Form-function Relationships Research Articles

Atomically Precise Lanthanide-Iron-Oxo Clusters Featuring the ϵ-Keggin Ion.

Atomically precise molecular metal-oxo clusters provide ideal models to understand metal oxide surfaces, self-assembly, and form-function relationships. Devising strategies for synthesis and isolation of these molecular forms remains a challenge. Here, the synthesis of four Ln-Fe oxo clusters that feature the ϵ-{Fe13 } Keggin cluster in their core is reported. The {Fe13 } metal-oxo cluster motif is the building block of two important iron oxyhydroxyide phases in nature and technology, ferrihydrite (as the δ-isomer) and magnetite (the ϵ-isomer). The reported ϵ-{Fe13 } Keggin isomer as an isolated molecule provides the opportunity to study the formation of ferrihydrite and magnetite from this building unit. The four currently reported isostructural lanthanide-iron-oxo clusters are fully formulated [Y12 Fe33 (TEOA)12 (Hyp)6 (μ3 -OH)20 (μ4 -O)28 (H2 O)12 ](ClO4 )23 ⋅50 H2 O (1, Y12 Fe33 ), [Gd12 Fe33 (TEOA)12 (Hyp)6 (μ3 -OH)20 (μ4 -O)32 (H2 O)12 ](ClO4 )15 ⋅50 H2 O (2, Gd12 Fe33 ) and [Ln16 Fe29 (TEOA)12 (Hyp)6 (μ3 -OH)24 (μ4 -O)28 (H2 O)16 ](ClO4 )16 (NO3 )3 ⋅n H2 O (Ln=Y for 3, Y16 Fe29 , n=37 and Ln=Gd for 4, Gd16 Fe29 n=25; Hyp=trans-4-Hydroxyl-l-proline and TEOA=triethanolamine). The next metal layer surrounding the ϵ-{Fe13 } core within these clusters exhibits a similar arrangement as the magnetite lattice, and Fe and Ln can occupy the same positions. This provides the opportunity to construct a family of compounds and optimize magnetic exchange in these molecules through composition tuning. Small-angle X-ray scattering (SAXS) and high-resolution electrospray ionization mass spectrometry (HRESI-MS) show that these clusters are stable upon dissolution in both water and organic solvents, as a first step to performing further chemistry towards building magnetic arrays or investigating ferrihydrite and magnetite assembly from pre-nucleation clusters.

Referenzielle Kohärenz: Diskrepanz zwischen Theorie und Vermittlung.

Secondary school graduates are expected to write coherent texts for their respective occupations and other purposes later in life. Schooling should therefore prepare them adequately for this. It is thus paradoxical that textbooks for German provide pupils with very few explicit didactic instructions on how to write coherent texts. This applies in particular to referential coherence.
 Our article aims to contribute to the appropriate teaching of referential coherence in its complexity. To this end, first, the functions and the actual forms of referential means are examined in detail, from which the requirements for classroom instruction are derived. Next, textbook excerpts are examined to see whether and to what extent they meet these requirements.
 Our analysis shows that the way coherence is dealt with in textbooks is far from matching either linguistic or didactic demands. Very little attention is paid to form-function relationships. In some cases, tasks are even designed in such a manner that they lead pupils in the wrong direction and are thus counterproductive for the development of suitable writing or text skills.

What Determines the Distinct Morphology of Species with a Particular Ecology? The Roles of Many-to-One Mapping and Trade-Offs in the Evolution of Frog Ecomorphology and Performance.

Organisms inhabiting a specific environment often have distinct morphology, but the factors that affect this fit are unclear when multiple morphological traits affect performance in multiple behaviors. Does the realized morphology of a species reflect a compromise in performance among behaviors (i.e., trade-offs)? Or does many-to-one mapping result in morphological distinctness without compromising performance across behaviors? The importance of these principles in organismal design has rarely been compared at the macroevolutionary scale. Here I study 191 species of frogs from around the world that inhabit different microhabitats, using models of phenotypic evolution to examine how form-function relationships may explain the fit between ecology and morphology. I found three key results. First, despite being distinct in leg morphology, ecomorphs were similar in jumping performance. Second, ecomorphs that regularly swim showed higher swimming performance, which paralleled the higher leg muscle mass in these taxa. Third, many-to-one mapping of form onto function occurred at all but the highest levels of both jumping and swimming performance. The seemingly contradictory first two results were explained by the third: when one behavior occurs in all species while another is restricted to a subset, many-to-one mapping allows species with distinct ecologies to have distinct body forms that reflect their specialized behavior while maintaining similar performance in a more general shared behavior.

Time for a Plant Structural Economics Spectrum

We argue that tree and crown structural diversity can and should be integrated in the whole-plant economics spectrum. Ecologists have found that certain functional trait combinations have been more viable than others during evolution, generating a trait trade-off continuum which can be summarized along a few axes of variation, such as the “worldwide leaf economics spectrum” and the “wood economics spectrum”. However, for woody plants the crown structural diversity should be included as well in the recently introduced “global spectrum of plant form and function”, which now merely focusses on plant height as structural factor. The recent revolution in terrestrial laser scanning (TLS) unlocks the possibility to describe the three dimensional structure of trees quantitatively with unprecedented detail. We demonstrate that based on TLS data, a multidimensional structural trait space can be constructed, which can be decomposed into a few descriptive axes or spectra. We conclude that the time has come to develop a “structural economics spectrum” for woody plants based on structural trait data across the globe. We make suggestions as to what structural features might lie on this spectrum and how these might help improve our understanding of tree form-function relationships.

The thermal ecology of flowers.

BackgroundObtaining an optimal flower temperature can be crucial for plant reproduction because temperature mediates flower growth and development, pollen and ovule viability, and influences pollinator visitation. The thermal ecology of flowers is an exciting, yet understudied field of plant biology.ScopeThis review focuses on several attributes that modify exogenous heat absorption and retention in flowers. We discuss how flower shape, orientation, heliotropic movements, pubescence, coloration, opening–closing movements and endogenous heating contribute to the thermal balance of flowers. Whenever the data are available, we provide quantitative estimates of how these floral attributes contribute to heating of the flower, and ultimately plant fitness.OutlookFuture research should establish form–function relationships between floral phenotypes and temperature, determine the fitness effects of the floral microclimate, and identify broad ecological correlates with heat capture mechanisms.

The Evolutionary Dynamics of Mechanically Complex Systems

Animals use a diverse array of motion to feed, escape predators, and reproduce. Linking morphology, performance, and fitness is a foundational paradigm in organismal biology and evolution. Yet, the influence of mechanical relationships on evolutionary diversity remains unresolved. Here, I focus on the many-to-one mapping of form to function, a widespread, emergent property of many mechanical systems in nature, and discuss how mechanical redundancy influences the tempo and mode of phenotypic evolution. By supplying many possible morphological pathways for functional adaptation, many-to-one mapping can release morphology from selection on performance. Consequently, many-to-one mapping decouples morphological and functional diversification. In fish, for example, parallel morphological evolution is weaker for traits that contribute to mechanically redundant motions, like suction feeding performance, than for systems with one-to-one form–function relationships, like lower jaw lever ratios. As mechanical complexity increases, historical factors play a stronger role in shaping evolutionary trajectories. Many-to-one mapping, however, does not always result in equal freedom of morphological evolution. The kinematics of complex systems can often be reduced to variation in a few traits of high mechanical effect. In various different four-bar linkage systems, for example, mechanical output (kinematic transmission) is highly sensitive to size variation in one or two links, and insensitive to variation in the others. In four-bar linkage systems, faster rates of evolution are biased to traits of high mechanical effect. Mechanical sensitivity also results in stronger parallel evolution—evolutionary transitions in mechanical output are coupled with transition in linkages of high mechanical effect. In other words, the evolutionary dynamics of complex systems can actually approximate that of simpler, one-to-one systems when mechanical sensitivity is strong. When examined in a macroevolutionary framework, the same mechanical system may experience distinct selective pressures in different groups of organisms. For example, performance tradeoffs are stronger for organisms that use the same mechanical structure for more functions. In general, stronger performance tradeoffs result in less phenotypic diversity in the system and, sometimes, a slower rate of evolution. These macroevolutionary trends can contribute to unevenness in functional and lineage diversity across the tree of life. Finally, I discuss how the evolution of mechanical systems informs our understanding of the relative roles of determinism and contingency in evolution.

Long bone structural proportions and locomotor behavior in Cercopithecidae

Limb bone articular and diaphyseal proportions have been shown to relate to locomotor behavior in broad comparisons across catarrhines, but comparisons among phylogenetically and functionally more closely related species may be particularly useful in investigating form-function relationships that can be applied to fossil taxa. Here we compare inter- and intra-limb proportions of diaphyseal strength and articular surface area and breadth of the femur and humerus with frequencies of leaping and vertical climbing behavior in 13 cercopithecid species. Leaping frequency is highly positively correlated with femoral/humeral diaphyseal strength, moderately positively correlated with femoral/humeral articular breadth, and less highly correlated with femoral/humeral articular surface area. These results are consistent with predicted higher bending loads as well as joint reaction forces on the femora of leapers. Surface areas may show a weaker association because they also directly impact joint excursion and are thus more influenced by other aspects of locomotion, including climbing. Climbing frequency is positively correlated with humeral head articular surface area/diaphyseal strength, but weakly negatively correlated with femoral head articular surface area/diaphyseal strength. These combined trends lead to a strong negative association between climbing and femoral/humeral head surface area. Femoral/humeral diaphyseal strength and distal articular breadth are not correlated with climbing frequency. The climbing results are consistent with greater shoulder mobility in more frequent vertical climbers. The lack of such a relationship in the femur among these taxa contrasts with earlier findings for catarrhines more generally, including hominoids, and may be a result of different climbing kinematics in cercopithecoids involving less hip abduction than in hominoids. Different use of the forelimb during climbing in cercopithecoids and hominoids may also explain the lack of association between femoral/humeral diaphyseal strength and climbing in the present study, in contrast to comparisons across catarrhines more generally.

Decoupling of biomechanics of hyoid movement and bolus flow in preterm infants

Determining the timing of bolus passage over the airway, and into the esophagus, is critical for biomechanical studies of swallowing. Videofluroscopy is the gold standard for determining fluid movement, but is not always possible. Hylolaryngeal movement, measured from light film or standard videography, is a reliable marker for adult human swallowing, but its validity for the biomechanics of swallowing in immature infants is unknown. We tested the relationship between hyolaryngeal movement from light camera data compared to bolus movement from video fluoroscopy in pre‐term and term infant pigs.Three term and four pre‐term pigs were fed from a bottle containing barium and a milk solution. At seven days after birth pigs were recorded feeding from the bottle using simultaneous high speed (100 fps) x‐ray and light video cameras. In the light video, the frame of most rapid elevation of the hyoid was scored as the swallow. In the x‐ray, the swallows were scored as the beginning of posterior bolus movement. The number of frames separating x‐ray and light camera swallow identifications was calculated for each swallow.Hyoid movement was found to be closely correlated to bolus movement in term pigs, but no correlation existed in pre‐term pigs. The mean frame offsets for term and pre‐term pigs were different (Wilcox test, p<0.001). The variance for the pre‐term pigs was significantly larger (Levene's test p<0.001).The light videos were found to be a good measure of swallows in term pigs, but were not a good measure of swallows in pre‐term pigs. The biomechanics of bolus movement are altered in the neurologically poorly coordinated pre‐term pigs. Specifically, hyolaryngeal elevation and bolus movement are decoupled in pre‐terms whereas they are tightly coordinated in term pigs. Prematurity leads to altered form function relationships through immature development.Support or Funding InformationNICHD grant 088561This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Scaling of statically derived osteocyte lacunae in extant birds: implications for palaeophysiological reconstruction.

Osteocytes are mature versions of osteoblasts, bone-forming cells that develop in two ways: via 'static' osteogenesis, differentiating and ossifying tissue in situ to form a scaffold upon which other bone can form, or 'dynamic' osteogenesis, migrating to infill or lay down bone around neurovasculature. A previous study regressed the volume of osteocyte lacunae derived from dynamic osteogenesis (DO) of a broad sample of extant bird species against body mass, the growth rate constant ( k), mass-specific metabolic rate, genome size, and erythrocyte size. There were significant relationships with body mass, growth rate, metabolic rate, and genome size, with the latter being the strongest. Using the same avian histological dataset, we measured over 3800 osteocyte lacunar axes derived from static osteogenesis (SO) in order to look for differences in the strength of form-function relationships inferred for DO-derived lacunae at the cellular and tissue levels. The relationship between osteocyte lacunar volume and body mass was stronger when measuring SO lacunae, whereas relationships between osteocyte lacunar volume versus growth rate and basal metabolic rate disappeared. The relationship between osteocyte lacuna volume and genome size remained significant and moderately strong when measuring SO lacunae, whereas osteocyte lacuna volume was still unrelated to erythrocyte size. Our results indicate that growth and metabolic rate signals are contained in avian DO but not SO osteocyte lacunae, suggesting that the former should be used in estimating these parameters in extinct animals.

The Organismal Form and Function Lab-Course: A New CURE for a Lack of Authentic Research Experiences in Organismal Biology.

SynopsisThere are many benefits to engaging students in authentic research experiences instead of traditional style lectures and “cookbook” labs. Many Course-based Undergraduate Research Experiences (CUREs) have been developed that provide research experiences to a more inclusive and diverse student body, allow more students to obtain research experiences, and expose students to the scientific process. Most CUREs in the biological sciences focus on cellular and molecular biology, with few being developed in ecology, evolution, and organismal biology. Here, I present a one-semester CURE focused on organismal form and function. The goal of the course was to have students develop their own research questions and hypotheses in relation to invertebrate form and movement, using high-speed cinematography to collect their data. In this paper, I describe the motivation for the course, provide the details of teaching the course, including rubrics for several assignments, the outcomes of the course, caveats, and ways a similar course can be implemented at other institutions. The course was structured to use a scaffolding approach during the first half of the semester to provide the content of form–function relationships and allow students to acquire the laboratory skills to quantify animal movement. The second half of the course focused on student-driven inquiry, with class time dedicated to conducting research. As there is a push to engage more students in research, I hope this course will inspire others to implement similar classes at other universities, providing a network of collaboration on integrative organismal student-driven research.

On the form and bio-mechanics of venom-injection elements

A wide variety of animals—from insects to snakes—crucially depend on their ability to inject venom into their target, be it their prey or their predator. To effectively deliver their venom, venomous animals use a specialized biomechanical element whose tip must penetrate through the integument of the target. During this process, the tip of the venom-injection element (VIE) is subject to local forces, which may deform it and cause considerable structural damage to the VIE, with devastating consequences for the survival of the animal or, in the case of eusocial insects, to the colony. Hence, it is plausible that millions of years of evolution have carefully ‘shaped’ the architecture of VIEs across different taxa toward a similar mechanical function, namely, to effectively resist the mechanical forces exerted on the tip. The present study aims to identify such a common architecture by analyzing the form–function relationships in various biological VIEs. A universal structural modeling, which quantifies the fundamental geometrical characteristics of a wide range of VIEs is constituted, and a theoretical mechanical framework that analytically correlates these characteristics with the material stress fields is introduced. This investigation reveals that the architecture of biological VIEs reduces the magnitude of applied stresses and confines the maximal stress to the near-tip region of the element. The presented analytical approach and modeling can be straightforwardly applied to various other types of bio-mechanical elements and can potentially be employed for developing a new class of microscopic injection elements for bio-medical and engineering applications. Statement of SignificanceVenomous animals—both vertebrate and invertebrate—use an extremely wide variety of venom-injection elements to incapacitate their prey or predator. Despite the clear differences in their typical dimensions, shapes, and evolutionary paths, all venom-injection elements have evolved to perform a single mechanical function, namely, to penetrate a target surface. Accordingly, the architecture of many such elements appears to follow similar principles and their material exhibits similar stress characteristics upon biologically relevant mechanical loadings. The current study introduces a theoretical model that draws connections between the ‘universal’ structural characteristics of such elements and their bio-mechanical functions. It is found that all examined venom-injection elements provide extreme load-bearing capabilities and unusual post-failure functionalities, which are in good agreement with the wide range of numerical and experimental findings from the literature. The emerging theoretical insights from this study thus shed light on the biomechanical origins of the naturally evolved forms of various biological organisms, including bee and wasp stingers, spider and snake fangs, porcupine fish spines, and scorpion stingers.

Intonazione e significato: l’esempio dell’italiano regionale di Bergamo

Abstract In this paper we present a selection of preliminary results of our research project “Intonation and Meaning”, in which we compare recurrent intonation contours in German and Italian regional varieties. We apply the method of German Interactional Prosody Research (Interaktionale Prosodieforschung), which in turn is based on Conversation Analysis, to a sample of selfcollected empirical data. Our aim is to show the value of intonation as a resource to contextualize speech activities and to point out form-function relationships between intonation patterns and speech act types. In this respect, we observe the usage of intonation contours with rising accent (L*H) and with falling accent (H*L) in the utterance of question activities, and provide evidence for the fact that the latter represent a distinctive type of questions with epistemic presupposition, whereas L*H correlates rather with default, modally unmarked questions.

The 'niche' city: A multifactor spatial approach to identify local-scale dimensions of urban complexity

Metropolitan systems were constituted by spatial components with different specialization 'niches' based on characteristic attributes (demography, economic structure and performances, socio-spatial patterns, urban morphology, topography, land-use and spatial planning). The present study investigates the multiple dimensions of urban complexity in the light of the 'ecological niche' theory, assessing the spatial structure of a vast ensemble of socioeconomic and territorial indicators that reflect processes of growth and change in contemporary cities. To assess jointly patterns and processes of urban expansion and their impact on recent socioeconomic transformations at the local scale, Athens, the capital of Greece, was taken as a prototype of metropolitan systems with a socioeconomic context evolving under specific form-function relationships. An exploratory framework based on principal component analysis, hierarchical clustering and spatial autocorrelation indexes was used to identify and characterize 8 dimensions that reflect different specialization 'niches' at local scale. Clusters of municipalities were identified according to the dominant socioeconomic dimensions and urban specialization niches. A composite index of urban complexity was finally proposed with the aim to outline latent spatial gradients associated with settlement morphology, social diversification, local development and economic performances. The empirical results of this study contribute to a better understanding of complex urban systems, providing the necessary knowledge base to support implementation of policies for sustainable development of metropolitan regions.

Food, Form and Function: Motor Control, Movement and Modulation during Mastication in Mammals

Mammalian feeding is one of the many dynamic behaviors in which close form‐function relationships are readily apparent across the phylogeny. The link between masticatory morphology and function, for example, has been highlighted time and again with classic contrasts being made between major dietary groups, such as herbivores and carnivores. These contrasts emphasize differences between the teeth, muscle anatomy, temporomandibular joint (TMJ) and masticatory kinematics. In some cases, masticatory anatomy is hypothesized to significantly limit movement. Yet it has also been shown in diverse species that mastication is a behavior that has the potential for significant functional variability depending on a number of factors, including the textural, mechanical and/or physical properties of the food being consumed and jaw muscle activation patterns that move the jaw and produce the force to break down food. Here, I will explore the relationship between masticatory morphology, jaw‐muscle activity and jaw kinematics in select species representing different dietary groups (e.g., herbivory, carnivory, and omnivory) and examine the effect that food properties have on the dynamic response of the feeding system. Jaw‐muscle activity patterns were collected using electromyography and kinematic data were collected using X‐ray Reconstructing of Moving Morphology (XROMM). In goats (herbivore), increasing food toughness increases total cycle duration and the duration of jaw closing during chewing, whereas increasing food stiffness has little effect on overall temporal dynamics. Differences are observed in the jaw‐muscle firing patterns when chewing on different foods. Kinematic data from pigs (omnivore) reveal that changes in food toughness affect the chewing cycle as a whole, whereas changes in food stiffness alter the relative contribution and duration of the constituent phases of the chewing cycle, while total cycle duration remains more or less constant. Comparisons between ferrets (carnivore) and two closely related omnivorous species, skunks and raccoons in jaw kinematics, also indicate that the morphology of the TMJ and dentition may impact how jaw‐movements are modulated during mastication. Finally, kinematic data also reveal that occlusion is facilitated by rotation of the jaw about a vertical axis (“yaw”), mediolateral translation of the condyles, and/or rotation of the working‐side hemimandible around its long axis (“roll”), yet there are differences in the relative contribution of each type of movement that may be related to tooth and TMJ morphology. Combined, these experimental datasets from different species reveal new complexities to mastication and the modulation of jaw movements in mammals and help to clarify interpretations of function from morphology.Support or Funding InformationThis research was funded by National Science Foundation grants IOS‐0520855, IOS‐1456810 and DBI‐0922988.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Form–function relationships in a marine foundation species depend on scale: a shoot to global perspective from a distributed ecological experiment

Form–function relationships in plants underlie their ecosystem roles in supporting higher trophic levels through primary production, detrital pathways, and habitat provision. For widespread, phenotypically‐variable plants, productivity may differ not only across abiotic conditions, but also from distinct morphological or demographic traits. A single foundation species, eelgrass Zostera marina, typically dominates north temperate seagrass meadows, which we studied across 14 sites spanning 32–61°N latitude and two ocean basins. Body size varied by nearly two orders of magnitude through this range, and was largest at mid‐latitudes and in the Pacific Ocean. At the global scale, neither latitude, site‐level environmental conditions, nor body size helped predict productivity (relative growth rate 1–2% day‐1 at most sites), suggesting a remarkable capacity of Z. marina to achieve similar productivity in summer. Furthermore, among a suite of stressors applied within sites, only ambient leaf damage reduced productivity; grazer reduction and nutrient addition had no effect on eelgrass size or growth. Scale‐dependence was evident in different allometric relationships within and across sites for productivity and for modules (leaf count) relative to size. Zostera marina provides a range of ecosystem functions related to both body size (habitat provision, water flow) and growth rates (food, carbon dynamics). Our observed decoupling of body size and maximum production suggests that geographic variation in these ecosystem functions may be independent, with a future need to resolve how local adaptation or plasticity of body size might actually enable more consistent peak productivity across disparate environmental conditions.

Comparative analysis of vestibular ecomorphology in birds.

The bony labyrinth of vertebrates houses the semicircular canals. These sense rotational accelerations of the head and play an essential role in gaze stabilisation during locomotion. The sizes and shapes of the semicircular canals have hypothesised relationships to agility and locomotory modes in many groups, including birds, and a burgeoning palaeontological literature seeks to make ecological interpretations from the morphology of the labyrinth in extinct species. Rigorous tests of form-function relationships for the vestibular system are required to support these interpretations. We test the hypothesis that the lengths, streamlines and angles between the semicircular canals are related to body size, wing kinematics and flying style in birds. To do this, we applied geometric morphometrics and multivariate phylogenetic comparative methods to a dataset of 64 three-dimensional reconstructions of the endosseous labyrinth obtained using micro-computed tomography scanning of bird crania. A strong relationship between centroid size of the semicircular canals and body size indicates that larger birds have longer semicircular canals compared with their evolutionary relatives. Wing kinematics related to manoeuvrability (and quantified using the brachial index) explain a small additional portion of the variance in labyrinth size. We also find strong evidence for allometric shape change in the semicircular canals of birds, indicating that major aspects of the shape of the avian labyrinth are determined by spatial constraints. The avian braincase accommodates a large brain, a large eye and large semicircular canals compared with other tetrapods. Negative allometry of these structures means that the restriction of space within the braincase is intense in small birds. This may explain our observation that the angles between planes of the semicircular canals of birds deviate more strongly from orthogonality than those of mammals, and especially from agile, gliding and flying mammals. Furthermore, we find little support for relationships between labyrinth shape and flying style or wing kinematics. Overall, our results suggest that the topological problem of fitting long semicircular canals into a spatially constrained braincase is more important in determining the shape of the avian labyrinth than the specifics of locomotory style or agility. Our results tentatively indicate a link between visual acuity and proportional size of the labyrinth among birds. This suggests that the large labyrinths of birds compared with other tetrapods may result from their generally high visual acuities, and not directly from their ability to fly. The endosseous labyrinths of extinct birds and their close dinosaurian relatives may allow broad inferences about flight or vision, but so far provide few specific insights into detailed aspects of locomotion.

Imatinib Alters Agonists-mediated Cytoskeletal Biomechanics in Lung Endothelium

The endothelium serves as a size-selective barrier and tightly controls the fluid exchange from the circulation to the surrounding tissues. In this study, a multiplexed microscopy characterization is developed to study the spatio-temporal effects of Abl kinases on endothelial cytoskeletal structure using AFM, SEM, and immunofluorescence. Sphingosine 1-phosphate (S1P) produces significant endothelial barrier enhancement by means of peripheral actin rearrangement. However, Abl kinase inhibition by imatinib reduces rapid redistribution of the important cytoskeletal proteins to the periphery and their association with the cortical actin ring. Herein, it moderates the thickness of the cortical actin ring, and diminishes the increase in elastic modulus at the periphery and cytoplasm. These findings demonstrate that imatinib attenuates multiple cytoskeletal changes associated with S1P-mediated endothelial barrier enhancement and suggest a novel role for Abl kinases in mediating these S1P effects. These observations bridge the gap between molecule dynamics, structure complexity and function connectivity across varied length-scales to improve our understanding on human pulmonary endothelial barrier regulation. Moreover, our study suggests a framework for understanding form-function relationships in other biomechanical subsystems, wherein complex hierarchical organization programmed from the molecular scale to the cellular and tissue levels has an intimate relationship to the overall physiological function.

Talking grammatically: L1 adolescent metalinguistic reflection on writing

ABSTRACTThis study investigated the metalinguistic reflections of 12 students, aged 14–15 years, undertaking a unit of work focused on reading and writing non-fiction. The unit embedded contextualised grammar teaching into preparation for English Language examinations. Students were interviewed twice, with prompts to discuss a sample of argument text in interview one, and a sample of their own writing in interview two. The interviews and subsequent analysis drew on Gombert's taxonomy of metalinguistic understanding, focusing on metasemantic, metasyntactic and metatextual reflections, and probing students’ ability to link these to metapragmatic concerns. Similarly to previous studies, the findings suggest that students struggle to articulate the impact of metasyntactic choices; however, here it is suggested that this may be a particular artefact of the need for a specialised metalanguage for discussing syntax. Results also indicate a tendency to reify form-function relationships, and signal the potential benefit of using students’ own writing as a platform for exploring authorial choices. Finally, the study contributes to the theorisation of metalinguistic understanding by suggesting how declarative knowledge may emerge from procedural activity, with interviews scaffolding students’ ability to articulate what had initially been tacit language choices.

Advantages and Limitations in the Use of Extant Xenarthrans (Mammalia) as Morphological Models for Paleobiological Reconstruction

Extant species of Xenarthra represent a severely restricted sample of the total diversity achieved by the group. Given their shared history, the extant representatives of the three major groups of xenarthrans (Cingulata, Folivora, and Vermilingua) provide a valuable basis for paleobiological inference. However, many extinct taxa are morphologically so dissimilar from their extant relatives that they suggest very different ways of life. In these cases, extinct forms do not have modern models within the group and the application of a simplistic and strict approach can produce nonsensical reconstructions. In this contribution, we evaluate the limitations of the use of extant xenarthrans as morphological models for paleobiological reconstructions. A database of linear dimensions of the appendicular skeleton of extant and extinct xenarthrans and other mammals (marsupials, carnivorans, rodents, primates, perissodactyls, artiodactyls, and proboscideans) was constructed. Exploratory analyzes were performed on general morphometric similarity between existing and extinct xenarthrans (PCA) and the accuracy of body mass estimates of extinct xenarthrans based on their close relatives and other mammals (simple and multiple linear regressions) were tested. Extinct xenarthrans occupy similar relative positions in the morphospaces as extant mammals other than their closest relatives. Most allometric equations, particularly those based only on xenarthrans, produced remarkable underestimates. This can be explained by dimensional differences (up to four orders of magnitude) and shape differences between most of the extinct and extant xenarthrans. This does not invalidate actualism and the use of analogues, but suggests the need to apply other approaches, such as mechanics, that address form-function relationships but are not necessarily based on known biological comparators.

Functional associations between support use and forelimb shape in strepsirrhines and their relevance to inferring locomotor behavior in early primates

The evolution of primates is intimately linked to their initial invasion of an arboreal environment. However, moving and foraging in this milieu creates significant mechanical challenges related to the presence of substrates differing in their size and orientation. It is widely assumed that primates are behaviorally and anatomically adapted to movement on specific substrates, but few explicit tests of this relationship in an evolutionary context have been conducted. Without direct tests of form–function relationships in living primates it is impossible to reliably infer behavior in fossil taxa. In this study, we test a hypothesis of co-variation between forelimb morphology and the type of substrates used by strepsirrhines. If associations between anatomy and substrate use exist, these can then be applied to better understand limb anatomy of extinct primates. The co-variation between each forelimb long bone and the type of substrate used was studied in a phylogenetic context. Our results show that despite the presence of significant phylogenetic signal for each long bone of the forelimb, clear support use associations are present. A strong co-variation was found between the type of substrate used and the shape of the radius, with and without taking phylogeny into account, whereas co-variation was significant for the ulna only when taking phylogeny into account. Species that use a thin branch milieu show radii that are gracile and straight and have a distal articular shape that allows for a wide range of movements. In contrast, extant species that commonly use large supports show a relatively robust and curved radius with an increased surface area available for forearm and hand muscles in pronated posture. These results, especially for the radius, support the idea that strepsirrhine primates exhibit specific skeletal adaptations associated with the supports that they habitually move on. With these robust associations in hand it will be possible to explore the same variables in extinct early primates and primate relatives and thus improve the reliability of inferences concerning substrate use in early primates.