We present a survey of the morphological diversity of the bony labyrinth of the inner ear in Xenarthra, including the fossil ground sloth Megatherium. Using a combination of traditional and geometric ...morphometrics, correlation analyses, and qualitative observations, we attempt to extract independent and informative phylogenetic characters of the bony labyrinth for the superorder. Geometric morphometric analyses demonstrate a strong imprint of phylogenetic history on the shape of the bony labyrinth of xenarthrans and a weak influence of allometry. Discrete characters mapped on a consensus cladogram for xenarthrans show support for many traditional nodes within the superorder and may also provide critical information for problematic nodes within Cingulata. A relatively large lateral semicircular canal may, for instance, represent a synapomorphy for the molecular clade allying fairy armadillos (Chlamyphorinae) to the Tolypeutinae. Striking convergences were detected when comparing Megatherium, the giant ground sloth, with extant armadillos and Chlamyphorus, the pink fairy armadillo, with the extant three- and two-toed sloths. These findings have the potential to help understand the phylogenetic relationships of fossil xenarthrans.
The bony labyrinth provides a proxy for the morphology of the inner ear, a primary cognitive organ involved in hearing, body perception in space, and balance in vertebrates. Bony labyrinth shape ...variations often are attributed to phylogenetic and ecological factors. Here we use three‐dimensional (3D) geometric morphometrics to examine the phylogenetic and ecological patterns of variation in the bony labyrinth morphology of the most species‐rich and ecologically diversified traditionally recognized superfamily of Carnivora, the Musteloidea (e.g. weasels, otters, badgers, red panda, skunks, raccoons, coatis). We scanned the basicrania of specimens belonging to 31 species using high‐resolution X‐ray computed micro‐tomography (μCT) to virtually reconstruct 3D models of the bony labyrinths. Labyrinth morphology is captured by a set of six fixed landmarks on the vestibular and cochlear systems, and 120 sliding semilandmarks, slid at the center of the semicircular canals and the cochlea. We found that the morphology of this sensory structure is not significantly influenced by bony labyrinth size, in comparisons across all musteloids or in any of the individual traditionally recognized families (Mephitidae, Procyonidae, Mustelidae). PCA (principal components analysis) of shape data revealed that bony labyrinth morphology is clearly distinguishable between musteloid families, and permutation tests of the Kmult statistic confirmed that the bony labyrinth shows a phylogenetic signal in musteloids and in most mustelids. Both the vestibular and cochlear regions display morphological differences among the musteloids sampled, associated with the size and curvature of the semicircular canals, angles between canals, presence or absence of a secondary common crus, degree of lateral compression of the vestibule, orientation of the cochlea relative to the semicircular canals, proportions of the cochlea, and degree of curvature of its turns. We detected a significant ecological signal in the bony labyrinth shape of musteloids, differentiating semi‐aquatic taxa from non‐aquatic ones (the taxa assigned to terrestrial, arboreal, semi‐arboreal, and semi‐fossorial categories), and a significant signal for mustelids, differentiating the bony labyrinths of terrestrial, semi‐arboreal, arboreal, semi‐fossorial and semi‐aquatic species from each other. Otters and minks are distinguished from non‐aquatic musteloids by an oval rather than circular anterior canal, sinuous rather than straight lateral canal, and acute rather than straight angle between the posterior and lateral semicircular canals – each of these morphological characters has been related previously to animal sensitivity for detecting head motion in space.
Domestication has led to many changes in domestic animal biology, including their anatomy. The shape of the inner ear, part of the mammalian ear, has been found particularly relevant for ...discriminating domesticated species, their hybrids or differentiating the wild and domestic populations of a single species. Here we assessed the use of the size and shape of the semicircular canals (SCC) of the inner ear as a marker of pig domestication. We studied a total of 63 petrosal bones belonging to wild boar (Sus scrofa, two populations) and domestic pigs (extensively and intensively reared specimens) that were µCT‐scanned and from which the size and the shape of the inner ear were quantified through geometric morphometrics, analyzing the 3D coordinates of 6 landmarks and 60 sliding semilandmarks localized on the SCC and the common crus. The domestic pigs have larger SCC than the wild boar from which they also strongly differ in shape (correct cross validation of 95.5%, confidence interval: 92.3%–98.1%). Strong shape differences were detected between the two populations of wild boar, as well as a sexual size dimorphism. All together the results highlight the taxonomic discriminant power of the SCC of the inner ear shape, and its relevance for domestication studies.
Wild boar and domestic pigs strongly differ in their semicircular canals shape as highlithed by the two first axes of a Principal Component Analysis.
RESEARCH HIGHLIGHTS
The semicircular canals (SCC) shape allow to discriminate wild boar and domestic pig with a correct cross validation of 95.5%
Domestic pigs have larger SCC than the wild boar • Wild boar populations differ in their SCC shape not size.
The shape of the semicircular canal of the inner ear can be used as a marker of domestication
The vestibular system of the inner ear detects the motions of the head and is involved in maintaining balance. For this reason, this organ has been deeply studied and several scientists have tried to ...link its morphology with the locomotor behavior of an animal. Via high-resolution computed microtomography and geometric morphometric methods, we analyzed the intraspecific variation of the 3D morphology of the bony labyrinth (inner ear) in four species of primates differing in their locomotor adaptations: two being slow-moving taxa (
Nycticebus
and
Perodicticus
), and two being fast-moving taxa (
Callithrix
and
Microcebus
). Basically, there are very few analyses of the inter-individual variation of this organ in mammals in general, and this approach has never been attempted in primates thus far. Our results show that variation of the bony labyrinth morphology is expressed by the same ways in the different species (e.g., differences in the size, shape, and orientation of the semicircular canals, and in the width and height of the cochlea), but that slow-moving taxa exhibit a higher amount of intraspecific variation than do fast-moving taxa. Our results strengthen support for a previously published hypothesis, according to which a relaxation of the selective pressure applied to the morphology of the bony labyrinth is the likely reason for this higher amount of intraspecific variation in slow-moving taxa, and that it may be related to a reduced functional demand for rapid postural adjustments.
Endoscopic skull base surgery allows minimal invasive therapy through the nostrils to treat infectious or tumorous diseases. Surgical and anatomical education in this field is limited by the lack of ...validated training models in terms of geometric and mechanical accuracy. We choose to evaluate several consumer-grade materials to create a patient-specific 3D-printed skull base model for anatomical learning and surgical training.
Four 3D-printed consumer-grade materials were compared to human cadaver bone: calcium sulfate hemihydrate (named Multicolor), polyamide, resin and polycarbonate. We compared the geometric accuracy, forces required to break thin walls of materials and forces required during drilling.
All materials had an acceptable global geometric accuracy (from 0.083mm to 0.203mm of global error). Local accuracy was better in polycarbonate (0.09mm) and polyamide (0.15mm) than in Multicolor (0.90mm) and resin (0.86mm). Resin and polyamide thin walls were not broken at 200N. Forces needed to break Multicolor thin walls were 1.6-3.5 times higher than in bone. For polycarbonate, forces applied were 1.6-2.5 times higher. Polycarbonate had a mode of fracture similar to the cadaver bone. Forces applied on materials during drilling followed a normal distribution except for the polyamide which was melted. Energy spent during drilling was respectively 1.6 and 2.6 times higher on bone than on PC and Multicolor.
Polycarbonate is a good substitute of human cadaver bone for skull base surgery simulation. Thanks to short lead times and reasonable production costs, patient-specific 3D printed models can be used in clinical practice for pre-operative training, improving patient safety.
Diaphyseal morphology of long bones, in part, reflects in vivo loads experienced during the lifetime of an individual. The first metatarsal, as a cornerstone structure of the foot, presumably ...expresses diaphyseal morphology that reflects loading history of the foot during stance phase of gait. Human feet differ substantially from those of other apes in terms of loading histories when comparing the path of the center of pressure during stance phase, which reflects different weight transfer mechanisms. Here we use a novel approach for quantifying continuous thickness and cross-sectional geometric properties of long bones in order to test explicit hypotheses about loading histories and diaphyseal structure of adult chimpanzee, gorilla, and human first metatarsals. For each hallucal metatarsal, 17 cross sections were extracted at regularly-spaced intervals (2.5% length) between 25% and 65% length. Cortical thickness in cross sections was measured in one degree radially-arranged increments, while second moments of area were measured about neutral axes also in one degree radially-arranged increments. Standardized thicknesses and second moments of area were visualized using false color maps, while penalized discriminant analyses were used to evaluate quantitative species differences. Humans systematically exhibit the thinnest diaphyseal cortices, yet the greatest diaphyseal rigidities, particularly in dorsoplantar regions. Shifts in orientation of maximum second moments of area along the diaphysis also distinguish human hallucal metatarsals from those of chimpanzees and gorillas. Diaphyseal structure reflects different loading regimes, often in predictable ways, with human versus non-human differences probably resulting both from the use of arboreal substrates by non-human apes and by differing spatial relationships between hallux position and orientation of the substrate reaction resultant during stance. The novel morphological approach employed in this study offers the potential for transformative insights into form-function relationships in additional long bones, including those of extinct organisms (e.g., fossils).
While exceptional for an intense diversification of lineages, the evolutionary history of the order Rodentia comprises only a limited number of morphological morphotypes for the mandible. This ...situation could partly explain the intense debates about the taxonomic position of the latest described member of this clade, the Laotian rock rat Laonastes aenigmamus (Diatomyidae). This discovery has re-launched the debate on the definition of the Hystricognathi suborder identified using the angle of the jaw relative to the plane of the incisors. Our study aims to end this ambiguity. For clarity, it became necessary to revisit the entire morphological diversity of the mandible in extant and extinct rodents. However, current and past rodent diversity brings out the limitations of the qualitative descriptive approach and highlights the need for a quantitative approach. Here, we present the first descriptive comparison of the masticatory apparatus within the Ctenohystrica clade, in combining classic comparative anatomy with morphometrical methods. First, we quantified the shape of the mandible in rodents using 3D landmarks. Then, the analysis of osteological features was compared to myological features in order to understand the biomechanical origin of this morphological diversity. Among the morphological variation observed, the mandible of Laonastes aenigmamus displays an intermediate association of features that could be considered neither as sciurognathous nor as hystricognathous.
Analysing large numbers of brain samples can reveal minor, but statistically and biologically relevant variations in brain morphology that provide critical insights into animal behaviour, ecology and ...evolution. So far, however, such analyses have required extensive manual effort, which considerably limits the scope for comparative research. Here we used micro-CT imaging and deep learning to perform automated analyses of 3D image data from 187 honey bee and bumblebee brains. We revealed strong inter-individual variations in total brain size that are consistent across colonies and species, and may underpin behavioural variability central to complex social organisations. In addition, the bumblebee dataset showed a significant level of lateralization in optic and antennal lobes, providing a potential explanation for reported variations in visual and olfactory learning. Our fast, robust and user-friendly approach holds considerable promises for carrying out large-scale quantitative neuroanatomical comparisons across a wider range of animals. Ultimately, this will help address fundamental unresolved questions related to the evolution of animal brains and cognition.
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.
PDF
