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Baines R, Patiballa SK, Booth J, Ramirez L, Sipple T, Garcia A, Fish F, Kramer-Bottiglio R. Multi-environment robotic transitions through adaptive morphogenesis. Nature 2022; 610:283-289. [PMID: 36224418 DOI: 10.1038/s41586-022-05188-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 08/03/2022] [Indexed: 11/09/2022]
Abstract
The current proliferation of mobile robots spans ecological monitoring, warehouse management and extreme environment exploration, to an individual consumer's home1-4. This expanding frontier of applications requires robots to transit multiple environments, a substantial challenge that traditional robot design strategies have not effectively addressed5,6. For example, biomimetic design-copying an animal's morphology, propulsion mechanism and gait-constitutes one approach, but it loses the benefits of engineered materials and mechanisms that can be exploited to surpass animal performance7,8. Other approaches add a unique propulsive mechanism for each environment to the same robot body, which can result in energy-inefficient designs9-11. Overall, predominant robot design strategies favour immutable structures and behaviours, resulting in systems incapable of specializing across environments12,13. Here, to achieve specialized multi-environment locomotion through terrestrial, aquatic and the in-between transition zones, we implemented 'adaptive morphogenesis', a design strategy in which adaptive robot morphology and behaviours are realized through unified structural and actuation systems. Taking inspiration from terrestrial and aquatic turtles, we built a robot that fuses traditional rigid components and soft materials to radically augment the shape of its limbs and shift its gaits for multi-environment locomotion. The interplay of gait, limb shape and the environmental medium revealed vital parameters that govern the robot's cost of transport. The results attest that adaptive morphogenesis is a powerful method to enhance the efficiency of mobile robots encountering unstructured, changing environments.
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Affiliation(s)
- Robert Baines
- School of Engineering and Applied Science, Yale University, New Haven, CT, USA
| | - Sree Kalyan Patiballa
- School of Engineering and Applied Science, Yale University, New Haven, CT, USA.,Department of Mechanical Engineering, The University of Alabama, Tuscaloosa, AL, USA
| | - Joran Booth
- School of Engineering and Applied Science, Yale University, New Haven, CT, USA
| | - Luis Ramirez
- School of Engineering and Applied Science, Yale University, New Haven, CT, USA
| | - Thomas Sipple
- School of Engineering and Applied Science, Yale University, New Haven, CT, USA
| | - Andonny Garcia
- School of Engineering and Applied Science, Yale University, New Haven, CT, USA
| | - Frank Fish
- Department of Biology, West Chester University, West Chester, PA, USA
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Ewart H, Tickle P, Nudds R, Sellers W, Crossley D, Codd J. Mediterranean Spur-Thighed Tortoises (Testudo graeca) Have Optimal Speeds at Which They Can Minimise the Metabolic Cost of Transport, on a Treadmill. BIOLOGY 2022; 11:biology11071052. [PMID: 36101430 PMCID: PMC9312080 DOI: 10.3390/biology11071052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 06/29/2022] [Accepted: 07/07/2022] [Indexed: 11/25/2022]
Abstract
Simple Summary Understanding the energy that animals use to move around is important, as it can shed light on how they make decisions about where and how to locomote. Tortoises are unique among vertebrates in having a shell, which influences almost all aspects of their biology. Here, we experimentally quantified the metabolic cost of transport in Mediterranean spur-thighed tortoises walking on a treadmill while also quantifying the kinematics of their movement. We found, in line with previous studies, that tortoises move more efficiently than predicted and present the first data demonstrating a curvilinear cost of transport over their speed range. We conclude that tortoises have an optimum speed at which they move to minimise their metabolic cost of locomotion. Abstract Tortoises are famed for their slow locomotion, which is in part related to their herbivorous diet and the constraints imposed by their protective shells. For most animals, the metabolic cost of transport (CoT) is close to the value predicted for their body mass. Testudines appear to be an exception to this rule, as previous studies indicate that, for their body mass, they are economical walkers. The metabolic efficiency of their terrestrial locomotion is explainable by their walking gait biomechanics and the specialisation of their limb muscle physiology, which embodies a predominance of energy-efficient slow-twitch type I muscle fibres. However, there are only two published experimental reports of the energetics of locomotion in tortoises, and these data show high variability. Here, Mediterranean spur-thighed tortoises (Testudo graeca) were trained to walk on a treadmill. Open-flow respirometry and high-speed filming were simultaneously used to measure the metabolic cost of transport and to quantify limb kinematics, respectively. Our data support the low cost of transport previously reported and demonstrate a novel curvilinear relationship to speed in Testudines, suggesting tortoises have an energetically optimal speed range over which they can move in order to minimise the metabolic cost of transport.
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Affiliation(s)
- Heather Ewart
- School of Biological Sciences, University of Manchester, Manchester M13 9PL, UK; (H.E.); (R.N.)
| | - Peter Tickle
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK;
| | - Robert Nudds
- School of Biological Sciences, University of Manchester, Manchester M13 9PL, UK; (H.E.); (R.N.)
| | - William Sellers
- School of Natural Sciences, University of Manchester, Manchester M13 9PL, UK;
| | - Dane Crossley
- Department of Biological Sciences, University of North Texas, Denton, TX 76203-5017, USA;
| | - Jonathan Codd
- School of Biological Sciences, University of Manchester, Manchester M13 9PL, UK; (H.E.); (R.N.)
- Correspondence: ; Tel.: +44(0)-1612755474
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Gardner ST, Appel AG, Mendonça MT. Chasing Cane Toads: Assessing Locomotory Differences in Toads from Core and Edge Populations in Florida. HERPETOLOGICA 2022. [DOI: 10.1655/herpetologica-d-21-00005.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Steven T. Gardner
- Department of Biological Sciences, Auburn University, 331 Funchess Hall, 350 South College Street, Auburn, AL 36849, USA
| | - Arthur G. Appel
- Department of Entomology and Plant Pathology, Auburn University, 301 Funchess Hall, 350 South College Street, Auburn, AL 36849, USA
| | - Mary T. Mendonça
- Department of Biological Sciences, Auburn University, 331 Funchess Hall, 350 South College Street, Auburn, AL 36849, USA
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The metabolic cost of turning right side up in the Mediterranean spur-thighed tortoise (Testudo graeca). Sci Rep 2022; 12:431. [PMID: 35013453 PMCID: PMC8748805 DOI: 10.1038/s41598-021-04273-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 12/20/2021] [Indexed: 11/08/2022] Open
Abstract
Armoured, rigid bodied animals, such as Testudines, must self-right should they find themselves in an inverted position. The ability to self-right is an essential biomechanical and physiological process that influences survival and ultimately fitness. Traits that enhance righting ability may consequently offer an evolutionary advantage. However, the energetic requirements of self-righting are unknown. Using respirometry and kinematic video analysis, we examined the metabolic cost of self-righting in the terrestrial Mediterranean spur-thighed tortoise and compared this to the metabolic cost of locomotion at a moderate, easily sustainable speed. We found that self-righting is, relatively, metabolically expensive and costs around two times the mass-specific power required to walk. Rapid movements of the limbs and head facilitate successful righting however, combined with the constraints of breathing whilst upside down, contribute a significant metabolic cost. Consequently, in the wild, these animals should favour environments or behaviours where the risk of becoming inverted is reduced.
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Chessman BC. Effects of temperature and exercise on metabolism of three species of Australian freshwater turtles: implications for responses to climate change. AUST J ZOOL 2018. [DOI: 10.1071/zo18062] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Oxygen consumption () of Chelodina expansa, C. longicollis and Emydura macquarii (Pleurodira: Chelidae) was measured at rest and during induced exercise at 8, 13, 18, 22, 26, 30 and 34°C. Resting varied significantly among species, being lowest in C. expansa, which is the most sedentary of the three species in nature, and highest in E. macquarii, which is the most energetic, but active did not differ significantly among the three species overall. For both Chelodina species, resting was appreciably lower than expected from regression of on body mass for non-marine turtles globally, a result that reinforces previous evidence of low resting metabolism in Australian chelid turtles. Active of all three species at higher temperatures was similar to reported for active freshwater cryptodires. Resting of all three species increased similarly with temperature, but active and aerobic scope did not. In C. expansa and E. macquarii, active and aerobic scope increased over the full temperature range assessed but in C. longicollis these variables reached a plateau above 22°C. Projected increases in freshwater temperatures in south-eastern Australia as a result of global warming are likely to enhance activity, feeding and growth of the three species (subject to food availability), especially in cooler seasons for C. longicollis and warmer seasons for C. expansa and E. macquarii. However, other aspects of predicted climate change, especially increased drought, are likely to be detrimental.
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Schmidt M, Mehlhorn M, Fischer MS. Shoulder girdle rotation, forelimb movement and the influence of carapace shape on locomotion in Testudo hermanni (Testudinidae). ACTA ACUST UNITED AC 2016; 219:2693-703. [PMID: 27340203 DOI: 10.1242/jeb.137059] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Accepted: 06/20/2016] [Indexed: 11/20/2022]
Abstract
Studies into the function of structures are crucial for making connections between morphology and behaviour of organisms, but are still rare for the terrestrial Testudinidae. We investigated the kinematics of shoulder girdle and forelimb motion in Hermann's tortoise Testudo hermanni using biplanar X-ray fluoroscopy with a twofold aim: firstly, to understand how the derived shapes of shoulder girdle and carapace together influence rotation of the girdle; and, secondly, to understand how girdle rotation affects forelimb excursion. The total degree of shoulder rotation in the horizontal plane is similar to a species with a less domed shell, but because of the long and nearly vertically oriented scapular prong, shoulder girdle rotation contributes more than 30% to the horizontal arc of the humerus and nearly 40% to the rotational component of step length. The antebrachium and manus, which act as a functional unit, contribute roughly 50% to this component of the step length because of their large excursion almost parallel to the mid-sagittal plane. This large excursion is the result of the complex interplay between humerus long-axis rotation, counter-rotation of the antebrachium, and elbow flexion and extension. A significant proportion of forelimb step length results from body translation that is due to the propulsive effect of the other limbs during their stance phases. Traits that are similar to other tortoises and terrestrial or semi-aquatic turtles are the overall slow walk because of a low stride frequency, and the lateral-sequence, diagonally coupled footfall pattern with high duty factors. Intraspecific variation of carapace shape and shoulder girdle dimensions has a corresponding effect on forelimb kinematics.
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Affiliation(s)
- Manuela Schmidt
- Institute of Systematic Zoology and Evolutionary Biology, Friedrich-Schiller-University Jena, Erbertstraße 1, Jena 07743, Germany
| | - Martin Mehlhorn
- Institute of Systematic Zoology and Evolutionary Biology, Friedrich-Schiller-University Jena, Erbertstraße 1, Jena 07743, Germany
| | - Martin S Fischer
- Institute of Systematic Zoology and Evolutionary Biology, Friedrich-Schiller-University Jena, Erbertstraße 1, Jena 07743, Germany
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Slavenko A, Itescu Y, Ihlow F, Meiri S. Home is where the shell is: predicting turtle home range sizes. J Anim Ecol 2015; 85:106-14. [PMID: 26395451 DOI: 10.1111/1365-2656.12446] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 09/14/2015] [Indexed: 11/30/2022]
Abstract
Home range is the area traversed by an animal in its normal activities. The size of home ranges is thought to be tightly linked to body size, through size effect on metabolic requirements. Due to the structure of Eltonian food pyramids, home range sizes of carnivores are expected to exceed those of herbivorous species. The habitat may also affect home range size, with reduced costs of locomotion or lower food abundance in, for example, aquatic habitats selecting for larger home ranges. Furthermore, home range of males in polygamous species may be large due to sexual selection for increased reproductive output. Comparative studies on home range sizes have rarely been conducted on ectotherms. Because ectotherm metabolic rates are much lower than those of endotherms, energetic considerations of metabolic requirements may be less important in determining the home range sizes of the former, and other factors such as differing habitats and sexual selection may have an increased effect. We collected literature data on turtle home range sizes. We used phylogenetic generalized least squares analyses to determine whether body mass, sex, diet, habitat and social structure affect home range size. Turtle home range size increases with body mass. However, body mass explains relatively little of the variation in home range size. Aquatic turtles have larger home ranges than semiaquatic species. Omnivorous turtles have larger home ranges than herbivores and carnivores, but diet is not a strong predictor. Sex and social structure are unrelated to home range size. We conclude that energetic constraints are not the primary factor that determines home range size in turtles, and energetic costs of locomotion in different habitats probably play a major role.
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Affiliation(s)
- Alex Slavenko
- Department of Zoology, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Yuval Itescu
- Department of Zoology, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Flora Ihlow
- Herpetology Department, Zoologisches Forschungsmuseum Alexander Koenig (ZFMK), 53113, Bonn, Germany
| | - Shai Meiri
- Department of Zoology, Tel Aviv University, 6997801, Tel Aviv, Israel
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Rose KA, Nudds RL, Codd JR. Intraspecific scaling of the minimum metabolic cost of transport in leghorn chickens (Gallus gallus domesticus): links with limb kinematics, morphometrics and posture. ACTA ACUST UNITED AC 2015; 218:1028-34. [PMID: 25657211 PMCID: PMC4392593 DOI: 10.1242/jeb.111393] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 01/26/2015] [Indexed: 01/09/2023]
Abstract
The minimum metabolic cost of transport (CoTmin; J kg−1 m−1) scales negatively with increasing body mass (∝Mb−1/3) across species from a wide range of taxa associated with marked differences in body plan. At the intraspecific level, or between closely related species, however, CoTmin does not always scale with Mb. Similarity in physiology, dynamics of movement, skeletal geometry and posture between closely related individuals is thought to be responsible for this phenomenon, despite the fact that energetic, kinematic and morphometric data are rarely collected together. We examined the relationship between these integrated components of locomotion in leghorn chickens (Gallus gallus domesticus) selectively bred for large and bantam (miniature) varieties. Interspecific allometry predicts a CoTmin ∼16% greater in bantams compared with the larger variety. However, despite 38% and 23% differences in Mb and leg length, respectively, the two varieties shared an identical walking CoTmin, independent of speed and equal to the allometric prediction derived from interspecific data for the larger variety. Furthermore, the two varieties moved with dynamic similarity and shared geometrically similar appendicular and axial skeletons. Hip height, however, did not scale geometrically and the smaller variety had more erect limbs, contrary to interspecific scaling trends. The lower than predicted CoTmin in bantams for their Mb was associated with both the more erect posture and a lower cost per stride (J kg−1 stride−1). Therefore, our findings are consistent with the notion that a more erect limb is associated with a lower CoTmin and with the previous assumption that similarity in skeletal shape, inherently linked to walking dynamics, is associated with similarity in CoTmin. Summary: Chickens with differing body size and posture but similar skeletal shape show no difference in the cost of transport.
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Affiliation(s)
- Kayleigh A Rose
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - Robert L Nudds
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - Jonathan R Codd
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
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Biancardi CM, Fabrica CG, Polero P, Loss JF, Minetti AE. Biomechanics of octopedal locomotion: kinematic and kinetic analysis of the spider Grammostola mollicoma. J Exp Biol 2011; 214:3433-42. [DOI: 10.1242/jeb.057471] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Despite the abundance of octapodal species and their evolutionary importance in originating terrestrial locomotion, the locomotion mechanics of spiders has received little attention so far. In this investigation we use inverse dynamics to study the locomotor performance of Grammostola mollicoma (18 g). Through 3-D kinematic measurements, the trajectory of the eight limbs and cephalothorax or abdomen allowed us to estimate the motion of the body centre of mass (COM) at different speeds. Classic mechanics of locomotion and multivariate analysis of several variables such as stride length and frequency, duty factor, mechanical external work and energy recovery, helped to identify two main gaits, a slow (speed <11 cm s–1) one and a fast one characterised by distinctive 3-D trajectories of COM. The total mechanical work (external + internal) calculated in the present study and metabolic data from the literature allowed us to estimate the locomotion efficiency of this species, which was less than 4%. Gait pattern due to alternating limb support, which generates asymmetrical COM trajectories and a small but consistent energy transfer between potential and kinetic energies of COM, is discussed both in terms of coordination indices and by referring to the octopod as formed by two quadrupeds in series. Analogies and differences of the newly obtained parameters with the allometric data and predictions are also illustrated.
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Affiliation(s)
- Carlo M. Biancardi
- Physiomechanics of Locomotion Laboratory, Department of Human Physiology, University of Milan, 20133 Milan, Italy
| | - C. Gabriel Fabrica
- Departamento de Biofísica (Unidad de Investigación en Biomecánica de la Locomoción Humana), Facultad de Medicina, Universidad de la República, General Flores 2125, Montevideo, Uruguay
| | - Patricia Polero
- Departamento de Biofísica (Unidad de Investigación en Biomecánica de la Locomoción Humana), Facultad de Medicina, Universidad de la República, General Flores 2125, Montevideo, Uruguay
| | - Jefferson Fagundes Loss
- Esçola de Educación Física (Laboratorio de Pesquisa en el Ejercicio), Universidade Federal do Rio Grande Do Sul, Rua Felizardo 750, Campus Olímpico, 90040-060Porto Alegre/RS
| | - Alberto E. Minetti
- Physiomechanics of Locomotion Laboratory, Department of Human Physiology, University of Milan, 20133 Milan, Italy
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Southwood A, Avens L. Physiological, behavioral, and ecological aspects of migration in reptiles. J Comp Physiol B 2010; 180:1-23. [PMID: 19847440 DOI: 10.1007/s00360-009-0415-8] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 09/25/2009] [Accepted: 09/29/2009] [Indexed: 11/30/2022]
Abstract
Seasonal movements between foraging, breeding, and overwintering sites occur in a wide variety of reptile species. Terrestrial snakes, lizards, and turtles migrate short distances (\20 km) between seasonal habitats, whereas fully aquatic marine turtles migrate hundreds to thousands of kilometers between foraging and breeding areas. The purpose of this article is to summarize aspects of migratory physiology and behavior in reptiles, particularly with regards to energetics and sensory mechanisms for navigation and orientation. We discuss the influence of aerobic scope, endurance, and cost of transport on migratory capacity, the effects of temperature and circulating hormones on activity and behavior, and mechanisms of detecting and transducing environmental cues to successfully navigate and orient toward a goal during migration. Topics worthy of further research are highlighted in the text, and we conclude with a discussion of how information on migration patterns of reptiles may be used to manage and conserve threatened populations.
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Affiliation(s)
- Amanda Southwood
- Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC 28403, USA.
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Zani PA, Kram R. Low metabolic cost of locomotion in ornate box turtles, Terrapene ornata. ACTA ACUST UNITED AC 2009; 211:3671-6. [PMID: 19011205 DOI: 10.1242/jeb.019869] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Evolution has produced a wide range of body plans, but for a given body mass, the energetic cost of transport (COT) of terrestrial animals falls in a relatively narrow range. Previous research indicates that the COT depends on the proficiency of minimizing mechanical work performed, efficiency of performing that work, and cost of generating force to support weight. Turtles are unique in that their protective shell and shoulder-girdle articulation may eliminate the need for the ;muscular sling'. In addition, turtles have slower, more efficient muscles than other vertebrates. However, slow locomotion may raise the COT by confounding mechanical-energy conservation via the inverted-pendulum mechanism. Our goal was to determine the metabolic COT and efficiency of a terrestrial turtle species during locomotion. We studied 18 ornate box turtles, Terrapene ornata. Walking speed was extremely slow (0.07+/-0.005 m s(-1)). The average minimum COT was 8.0+/-0.70 J kg(-1) m(-1) attained at approximately 0.1 m s(-1). Ornate box turtles consume only half the energy predicted by the allometric relationship for all terrestrial animals (15.9+/-0.35 J kg(-1) m(-1)), and, thus, appear to be very economical walkers. When walking up a 24 deg. incline turtles moved significantly slower (0.04+/-0.004 m s(-1)), but performed the extra work required to walk uphill with very high efficiencies (>49%). It appears that the co-evolution of a protective shell, the associated shoulder morphology, and very slow, efficient muscles produce both economical level walking and efficient uphill walking.
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Affiliation(s)
- Peter A Zani
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80309, USA.
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Roe J, Georges A, Green B. Energy and Water Flux during Terrestrial Estivation and Overland Movement in a Freshwater Turtle. Physiol Biochem Zool 2008; 81:570-83. [DOI: 10.1086/589840] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Elnitsky MA, Claussen DL. The effects of temperature and inter-individual variation on the locomotor performance of juvenile turtles. J Comp Physiol B 2006; 176:497-504. [PMID: 16496156 DOI: 10.1007/s00360-006-0071-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Revised: 12/27/2005] [Accepted: 02/01/2006] [Indexed: 10/25/2022]
Abstract
The effects of temperature on aquatic and terrestrial locomotor performance, including measures of burst speed, endurance, and righting response, the inter-individual correlation between measures of locomotor performance, and the temporal repeatability of performance were assessed in juvenile western painted turtles, Chrysemys picta bellii. Locomotor performance increased as temperature increased, with Q(10) values ranging from 1.33 to 1.98 for burst speed and 2.28 to 2.76 for endurance measures. Righting response performance also increased with temperature. Aquatic and terrestrial measures of locomotor performance were highly correlated; however, righting response was not correlated with any other measure of performance. Measures of terrestrial locomotor performance were highly repeatable over the entire 30-week study period, whereas aquatic locomotor performance was only repeatable through week 12. The righting response was repeatable over a 6-week study period. Both the interindividual variation and temperature effects on locomotor performance likely influences the survival of turtles, especially juveniles, by affecting the length of time turtles are exposed to potential predators and their ability to escape.
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Zani PA, Gottschall JS, Kram R. Giant Galápagos tortoises walk without inverted pendulum mechanical-energy exchange. J Exp Biol 2005; 208:1489-94. [PMID: 15802673 DOI: 10.1242/jeb.01554] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYAnimals must perform mechanical work during walking, but most conserve substantial mechanical energy via an inverted-pendulum-like mechanism of energy recovery in which fluctuations of kinetic energy (KE) and gravitational potential energy (GPE) are of similar magnitude and 180° out of phase. The greatest energy recovery typically occurs at intermediate speeds. Tortoises are known for their slow speeds, which we anticipated would lead to small fluctuations in KE. To have an effective exchange of mechanical energy using the inverted-pendulum mechanism, tortoises would need to walk with only small changes in GPE corresponding to vertical center-of-mass (COM)fluctuations of <0.5 mm. Thus, we hypothesized that giant Galápagos tortoises would not conserve substantial mechanical energy using the inverted-pendulum mechanism.We studied five adult giant Galápagos tortoises Geochelone elephantopus (mean mass=142 kg; range= 103–196 kg). Walking speed was extremely slow (0.16±0.052 m s–1; mean ± 1 s.d.). The fluctuations in kinetic energy(8.1±3.98 J stride–1) were only one-third as large as the fluctuations in gravitational potential energy (22.7±8.04 J stride–1). In addition, these energies fluctuated nearly randomly and were only sporadically out of phase. Because of the dissimilar amplitudes and inconsistent phase relationships of these energies, tortoises conserved little mechanical energy during steady walking, recovering only 29.8±3.77% of the mechanical energy (range=13–52%). Thus, giant Galápagos tortoises do not utilize effectively an inverted-pendulum mechanism of energy conservation. Nonetheless, the mass-specific external mechanical work required per distance (0.41±0.092 J kg–1 m–1) was not different from most other legged animals. Other turtle species use less than half as much metabolic energy to walk as other terrestrial animals of similar mass. It is not yet known if Galápagos tortoises are economical walkers. Nevertheless,contrary to biomechanical convention, poor inverted-pendulum mechanics during walking do not necessarily correspond to high mechanical work and may not result in a high metabolic cost.
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Affiliation(s)
- Peter A Zani
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA.
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15
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Affiliation(s)
- D F Boggs
- Department of Biology, Eastern Washington University, 526 Fifth Street, Cheney, WA 99004, USA
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