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Lowie A, De Kegel B, Wilkinson M, Measey J, O'Reilly JC, Kley NJ, Gaucher P, Adriaens D, Herrel A. The anatomy of the head muscles in caecilians (Amphibia: Gymnophiona): Variation in relation to phylogeny and ecology? J Anat 2023; 242:312-326. [PMID: 36087281 PMCID: PMC9877473 DOI: 10.1111/joa.13763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 08/07/2022] [Accepted: 08/29/2022] [Indexed: 02/01/2023] Open
Abstract
In limbless fossorial vertebrates such as caecilians (Gymnophiona), head-first burrowing imposes severe constraints on the morphology and overall size of the head. As such, caecilians developed a unique jaw-closing system involving the large and well-developed m. interhyoideus posterior, which is positioned in such a way that it does not significantly increase head diameter. Caecilians also possess unique muscles among amphibians. Understanding the diversity in the architecture and size of the cranial muscles may provide insights into how a typical amphibian system was adapted for a head-first burrowing lifestyle. In this study, we use dissection and non-destructive contrast-enhanced micro-computed tomography (μCT) scanning to describe and compare the cranial musculature of 13 species of caecilians. Our results show that the general organization of the head musculature is rather constant across extant caecilians. However, the early-diverging Rhinatrema bivittatum mainly relies on the 'ancestral' amphibian jaw-closing mechanism dominated by the m. adductores mandibulae, whereas other caecilians switched to the use of the derived dual jaw-closing mechanism involving the additional recruitment of the m. interhyoideus posterior. Additionally, the aquatic Typhlonectes show a greater investment in hyoid musculature than terrestrial caecilians, which is likely related to greater demands for ventilating their large lungs, and perhaps also an increased use of suction feeding. In addition to three-dimensional interactive models, our study provides the required quantitative data to permit the generation of accurate biomechanical models allowing the testing of further functional hypotheses.
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Affiliation(s)
- Aurélien Lowie
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, Ghent, Belgium
| | - Barbara De Kegel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, Ghent, Belgium
| | - Mark Wilkinson
- Department of Life Sciences, Natural History Museum, London, UK
| | - John Measey
- Centre for Invasion Biology, Department of Botany & Zoology, Stellenbosch University, Stellenbosch, South Africa
| | - James C O'Reilly
- Department of Biomedical Sciences, Ohio University, Cleveland Campus, Cleveland, Ohio, USA
| | - Nathan J Kley
- Department of Anatomical Sciences, Health Sciences Center, Stony Brook University, Stony Brook, New York, USA
| | - Philippe Gaucher
- USR 3456, CNRS, Centre de recherche de Montabo IRD, Cayenne, France
| | - Dominique Adriaens
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, Ghent, Belgium
| | - Anthony Herrel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, Ghent, Belgium.,UMR 7179 C.N.R.S/M.N.H.N., Département d'Ecologie et de Gestion de la Biodiversité, Paris Cedex 5, France
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Lowie A, De Kegel B, Wilkinson M, Measey J, O'Reilly JC, Kley NJ, Gaucher P, Brecko J, Kleinteich T, Adriaens D, Herrel A. Is vertebral shape variability in caecilians (Amphibia: Gymnophiona) constrained by forces experienced during burrowing? J Exp Biol 2022; 225:275610. [PMID: 35662342 DOI: 10.1242/jeb.244288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 05/18/2022] [Indexed: 11/20/2022]
Abstract
Caecilians are predominantly burrowing, elongate, limbless amphibians that remain relatively poorly studied. Although it has been suggested that the sturdy and compact skulls of caecilians are an adaptation to their head-first burrowing habits, no clear relationship between skull shape and burrowing performance appears to exist. However, the external forces encountered during burrowing are transmitted by the skull to the vertebral column, and as such, may impact vertebral shape. Additionally, the muscles that generate the burrowing forces attach onto the vertebral column and consequently may impact vertebral shape that way as well. Here, we explore the relationships between vertebral shape and maximal in vivo push forces in 13 species of caecilian amphibians. Our results show that the shape of the two most anterior vertebrae, as well as the shape of the vertebrae at 90% of the total body length, are not correlated with peak push forces. Conversely, the shape of the third vertebrae, and the vertebrae at 20% and 60% of the total body length, do show a relationship to push forces measured in vivo. Whether these relationships are indirect (external forces constraining shape variation) or direct (muscles forces constraining shape variation) remains unclear and will require quantitative studies of the axial musculature. Importantly, our data suggest that mid-body vertebrae may potentially be used as proxies to infer burrowing capacity in fossil representatives.
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Affiliation(s)
- Aurélien Lowie
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Barbara De Kegel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Mark Wilkinson
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
| | - John Measey
- Centre for Invasion Biology, Department of Botany & Zoology, Stellenbosch University, Private Bag X1, 7602 Matieland, Stellenbosch, South Africa
| | - James C O'Reilly
- Department of Biomedical Sciences, Ohio University, Cleveland Campus, SPS-334C, Cleveland, OH 45701, USA
| | - Nathan J Kley
- Department of Anatomical Sciences, Health Sciences Center, T8-082, Stony Brook University, Stony Brook, NY 11794-8081, USA
| | - Philippe Gaucher
- USR 3456, CNRS, Centre de recherche de Montabo IRD, CNRS-Guyane, 97334 Cayenne, French Guiana
| | - Jonathan Brecko
- Royal Museum for Central Africa, Biological Collections and Data Management, 3080 Tervuren, Belgium
| | | | - Dominique Adriaens
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Anthony Herrel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium.,UMR 7179 C.N.R.S/M.N.H.N., Département d'Ecologie et de Gestion de la Biodiversité, 57 rue Cuvier, Case postale 55, 75231, Paris Cedex 5, France
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Lowie A, De Kegel B, Wilkinson M, Measey J, O'Reilly JC, Kley NJ, Gaucher P, Brecko J, Kleinteich T, Herrel A, Adriaens D. Regional differences in vertebral shape along the axial skeleton in caecilians (Amphibia: Gymnophiona). J Anat 2022; 241:716-728. [PMID: 35488423 DOI: 10.1111/joa.13682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 04/13/2022] [Accepted: 04/13/2022] [Indexed: 10/18/2022] Open
Abstract
Caecilians are elongate, limbless and annulated amphibians that, as far as is known, all have an at least partly fossorial lifestyle. It has been suggested that elongate limbless vertebrates show little morphological differentiation throughout the postcranial skeleton. However, relatively few studies have explored the axial skeleton in limbless tetrapods. In this study, we used μCT data and three-dimensional geometric morphometrics to explore regional differences in vertebral shape across a broad range of caecilian species. Our results highlight substantial differences in vertebral shape along the axial skeleton, with anterior vertebrae being short and bulky, whereas posterior vertebrae are more elongated. This study shows that despite being limbless, elongate tetrapods such as caecilians still show regional heterogeneity in the shape of individual vertebrae along the vertebral column. Further studies are needed, however, to understand the possible causes and functional consequences of the observed variation in vertebral shape in caecilians.
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Affiliation(s)
- Aurélien Lowie
- Department of Biology, Evolutionary Morphology of Vertebrates, Ghent University, Ghent, Belgium
| | - Barbara De Kegel
- Department of Biology, Evolutionary Morphology of Vertebrates, Ghent University, Ghent, Belgium
| | - Mark Wilkinson
- Department of Life Sciences, Natural History Museum, London, UK
| | - John Measey
- Centre for Invasion Biology, Department of Botany & Zoology, Stellenbosch University, Stellenbosch, South Africa
| | - James C O'Reilly
- Department of Biomedical Sciences, Ohio University, Cleveland, Ohio, USA
| | - Nathan J Kley
- Department of Anatomical Sciences, Health Sciences Center, Stony Brook University, Stony Brook, New York, USA
| | - Philippe Gaucher
- USR 3456, CNRS, Centre de recherche de Montabo IRD, CNRS-Guyane, Cayenne, France
| | - Jonathan Brecko
- Royal Museum for Central Africa, Biological Collections and Data Management, Tervuren, Belgium
| | | | - Anthony Herrel
- Department of Biology, Evolutionary Morphology of Vertebrates, Ghent University, Ghent, Belgium.,UMR 7179 C.N.R.S/M.N.H.N, Département d'Ecologie et de Gestion de la Biodiversité, Paris Cedex 5, France
| | - Dominique Adriaens
- Department of Biology, Evolutionary Morphology of Vertebrates, Ghent University, Ghent, Belgium
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Lowie A, De Kegel B, Wilkinson M, Measey J, O'Reilly JC, Kley NJ, Gaucher P, Brecko J, Kleinteich T, Adriaens D, Herrel A. The relationship between head shape, head musculature and bite force in caecilians (Amphibia: Gymnophiona). J Exp Biol 2021; 225:273674. [PMID: 34897477 DOI: 10.1242/jeb.243599] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 12/06/2021] [Indexed: 11/20/2022]
Abstract
Caecilians are enigmatic limbless amphibians that, with a few exceptions all have an at least partly burrowing lifestyle. Although it has been suggested that caecilian evolution resulted in sturdy and compact skulls as an adaptation to their head-first burrowing habits, no relationship between skull shape and burrowing performance has been demonstrated to date. However, the unique dual jaw-closing mechanism and the osteological variability of their temporal region suggest a potential relationship between skull shape and feeding mechanics. Here, we explored the relationships between skull shape, head musculature, and in vivo bite forces. Although there is a correlation between bite force and external head shape, no relationship between bite force and skull shape could be detected. Whereas our data suggest that muscles are the principal drivers of variation in bite force, the shape of the skull is constrained by factors other than demands for bite force generation. However, a strong covariation between the cranium and mandible exists. Moreover, both cranium and mandible shape covary with jaw muscle architecture. Caecilians show a gradient between species with a long retroarticular process associated with a large and pennate-fibered m. interhyoideus posterior and species with a short process but long and parallel-fibered jaw adductors. Our results demonstrate the complexity of the relationship between form and function of this jaw system. Further studies that focus on factors such as gape distance or jaw velocity will be needed in order to fully understand the evolution of feeding mechanics in caecilians.
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Affiliation(s)
- Aurélien Lowie
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Barbara De Kegel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Mark Wilkinson
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
| | - John Measey
- Centre for Invasion Biology, Department of Botany & Zoology, Stellenbosch University, Private Bag X1, 7602 Matieland, Stellenbosch, South Africa
| | - James C O'Reilly
- Department of Biomedical Sciences, Ohio University, Cleveland Campus, SPS-334C, Cleveland, OH 45701, USA
| | - Nathan J Kley
- Department of Anatomical Sciences, Health Sciences Center, T8-082, Stony Brook University, Stony Brook, NY 11794-8081, USA
| | - Philippe Gaucher
- USR 3456, CNRS, Centre de recherche de Montabo IRD, CNRS-Guyane, 97334 Cayenne, France
| | - Jonathan Brecko
- Royal Museum for Central Africa, Biological Collections and Data Management, 3080 Tervuren, Belgium
| | | | - Dominique Adriaens
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Anthony Herrel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium.,UMR 7179 C.N.R.S/M.N.H.N., Département d'Ecologie et de Gestion de la Biodiversité, 57 rue Cuvier, Case postale 55, 75231, Paris Cedex 5, France
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Lowie A, De Kegel B, Wilkinson M, Measey J, O'Reilly JC, Kley NJ, Gaucher P, Brecko J, Kleinteich T, Van Hoorebeke L, Herrel A, Adriaens D. Under pressure: the relationship between cranial shape and burrowing force in caecilians (Gymnophiona). J Exp Biol 2021; 224:272111. [PMID: 34494653 DOI: 10.1242/jeb.242964] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 08/27/2021] [Indexed: 11/20/2022]
Abstract
Caecilians are elongate, limbless and annulated amphibians that, with the exception of one aquatic family, all have an at least partly fossorial lifestyle. It has been suggested that caecilian evolution resulted in sturdy and compact skulls with fused bones and tight sutures, as an adaptation to their head-first burrowing habits. However, although their cranial osteology is well described, relationships between form and function remain poorly understood. In the present study, we explored the relationship between cranial shape and in vivo burrowing forces. Using micro-computed tomography (µCT) data, we performed 3D geometric morphometrics to explore whether cranial and mandibular shapes reflected patterns that might be associated with maximal push forces. The results highlight important differences in maximal push forces, with the aquatic Typhlonectes producing a lower force for a given size compared with other species. Despite substantial differences in head morphology across species, no relationship between overall skull shape and push force could be detected. Although a strong phylogenetic signal may partly obscure the results, our conclusions confirm previous studies using biomechanical models and suggest that differences in the degree of fossoriality do not appear to be driving the evolution of head shape.
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Affiliation(s)
- Aurélien Lowie
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Barbara De Kegel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Mark Wilkinson
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
| | - John Measey
- Centre for Invasion Biology, Department of Botany & Zoology, Stellenbosch University, Private Bag X1, 7602 Matieland, Stellenbosch, South Africa
| | - James C O'Reilly
- Department of Biomedical Sciences, Ohio University, Cleveland Campus, SPS-334C, Cleveland, OH 45701, USA
| | - Nathan J Kley
- Department of Anatomical Sciences, Health Sciences Center, T8 (082), Stony Brook University, Stony Brook, NY 11794-8081, USA
| | - Philippe Gaucher
- USR 3456, CNRS, Centre de recherche de Montabo IRD, CNRS-Guyane, 97334 Cayenne, France
| | - Jonathan Brecko
- Royal Museum for Central Africa, Biological Collections and Data Management, 3080 Tervuren, Belgium
| | | | - Luc Van Hoorebeke
- UGCT - Department of Physics and Astronomy, Ghent University, Proeftuinstraat 86/N12, 9000 Gent, Belgium
| | - Anthony Herrel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium.,UMR 7179 C.N.R.S./M.N.H.N., Département d'Ecologie et de Gestion de la Biodiversité, 57 rue Cuvier, Case postale 55, 75231 Paris Cedex 5, France
| | - Dominique Adriaens
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
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Porro LB, Ross CF, Iriarte-Diaz J, O'Reilly JC, Evans SE, Fagan MJ. In vivo cranial bone strain and bite force in the agamid lizard Uromastyx geyri. ACTA ACUST UNITED AC 2014; 217:1983-92. [PMID: 24577443 PMCID: PMC4059540 DOI: 10.1242/jeb.096362] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In vivo bone strain data are the most direct evidence of deformation and strain regimes in the vertebrate cranium during feeding and can provide important insights into skull morphology. Strain data have been collected during feeding across a wide range of mammals; in contrast, in vivo cranial bone strain data have been collected from few sauropsid taxa. Here we present bone strain data recorded from the jugal of the herbivorous agamid lizard Uromastyx geyri along with simultaneously recorded bite force. Principal and shear strain magnitudes in Uromastyx geyri were lower than cranial bone strains recorded in Alligator mississippiensis, but higher than those reported from herbivorous mammals. Our results suggest that variations in principal strain orientations in the facial skeleton are largely due to differences in feeding behavior and bite location, whereas food type has little impact on strain orientations. Furthermore, mean principal strain orientations differ between male and female Uromastyx during feeding, potentially because of sexual dimorphism in skull morphology.
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Affiliation(s)
- Laura B Porro
- Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK
| | - Callum F Ross
- Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA
| | - Jose Iriarte-Diaz
- Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA
| | - James C O'Reilly
- Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA
| | - Susan E Evans
- Research Department of Cell and Developmental Biology, University College London, Gower Street, London WCIE 6BT, UK
| | - Michael J Fagan
- School of Engineering, University of Hull, Cottingham Road, Hull HU6 7RX, UK
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Abstract
SUMMARYMany plethodontid salamanders project their tongues ballistically at high speed and for relatively great distances. Capturing evasive prey relies on the tongue reaching the target in minimum time, therefore it is expected that power production, or the rate of energy release, is maximized during tongue launch. We examined the dynamics of tongue projection in three genera of plethodontids (Bolitoglossa, Hydromantes and Eurycea), representing three independent evolutionary transitions to ballistic tongue projection, by using a combination of high speed imaging,kinematic and inverse dynamics analyses and electromyographic recordings from the tongue projector muscle. All three taxa require high-power output of the paired tongue projector muscles to produce the observed kinematics. Required power output peaks in Bolitoglossa at values that exceed the greatest maximum instantaneous power output of vertebrate muscle that has been reported by more than an order of magnitude. The high-power requirements are likely produced through the elastic storage and recovery of muscular kinetic energy. Tongue projector muscle activity precedes the departure of the tongue from the mouth by an average of 117 ms in Bolitoglossa, sufficient time to load the collagenous aponeuroses within the projector muscle with potential energy that is subsequently released at a faster rate during tongue launch.
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Affiliation(s)
- Stephen M Deban
- Department of Biology, 4202 East Fowler Avenue, SCA 110, University of South Florida, Tampa, FL 33620, USA.
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Deban SM, O'Reilly JC. The ontogeny of feeding kinematics in a giant salamander Cryptobranchus alleganiensis: Does current function or phylogenetic relatedness predict the scaling patterns of movement? ZOOLOGY 2005; 108:155-67. [PMID: 16351963 DOI: 10.1016/j.zool.2005.03.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2005] [Accepted: 03/11/2005] [Indexed: 10/25/2022]
Abstract
Studies of the scaling of feeding movements in vertebrates have included three species that display both near-geometric growth and isometry of kinematic variables. These scaling characteristics allow one to examine the "pure" relationship of growth and movement. Despite similar growth patterns, the feeding movements of toads (Bufo) slow down more with increasing body size than those of bass (Micropterus), and sharks (Ginglymostoma). This variation might be due to major differences in the mechanism of prey capture; the bass and sharks use suction to capture prey in water, while the toad uses tongue prehension to capture prey on land. To investigate whether or not these different scaling patterns are correlated with differences in feeding mechanics, we examined the ontogenetic scaling of prey capture movements in the hellbender salamander (Cryptobranchus alleganiensis), which also has near-geometric growth. The hellbender suction feeds in the same general manner as the teleosts and shark, but is much more closely related to the toad. The feeding movements of the hellbender scale more similarly to the feeding movements of toads than to those of fishes or sharks, indicating that phylogenetic relatedness rather than biomechanical similarity predicts ontogenetic scaling patterns of movement.
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Affiliation(s)
- Stephen M Deban
- Museum of Vertebrate Zoology and Department of Integrative Biology, 3101 Valley Life Sciences Building #3160, University of California, Berkeley, CA 94720-3160, USA.
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Wassersug RJ, Roberts L, Gimian J, Hughes E, Saunders R, Devison D, Woodbury J, O'Reilly JC. The behavioral responses of amphibians and reptiles to microgravity on parabolic flights. ZOOLOGY 2005; 108:107-20. [PMID: 16351959 DOI: 10.1016/j.zool.2005.03.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2005] [Revised: 03/02/2005] [Accepted: 03/02/2005] [Indexed: 10/25/2022]
Abstract
In the present study, we exposed 53 animals from 23 different species of amphibians and reptiles to microgravity (mug). This nearly doubles the number of amphibians and reptiles observed so far in mug. The animals were flown on a parabolic flight, which provided 20-25s of mug, to better characterize behavioral reactions to abrupt exposure to mug. Highly fossorial limbless caecilians and amphisbaenians showed relatively limited movement in mug. Limbed quadrupedal reptiles that were non-arboreal in the genera Leiocephalus, Anolis, and Scincella showed the typical righting response and enormous amounts of body motion and tail rotation, which we interpreted as both righting responses and futile actions to grasp the substrate. Both arboreal and non-arboreal geckos in the genera Uroplatus, Palmatogecko, Stenodactylus, Tarentola, and Eublepharis instead showed a skydiving posture previously reported for highly arboreal anurans. Some snakes, in the genera Thamnophis and Elaphe, which typically thrashed and rolled in mug, managed to knot their own bodies with their tails and immediately became quiescent. This suggests that these reptiles gave stable physical contact, which would indicate that they were not falling, primacy over vestibular input that indicated that they were in freefall. The fact that they became quiet upon self-embrace further suggests a failure to distinguish self from non-self. The patterns of behavior seen in amphibians and reptiles in mug can be explained in light of their normal ecology and taxonomic relations.
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Affiliation(s)
- Richard J Wassersug
- Department of Anatomy & Neurobiology, Sir Charles Tupper Medical Building, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5.
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Abstract
SUMMARY
High-speed videography and muscle denervation experiments were used to elucidate the mechanism of tongue protraction in the microhylid frog Phrynomantis bifasciatus. Unlike most frogs, Phrynomantishas the ability to protract the tongue through a lateral arc of over 200°in the frontal plane. Thus, the tongue can be aimed side to side,independently of head and jaw movements. Denervation experiments demonstrate that the m. genioglossus complex controls lateral tongue aiming with a hydrostatic mechanism. After unilateral denervation of the m. genioglossus complex, the tongue can only be protracted towards the denervated (inactive)side and the range through which the tongue can be aimed is reduced by 75%. Histological sections of the tongue reveal a compartment of perpendicularly arranged muscle fibers, the m. genioglossus dorsoventralis. This compartment,in conjunction with the surrounding connective tissue, generates hydrostatic pressure that powers tongue movements in Phrynomantis. A survey of aiming abilities in 17 additional species of microhylid frogs, representing a total of 12 genera and six subfamilies, indicates that hydrostatic tongues are found throughout this family. Among frogs, this mechanism of tongue protraction was previously known only in Hemisus and may represent a synapomorphy of Hemisus and Microhylidae.
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Affiliation(s)
- Jay J Meyers
- Physiology and Functional Morphology Group, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011-5640, USA.
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Abstract
Unlike other amphibians, frogs often use their forelimbs to capture and transport prey. In the present study, high-speed videography was used to observe forelimb use during feeding in a diverse group of anurans in order to determine the evolution of forelimb movement patterns among anuran taxa. Data were gathered from 488 individuals representing 104 species, 55 genera, and 16 families. Five distinct behavior patterns were identified: scooping entails using the back of the hand to push prey into the mouth; wiping involves the use of the palm of the hand to push prey, protruding laterally from the mouth, toward the midline; during prey stretching, one end of the prey is held in a stationary position by the hands while the other end is pulled upward by the jaws; in grasping, the palms face the midline or the substrate as the fingers are wrapped around the prey; grasping with wrist rotation is similar to grasping, but the wrists rotate inward as the hands grasp the prey so that the palms face the mouth. The distribution of these behavior patterns was mapped onto the most recent phylogenetic hypothesis for anurans. Maximum parsimony analyses suggest that scooping and wiping are primitive and have been retained by many frog lineages. Wiping was not observed in the pipids, which are the only anurans that lack tongues and use hydraulic transport. Prey stretching appears to have evolved several times in unrelated taxa. Grasping and grasping with wrist rotation appear to have evolved only in arboreal groups, suggesting that the ability to climb is a preadaptation for the ability to grasp prey. Several species were observed using grasping motions in place of the tongue to capture prey.
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Affiliation(s)
- L A Gray
- Department of Biological Sciences, Northern Arizona University, Flagstaff 86011-5640, USA
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Nishikawa KC, Anderson CW, Deban SM, O'Reilly JC. The evolution of neural circuits controlling feeding behavior in frogs. Brain Behav Evol 1992; 40:125-40. [PMID: 1422806 DOI: 10.1159/000113908] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Our approach to understanding motor systems is a phylogenetic, 'outside-in' approach, the goal of which is to identify behavioral transitions during phylogenesis and elucidate their neurological basis. In this paper, we review the results of recent behavioral, biomechanical and neurological studies on frog feeding behavior. These studies show that highly protrusible tongues have evolved numerous times independently among frogs, and that the biomechanics and neuromuscular control of feeding behavior have been transformed repeatedly during frog evolution. Many of the independent lineages possess unique biomechanical mechanisms for protracting their tongues and unique neural mechanisms for coordinating feeding behavior. In frogs, there has been considerable evolution at the interface between reticular central pattern generators (CPGs) associated with feeding and sensory feedback circuits that modulate feeding motor output. In particular, the roles of hypoglossal and glossopharyngeal sensory feedback appear to have been relatively plastic in their evolution. Prey-type dependence of hypoglossal sensory feedback in Rana suggests that the interaction between descending visual control and sensory feedback also may be evolutionarily plastic. Comparative studies have found that motor systems sometimes evolve conservatively across morphological and behavioral transitions (i.e., the shoulder in birds) or, alternatively, they may be subject to considerably more evolutionary change than is reflected in morphological characteristics (i.e., feeding in cichlids). We hypothesize that the CPG circuits for feeding behavior in the reticular formation may evolve conservatively because they are highly integrated, multifunctional networks which cannot be optimized for one function without compromising others. In contrast, the interfaces between the CPG, sensory feedback and descending control should be less constrained. When changes in motor patterns occur during evolution, it is likely that sensory feedback or descending control may be involved.
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Affiliation(s)
- K C Nishikawa
- Department of Biological Sciences, Northern Arizona University, Flagstaff
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