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Segesdi M, Brabant D, Cornette R, Houssaye A. How does the shape of the wing and hindlimb bones of aquatic birds relate to their locomotor abilities? Anat Rec (Hoboken) 2024. [PMID: 38803316 DOI: 10.1002/ar.25512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 05/07/2024] [Accepted: 05/08/2024] [Indexed: 05/29/2024]
Abstract
Aquatic birds represent diverse ecologies and locomotion types. Some became flightless or lost the ability for effective terrestrial locomotion, yet, certain species excel in water, on land, and in air, despite differing physical characteristics associated with each medium. In this exploratory study, we intend to quantitatively analyze the morphological variety of multiple limb bones of aquatic birds using 3D geometric morphometrics. Morphological variation is mainly driven by phylogeny, which also affects size and locomotion. However, the shape of the ulna, including the proportion and orientation of the epiphyses is influenced by size and aquatic propulsive techniques even when phylogeny is taken into consideration. Certain trends, possibly linked to functions, can be observed too in other bones, notably in cases where phylogenetic and functional signals are probably mixed when some taxa only englobe species with similar functional requirements: penguins exhibit the most distinctive wing bone morphologies, highly adapted to wing-propulsion; advanced foot-propellers exhibit femur morphology that reduces proximal mobility but supports stability; knee structures, like cnemial crests of varied sizes and orientations, are crucial for muscle attachments and efficient movement in water and on land; taxa relying on their feet in water but retaining terrestrial abilities share features enabling swimming and walking postures. Size-linked changes distinguish the wing bones of non-wing-propelled taxa. For hindlimbs, larger size relates to robust bones probably linked to terrestrial abilities, but robustness in femora can be connected to foot-propulsion. These results help us better understand birds' skeletal adaptation and can be useful inferring extinct species' ecology.
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Affiliation(s)
- Martin Segesdi
- Department of Paleontology, ELTE Eötvös Loránd University, Institute of Geography and Earth Sciences, Budapest, Hungary
- Department of Zoology, Hungarian Natural History Museum, Budapest, Hungary
- Department of Paleontology and Geology, Hungarian Natural History Museum, Budapest, Hungary
| | - Delphine Brabant
- Plateforme Surfaçus, Délégation de l'Innovation Numérique, Direction générale déléguée aux collections, Muséum National d'Histoire Naturelle, Paris, France
| | - Raphaël Cornette
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d'Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, Paris, France
| | - Alexandra Houssaye
- Mécanismes adaptatifs et évolution (MECADEV), UMR 7179, MNHN, Paris, France
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2
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Gutiérrez-Ibáñez C, Wylie DR. Investigation of central pattern generators in the spinal cord of chicken embryos. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024:10.1007/s00359-024-01694-6. [PMID: 38521869 DOI: 10.1007/s00359-024-01694-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 01/29/2024] [Accepted: 02/01/2024] [Indexed: 03/25/2024]
Abstract
For most quadrupeds, locomotion involves alternating movements of the fore- and hindlimbs. In birds, however, while walking generally involves alternating movements of the legs, to generate lift and thrust, the wings are moved synchronously with each other. Neural circuits in the spinal cord, referred to as central pattern generators (CPGs), are the source of the basic locomotor rhythms and patterns. Given the differences in the patterns of movement of the wings and legs, it is likely that the neuronal components and connectivity of the CPG that coordinates wing movements differ from those that coordinate leg movements. In this study, we used in vitro preparations of embryonic chicken spinal cords (E11-E14) to compare the neural responses of spinal CPGs that control and coordinate wing flapping with those that control alternating leg movements. We found that in response to N-methyl-D-aspartate (NMDA) or a combination of NMDA and serotonin (5-HT), the intact chicken spinal cord produced rhythmic outputs that were synchronous both bilaterally and between the wing and leg segments. Despite this, we found that this rhythmic output was disrupted by an antagonist of glycine receptors in the lumbosacral (legs), but not the brachial (wing) segments. Thus, our results provide evidence of differences between CPGs that control the wings and legs in the spinal cord of birds.
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Affiliation(s)
- Cristián Gutiérrez-Ibáñez
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E0, Canada.
- Grass Laboratory, Marine Biological Laboratory, Woods Hole, MA, USA.
| | - Douglas R Wylie
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E0, Canada
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3
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Leblanc K, Pintore R, Galvão A, Heitz E, Provini P. Foot adaptation to climbing in ovenbirds and woodcreepers (Furnariida). J Anat 2023; 242:607-626. [PMID: 36525307 PMCID: PMC10008296 DOI: 10.1111/joa.13805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 10/27/2022] [Accepted: 11/25/2022] [Indexed: 12/23/2022] Open
Abstract
Furnariida (i.e. ovenbirds, woodcreepers and antbirds) cover diverse ecologies and locomotor habits, ranging from strictly terrestrial to climbing birds, with different degrees of acrobatic performances. We know that this variety of locomotor modes is linked to different limb morpho-functional adaptations in other climbing clades of birds, such as woodpeckers and nuthatches. Here, we link the morphological variations to ecological categories, such as different locomotor habits and a gradient of acrobatic performances, in a phylogenetically informed analysis. We used a high-density three-dimensional (3D) geometric morphometric approach on foot bones (tarsometatarsus and all toes) of 55 specimens from 39 species of Furnariida. We found a significant correlation between acrobatic performances and foot bone shapes, partly explained by the phylogenetic relationship between species. Dendrocolaptidae show specific anatomical features, linked to their acrobatic locomotor habits. More specifically, we found that: (1) foot bones are more robust amongst climbing Furnariida, (2) the spread between toes is wider amongst highly acrobatic Furnariida, (3) dermal syndactyly between digits II and III is linked to special osteological features interpreted as functional osteological syndactyly in woodcreepers (tail-assisted climbers) and (4) the hallux claw is straighter than other claws in climbing Furnariida. Our study demonstrates that climbing Furnariida evolved common foot adaptations with subtle phenotypic variations depending on their climbing performances, refining our understanding of how evolution shapes interactions amongst structure, function and ecological traits.
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Affiliation(s)
- Killian Leblanc
- Université Paris Cité, Inserm, System Engineering and Evolution Dynamics, Paris, France.,Learning Planet Institute, Paris, France
| | - Romain Pintore
- UMR 7179 C.N.R.S/M.N.H.N. MECADEV, Département Adaptations du Vivant, Paris, France.,Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK
| | - Ana Galvão
- Laboratório de Ornitologia, Departamento de Zoologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Ezekiel Heitz
- Université Paris Cité, Inserm, System Engineering and Evolution Dynamics, Paris, France.,Learning Planet Institute, Paris, France.,UMR 7179 C.N.R.S/M.N.H.N. MECADEV, Département Adaptations du Vivant, Paris, France
| | - Pauline Provini
- Université Paris Cité, Inserm, System Engineering and Evolution Dynamics, Paris, France.,Learning Planet Institute, Paris, France.,UMR 7179 C.N.R.S/M.N.H.N. MECADEV, Département Adaptations du Vivant, Paris, France
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Dickinson E, Young MW, Kim CJ, Hadjiargyrou M, Granatosky MC. The influence of substrate size upon pulling and gripping forces in parrots (Psittaciformes: Agapornis roseicollis). J Exp Biol 2022; 225:jeb244818. [PMID: 36106504 DOI: 10.1242/jeb.244818] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 08/29/2022] [Indexed: 01/03/2024]
Abstract
The ability to securely grasp substrates of variable diameter is critical to arboreal animals. Arboreal specialists have emerged across several vertebrate lineages - including mammals, lizards and amphibians - and several attempts have been made to quantify their grasping performance, by measuring either gripping (i.e. forces generated about an object or substrate enclosed within the digits) or pulling (i.e. the ability to resist being removed from a substrate) forces. In this study, we present data on both pulling and gripping performance across a range of substrate diameters (0.5-17.5 mm) within a model parrot species (Agapornis roseicollis). Parrots represent an ancient arboreal lineage, allowing us to compare their abilities with those of arboreal specialists within other tetrapod groups. Data were collected using 3D-printed perches of variable diameter, and forces were registered using either an AMTI low-load force plate (grip force) or a Harvard Apparatus portable strength tester (pull force). Gripping forces peaked at a 5 mm diameter perch, while pulling forces were greatest at a 2.5 mm diameter. All forces strongly diminished above 10 mm size, suggesting grip force is optimized when utilizing small perches, a finding which corresponds to observational studies of preferential perching habits among free-ranging parrots. Relative grasping performance (adjusted for body size) in parrots is roughly equivalent to that of other arboreal specialists from other tetrapod lineages, but low when compared with that of raptorial birds that utilize their feet during aerial prey capture. Further taxonomic sampling is encouraged to contextualize how grasping performance varies in an adaptive evolutionary context.
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Affiliation(s)
- Edwin Dickinson
- Department of Anatomy, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568-8000, USA
| | - Melody W Young
- Department of Anatomy, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568-8000, USA
- College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568-8000, USA
| | - Charles J Kim
- College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568-8000, USA
| | - Michael Hadjiargyrou
- Department of Biological and Chemical Sciences, New York Institute of Technology, Old Westbury, NY 11568-8000, USA
| | - Michael C Granatosky
- Department of Anatomy, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568-8000, USA
- Center for Biomedical Innovation, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY 11568-8000, USA
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Positional Behavior of Introduced Monk Parakeets (Myiopsitta monachus) in an Urban Landscape. Animals (Basel) 2022; 12:ani12182372. [PMID: 36139232 PMCID: PMC9494974 DOI: 10.3390/ani12182372] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 09/07/2022] [Accepted: 09/08/2022] [Indexed: 11/17/2022] Open
Abstract
Simple Summary Positional behaviors comprise the entirety of animals’ locomotion and posture. Often, these positional behaviors are paired with information about sußbstrate characteristics (e.g., orientation, diameter, texture, height) and frequency to gain an ecological perspective of when and why an animal utilizes a particular behavior. Thus far, quantitative studies of positional behavior have been limited to mammals, leaving a major gap in our understanding of how animals utilize their environment. In this study, we present the first quantitative report of positional behavior within Aves, presenting scan sampling data from an established colony of Monk Parakeets (Myiopsitta monachus) from Brooklyn, New York City. Parrots exhibited a strong preference for small and terminal branches when perching arboreally. Such a pattern is consistent with arboreal primates. We also observed an increase in locomotor diversity on artificial versus naturally occurring substrates. This demonstrates the potential importance of a flexible behavioral repertoire in facilitating a successful transition towards an urban landscape in introduced species and underscores the need for further studies exploring positional behaviors among urban wildlife. Abstract Positional behaviors have been broadly quantified across the Order Primates, and in several other mammalian lineages, to contextualize adaptations to, and evolution within, an arboreal environment. Outside of Mammalia, however, such data are yet to be reported. In this study, we present the first quantitative report of positional behavior within Aves, presenting 11,246 observations of scan sampling data from a colony of Monk Parakeets (Myiopsitta monachus) from Brooklyn, New York City. Each scan recorded locomotor and postural behavior and information about weather condition, temperature, and substrate properties (e.g., type, size, orientation). A distinction was also recorded between natural and artificial substrates. Parrots exhibited a strong preference for small and terminal branches, a selection which may reflect targeted foraging of new fruit growth and leaf-buds. We further observed that the gait transition from walking to sidling appears primarily driven by substrate size, with the former preferred on the ground and on large, broad substrates and the latter used to navigate smaller branches. Finally, we observed an increase in locomotor diversity on artificial versus naturally occurring substrates. This demonstrates the importance of a flexible behavioral repertoire in facilitating a successful transition towards an urban landscape in introduced species.
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Young MW, Lynch SK, Dickinson E, Currier AA, Davoli EC, Hanna CS, Fischer HM, DiUbaldi GA, Granatosky MC. Patterns of single limb forces during terrestrial and arboreal locomotion in rosy-faced lovebirds (Psittaciformes: Agapornis roseicollis). J Exp Biol 2022; 225:276123. [PMID: 35822351 DOI: 10.1242/jeb.244571] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 06/29/2022] [Indexed: 11/20/2022]
Abstract
The biomechanical demands of arboreal locomotion are generally thought to necessitate specialized kinetic and kinematic gait characteristics. While such data has been widely collected across arboreal quadrupeds, no study has yet explored how arboreal substrates influence the locomotor behavior of birds. Parrots - an ancient arboreal lineage that exhibit numerous anatomical specializations towards life in the trees - represent an ideal model group within which to examine this relationship. Here, we quantify limb loading patterns within the rosy-faced lovebird (Agapornis roseicollis) across a range of experimental conditions to define under which circumstances arboreal gaits are triggered, and how, during arboreal walking, gait patterns change across substrates of varying diameter. In so doing, we address longstanding questions as to how the challenges associated with arboreality affect gait parameters. Arboreal locomotion was associated with the adoption of a sidling gait, which was employed exclusively on the small- and medium-poles but not terrestrially. When sidling, the hindlimbs are decoupled into a distinct leading limb (which imparts exclusively braking forces) and trailing limb (which generates only propulsive forces). Sidling was also associated with relatively low pitching forces, even on the smallest substrate. Indeed, these forces were significantly lower than mediolateral forces experienced during striding on terrestrial and large-diameter substrates. We propose that the adoption of sidling gaits is a consequence of avian foot morphology and represents a novel form of arboreal locomotion where inversion/eversion is impossible. Such movement mechanics is likely widespread among avian taxa and may also typify patterns of arboreal locomotion in humans.
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Affiliation(s)
- Melody W Young
- New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA
| | - Samantha K Lynch
- New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA
| | - Edwin Dickinson
- New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA.,Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA
| | - Allen A Currier
- New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA
| | - Elizabeth C Davoli
- New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA
| | - Christopher S Hanna
- New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA
| | - Hannah M Fischer
- New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA
| | - Gianluca A DiUbaldi
- New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA
| | - Michael C Granatosky
- Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA.,Center for Biomedical Innovation, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA
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7
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Young MW, Dickinson E, Flaim ND, Granatosky MC. Overcoming a 'forbidden phenotype': the parrot's head supports, propels and powers tripedal locomotion. Proc Biol Sci 2022; 289:20220245. [PMID: 35582799 PMCID: PMC9115034 DOI: 10.1098/rspb.2022.0245] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
No vertebrate, living or extinct, is known to have possessed an odd number of limbs. Despite this 'forbidden phenotype', gaits that use odd numbers of limbs (e.g. tripedalism or pentapedalism) have evolved in both avian and mammalian lineages. Tripedal locomotion is commonly employed by parrots during climbing, who use their beaks as an additional support. However, it is unclear whether the beak functions simply as a stabilizing hook, or as a propulsive limb. Here, we present data on kinetics of tripedal climbing in six rosy-faced lovebirds (Agapornis roseicollis). Our findings demonstrate that parrots use cyclical tripedal gaits when climbing and the beak and hindlimbs generate comparable propulsive and tangential substrate reaction forces and power. Propulsive and tangential forces generated by the beak are of magnitudes equal to or greater than those forces generated by the forelimbs of humans and non-human primates during vertical climbing. We conclude that the feeding apparatus and neck flexors of parrots have been co-opted to function biomechanically as a propulsive third limb during vertical climbing. We hypothesize that this exaptation required substantive alterations to the neuromuscular system including enhanced force-generating capabilities of the neck flexors and modifications to locomotor central pattern generators.
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Affiliation(s)
- Melody W. Young
- Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, USA
| | - Edwin Dickinson
- Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, USA
| | - Nicholas D. Flaim
- Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, USA
| | - Michael C. Granatosky
- Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, USA,Center for Biomedical Innovation, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, USA
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8
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De Mendoza RS, Gómez RO. Ecomorphology of the tarsometatarsus of waterfowl (Anseriformes) based on geometric morphometrics and its application to fossils. Anat Rec (Hoboken) 2022; 305:3243-3253. [PMID: 35132811 DOI: 10.1002/ar.24891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 01/24/2022] [Accepted: 01/26/2022] [Indexed: 11/08/2022]
Abstract
Anseriformes is a diverse group of birds that comprises screamers, the Magpie Goose, and swans ducks and geese, with a relatively rich fossil record. Waterfowl live in close relation to water bodies, but show a diversity of locomotory habits, being typically categorized as walkers, dabblers, and divers. Owing to its functional significance and high preservation potential, the tarsometatarsus has been considered to be a "key" element upon which to base ecomorphological inferences in fossil waterfowl. For instance, based on features of the tarsometatarsus the Miocene flightless duck Cayaoa bruneti and the Oligocene-Miocene large waterfowl Paranyroca have been inferred as divers. Herein, we use a geometric morphometric approach and comparative methods to assess the phylogenetic and ecomorphological signals in the shape and size of waterfowl tarsometatarsi in relation to their locomotory habits. We also apply phylogenetic flexible discriminant analysis (pFDA) to test the inferred diving habits in the extinct waterfowl Cayaoa and Paranyroca. Extant waterfowl species are largely distributed according to their locomotory habit along the main axis of variation in the shape space, a pattern mirrored by the phylogenetic generalized least squares model, which shows that a third of the shape variation is significantly explained by the habit. The pFDA reclassifies correctly almost all extant species and classified with high posterior probabilities the fossil Cayaoa and Paranyroca as a diver and as a dabbler, respectively. Our quantitative multivariate approach confirms the tarsometatarsus as a useful source of data upon which reliably assesses locomotory habits of fossil waterfowl.
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Affiliation(s)
- Ricardo Santiago De Mendoza
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Laboratorio de Histología y Embriología Descriptiva, Experimental y Comparada (LHYEDEC). Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, Buenos Aires, Argentina
| | - Raúl Orencio Gómez
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina
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Ryding S, Klaassen M, Tattersall GJ, Gardner JL, Symonds MRE. Shape-shifting: changing animal morphologies as a response to climatic warming. Trends Ecol Evol 2021; 36:1036-1048. [PMID: 34507845 DOI: 10.1016/j.tree.2021.07.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 07/14/2021] [Accepted: 07/19/2021] [Indexed: 12/19/2022]
Abstract
Many animal appendages, such as avian beaks and mammalian ears, can be used to dissipate excess body heat. Allen's rule, wherein animals in warmer climates have larger appendages to facilitate more efficient heat exchange, reflects this. We find that there is widespread evidence of 'shape-shifting' (changes in appendage size) in endotherms in response to climate change and its associated climatic warming. We re-examine studies of morphological change over time within a thermoregulatory context, finding evidence that temperature can be a strong predictor of morphological change independently of, or combined with, other environmental changes. Last, we discuss how Allen's rule, the degree of temperature change, and other ecological factors facilitate morphological change and make predictions about what animals will show shape-shifting.
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Affiliation(s)
- Sara Ryding
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia.
| | - Marcel Klaassen
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia
| | - Glenn J Tattersall
- Department of Biological Sciences, Brock University, 500 Glenridge Avenue, Saint Catharines, Ontario L2S 3A1, Canada
| | - Janet L Gardner
- Division of Ecology & Evolution, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Matthew R E Symonds
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia
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Höfling E, Abourachid A. The skin of birds' feet: Morphological adaptations of the plantar surface. J Morphol 2020; 282:88-97. [PMID: 33098345 DOI: 10.1002/jmor.21284] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/24/2020] [Accepted: 10/08/2020] [Indexed: 11/09/2022]
Abstract
The skin of the foot provides the interface between the bird and the substrate. The foot morphology involves the bone shape and the integument that is in contact with the substrate. The podotheca is a layer of keratinized epidermis forming scales that extends from the tarsometatarsus to the toe extremities. It varies in size, shape, amount of overlap and interacts with the degree of fusion of the toes (syndactyly). A study of toe shape and the podotheca provides insights on the adaptations of perching birds. Our analysis is based on micro-CT scans and scanning electron microscopy images of 21 species from 17 families, and includes examples with different orientations of the toes: zygodactyl (toes II and III forward), anisodactyl (toes II, III, and IV forward), and heterodactyl (toes III and IV forward). We show that in these three groups, the skin forms part of a perching adaptation that involves syndactyly to different degrees. However, syndactyly does not occur in Psittacidae that use their toes also for food manipulation. The syndactyly increases the sole surface and may reinforce adherence with the substrate. Scale shape and toe orientation are involved in functional adaptations to perch. Thus, both bone and skin features combine to form a pincer-like foot.
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Affiliation(s)
- Elizabeth Höfling
- Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.,Museu de História Natural de Taubaté, Taubaté, SP, Brazil
| | - Anick Abourachid
- Mécanismes adapatatifs et évolution, Muséum National d'Histoire Naturelle - CNRS, 57 rue Cuvier, Paris, France, 75005, France
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