, have multiple openings, end wall remnants in the form of parallel bars, and are generally orien... more , have multiple openings, end wall remnants in the form of parallel bars, and are generally orientated at Key words: Flow, xylem vessel, perforation plate, models.
Your article is protected by copyright and all rights are held exclusively by Springer Science+Bu... more Your article is protected by copyright and all rights are held exclusively by Springer Science+Business Media, LLC. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your work, please use the accepted author's version for posting to your own website or your institution's repository. You may further deposit the accepted author's version on a funder's repository at a funder's request, provided it is not made publicly available until 12 months after publication.
Muscle metabolism dominates the energy costs of locomotion. Although in vivo measures of muscle s... more Muscle metabolism dominates the energy costs of locomotion. Although in vivo measures of muscle strain, activity and force can indicate mechanical function, similar muscle-level measures of energy use are challenging to obtain. Without this information locomotor systems are essentially a black box in terms of the distribution of metabolic energy. Although in situ measurements of muscle metabolism are not practical in multiple muscles, the rate of blood flow to skeletal muscle tissue can be used as a proxy for aerobic metabolism, allowing the cost of particular muscle functions to be estimated. Axial, undulatory swimming is one of the most common modes of vertebrate locomotion. In fish, segmented myotomal muscles are the primary power source, driving undulations of the body axis that transfer momentum to the water. Multiple fins and the associated fin muscles also contribute to thrust production, and stabilization and control of the swimming trajectory. We have used blood flow tracers in swimming rainbow trout (Oncorhynchus mykiss) to estimate the regional distribution of energy use across the myotomal and fin muscle groups to reveal the functional distribution of metabolic energy use within a swimming animal for the first time. Energy use by the myotomal muscle increased with speed to meet thrust requirements, particularly in posterior myotomes where muscle power outputs are greatest. At low speeds, there was high fin muscle energy use, consistent with active stability control. As speed increased, and fins were adducted, overall fin muscle energy use declined, except in the caudal fin muscles where active fin stiffening is required to maintain power transfer to the wake. The present data were obtained under steady-state conditions which rarely apply in natural, physical environments. This approach also has potential to reveal the mechanical factors that underlie changes in locomotor cost associated with movement through unsteady flow regimes.
Estimation of muscle parameters specifying force–length and force–velocity behavior requires in g... more Estimation of muscle parameters specifying force–length and force–velocity behavior requires in general a large number of sophisticated experiments often including a combination of isometric, isokinetic, isotonic, and quick-release experiments. This study validates a simpler method (ISOFIT) to determine muscle properties by fitting a Hill-type muscle model to a set of isovelocity data. Muscle properties resulting from the ISOFIT method agreed well with muscle properties determined separately in in vitro measurements using frog semitendinosus muscles. The force–length curve was described well by the results of the model. The force–velocity curve resulting from the model coincided with the experimentally determined curve above approximately 20% of maximum isometric force (correlation coefficient R>0.99). At lower forces and thus higher velocities the predicted curve underestimated velocity. The stiffness of the series elastic component determined with direct experiments was approximately 10% lower than that determined by the ISOFIT method. Use of the ISOFIT method can decrease experimental time up to 80% and reduce potential changes in muscle parameters due to fatigue.
Although mechanical linkages between the proximal and distal limb are present in a range of speci... more Although mechanical linkages between the proximal and distal limb are present in a range of species, their functional significance is unknown. We have investigated the mechanical function of the flexor cruris lateralis pars pelvica (FCLP), flexor cruris lateralis pars accessoria (FCLA) and gastrocnemius intermedia (GI), a system of linked muscles spanning proximal and distal limb segments in the guinea fowl (Numida meleagris) hind limb. The FCLP, which is in the anatomical position of a hamstring muscle, is the primary component of the linkage. It is connected to the distal femur via the FCLA, the tarsometatarsus via the tendon of insertion of the GI and the common Achilles tendon, and the tibiotarsus via a distal tendon of insertion. The FCLP may, therefore, potentially exert moments at the hip, knee and ankle joints depending on the joint angles and the relative states of activation in the three muscles. Evidence presented here suggests that the GI and FCLA act as actively controlled links that alter distal action of the FCLP. The FCLP and GI are coactive in the late swing and early stance phases of the stride, forming a triarticular complex, and likely act together to resist and control ankle flexion immediately after foot-down in addition to providing hip extension and knee flexion moments. The FCLP and FCLA are coactive from mid-through to late stance, acting together as a uniarticular hip extensor. Available evidence suggests that this role of the FCLP and FCLA is of increased importance in inclined running and accelerations. This linkage between a proximal muscle and alternate distal connections allows for functional flexibility, both in terms of the site at which the muscle exerts force and the nature of the muscle's mechanical function. The interactions generated between the proximal and distal limb by linkages of this type suggest that less emphasis should be placed on the distinct functional roles of specific anatomical classes of muscle within proximal and distal limb segments.
Bluegill Lepomis macrochirus showed intraspecific morphological and behavioural differences depen... more Bluegill Lepomis macrochirus showed intraspecific morphological and behavioural differences dependent on the environment. Pelagic L. macrochirus had more fusiform bodies, a higher pectoral fin aspect ratio, a larger spiny dorsal fin area and pectoral fins located farther from the centre of mass than littoral L. macrochirus (P < 0·05). The shape of the body and pectoral fins, in particular, were suggestive of adaptation for sustained high-speed and economical labriform swimming. Littoral L. macrochirus had a deeper and wider body, deeper caudal fins and wider mouths than pelagic L. macrochirus (P < 0·05). Additionally, the soft dorsal, pelvic, anal and caudal fins of littoral L. macrochirus were positioned farther from the centre of mass (P < 0·05). The size and placement of these fins suggested that they will be effective in creating turning moments to facilitate manoeuvring in the macrophyte-dense littoral habitat.
A major goal of flight research has been to establish the relationship between the mechanical pow... more A major goal of flight research has been to establish the relationship between the mechanical power requirements of flight and flight speed. This relationship is central to our understanding of the ecology and evolution of bird flight behaviour. Current approaches to determining flight power have relied on a variety of indirect measurements and led to a controversy over the shape of the power-speed relationship and a lack of quantitative agreement between the different techniques. We have used a new approach to determine flight power at a range of speeds based on the performance of the pectoralis muscles. As such, our measurements provide a unique dataset for comparison with other methods. Here we show that in budgerigars (Melopsittacus undulatus) and zebra finches (Taenopygia guttata) power is modulated with flight speed, resulting in U-shaped power-speed relationship. Our measured muscle powers agreed well with a range of powers predicted using an aerodynamic model. Assessing the accuracy of mechanical power calculated using such models is essential as they are the basis for determining flight efficiency when compared to measurements of flight metabolic rate and for predicting minimum power and maximum range speeds, key determinants of optimal flight behaviour in the field.
Explosive dehiscence ballistically disperses seeds in a number of plant species. During dehiscenc... more Explosive dehiscence ballistically disperses seeds in a number of plant species. During dehiscence, mechanical energy stored in specialized tissues is transferred to the seeds to increase their kinetic and potential energies. The resulting seed dispersal patterns have been investigated in some ballistic dispersers, but the mechanical performance of a launch mechanism of this type has not been measured. The properties of the energy storage tissue and the energy transfer efficiency of the launch mechanism were quantified in Impatiens capensis. In this species the valves forming the seed pod wall store mechanical energy. Their mass specific energy storage capacity (124 J kg 21 ) was comparable with that of elastin and spring steel. The energy storage capacity of the pod tissues was determined by their level of hydration, suggesting a role for turgor pressure in the energy storage mechanism. During dehiscence the valves coiled inwards, collapsing the pod and ejecting the seeds. Dehiscence took 4.260.4 ms (mean 6SEM, n¼13). The estimated efficiency with which energy was transferred to the seeds was low (0.5160.26%, mean 6SEM, n¼13). The mean seed launch angle (17.465.2, mean 6SEM, n¼45) fell within the range predicted by a ballistic model to maximize dispersal distance. Low ballistic dispersal efficiency or effectiveness may be characteristic of species that also utilize secondary seed dispersal mechanisms.
The obliquely striated muscle in the leech body wall has a broad functional repertoire; it provid... more The obliquely striated muscle in the leech body wall has a broad functional repertoire; it provides power for both locomotion and suction feeding. It also operates over an unusually high strain range, undergoing up to threefold changes in length. Serotonin (5-HT) may support this functional flexibility, integrating behavior and biomechanics. It can act centrally, promoting motor outputs that drive body wall movements, and peripherally, modulating the mechanical properties of body wall muscle. During isometric contractions 5-HT enhances active force production and reduces resting muscle tone. We therefore hypothesized that 5-HT would increase net work output during the cyclical contractions associated with locomotion and feeding. Longitudinal strains measured during swimming, crawling and feeding were applied to body wall muscle in vitro with the timing and duration of stimulation selected to maximize net work output. The net work output during all simulated behaviors significantly increased in the presence of 100 M 5-HT relative to the 5-HT-free control condition. Without 5-HT the muscle strips could not achieve a net positive work output during simulated swimming. The decrease in passive tension associated with 5-HT may also be important in reducing muscle antagonist work during longitudinal muscle lengthening. The behavioral and mechanical effects of 5-HT during locomotion are clearly complementary, promoting particular behaviors and enhancing muscle performance during those behaviors. Although 5-HT can enhance muscle mechanical performance during simulated feeding, low in vivo activity in serotonergic neurons during feeding may mean that its mechanical role during this behavior is less important than during locomotion.
, have multiple openings, end wall remnants in the form of parallel bars, and are generally orien... more , have multiple openings, end wall remnants in the form of parallel bars, and are generally orientated at Key words: Flow, xylem vessel, perforation plate, models.
Your article is protected by copyright and all rights are held exclusively by Springer Science+Bu... more Your article is protected by copyright and all rights are held exclusively by Springer Science+Business Media, LLC. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your work, please use the accepted author's version for posting to your own website or your institution's repository. You may further deposit the accepted author's version on a funder's repository at a funder's request, provided it is not made publicly available until 12 months after publication.
Muscle metabolism dominates the energy costs of locomotion. Although in vivo measures of muscle s... more Muscle metabolism dominates the energy costs of locomotion. Although in vivo measures of muscle strain, activity and force can indicate mechanical function, similar muscle-level measures of energy use are challenging to obtain. Without this information locomotor systems are essentially a black box in terms of the distribution of metabolic energy. Although in situ measurements of muscle metabolism are not practical in multiple muscles, the rate of blood flow to skeletal muscle tissue can be used as a proxy for aerobic metabolism, allowing the cost of particular muscle functions to be estimated. Axial, undulatory swimming is one of the most common modes of vertebrate locomotion. In fish, segmented myotomal muscles are the primary power source, driving undulations of the body axis that transfer momentum to the water. Multiple fins and the associated fin muscles also contribute to thrust production, and stabilization and control of the swimming trajectory. We have used blood flow tracers in swimming rainbow trout (Oncorhynchus mykiss) to estimate the regional distribution of energy use across the myotomal and fin muscle groups to reveal the functional distribution of metabolic energy use within a swimming animal for the first time. Energy use by the myotomal muscle increased with speed to meet thrust requirements, particularly in posterior myotomes where muscle power outputs are greatest. At low speeds, there was high fin muscle energy use, consistent with active stability control. As speed increased, and fins were adducted, overall fin muscle energy use declined, except in the caudal fin muscles where active fin stiffening is required to maintain power transfer to the wake. The present data were obtained under steady-state conditions which rarely apply in natural, physical environments. This approach also has potential to reveal the mechanical factors that underlie changes in locomotor cost associated with movement through unsteady flow regimes.
Estimation of muscle parameters specifying force–length and force–velocity behavior requires in g... more Estimation of muscle parameters specifying force–length and force–velocity behavior requires in general a large number of sophisticated experiments often including a combination of isometric, isokinetic, isotonic, and quick-release experiments. This study validates a simpler method (ISOFIT) to determine muscle properties by fitting a Hill-type muscle model to a set of isovelocity data. Muscle properties resulting from the ISOFIT method agreed well with muscle properties determined separately in in vitro measurements using frog semitendinosus muscles. The force–length curve was described well by the results of the model. The force–velocity curve resulting from the model coincided with the experimentally determined curve above approximately 20% of maximum isometric force (correlation coefficient R>0.99). At lower forces and thus higher velocities the predicted curve underestimated velocity. The stiffness of the series elastic component determined with direct experiments was approximately 10% lower than that determined by the ISOFIT method. Use of the ISOFIT method can decrease experimental time up to 80% and reduce potential changes in muscle parameters due to fatigue.
Although mechanical linkages between the proximal and distal limb are present in a range of speci... more Although mechanical linkages between the proximal and distal limb are present in a range of species, their functional significance is unknown. We have investigated the mechanical function of the flexor cruris lateralis pars pelvica (FCLP), flexor cruris lateralis pars accessoria (FCLA) and gastrocnemius intermedia (GI), a system of linked muscles spanning proximal and distal limb segments in the guinea fowl (Numida meleagris) hind limb. The FCLP, which is in the anatomical position of a hamstring muscle, is the primary component of the linkage. It is connected to the distal femur via the FCLA, the tarsometatarsus via the tendon of insertion of the GI and the common Achilles tendon, and the tibiotarsus via a distal tendon of insertion. The FCLP may, therefore, potentially exert moments at the hip, knee and ankle joints depending on the joint angles and the relative states of activation in the three muscles. Evidence presented here suggests that the GI and FCLA act as actively controlled links that alter distal action of the FCLP. The FCLP and GI are coactive in the late swing and early stance phases of the stride, forming a triarticular complex, and likely act together to resist and control ankle flexion immediately after foot-down in addition to providing hip extension and knee flexion moments. The FCLP and FCLA are coactive from mid-through to late stance, acting together as a uniarticular hip extensor. Available evidence suggests that this role of the FCLP and FCLA is of increased importance in inclined running and accelerations. This linkage between a proximal muscle and alternate distal connections allows for functional flexibility, both in terms of the site at which the muscle exerts force and the nature of the muscle's mechanical function. The interactions generated between the proximal and distal limb by linkages of this type suggest that less emphasis should be placed on the distinct functional roles of specific anatomical classes of muscle within proximal and distal limb segments.
Bluegill Lepomis macrochirus showed intraspecific morphological and behavioural differences depen... more Bluegill Lepomis macrochirus showed intraspecific morphological and behavioural differences dependent on the environment. Pelagic L. macrochirus had more fusiform bodies, a higher pectoral fin aspect ratio, a larger spiny dorsal fin area and pectoral fins located farther from the centre of mass than littoral L. macrochirus (P < 0·05). The shape of the body and pectoral fins, in particular, were suggestive of adaptation for sustained high-speed and economical labriform swimming. Littoral L. macrochirus had a deeper and wider body, deeper caudal fins and wider mouths than pelagic L. macrochirus (P < 0·05). Additionally, the soft dorsal, pelvic, anal and caudal fins of littoral L. macrochirus were positioned farther from the centre of mass (P < 0·05). The size and placement of these fins suggested that they will be effective in creating turning moments to facilitate manoeuvring in the macrophyte-dense littoral habitat.
A major goal of flight research has been to establish the relationship between the mechanical pow... more A major goal of flight research has been to establish the relationship between the mechanical power requirements of flight and flight speed. This relationship is central to our understanding of the ecology and evolution of bird flight behaviour. Current approaches to determining flight power have relied on a variety of indirect measurements and led to a controversy over the shape of the power-speed relationship and a lack of quantitative agreement between the different techniques. We have used a new approach to determine flight power at a range of speeds based on the performance of the pectoralis muscles. As such, our measurements provide a unique dataset for comparison with other methods. Here we show that in budgerigars (Melopsittacus undulatus) and zebra finches (Taenopygia guttata) power is modulated with flight speed, resulting in U-shaped power-speed relationship. Our measured muscle powers agreed well with a range of powers predicted using an aerodynamic model. Assessing the accuracy of mechanical power calculated using such models is essential as they are the basis for determining flight efficiency when compared to measurements of flight metabolic rate and for predicting minimum power and maximum range speeds, key determinants of optimal flight behaviour in the field.
Explosive dehiscence ballistically disperses seeds in a number of plant species. During dehiscenc... more Explosive dehiscence ballistically disperses seeds in a number of plant species. During dehiscence, mechanical energy stored in specialized tissues is transferred to the seeds to increase their kinetic and potential energies. The resulting seed dispersal patterns have been investigated in some ballistic dispersers, but the mechanical performance of a launch mechanism of this type has not been measured. The properties of the energy storage tissue and the energy transfer efficiency of the launch mechanism were quantified in Impatiens capensis. In this species the valves forming the seed pod wall store mechanical energy. Their mass specific energy storage capacity (124 J kg 21 ) was comparable with that of elastin and spring steel. The energy storage capacity of the pod tissues was determined by their level of hydration, suggesting a role for turgor pressure in the energy storage mechanism. During dehiscence the valves coiled inwards, collapsing the pod and ejecting the seeds. Dehiscence took 4.260.4 ms (mean 6SEM, n¼13). The estimated efficiency with which energy was transferred to the seeds was low (0.5160.26%, mean 6SEM, n¼13). The mean seed launch angle (17.465.2, mean 6SEM, n¼45) fell within the range predicted by a ballistic model to maximize dispersal distance. Low ballistic dispersal efficiency or effectiveness may be characteristic of species that also utilize secondary seed dispersal mechanisms.
The obliquely striated muscle in the leech body wall has a broad functional repertoire; it provid... more The obliquely striated muscle in the leech body wall has a broad functional repertoire; it provides power for both locomotion and suction feeding. It also operates over an unusually high strain range, undergoing up to threefold changes in length. Serotonin (5-HT) may support this functional flexibility, integrating behavior and biomechanics. It can act centrally, promoting motor outputs that drive body wall movements, and peripherally, modulating the mechanical properties of body wall muscle. During isometric contractions 5-HT enhances active force production and reduces resting muscle tone. We therefore hypothesized that 5-HT would increase net work output during the cyclical contractions associated with locomotion and feeding. Longitudinal strains measured during swimming, crawling and feeding were applied to body wall muscle in vitro with the timing and duration of stimulation selected to maximize net work output. The net work output during all simulated behaviors significantly increased in the presence of 100 M 5-HT relative to the 5-HT-free control condition. Without 5-HT the muscle strips could not achieve a net positive work output during simulated swimming. The decrease in passive tension associated with 5-HT may also be important in reducing muscle antagonist work during longitudinal muscle lengthening. The behavioral and mechanical effects of 5-HT during locomotion are clearly complementary, promoting particular behaviors and enhancing muscle performance during those behaviors. Although 5-HT can enhance muscle mechanical performance during simulated feeding, low in vivo activity in serotonergic neurons during feeding may mean that its mechanical role during this behavior is less important than during locomotion.
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