Side Differences in the Skull of Sheep: An Assessment by Geometric Morphometrics

Effects of perturbations during development can be due to environmental and/or genetic factors, resulting in increased developmental instability which in turn can be expressed as fluctuating asymmetry (FA), defined as the non-directional deviation (right-left differences) from bilateral symmetry. However, other asymmetry types can appear, such as and directional asymmetry (DA), characterized by a distribution skewed to one side (right or left) at the, which is originated as a response to external stimuli that affect differentially on both sides of the organism. In order to describe asymmetric patterns in the ovine skull, we studied 165 specimens from animals belonging to the sheep breed “Navarra” from North Spain, using geometric morphometric methods. On digital pictures, we analyzed two midline and 8 bilateral two-dimensional landmarks on skull dorsal aspect. Results showed that FA accounted for a reduced amount of total variation, while DA explained most of it. We suggest that the presence of side differences due to lateralized muscular function (mastication) is the most important factor in skull asymmetry. Obtained results should provide a basis for relating asymmetries to the mechanics of cranial skeletum in sheep.

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No Directional Scapular Asymmetry among Tamarines of the Genus Saguinus (Primates: Callitrichidae)

Annual Research & Review in Biology ◽

10.9734/arrb/2020/v35i1030284 ◽

2020 ◽

pp. 7-13

Author(s):

P. M. Parés- Casanova ◽

J. F. Vélez- García

Keyword(s):

Fluctuating Asymmetry ◽

Lateral Surface ◽

The Other ◽

Directional Asymmetry ◽

Geometric Morphometric ◽

Terrestrial Locomotion ◽

Developmental Variation ◽

Morphometric Methods ◽

Perfect Symmetry ◽

Left Scapula

Bilateral asymmetry is defined as a deviation of a whole organism or a part of it from a perfect symmetry, and different categories can be recognized. One is the fluctuating asymmetry, defined as the random developmental variation of a trait (or character) that is expected to be perfectly symmetrical on average, and the other one is directional asymmetry, which occurs when one of the sides shows stronger morphological structures or marks than the other. The aim of this study was to determine the kind of scapula asymmetry in Saguinus scapulae. On lateral surface of each right and left scapula, a set of 5 landmarks and 3 curves with semi-landmarks along the margins, on a sample of 16 pairs from different Saguinus species, were considered. Asymmetries (fluctuating and directional) on size and shape of the scapulae were analysed by means of geometric morphometric methods. Directional asymmetry was not detected, demonstrating no side scapular shape bias. The absence of significant directional asymmetry may indicate a similar contralateral pattern of employment of the shoulder, at least for one-arm vertical suspension, as it needs stronger forces than those for terrestrial locomotion and thus would cause more asymmetry in case side loadings were different. To our knowledge, this is the first investigation on the symmetrical/asymmetrical nature of scapulae in Saguinus. Our findings increase knowledge and understanding of humeral joint and arboreal locomotion in primates.

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Functional skull asymmetries in Carollia perspicillata (Phyllostomidae Gray, 1825: Carollinae)

Acta Biologica Szegediensis ◽

10.14232/abs.2020.1.37-42 ◽

2020 ◽

Vol 64 (1) ◽

pp. 37-42

Author(s):

Pere M. Parés-Casanova ◽

Gerard Otin

Keyword(s):

Fluctuating Asymmetry ◽

Directional Asymmetry ◽

Functional Requirements ◽

Carollia Perspicillata ◽

Geometric Morphometric ◽

Domestic Species ◽

Cranial Asymmetry ◽

Dorsal Aspect ◽

Morphological Responses

Analysing asymmetry in wild or domestic species enables the evaluation of the morphological responses to functional requirements and/or stress. This report is a study of the cranial asymmetry of Seba's short-tailed bat Carollia perspicillata by means of geometric morphometric techniques. We studied three types of bilateral asymmetries -ﬂuctuating asymmetry, directional asymmetry and antisymmetry- using 15 skull landmarks on dorsal aspect of 45 skulls of Carollia perspicillata (21 males and 24 females) from different localities in Colombia. Directional asymmetry appeared to be significant and clearly higher than ﬂuctuating asymmetry, with the braincase presenting the larger variance. There were no differences between sexes. Echolocation has a great anatomical effect on the bat cranium, and this would explain detected asymmetry.

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Marked Directional Skull Asymmetry in the Araucan Horse

VCOT Open ◽

10.1055/s-0040-1702986 ◽

2020 ◽

Vol 03 (01) ◽

pp. e11-e18 ◽

Cited By ~ 1

Author(s):

Pere M. Parés-Casanova ◽

René Alejandro Crosby-Granados ◽

Fabián Muñoz ◽

Arcesio Salamanca-Carreño

Keyword(s):

Individual Development ◽

Directional Asymmetry ◽

Geometric Morphometric ◽

Rightward Shift ◽

Developmental Variation ◽

Multiple Factors ◽

Dorsal Aspect ◽

Morphometric Methods ◽

Perfect Symmetry ◽

Masticatory Biomechanics

Abstract Background Deviations from the perfect symmetry of normally bilateral symmetrical characters occur during individual development due to the influence of multiple factors. Fluctuating asymmetry (FA) is the random developmental variation of a trait (or character) that is perfectly symmetrical, on average, across a population. Directional asymmetry (DA) occurs when one side of the pair of body sides is strongly more marked. Objective We investigated the presence and level of skull FA and DA in the Araucan horse, a breed from East Colombia. Study Design A sample of 21 skulls belonging to adult animals was studied by means of standard geometric–morphometric methods using 16 landmarks on the dorsal aspect of the crania. Results Measurements showed a significant DA with a consistent rightward shift of the splanchnocrania. Conclusions The results of this study raise questions about the influence of masticatory biomechanics on the asymmetric development of the skull, and also about how management and ingesta-specific properties (such as abrasiveness) may influence this asymmetry.

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Beyond bilateral symmetry: geometric morphometric methods for any type of symmetry

BMC Evolutionary Biology ◽

10.1186/1471-2148-11-280 ◽

2011 ◽

Vol 11 (1) ◽

pp. 280 ◽

Cited By ~ 69

Author(s):

Yoland Savriama ◽

Christian Klingenberg

Keyword(s):

Bilateral Symmetry ◽

Geometric Morphometric ◽

Morphometric Methods

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Morphometric Analyses of (Hidden) Directional Asymmetry in Leaf Blades

Emerging Science Journal ◽

10.28991/esj-2018-01141 ◽

2018 ◽

Vol 2 (4) ◽

Author(s):

Sergey Gennadevich Baranov

Keyword(s):

Fluctuating Asymmetry ◽

Leaf Blade ◽

Permutation Test ◽

Principal Component ◽

Bilateral Symmetry ◽

Procrustes Analysis ◽

Directional Asymmetry ◽

Asymmetry Factor ◽

Shape Deviation ◽

Data Set

The deviation from perfect bilateral symmetry is a phenomenon actively exploring in evolutionary and environmental studies. The bilateral variation presents on different ecosystem level. The methods applied vary depending on the task and the final goal of study. The present study demonstrates the statistically significant presence of components (traces) of directional asymmetry (DA), fluctuating asymmetry (FA) and antisymmetry (AS) in leaf blade of Betula pendula on low level of ecosystem such as tree and leaf blade. The Generalized Procrustes Analysis was applied for testing asymmetry of shape in all data set and subgroups. The category ‘population’ revealed no significant value of DA (factor ‘side’). In the levels ‘tree’ and ‘leaf blade’ the factor ‘side’ was statistically significant as well as fluctuating asymmetry (factor interaction ‘leaf × side’).The principal component analysis showed visually the difference in PC scores between antisymmetry matrices of the left and right halves of the leaf blade. Covariate analysis matrices demonstrated the shape deviation from strict symmetry. The metric traits showed directional asymmetry in t-test in the leaf blade and the low kurtosis values. Permutation test of kurtosis values in geometric morphometric approach showed deviation from normality that could verified as a weak presence AS traces. The discriminant analysis results showed that traces of DA differed at the subpopulation level, as three of 10 populations revealed not significant factor ‘side’. Descriptive statistics of the metric train showed a correspondence to the trace of directional asymmetry in the shape of leaf blade. Fluctuating asymmetry in its pure form, at three levels of ecosystem was met only in single population of ten that should be taken into account testing developmental stability of birch and possibly other woody plants.

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Male sterility significantly elevates shape variation and fluctuating asymmetry of zygomorphic corolla in gynodioecious Glechoma hederacea L. (Lamiaceae)

AoB Plants ◽

10.1093/aobpla/plab013 ◽

2021 ◽

Author(s):

Jiri Neustupa ◽

Katerina Woodard

Keyword(s):

Fluctuating Asymmetry ◽

Bilateral Symmetry ◽

Size Difference ◽

Shape Variation ◽

Male Sterile ◽

Geometric Morphometric ◽

Morphometric Analyses ◽

Developmental Consequence ◽

Selection For ◽

Glechoma Hederacea

Abstract Female flowers of gynodioecious plants usually have smaller corollas than bisexual flowers. This difference is explained as a developmental consequence of stamen abortion and as a result of stronger selection for larger corolla size in hermaphroditic flowers that solely ensure male function within populations. This study evaluated whether the size difference of zygomorphic corollas in a widely distributed gynodioecious herb Glechoma hederacea L. is accompanied by variation in shape and bilateral fluctuating asymmetry of sexually differentiated flowers. Geometric morphometric analyses of bilateral symmetry in the shapes of corolla lower lips showed that male-sterile flowers were significantly more plastic and asymmetric, implying that they may be subjected to weaker stabilising selection for corolla shape in comparison to hermaphrodites. These results illustrated that sexual differentiation may be an important factor contributing to bilateral fluctuating asymmetry in the shape of zygomorphic flowers.

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Comparative Study of the Cranio-osteology of Two Lonchophyllinae from Colombia

Annual Research & Review in Biology ◽

10.9734/arrb/2020/v35i1030283 ◽

2020 ◽

pp. 1-6

Author(s):

P. M. Parés- Casanova

Keyword(s):

Comparative Study ◽

Morphological Analysis ◽

Dietary Analysis ◽

Geometric Morphometric ◽

Skull Length ◽

Zygomatic Process ◽

Dorsal Aspect ◽

Morphometric Methods ◽

Diet Preferences

Lonchophyllinae comprises four genera of Neotropical nectarivorous bats. Inside this subfamily the genus Lonchophylla is one of the most diverse. A total of 51 Lonchophylla skulls from Colombia (L. robusta n=34 and L. thomasi n=17) was studied by means of geometric morphometric methods with the aim to determine their morphological differential characteristics. For this purpose, viscero and neurocranium were evaluated with 12 landmarks on the dorsal aspect of left hemicranium. The two species were statistically different according to size (expressed as skull length) but also to shape (expressed as the set of Procrustes coordinates). Skulls in L. robusta were clearly bigger, with shorter braincase and longer rostra, and their zygomatic process was more latero-caudally displaced, whereas L. thomasi presented a zygomatic process which was displaced more rostrally as well longer braincases. All these detected skull form dissimilarities between both species would be explained by their different alimentary habits, but a combination of dietary analysis and morphological analysis is needed to make stronger inference about diet preferences.

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Carapace asymmetries in crabs

Crustaceana ◽

10.1163/15685403-00003835 ◽

2018 ◽

Vol 91 (11) ◽

pp. 1281-1290

Author(s):

Federica Spani ◽

Massimiliano Scalici

Keyword(s):

Fluctuating Asymmetry ◽

Statistical Analyses ◽

Directional Asymmetry ◽

Environmental Constraints ◽

Soil Composition ◽

Geometric Morphometric ◽

The Right ◽

Predatory Pressure

Abstract Through the geometric morphometric approach of the landmark-based method applied on adult right-handed specimens of Carcinus aestuarii, Liocarcinus depurator and Potamon fluviatile, statistical analyses showed significant outcomes for fluctuating asymmetry in the three studied species, and directional asymmetry only in P. fluviatile (that showed a less convex carapace shape on the right side, where larger chela occurred). Although these findings may be correlated to some environmental constraints, such as soil composition, refuge occurrence and predatory pressure, also other interpretations may be proposed.

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