1
|
Shape asymmetry - what's new? Emerg Top Life Sci 2022; 6:285-294. [PMID: 35758318 DOI: 10.1042/etls20210273] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 05/27/2022] [Accepted: 05/30/2022] [Indexed: 11/17/2022]
Abstract
Studies of shape asymmetry have become increasingly abundant as the methods of geometric morphometrics have gained widespread use. Most of these studies have focussed on fluctuating asymmetry and have largely obtained similar results as more traditional analyses of asymmetry in distance measurements, but several notable differences have also emerged. A key difference is that shape analyses provide information on the patterns, not just the amount of variation, and therefore tend to be more sensitive. Such analyses have shown that apparently symmetric structures in animals consistently show directional asymmetry for shape, but not for size. Furthermore, the long-standing prediction that phenotypic plasticity in response to environmental heterogeneity can contribute to fluctuating asymmetry has been confirmed for the first time for the shape of flower parts (but not for size). Finally, shape analyses in structures with complex symmetry, such as many flowers, can distinguish multiple types of directional asymmetry, generated by distinct direction-giving factors, which combine to the single component observable in bilaterally symmetric structures. While analyses of shape asymmetry are broadly compatible with traditional analyses of asymmetry, they incorporate more detailed morphological information, particularly for structures with complex symmetry, and therefore can reveal subtle biological effects that would otherwise not be apparent. This makes them a promising tool for a wide range of studies in the basic and applied life sciences.
Collapse
|
2
|
Cárdenas-Serna M, Jeffery N. Human semicircular canal form: Ontogenetic changes and variation of shape and size. J Anat 2022; 240:541-555. [PMID: 34674260 PMCID: PMC8819049 DOI: 10.1111/joa.13576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 10/04/2021] [Accepted: 10/08/2021] [Indexed: 11/29/2022] Open
Abstract
The semicircular canals (SCCs) transduce angular acceleration of the head into neuronal signals, and their morphology has been used to infer function. Once formed, the bony labyrinth, that surrounds the canals, is tightly regulated and has a very low bone turnover. However, relaxed postnatal inhibition of bone remodelling later in ontogeny may allow for some organised adjustments of shape and size or for greater stochastic variation. In the present study, we test the hypotheses that after birth, the shape and size of the bony canal changes or becomes more variable, or both. We study microCT scans of human perinatal and adult temporal bones using a combination of geometric morphometric analysis and cross-sectional measures. Results revealed marginal differences of size (<5%), of cross-sectional shape and of measurement variability. Geometry of the three canals together and their cross-sectional areas were, however, indistinguishable between perinates and adults. These mixed findings are indicative of diminutive levels of relaxed inhibition superimposed over a constrained template of SCC morphology.
Collapse
Affiliation(s)
- Marcela Cárdenas-Serna
- Department of Musculoskeletal Biology, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | - Nathan Jeffery
- Department of Musculoskeletal Biology, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| |
Collapse
|
3
|
Ward DL, Schroeder L, Tinius A, Niccoli S, Voth R, Lees SJ, Silcox M, Viola B, Sanzo P. Ovariectomized Rat Model and Shape Variation in the Bony Labyrinth. Anat Rec (Hoboken) 2022; 305:3283-3296. [PMID: 35103405 DOI: 10.1002/ar.24878] [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: 08/11/2021] [Revised: 11/23/2021] [Accepted: 11/26/2021] [Indexed: 11/10/2022]
Abstract
Postmenopausal osteoporosis is a serious concern in aging individuals, but has not been explored for its potential to alter the shape of the inner ear by way of increased remodelling in the otic capsule. The otic capsule, or bony labyrinth, is thought to experience uniquely limited remodelling after development due to high levels of osteoprotegerin. On this basis, despite the widespread remodelling that accompanies osteoporosis, we hypothesize that both the shape and volume of the semicircular canals will resist such changes. To test this hypothesis, we conducted three-dimensional geometric morphometric shape analysis on microcomputed tomographic data collected on the semicircular canals of an ovariectomized (OVX) rat model. A Procrustes ANOVA found no statistically significant differences in shape between surgery and sham groups, and morphological disparity testing likewise found no differences in shape variation. Univariate testing found no differences in semicircular volume between OVX and control groups. The range of variation in the OVX group, however, is greater than in the sham group but this difference does not reach statistical significance, perhaps because of a combination of small effect size and low sample size. This finding suggests that labyrinthine shape remains a tool for assessing phylogeny and function in the fossil record, but that it is possible that osteoporosis may be contributing to intraspecific shape variation in the bony labyrinth. This effect warrants further exploration at a microstructural level with continued focus on variables related to remodelling. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Devin L Ward
- University of Toronto, Department of Anthropology, Toronto, Ontario
| | - Lauren Schroeder
- University of Toronto Mississauga, Department of Anthropology, Mississauga, Ontario
| | - Alexander Tinius
- University of Toronto, Department of Ecology & Evolutionary Biology, Toronto, Ontario
| | - Sarah Niccoli
- Northern Ontario School of Medicine, Thunder Bay, Ontario
| | - Riley Voth
- Northern Ontario School of Medicine, Thunder Bay, Ontario
| | - Simon J Lees
- Northern Ontario School of Medicine, Thunder Bay, Ontario
| | - Mary Silcox
- University of Toronto Scarborough, Department of Anthropology, Scarborough, Ontario
| | - Bence Viola
- University of Toronto, Department of Anthropology, Toronto, Ontario
| | - Paolo Sanzo
- Lakehead University, Northern Ontario School of Medicine and School of Kinesiology, Thunder Bay, Ontario
| |
Collapse
|
4
|
Lower Levels of Vestibular Developmental Stability in Slow-Moving than Fast-Moving Primates. Symmetry (Basel) 2021. [DOI: 10.3390/sym13122305] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The vestibular system of the mammalian inner ear senses angular and linear velocity of the head and enables animals to maintain their balance. Vestibular anatomy has been studied extensively in order to link its structure to particular kinds of locomotion. Available evidence indicates that, in primates, slow-moving species show higher levels of vestibular variation than fast-moving taxa. We analysed intraspecific morphological variation and fluctuating asymmetry (FA) levels in the semicircular canal systems of six species of lorisiform primates: three slow-moving lorisids and three fast-moving galagids. Our results showed clear differences in levels of intraspecific variation between slow-moving and fast-moving taxa. Higher levels of variation were responsible for deviations from coplanarity for synergistic pairs of canals in slower taxa. Lorisids also presented higher levels of FA than galagids. FA is a better indicator of agility than intraspecific variation. These results suggest that in order to function efficiently in fast taxa, semicircular canal systems must develop as symmetrically as possible, and should minimise the deviation from coplanarity for synergistic pairs. Higher levels of variation and asymmetry in slow-moving taxa may be related to lower levels of stabilising selection on the vestibular system, linked to a lower demand for rapid postural changes.
Collapse
|
5
|
Braga J, Samir C, Fradi A, Feunteun Y, Jakata K, Zimmer VA, Zipfel B, Thackeray JF, Macé M, Wood BA, Grine FE. Cochlear shape distinguishes southern African early hominin taxa with unique auditory ecologies. Sci Rep 2021; 11:17018. [PMID: 34426640 PMCID: PMC8382707 DOI: 10.1038/s41598-021-96543-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 08/11/2021] [Indexed: 02/07/2023] Open
Abstract
Insights into potential differences among the bony labyrinths of Plio-Pleistocene hominins may inform their evolutionary histories and sensory ecologies. We use four recently-discovered bony labyrinths from the site of Kromdraai to significantly expand the sample for Paranthropus robustus. Diffeomorphometry, which provides detailed information about cochlear shape, reveals size-independent differences in cochlear shape between P. robustus and Australopithecus africanus that exceed those among modern humans and the African apes. The cochlea of P. robustus is distinctive and relatively invariant, whereas cochlear shape in A. africanus is more variable, resembles that of early Homo, and shows a degree of morphological polymorphism comparable to that evinced by modern species. The curvature of the P. robustus cochlea is uniquely derived and is consistent with enhanced sensitivity to low-frequency sounds. Combined with evidence for selection, our findings suggest that sound perception shaped distinct ecological adaptations among southern African early hominins.
Collapse
Affiliation(s)
- J. Braga
- grid.15781.3a0000 0001 0723 035XCentre d’Anthropobiologie et de Génomique de Toulouse, Université Paul Sabatier Toulouse III, Faculté de Médecine Purpan, 37 allées Jules Guesde, Toulouse, France ,grid.11951.3d0000 0004 1937 1135Evolutionary Studies Institute, University of the Witwatersrand, PO WITS, Johannesburg, 2050 South Africa
| | - C. Samir
- grid.503317.30000 0000 9971 4898LIMOS, UMR 6158 CNRS-Université Clermont Auvergne, 63173 Aubière, France
| | - A. Fradi
- grid.503317.30000 0000 9971 4898LIMOS, UMR 6158 CNRS-Université Clermont Auvergne, 63173 Aubière, France
| | - Y. Feunteun
- grid.503317.30000 0000 9971 4898LIMOS, UMR 6158 CNRS-Université Clermont Auvergne, 63173 Aubière, France
| | - K. Jakata
- grid.11951.3d0000 0004 1937 1135Evolutionary Studies Institute, University of the Witwatersrand, PO WITS, Johannesburg, 2050 South Africa
| | - V. A. Zimmer
- grid.6936.a0000000123222966Faculty of Informatics, Technical University of Munich, Munich, Germany
| | - B. Zipfel
- grid.11951.3d0000 0004 1937 1135Evolutionary Studies Institute, University of the Witwatersrand, PO WITS, Johannesburg, 2050 South Africa
| | - J. F. Thackeray
- grid.11951.3d0000 0004 1937 1135Evolutionary Studies Institute, University of the Witwatersrand, PO WITS, Johannesburg, 2050 South Africa
| | - M. Macé
- Véto 31, 73 Avenue du Général de Gaulle, 47000 Agen, France
| | - B. A. Wood
- grid.253615.60000 0004 1936 9510Center for the Advanced Study of Human Paleobiology, George Washington University, Washington, DC 20052 USA
| | - F. E. Grine
- grid.36425.360000 0001 2216 9681Department of Anthropology, Stony Brook University, Stony Brook, NY 11794 USA ,grid.36425.360000 0001 2216 9681Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794 USA
| |
Collapse
|