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Abstract Sea star armor comes in the form of a highly articulated endoskeleton made up of individual elements called ossicles. Many descriptive studies have been conducted on the basic patterning of sea star skeletons, with differences in ossicle shape forming the basis of some echinoderm phylogenies. However, ossicle function is not related only to individual element morphology, but rather the whole system. In this study, we use micro-computed tomography (CT) to describe and compare skeletal anatomy of nine sea star species from the Salish Sea, Washington, USA. We quantified 14 morphological traits and tested whether or not they were predictors of ecology. We expected to see that differences in the amount of armoring (relative volume of skeleton) arise from varying arrangement and shape of ossicles across distinct regions of the body. For broad comparability, we grouped skeletal elements into five basic types of ossicles. The amount of skeletal armoring across the body varied by at least an order of magnitude across species and differed in its distribution across ossicle types. Heavily armored sea stars invest in larger, boxy body wall ossicles, whereas a reduction in armor volume was often paired with more intricately-shaped body wall ossicles and an increase in the number and complexity of spines. 

Synopsis Dermal armor serves a variety of functions across animal lineages including defense, offense, display, and prehension. Small differences in armor structure, plate size, or overlap may complement large differences in behavior or ecology. We characterized damage to an armored fish—the gray starsnout poacher (Bathyagonus alascanus) to probe whether there are differences in plate function within a single species. We quantified damage to poacher armor and skeleton under different force modes, including crushing, puncture, abrasion, and blunt impact, using micro-computed tomography, scanning electron microscopy, and material testing. Armor in the posterior region of the fish can withstand higher stress during crushing, suggesting they are well protected while fleeing from a crushing predator. It takes more work to puncture the anterior armor, perhaps poachers tend to face an animal threatening a puncturing attack. The dorsal plate spines are often eroded away from abrasion and/or blunt impact; we posit that the spineless ventral plates are smooth because strong sub-tidal currents cause collisions with a rocky substrate that would quickly destroy ventral spines if the plates were so equipped. The imbricated armor of B. alascanus has a diversity of performance against different threats, and this varies with location. 

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 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 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.