Integrative and Comparative Biology最新文献

Hydrostatic skeletons enable the transmission of mechanical work through a soft body. Despite the ubiquity of these structures among animals, we have a relatively rudimentary understanding of how they operate mechanically. Here we consider a mathematical model of the mechanics of a relatively tractable hydrostatic skeleton, the tube feet of sea stars. Tube feet drive locomotion by generating a pushing force against the environment. This pushing force is created by the transmission of pressure from one chamber, the ampulla, to another, the stem, which extends from the oral surface of the body. This system operates as a compound machine with a mechanical advantage (MA, the ratio of output to input force) that varies with the geometry of its two chambers. We present an analytical approach for parameterizing the model from morphometric measurements and formulating predictions for representative morphologies. Our analysis predicts that MA initially increases as the stem extends, but collapses to zero near maximum extension. The decrease in force output occurs because the angle of cross-helical fiber winding in the stem approaches the critical point of 54.7°, an angle at which the force components exactly balance the hoop and longitudinal forces from pressure. Though producing no axial force at full extension, a bent tube foot can still generate perpendicular forces that generate torque to lift and propel the body, a proposition that is supported by kinematic observations of the tube feet. These results provide a framework for understanding tube foot mechanics across echinoderms and highlight the functional significance of helical-fiber arrangements in hydrostatic skeletons.

The pandemic-driven shift to online learning necessitated a re-evaluation of traditional exams, revealing their limitations in fostering essential scientific skills and potentially disadvantaging some students. This paper presents sketchnoting, a visual note-taking method, as an authentic alternative assessment. By integrating scientific concepts, peer review, and graphical literacy, this approach aimed to cultivate skills like critical thinking and communication while assessing content. Student feedback indicated enhanced learning, skill development, and preference for sketchnotes over exams, despite similar workload. Notably, this flexible assessment correlated with reduced performance disparities. This study advocates for reimagining assessment to prioritize skill development, promote equity, and improve learning outcomes, emphasizing the value of pedagogical collaboration in driving innovation.

Plants are fundamental to life, providing oxygen, food, and climate regulation, while also offering solutions to global challenges. Integrating plant biology into an undergraduate curriculum, while supporting and nurturing students' career interests present both opportunities and challenges. Undergraduate biology education often overlooks plants due to limited student interest and a strong focus on health professions, particularly among women and underrepresented minorities. Here, we describe how plants are incorporated in the Biology curriculum at Spelman College, a women's liberal arts college and a Historically Black College and University where Biology is a popular major. The department has successfully embedded plant biology across its skills and competency-based curriculum, from the foundational introductory sequence to upper-level electives and research experiences. Students learn core biological concepts in the introductory core curriculum, consisting of four courses progressing from ecological to molecular levels, where plant-related content is integrated through inquiry driven, hands-on activities or field trips. In upper-level electives and research-based courses, faculty offer a robust program in plant biology that enables deeper understanding and integration across disciplines as they address real world problems that intersect with students' diverse interests. Survey data indicate that students perceive a balanced exposure to plants and other organisms in introductory courses and recognize the importance of plants for understanding core biological principles. Although this exposure does not significantly shift their primary career interest in medicine, it contributes to a broad biology education, skill development, and an increased interest in research.

Proprioception can be seen as a somatic sense stimulated by the action of the body itself. It is perceived through proprioceptors and is tightly linked to the animal body, as it is influenced by the biomechanical properties of the structures in which it is embedded. A specific class of these receptors, the muscle proprioceptors, project at several levels of the nervous system and provide information about limb position, whether in the presence or absence of movement, as well as muscle length, the sense of effort, and the sense of balance. In skeletal systems, proprioception is involved in postural maintenance, reflex actions, and rhythmic behaviors, but also in higher functions such as action planning and prediction. Proprioception can also be found in structures that are capable of movement without any real skeleton and are therefore called hydrostatic skeletons, both in humans and other animals. Hydrostatic bodies, including cephalopod limbs, the elephant trunk, and the human tongue, use muscle contractile forces to generate hydrostatic pressure, which acts as a skeleton to stabilize the structure and create motion. To provide online motion control of these bodies, the animal nervous system must cope with a huge amount of information coming from variables (such as length, angle, stiffness, and orientation) that continuously change throughout the entire structure. To limit this central burden, these structures may benefit from the presence of a muscle proprioceptive system used locally to control muscle contraction. Based on the current knowledge, many of the basic components of the proprioceptive system of soft-bodied and skeletal animals are essentially the same. Here, we aim to provide a forward-looking perspective on the role of muscle proprioception in motion, with a special focus on proprioception in muscular hydrostats. We wish to highlight the relevance of this topic across several fields of investigation, from human sensorimotor pathologies to soft robotics, where a high degree of autonomy in soft structures, combined with a reduced control demand, remains an unmet need. To address these gaps, we emphasize the need for improved knowledge and methodological assessment of this "sixth sense."

Representation in science, science curricular development, and scientific outcomes is driven by our motivated thinking and reasoning. This in turn influences how we reason about issues related to equity, diversity, inclusion, and social justice. This paper unpacks perspectives about the influence of motivated thinking on representation and on perceptions of representation in the science curricula, more specifically Black representation in the qualitative and quantitative works of the first author. Motivated thinking influences many aspects of science and science education, including the research questions we choose, the scientists whom we choose to highlight in our classroom examples, the outcomes we desire from our research and teaching, and even the scope of our scientific disciplines. Molden and Higgins' breakdown of motivated thinking is used to frame observations about the influence of motivated thinking on the outcomes and processes of research, and to provide thought provoking questions and considerations given our current, future, and past social, cultural, political, historical, and scientific context and underpinnings. As a perspective piece, this paper toggles between the first-person narrations of the first author and the supporting research.

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.

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.

The anatomy and function of tactile structures, such as vibrissae, are typically studied in captive animals, but we know little about how tactile structures compare between captive and wild animals. We analyzed trunk tip morphology in wild (n = 6) and captive (n = 6) adult African savanna elephants (Loxodonta africana). We found striking differences in both vibrissae and skin structure between the two groups. Wild elephants showed significant vibrissae abrasion, with frontal trunk tip vibrissae often entirely worn down, whereas captive elephants retained proportionally more long vibrissae, particularly along the trunk tip rim. In wild elephants, vibrissae rarely exceeded 1 cm in length, whereas many captive individuals had vibrissae several centimeters long. In contrast, vibrissae inside the nostril-a trunk region not directly exposed to feeding-were similar in length and density between wild and captive elephants. Additionally, trunk tip skin in wild elephants appeared to be worn down to a smooth surface, whereas all captive elephants showed distinct papillary skin structure and folds at the lateral trunk tip opening and nasal septum. These findings suggest that wild elephants experience feeding-related trunk abrasion, leading to significant alterations in both vibrissa structure and skin texture. Our results highlight the importance of studying sensory structures in wild animals to understand sensing in natural environments.

Tails serve diverse evolutionary functions across species, but their mechanical role during complex climbing maneuvers remains understudied. We investigated how Long-Evans rats (Rattus norvegicus) use their tails when climbing up and over a ledge with a climbing bar positioned 23-32 cm above a bottom platform. Using force measurements and motion tracking, we quantified tail-generated impulse during climbing and found that tail usage followed an inverse relationship between the impulse they imparted to the bottom platform and the usage of their tail: a higher initial jumping impulse required less assistance from the tail, while a lower initial momentum required a greater compensatory force from the tail. When climbing from greater depths (up to 32 cm), rats maintained consistent jumping impulse but significantly increased tail usage, suggesting a preference for a reliable strategy with mid-climb adjustments rather than pre-calibrated jumping force. Rats demonstrated one-shot learning when the forelimb torque was eliminated by covertly unlocking the climbing bar. After a single near-failure, they shifted from a dynamic, ballistic climbing style to a more controlled, quasistatic approach. This new method involved increased tail usage and adjusted body positioning to reduce gravitational moments. These findings reveal that rats employ their tails as actively controlled limbs that contribute substantial forces during complex maneuvers, adapting usage based on initial conditions and mechanical constraints.

Inaquatic ecosystems, freshwater planarians (Dugesia spp.) function as predators, employing specialized adaptations for capturing live prey. This exploratory study examines the predatory interactions between the freshwater planarian Dugesia spp. and the California blackworm (Lumbriculus variegatus). Observations demonstrate that Dugesia is capable of capturing prey more than twice its own length. The predation process involves a dual adhesion mechanism whereby the planarian adheres simultaneously to the blackworm and the substrate, effectively immobilizing its prey. Despite the rapid escape response of blackworms, characterized by a helical swimming gait with alternating handedness, planarian adhesion frequently prevents successful escape, with no significant effect of worm size. Subsequently, Dugesia employs an eversible pharynx to initiate ingestion, consuming the internal tissues of the blackworm through suction. Blackworm injury significantly increased vulnerability to predation, suggesting that chemical cues from wounds may aid planarians in prey detection. This study provides insights into the biomechanics and behaviors of predation involving two interacting muscular hydrostats, highlighting the critical adaptations that enable planarians to subdue and consume relatively large, mobile prey.