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Synopsis Crossing traditional disciplinary boundaries can accelerate advances in scientific knowledge, often to the great service of society. However, integrative work entails certain challenges, including the tendency for individual specialization and the difficulty of communication across fields. Tools like the AskNature database and an engineering-to-biology thesaurus partially reduce the barrier to information flow between biology and engineering. These tools would be complemented by a big-picture framework to help researchers and designers conceptually approach conversations with colleagues across disciplines. Here, I synthesize existing ideas to propose a conceptual framework organized around function. The basic framework highlights the contributions of sub-organismal traits (e.g., morphology, physiology, biochemistry, material properties), behavior, and the environment to functional outcomes. I also present several modifications of the framework that researchers and designers can use to make connections to higher levels of biological organization and to understand the influence neural control, development/ontogeny, evolution, and trade-offs in biological systems. The framework can be used within organismal biology to unite subfields, and also to aid the leap from organismal biology to bioinspired design. It provides a means for mapping the often-complex pathways among organismal and environmental characteristics, ultimately guiding us to a deeper understanding of organismal function. 

ABSTRACT Multiarticular muscle systems are widespread across vertebrates, including in their necks, digits, tails and trunks. In secondarily limbless tetrapods, the multiarticular trunk muscles power nearly all behaviors. Using snakes as a study system, we previously used anatomical measurements and mathematical modeling to derive an equation relating multiarticular trunk muscle shortening to postural change. However, some snake trunk muscles have long, thin tendinous connections, raising the possibility of elastic energy storage, which could lead to a decoupling of muscle length change from joint angle change. The next step, therefore, is to determine whether in vivo muscle shortening produces the postural changes predicted by mathematical modeling. A departure from predictions would implicate elastic energy storage. To test the relationship between muscle strain and posture in vivo, we implanted radio-opaque metal beads in three muscles of interest in four corn snakes (Pantherophis guttatus), then recorded X-ray videos to directly measure muscle shortening and vertebral column curvature during locomotion. Our in vivo results produced evidence that elastic energy storage does not play a substantial role in corn snake lateral undulation or tunnel concertina locomotion. The ability to predict muscle shortening directly from observed posture will facilitate future work. Moreover, the generality of our equation, which uses anatomical values that can be measured in many types of animals, means that our framework for understanding multiarticular muscle function can be applied in numerous study systems to provide a stronger mechanistic understanding of organismal function. 

Abstract Organismal solutions to natural challenges can spark creative engineering applications. However, most engineers are not experts in organismal biology, creating a potential barrier to maximally effective bioinspired design. In this review, we aim to reduce that barrier with respect to a group of organisms that hold particular promise for a variety of applications: snakes. Representing >10% of tetrapod vertebrates, snakes inhabit nearly every imaginable terrestrial environment, moving with ease under many conditions that would thwart other animals. To do so, they employ over a dozen different types of locomotion (perhaps well over). Lacking limbs, they have evolved axial musculoskeletal features that enable their vast functional diversity, which can vary across species. Different species also have various skin features that provide numerous functional benefits, including frictional anisotropy or isotropy (as their locomotor habits demand), waterproofing, dirt shedding, antimicrobial properties, structural colors, and wear resistance. Snakes clearly have much to offer to the fields of robotics and materials science. We aim for this review to increase knowledge of snake functional diversity by facilitating access to the relevant literature.