Integrative and Comparative Biology最新文献

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.

Evolution of the mobile tetrapod tongue replaced the functional roles of water during feeding in ancestral fish. The tongue as an analogue of water is most clearly manifested in the protean shape changes permitted by hydrostatic mechanisms intrinsic to the complexly muscled tongues of mammals and lepidosaurian reptiles (tuatara, lizards, and snakes), which include the orthogonal and circular fiber systems characteristic of muscular hydrostats. I examine the morphology of lepidosaurian tongues and evidence for their use of hydrostatic mechanisms during several behaviors encompassing two major biological roles: feeding and chemoreception. Specifically, I consider, (a) lingual prey capture in iguanian lizards (and tuatara); (b) lingual prey capture in a non-iguanian species, the blue-tongued skink (Tiliqua scincoides); (c) tongue projection in chameleons; and (d) chemosensory tongue-flicking in lizards and snakes (squamates). All behaviors result in significant tongue protrusion beyond the jaw margins. During lingual prey capture in (non-chameleon) iguanians, tongue protrusion is tightly coupled to hyobranchial movement, with little evidence of hydrostatic shape change while visible, whereas lingual prey capture in Tiliqua is entirely dependent on extensive hydrostatic tongue deformation, including elongation, broadening, and elaborate, localized shape changes. Tuatara (Sphenodon) show no evidence of hydrostatic shape change as of yet. Tongue projection in chameleons depends on preloading elastic energy within the accelerator muscle via hydrostatic elongation. In vivo measurements from x-ray film of a chameleon with implanted markers show that elongation continues after projection throughout the ballistic phase until prey capture and that total accelerator muscle elongation is 267% of resting length. Finally, chemosensory tongue-flicking in all squamates, including iguanians, is driven by hydrostatic elongation. However, protrusion distance in iguanians is limited by the tongue's extensive anatomical coupling to the hyobranchium. Snakes exhibit a unique form of rapid, oscillatory tongue-flicking that is reflected in the tongue's derived muscle fiber architecture. I suggest that the extensive phenotypic variation present in lepidosaurian tongues might make them more effective than the better studied mammals as a model system for elucidating form-function relationships in a muscular hydrostat.

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.

Animals encounter information simultaneously, combining input from multiple sensory systems before responding behaviorally. When cues in different sensory modalities interact, they may have direct impacts on sensory perception, allowing the animal to perceive stimuli that it would otherwise have missed, or the cues may instead impact motivation, tightly honing the animal's focus onto a stimulus or distracting it. Here, we investigated how interacting chemical and visual cues affected behavior in adult zebrafish (Danio rerio). Chemical cues can enhance the visual perception of zebrafish directly, for example, through the terminal nerve axons of the olfactory bulb that project to the neural retina. Alternatively, chemical cues may increase attention to or distract individuals from visual cues. Furthermore, the salience or strength of each cue may determine how the animal responds. Specifically, we tested if the reflexive response to an optomotor response (OMR) visual cue differed when presented with alanine, an amino acid that mimics foraging chemical cues, to explore if cues in a second sensory modality can affect reflexive responses. We found that foraging chemical cues did not affect zebrafish's likelihood of responding to the visual cue, and thus likely did not affect perception of visual cues. However, fish took longer to respond to visual cues in the presence of chemical cues, and this delayed response was significant only when the visual cue was weak. These findings suggest that the primary effect of secondary sensory cues may be through shifts in motivation rather than perception. We also found that the relative significance (salience) of interacting cues has important implications on determining the outcomes of sensory interactions.

Perhaps no other biological structure has inspired as many engineering applications as the nest of the honeybee Apis mellifera. It is primarily just the hexagonal unit cell, with its material-minimizing benefits, that has been abstracted as a design principle for bio-inspired structures. This is in part because of design constraints associated with manufacturing honeycomb panels, but also due to our limited understanding of the benefits of other design features of interest. The bee's honeycomb has several interesting meso-structural design elements, like the corner radius and the wall coping, which can be replicated using additive manufacturing processes. In this paper, we first identify and categorize these meso-scale design elements at four levels: (i) the unit cell shape, (ii) its size and distribution, (iii) the features that make up the unit cell and the parameters associated with them, and (iv) the integration of the cells into the build environment. Once identified, we attribute functional bases to each of these features, leveraging prior and ongoing studies in biology, as well as in materials science and mechanics. We then identify promising design principles for further advancing the engineering of honeycomb structures using additive manufacturing, as well as call out opportunities for future research. More generally, this paper argues for the importance of considering meso-structural design elements, beyond just unit cell selection, in the design of cellular materials.

Animal locomotion arises from the interaction between motor commands from the nervous system and the body's mechanical properties. The field of neuromechanics has traditionally framed locomotion as a product of neural control, body mechanics, and sensory feedback. However, many animals deviate from this conventional paradigm. An example includes echinoderms that combine centralized nervous control with local control that is distributed across hundreds of their locally regulated tube feet that collectively generate locomotion. Here, we review our work combining animal experiments, robotics, and computational modeling to investigate the control architecture of sea stars. Based on our findings, we propose the concept of collective neuromechanics-a control architecture that balances centralized and local collective control among hundreds of autonomous appendages within a single system. This framework expands the scope of neuromechanics by incorporating collective behavior and offers insights into novel control architectures in both biological and engineered systems.

Advanced biology courses, particularly terminology-heavy organismal biology courses, pose unique challenges, which were further compounded by the Covid-19 pandemic. While attending to instructional strategies is one evident way to address these challenges, grading schemes can also be modified or completely restructured to accomplish this goal. What if the grading expectations could be aligned to how students learn in a way that supports their agency and empowers them? What if our grading schemes facilitate learning in students and provide opportunities for students to further study the material, even after they performed poorly in those areas? This paper unpacks the perspectives, course procedures, and thinking in two advanced biology courses that led the instructor to move away from traditional grading procedures and to adopt a more open grading schematic that facilitated student change and learning. The resulting grading model aligns with applied cognitive theories on knowledge acquisition and would be of interest to instructors interested in focusing on student learning progression and student improvement and retention in biology and other STEM subjects.

Bats play a critical role controlling agricultural pests, yet foraging in croplands exposes them to hazardous pesticides. These chemicals pose significant risks for bats by impairing immune function, locomotion, and cognition even at low doses, jeopardizing their survival and ecological role. Here, we employed proteomics-a powerful, yet underused, tool in ecotoxicology-to examine the systemic effects of chlorpyrifos (CPF), a commonly used insecticide, on big brown bats (Eptesicus fuscus). We exposed bats through their diet to an environmentally relevant concentration of CPF for three or seven consecutive days and took plasma samples before and after exposure for non-targeted proteomics. We identified over 100 proteins with significant abundance changes before and after exposure to the pesticide. Exposure to CPF altered a wide range of molecular processes, including cell communication, cell metabolism, and DNA maintenance. Remarkably, we found changes in key proteins involved in immune response, T cell activation, and inflammation. These effects could reduce a bat's immune response, increasing their susceptibility to viral infections, and intensifying the risk of shedding and transmitting pathogens to other species. Our results provide new insights into the toxicity of pesticides and highlight the utility of proteomics for assessing toxicant effects in understudied and vulnerable species such as bats. Considering a One Health approach and the role of bats as reservoirs for numerous zoonotic pathogens, our work has broad implications for bat and human health.

Shark skin is covered superficially by the crowns of dermal denticles, tooth-shaped scales, whose bases are embedded into the dermis. Denticles provide sharks with functional benefits, including protection during mating and enhanced drag reduction during high-speed swimming. In a few species, research showed that denticle morphology changes as a shark matures and differs between sexes, especially in regions where males bite females during mating. We quantified the denticle morphometrics of bonnethead sharks to investigate potential ontogenetic and body region differences as well as sexual dimorphisms. We examined abdominal skin from 24 bonnethead sharks (12 male and 12 female) between the first and second dorsal fins using scanning electron microscopy. Denticle morphometrics-including denticle shape (pointedness), crown width, crown length, % of overlap, ridge width, ridge angle, and the number of ridges-were measured using ImageJ. We hypothesized that embryonic sharks would have denticles shorter in length and width when compared to juvenile and mature sharks to follow a natural growth pattern, and that female sharks would have a higher % overlap and longer denticle crowns, to provide greater protection during mating. Denticle morphology varied significantly across maturity levels, with differences observed in the denticle shape, crown width, and % overlap. These data support our hypothesis that denticle morphology changes with development, potentially to optimize swimming performance. However, sex was only a significant factor for ridge angle and body region was not a significant effect for any variable measured here. These findings suggest that ontogeny drives denticle morphology variation more than sex or body region does for abdominal skin between the two dorsal fins. These results suggest that denticle shape remains consistent in the male and female adults but varies across maturity levels, possibly due to the hydrodynamic constraints of water flow during swimming or to provide a shark with greater protection as it matures. Understanding the developmental and functional adaptations of shark denticles provides insights into their evolutionary role in facilitating survival, locomotion, and reproductive methods.