Canalization and developmental stability of the yellow-necked mouse (Apodemus flavicollis) mandible and cranium related to age and nematode parasitism

Background Mammalian mandible and cranium are well-established model systems for studying canalization and developmental stability (DS) as two elements of developmental homeostasis. Nematode infections are usually acquired in early life and increase in intensity with age, while canalization and DS of rodent skulls could vary through late postnatal ontogeny. We aimed to estimate magnitudes and describe patterns of mandibular and cranial canalization and DS related to age and parasite intensity (diversity) in adult yellow-necked mice (Apodemus flavicollis). Results We found the absence of age-related changes in the levels of canalization for mandibular and cranial size and DS for mandibular size. However, individual measures of mandibular and cranial shape variance increased, while individual measures of mandibular shape fluctuating asymmetry (FA) decreased with age. We detected mandibular and cranial shape changes during postnatal ontogeny, but revealed no age-related dynamics of their covariance structure among and within individuals. Categories regarding parasitism differed in the level of canalization for cranial size and the level of DS for cranial shape. We observed differences in age-related dynamics of the level of canalization between non-parasitized and parasitized animals, as well as between yellow-necked mice parasitized by different number of nematode species. Likewise, individual measures of mandibular and cranial shape FA decreased with age for the mandible in the less parasitized category and increased for the cranium in the most parasitized category. Conclusions Our age-related results partly agree with previous findings. However, no rodent study so far has explored age-related changes in the magnitude of FA for mandibular size or mandibular and cranial FA covariance structure. This is the first study dealing with the nematode parasitism-related canalization and DS in rodents. We showed that nematode parasitism does not affect mandibular and cranial shape variation and covariance structure among and within individuals. However, parasite intensity (diversity) is related to ontogenetic dynamics of the levels of canalization and DS. Overall, additional studies on animals from natural populations are required before drawing some general conclusions.

Under pressure: the relationship between cranial shape and burrowing force in caecilians (Gymnophiona)

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 µCT-data, we performed three-dimensional 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 to other species. Despite substantial differences in head morphology across species, no relation 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.

The limits of convergence: the roles of phylogeny and dietary ecology in shaping non-avian amniote crania

Cranial morphology is remarkably varied in living amniotes and the diversity of shapes is thought to correspond with feeding ecology, a relationship repeatedly demonstrated at smaller phylogenetic scales, but one that remains untested across amniote phylogeny. Using a combination of morphometric methods, we investigate the links between phylogenetic relationships, diet and skull shape in an expansive dataset of extant toothed amniotes: mammals, lepidosaurs and crocodylians. We find that both phylogeny and dietary ecology have statistically significant effects on cranial shape. The three major clades largely partition morphospace with limited overlap. Dietary generalists often occupy clade-specific central regions of morphospace. Some parallel changes in cranial shape occur in clades with distinct evolutionary histories but similar diets. However, members of a given clade often present distinct cranial shape solutions for a given diet, and the vast majority of species retain the unique aspects of their ancestral skull plan, underscoring the limits of morphological convergence due to ecology in amniotes. These data demonstrate that certain cranial shapes may provide functional advantages suited to particular dietary ecologies, but accounting for both phylogenetic history and ecology can provide a more nuanced approach to inferring the ecology and functional morphology of cryptic or extinct amniotes.

Correlation Between Corpus Callosum Shape and Craniometric Measurements According to Mri Data

The correlation between the cranial height and the height of the corpus callosum trunk bulge, and the relationship between the corpus callosum shape and the cranial shape have not been studied. The purpose of the article was to determine the individual variability of the corpus callosum height and shape of adults, and their dependence on the cranial height and shape. The material was two samples from a series of MR scans of the head of men and women of the second period of adulthood (19 variations in each group) without the central nervous system pathology. Magnetic resonance tomographic scanner Magnetom C was used for obtaining MRI images. Morphometric study was conducted using RadiAnt Dicom Viewer software on MR scans performed in the sagittal area in T1- and T2-weighted images modes. According to the findings, the height of the corpus callosum trunk bulge of men is on average – 26.1 ± 2.8 mm, women – 25.2 ± 2.6 mm, and the neurocranium height – 150.4 ± 6.9 mm and 140.2 ± 4.2 mm, respectively. Wherein the aspect ratio of the neurocranium height to the corpus callosum trunk bulge height in men is 5.8 ± 0.7, in women – 5.6 ± 0.5. The aspect ratio of the corpus callosum longitudinal size along the constricting chord to its trunk bulge height in men is on average 2.8 ± 0.3, in women – 2.7 ± 0.3. The absence of correlation between the cranial height and the corpus callosum trunk bulge height, and the absence of correlation between the corpus callosum shape and cranial shape in people of the second period of adulthood have been concluded.

Intracranial Volume Not Correlated With Severity in Trigonocephaly

Objectives: Severity of trigonocephaly varies and potentially affects intracranial volume (ICV) and intracranial pressure (ICP). The aim of this study is to measure ICV in trigonocephaly patients and compare it to normative data and correlate ICV with the severity of the skull deformity according to UCSQ (Utrecht Cranial Shape Quantifier). Design: Retrospective study. Setting: Primary craniofacial center. Patients, Participants: Nineteen preoperative patients with nonsyndromic trigonocephaly (age ≤12 months). Intervention: Intracranial volume was measured on preoperative computed tomography (CT) scans by manual segmentation (OsiriX Fondation). Utrecht Cranial Shape Quantifier was used to quantify the severity of the skull deformity. When present, papilledema as sign of elevated ICP was noted. Main Outcome Measures(s): Measured ICV was compared to Lichtenberg normative cranial volume growth curves, and Pearson correlation coefficient was used to correlate UCSQ with the ICV. Results: Mean age at CT scan was 6 months (2-11). Mean measured ICV was 842 mL (579-1124). Thirteen of h19 patients (11/15 boys and 2/4 girls) had an ICV between ±2 SD curves of Lichtenberg, 2 of 19 (1/15 boys and 1/4 girls) had an ICV less than −2 SD and 4 of 19 (3/15 boys and 1/4 girls) had an ICV greater than +2 SD. Mean UCSQ severity of trigonocephaly was 2.40 (−622.65 to 1279.75). Correlation between severity and ICV was negligible (r = −0.11). No papilledema was reported. Conclusions: Measured ICV was within normal ranges for trigonocephaly patients, in both mild and severe cases. No correlation was found between severity of trigonocephaly and ICV.

Ecomorphometric analysis of diversity in cranial shape of pygopodid geckos

Pygopodids are elongate, functionally limbless geckos found throughout Australia. The clade presents low taxonomic diversity (∼45 spp.), but a variety of cranial morphologies, habitat use, and locomotor abilities that vary between and within genera. In order to assess potential relationships between cranial morphology and ecology, CT scans of 29 species were used for 3D geometric morphometric analysis. A combination of 24 static landmarks and 20 sliding semi-landmarks were subjected to Generalized Procrustes Alignment. Disparity in cranial shape was visualized through Principal Components Analysis, and a MANOVA was used to test for an association between shape, habitat, and diet. A subset of 27 species with well-resolved phylogenetic relationships was used to generate a phylomorphospace and conduct phylogeny-corrected MANOVA. Similar analyses were done solely on Aprasia taxa to explore species-level variation. Most of the variation across pygopodids was described by PC1 (54%: cranial roof width, parabasisphenoid and occipital length), PC2 (12%: snout elongation and braincase width), and PC3 (6%: elongation and shape of the palate and rostrum). Without phylogenetic correction, both habitat and diet were significant influencers of variation in cranial morphology. However, in the phylogeny-corrected MANOVA, habitat remained weakly significant, but not diet, which can be explained by generic-level differences in ecology rather than among species. Our results demonstrate that at higher levels, phylogeny has a strong effect on morphology, but that influence may be due to small sample size when comparing genera. However, because some closely related taxa occupy distant regions of morphospace, diverging diets and use of fossorial habitats may contribute to variation seen in these geckos.

Image processing and machine learning for telehealth craniosynostosis screening in newborns

OBJECTIVE The authors sought to evaluate the accuracy of a novel telehealth-compatible diagnostic software system for identifying craniosynostosis within a newborn (< 1 year old) population. Agreement with gold standard craniometric diagnostics was also assessed. METHODS Cranial shape classification software accuracy was compared to that of blinded craniofacial specialists using a data set of open-source (n = 40) and retrospectively collected newborn orthogonal top-down cranial images, with or without additional facial views (n = 339), culled between April 1, 2008, and February 29, 2020. Based on image quality, midface visibility, and visibility of the cranial equator, 351 image sets were deemed acceptable. Accuracy, sensitivity, and specificity were calculated for the software versus specialist classification. Software agreement with optical craniometrics was assessed with intraclass correlation coefficients. RESULTS The cranial shape classification software had an accuracy of 93.3% (95% CI 86.8–98.8; p < 0.001), with a sensitivity of 92.0% and specificity of 94.3%. Intraclass correlation coefficients for measurements of the cephalic index and cranial vault asymmetry index compared to optical measurements were 0.95 (95% CI 0.84–0.98; p < 0.001) and 0.67 (95% CI 0.24–0.88; p = 0.003), respectively. CONCLUSIONS These results support the use of image processing–based neonatal cranial deformity classification software for remote screening of nonsyndromic craniosynostosis in a newborn population and as a substitute for optical scanner– or CT-based craniometrics. This work has implications that suggest the potential for the development of software for a mobile platform that would allow for screening by telemedicine or in a primary care setting.