Field swimming performance of bluegill sunfish,Lepomis macrochirus: implications for field activity cost estimates and laboratory measures of swimming performance

Mobility is essential to the fitness of many animals, and the costs of locomotion can dominate daily energy budgets. Locomotor costs are determined by the physiological demands of sustaining mechanical performance, yet performance is poorly understood for most animals in the field, particularly aquatic organisms. We have used 3‐D underwater videography to quantify the swimming trajectories and propulsive modes of bluegills sunfish (Lepomis macrochirus, Rafinesque) in the field with high spatial (1–3 mm per pixel) and temporal (60 Hz frame rate) resolution. Although field swimming trajectories were variable and nonlinear in comparison to quasi steady‐state swimming in recirculating flumes, they were much less unsteady than the volitional swimming behaviors that underlie existing predictive models of field swimming cost. Performance analyses suggested that speed and path curvature data could be used to derive reasonable estimates of locomotor cost that fit within measured capacities for sustainable activity. The distinct differences between field swimming behavior and performance measures obtained under steady‐state laboratory conditions suggest that field observations are essential for informing approaches to quantifying locomotor performance in the laboratory.     

Using the whole body as a sucker: Combining respiration and feeding with an attached lifestyle in hill stream loaches (Balitoridae,Cypriniformes)

Small fishes living in fast‐flowing rivers face a harsh environment as they can easily be swept away by the rapid currents. To survive such circumstances, teleosts evolved a wide variety of attachment mechanisms, based on friction, negative pressure or both. Balitorinae (Balitoridae, Cypriniformes) are exceptional in using their whole body as an adhesive apparatus. We investigated the morphological adaptations of Balitorinae by studying the osteology and myology of four species (Beaufortia leveretti, Sewellia lineolata, Pseudogastromyzon myersi, and Gastromyzon punctulatus) using clearing and staining, serial cross‐sections and CT‐scanning. A kinematic analysis was performed to study the respiration and feeding mechanisms and to identify key structures in these mechanisms. Our research showed that the whole body of Balitorinae acts as a suction disc, with friction‐enhancing structures (unculi) on the thickened anterior rays of the paired fins. The abruptly rising head profile, supported by the extremely enlarged lacrimal bone and the flat ventral body surface facilitate effective substrate attachment. During attachment, the pelvic girdle is pulled anterodorsally, suggesting the formation of a negative pressure underneath the body. Detachment by water inflow underneath the body is prevented by three mechanisms. 1) Barbels control the water inflow by detachment and reattachment to the substrate. 2) Most water present underneath the body is removed during inspiration. 3) Excess water is regularly removed by movements of the posterior pectoral fin rays. The balitorine body is thus modified as such that it allows effective attachment, while not impairing respiration. Comparison with other teleosts living in similar environments shows that most species use more locally concentrated modifications of the paired fins and/or the mouth for attachment. The high diversity in teleostean adhesive apparatuses and associated myological modifications suggest a substantial functional convergent evolution, without necessarily highly convergent anatomical adaptations. J. Morphol. 275:1066–1079, 2014. © 2014 Wiley Periodicals, Inc.     

MRI vs CT-based 2D-3D auto-registration accuracy for quantifying shoulder motion using biplane video-radiography

Biplane 2D-3D registration approaches have been used for measuring 3D, in vivo glenohumeral (GH) joint kinematics. Computed tomography (CT) has become the gold standard for reconstructing 3D bone models, as it provides high geometric accuracy and similar tissue contrast to video-radiography. Alternatively, magnetic resonance imaging (MRI) would not expose subjects to radiation and provides the ability to add cartilage and other soft tissues to the models. However, the accuracy of MRI-based 2D-3D registration for quantifying glenohumeral kinematics is unknown. We developed an automatic 2D-3D registration program that works with both CT- and MRI-based image volumes for quantifying joint motions. The purpose of this study was to use the proposed 2D-3D auto-registration algorithm to describe the humerus and scapula tracking accuracy of CT- and MRI-based registration relative to radiostereometric analysis (RSA) during dynamic biplanar video-radiography. The GH kinematic accuracy (RMS error) was 0.6–1.0 mm and 0.6–2.2° for the CT-based registration and 1.4–2.2 mm and 1.2–2.6° for MRI-based registration. Higher kinematic accuracy of CT-based registration was expected as MRI provides lower spatial resolution and bone contrast as compared to CT and suffers from spatial distortions. However, the MRI-based registration is within an acceptable accuracy for many clinical research questions.     

ALTERNATE PATHWAYS OF BODY SHAPE EVOLUTION TRANSLATE INTO COMMON PATTERNS OF LOCOMOTOR EVOLUTION IN TWO CLADES OF LIZARDS

Body shape has a fundamental impact on organismal function, but it is unknown how functional morphology and locomotor performance and kinematics relate across a diverse array of body shapes. We showed that although patterns of body shape evolution differed considerably between lizards of the Phrynosomatinae and Lerista, patterns of locomotor evolution coincided between clades. Specifically, we found that the phrynosomatines evolved a stocky phenotype through body widening and limb shortening, whereas Lerista evolved elongation through body lengthening and limb shortening. In both clades, relative limb length played a key role in locomotor evolution and kinematic strategies, with long‐limbed species moving faster and taking longer strides. In Lerista, the body axis also influenced locomotor evolution. Similar patterns of locomotor evolution were likely due to constraints on how the body can move. However, these common patterns of locomotor evolution between the two clades resulted in different kinematic strategies and levels of performance among species because of their morphological differences. Furthermore, we found no evidence that distinct body shapes are adaptations to different substrates, as locomotor kinematics did not change on loose or solid substrates. Our findings illustrate the importance of studying kinematics to understand the mechanisms of locomotor evolution and phenotype‐function relationships.     

A novel computational method to determine subject-specific bite force and occlusal loading during mastication

The evaluation of three-dimensional occlusal loading during biting and chewing may assist in development of new dental materials, in designing effective and long-lasting restorations such as crowns and bridges, and for evaluating functional performance of prosthodontic components such as dental and/or maxillofacial implants. At present, little is known about the dynamic force and pressure distributions at the occlusal surface during mastication, as these quantities cannot be measured directly. The aim of this study was to evaluate subject-specific occlusal loading forces during mastication using accurate jaw motion measurements. Motion data was obtained from experiments in which an individual performed maximal effort dynamic chewing cycles on a rubber sample with known mechanical properties. A finite element model simulation of one recorded chewing cycle was then performed to evaluate the deformation of the rubber. This was achieved by imposing the measured jaw motions on a three-dimensional geometric surface model of the subject’s dental impressions. Based on the rubber’s deformation and its material behaviour, the simulation was used to compute the resulting stresses within the rubber as well as the contact pressures and forces on the occlusal surfaces. An advantage of this novel modelling approach is that dynamic occlusal pressure maps and biting forces may be predicted with high accuracy and resolution at each time step throughout the chewing cycle. Depending on the motion capture technique and the speed of simulation, the methodology may be automated in such a way that it can be performed chair-side. The present study demonstrates a novel modelling methodology for evaluating dynamic occlusal loading during biting or chewing.     

Woodpeckers minimize cranial absorption of shocks

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Flight motor patterns of locusts responding to thermal stimuli

Correctional and intentional steering manoeuvres in locusts differ in several important respects. The most profound difference between the two is the production of large forewing asymmetries in angle of elevation during the downstroke in intentional steering that are not obvious in correctional steering. We investigated the flight motor patterns during intentional steering responses to a radiant heat source. We found asymmetries in the timing of forewing first basalar (m97) activity on the left and right sides that were strongly and positively correlated with forewing asymmetries. Timing asymmetry in the second basalar (m98) and pleuroalar (m85) muscles was not significantly different from the changes observed in m97. The hindwing first basalar (m127) shifted its asymmetry in the opposite direction. The forewing subalar muscle (m99) did not shift its asymmetry with the same magnitude as m97, but instead was phase-shifted relative to m97 on the left and right sides, suggesting its role as a supinator. We conclude that large asymmetries in the elevation angle of the forewings during the downstroke, as are evident in intentional steering, are generated by bulk shifts in the activation times of forewing depressor muscles to cause a relative shift in the time of stroke reversals of the two forewings. Accepted: 19 June 1998