles and materials used to make this low cost and scalable robot will lead to the development of useful, and commercially viable, terrestrial or extraterrestrial vehicles. 

Abstract The elongate body plan is present in many groups of fishes, and this morphology dictates functional consequences seen in swimming behavior. Previous work has shown that increasing the number of vertebrae, or decreasing the intervertebral joint length, in a fixed length artificial system increases stiffness. Tails with increased stiffness can generate more power from tail beats, resulting in an increased mean swimming speed. This demonstrates the impacts of morphology on both material properties and kinematics, establishing mechanisms for form contributing to function. Here, we wanted to investigate relationships between form and ecological function, such as differences in dietary strategies and habitat preferences among fish species. This study aims to characterize and compare the kinematics, material properties, and vertebral morphology of four species of elongate fishes: Anoplarchus insignis, Anoplarchus purpurescens, Xiphister atropurpureus, and Xiphister mucosus. We hypothesized that these properties would differ among the four species due to their differential ecological niches. To calculate kinematic variables, we filmed these fishes swimming volitionally. We also measured body stiffness by bending the abdominal and tail regions of sacrificed individuals in different stages of dissection (whole body, removed skin, removed muscle). Finally, we counted the number of vertebrae from CT scans of each species to quantify vertebral morphology. Principal component and linear discriminant analyses suggested that the elongate fish species can be distinguished from one another by their material properties, morphology, and swimming kinematics. With this information combined, we can draw connections between the physical properties of the fishes and their ecological niches. 

Abstract One key evolutionary innovation that separates vertebrates from invertebrates is the notochord, a central element that provides the stiffness needed for powerful movements. Later, the notochord was further stiffened by the vertebrae, cartilaginous and bony elements, surrounding the notochord. The ancestral notochord is retained in modern vertebrates as intervertebral material, but we know little about its mechanical interactions with surrounding vertebrae. In this study, the internal shape of the vertebrae—where this material is found—was quantified in sixteen species of fishes with various body shapes, swimming modes, and habitats. We used micro-computed tomography to measure the internal shape. We then created and mechanically tested physical models of intervertebral joints. We also mechanically tested actual vertebrae of five species. Material testing shows that internal morphology of the centrum significantly affects bending and torsional stiffness. Finally, we performed swimming trials to gather kinematic data. Combining these data, we created a model that uses internal vertebral morphology to make predictions about swimming kinematics and mechanics. We used linear discriminant analysis (LDA) to assess the relationship between vertebral shape and our categorical traits. The analysis revealed that internal vertebral morphology is sufficient to predict habitat, body shape, and swimming mode in our fishes. This model can also be used to make predictions about swimming in fishes not easily studied in the lab, such as deep sea and extinct species, allowing the development of hypotheses about their natural behavior.