Cranial Size Research Articles

Developmental toxicity in zebrafish embryos exposed to single, binary, and tertiary mixtures of Cd, Pb, and As

The present study was carried out to investigate developmental toxicity to zebrafish upon exposure singly to cadmium chloride monohydrate (25 µg/L), or lead acetate (40 µg/L), or arsenic trioxide (40 µg/L), and their toxicological interactions upon exposure to combinations of Cd + Pb, Pb + As, Cd + As, and Cd + Pb + As for 120 h post fertilization. Cumulative mortality at 72, 96, and 120 h were significantly higher in all toxicity groups. Cd, Pb, and Pb + As exposure caused 92–100% mortality at 96 h of the exposure. The highest reduction of hatching rate was observed in the Pb + As group followed by the Cd + Pb group. The heart rate was significantly decreased in Cd, As, Cd + Pb, and Cd + Pb + As groups as compared to the control group. Body length, eye size, and cranium size were significantly affected in most of the toxicity groups. The exposure of Cd and Pb increased yolk sac size in the larvae as compared to other treatments. The Pb and Cd exposure group exhibited more tail and spinal deformities. The Cd + Pb exposure group exhibited pericardial and yolk sac edema in the larvae. There may be a possibility of toxicological interaction among Cd, Pb, and As, and may cause developmental defects in fish at the early life stages.

Biometric analysis of the cranial features of common voles

Although cranial bones reliably identify the features of mammals, these traits can be affected by sex, population size and seasonality. This paper biometrically analyses the cranial features of the common vole. The research sample consisted of adult (n = 134), subadult (n = 57), of western Slovakia. Overall, software based on the highlighted marks measured 29 cranial features. Significant sexual dimorphism was observed for three features in adult individuals (width of the maxillary tooth row – right side “WMTRR”, maximum height of the mandibula excluding coronoid process “AMdm” and coronoid height of the mandibula “AMd”) and four features in subadults (length of the tooth row in the maxilla “LOSD”, “WMTRR”, length of the molar “LoM” and alveolar length of the lower molars “ALLM”). Results showed a significant positive relationship between body weight and cranial size in 18 of the 29 features. They also suggested a weak but significant positive effect of common vole abundance on cranium size (Chitty effect) likewise in 6 of the 29 features. In several cases, this effect affects, in addition to the abundance, the onset of sexual maturity of individuals.

Molecular genetics, neuroimaging outcomes, and structural analyses of novel and recurrent variants of WDR62 gene in two consanguineous Pakistani families with autosomal recessive primary microcephaly.

Autosomal recessive primary microcephaly (MCPH) is a rare neurodevelopmental and genetically heterogeneous disorder, characterized by small cranium size (> -3 SD below mean) and often results in varying degree of intellectual disability. Thirty genes have been identified for the etiology of this disorder due to its clinical and genetic heterogeneity. Here, we report two consanguineous Pakistani families affected with MCPH exhibiting mutation in WDR62 gene. The investigation approach involved Next Generation Sequencing (NGS) gene panel sequencing coupled with linkage analysis followed by validation of identified variants through automated Sanger sequencing and Barcode-Tagged (BT) sequencing. The molecular genetic analysis revealed one novel splice site variant (NM_001083961.2(WDR62):c.1372-1del) in Family A and one known exonic variant NM_001083961.2(WDR62):c.3936dup (p.Val1313Argfs*18) in Family B. Magnetic Resonance Imaging (MRI) scans were also employed to gain insights into the structural architecture of affected individuals. Neurological assessments showed the reduced gyral and sulcal patterns along with normal corpus callosum in affected individuals harboring novel variant. In silico assessments of the identified variants were conducted using different tools to confirm the pathogenicity of these variants. Through In silico analyses, both variants were identified as disease causing and protein modeling of exonic variant indicates subtle conformational alterations in prophesied protein structure. This study identifies a novel variant (c.1372-1del) and a recurrent pathogenic variant c.3936dup (p.Val1313Argfs*18) in the WDR62 gene among the Pakistani population, expanding the mutation spectrum for MCPH. These findings emphasize the importance of genetic counseling and awareness to reduce consanguinity and address the burden of this disorder.

Quantitative morphological analysis framework of infant cranial sutures and fontanelles based on CT images.

Characterizing the suture morphological variation is a crucial step to investigate the influence of sutures on infant head biomechanics. This study aimed to establish a comprehensive quantitative framework for accurately capturing the cranial suture and fontanelle morphologies in infants. A total of 69 CT scans of 2-4 month-old infant heads were segmented to identify semilandmarks at the borders of cranial sutures and fontanelles. Morphological characteristics, including length, width, sinuosity index (SI), and surface area, were measured. For this, an automatic method was developed to determine the junction points between sutures and fontanelles, and thin-plate-spline (TPS) was utilized for area calculation. Different dimensionality reduction methods were compared, including nonlinear and linear principal component analysis (PCA), as well as deep-learning-based variational autoencoder (VAE). Finally, the significance of various covariates was analyzed, and regression analysis was performed to establish a statistical model relating morphological parameters with global parameters. This study successfully developed a quantitative morphological framework and demonstrate its application in quantifying morphologies of infant sutures and fontanelles, which were shown to significantly relate to global parameters of cranial size, suture SI, and surface area for infants aged 2-4 months. The developed framework proved to be reliable and applicable in extracting infant suture morphology features from CT scans. The demonstrated application highlighted its potential to provide valuable insights into the morphologies of infant cranial sutures and fontanelles, aiding in the diagnosis of suture-related skull fractures. Infant suture, Infant fontanelle, Morphological variation, Morphology analysis framework, Statistical model.

Craniometric Characteristics of Selected Carnivora Species Kept in Captivity in Relation to Bite Force and Bending Strength of the Upper Canines.

The aim of this study was to analyse the bite forces of seven species from three carnivore families: Canidae, Felidae, and Ursidae. The material consisted of complete, dry crania and mandibles. A total of 33 measurements were taken on each skull, mandible, temporomandibular joint, and teeth. The area of the temporalis and masseter muscles was calculated, as was the length of the arms of the forces acting on them. Based on the results, the bite force was calculated using a mathematical lever model. This study compared the estimated areas of the masticatory muscles and the bending strength of the upper canines among seven species. A strong correlation was found between cranial size and bite force. The results confirmed the hypothesis that the weight of the animal and the size of the skull have a significant effect on the bite force.

Morphological and molecular data combined reveal inter- and intraspecific cranial shape variations in bats of Artibeus Leach, 1821 (Chiroptera: Phyllostomidae)

Abstract Since morphological traits may overlap among species within a complex, the integration of morphological and mitochondrial data could provide crucial insights for distinguishing species, as observed in fruit-eating bats of the genus Artibeus. Therefore, the application of geometric morphometric (GM) techniques could yield more refined and robust analyses of inter- and intraspecific variations. In this study, we generated two datasets: one with molecular delimitation data based on the barcode region (COI) and the other with cranial size and shape data using GM methods. Our aims were to investigate variations between large and small species within the genus Artibeus, as well as to explore potential factors influencing such variations. The results from species delimitation revealed molecular operational taxonomic units (MOTUs) supporting the morphological identification. Analyses using GM techniques demonstrated significant inter- and intraspecific variations in cranial size and shape among Artibeus species. The combined outcomes suggest the absence of a significant phylogenetic signal influencing skull variation. This scenario indicates that potential historical ecological factors may have directly influenced the cranial morphology of these species, acting as significant selection forces in geographical space and generating intraspecific variations in Artibeus planirostris.

Assessing Ecogeographic Rules in Two Sigmodontine Rodents along an Elevational Gradient in Central Chile.

Bergmann's and Allen's rules are two classic ecogeographic rules concerning the physiological mechanisms employed by endotherm vertebrates for heat conservation in cold environments, which correlate with adaptive morphological changes. Thus, larger body sizes (Bergmann's rule) and shorter appendages and limbs (Allen's rule) are expected in mammals inhabiting cold environments (higher latitudes). Both rules may also apply to elevational gradients, due to the decrease in external temperature as elevation increases. In this study, we evaluated whether these patterns were true in two coexisting sigmodontine rodents across an elevational gradient in central Chile. We analyzed whether the size of the skull, body, and appendages of Abrothrix olivacea (n = 70) and Phyllotis darwini (n = 58) correlated with elevation, as predicted by these rules in a range between 154 and 2560 m. Our data revealed weak support for the Bergmann and Allen predictions. Moreover, we observed opposite patterns when expectations of Bergmann's rules were evaluated, whereas Allen's rule just fitted for ear size in both rodent species. Our results suggest that morphological changes (cranial, body, and appendage sizes) may play a minor role in the thermoregulation of these two species at high elevations, although behavioral strategies could be more critical. Other ecological and environmental variables could explain the morphological trends observed in our study. These hypotheses should be assessed in future studies to consider the relative contribution of morphology, behavior, and physiological mechanisms to the thermal adaptation of these two rodent species at high elevations.

Three new shrews (Soricidae: Crocidura) from West Sumatra, Indonesia: elevational and morphological divergence in syntopic sister taxa

Abstract We describe 3 new species of shrews (Eulipotyphla, Soricidae, Crocidura) from West Sumatra, Indonesia. Two of these taxa were found above 1,800 m on Mt. Singgalang. The third taxon was found above 1,660 m on Mt. Talamau, 65 km northwest of Mt. Singgalang. We also resurrect Crocidura aequicauda based on 2 specimens from Mts. Tujuh and Kerinci, which lie near the border between West Sumatra and Jambi provinces. Several methodological approaches support our findings: linear cranial morphometrics, landmark-based 2D geometric morphometrics, and molecular phylogenetics using both mtDNA and 6 nuclear exons. A multilocus species-tree analysis places the 3 new species and C. aequicauda in a clade with the Javan endemics C. monticola and C. umbra. Although the 2 taxa from Mt. Singgalang are recovered as sister species, 1 is nearly twice the size of the other, and they are divergent in several other morphological characters, such as tail length, cranium size, and pelage color and texture. Recently diverged yet morphologically disparate sister taxa living syntopically in an isolated habitat “island,” like the montane forests of Mt. Singgalang, is unusual in mammals but documented in other Crocidura on neighboring Java and Borneo; these 2 new taxa represent the first known case of this phenomenon on Sumatra. Our results bring the number of Sumatran Crocidura to 10, 9 of which are endemic to the island. All 3 of the new species appear to be endemic to a single mountain and were not detected in similar surveys of nearby mountains. If this local endemism pattern is common, it would indicate that Sumatra’s mammal diversity may be severely underestimated, largely due to the paucity of small-mammal surveys and museum specimens.

The impact of in utero cannabis exposure on fetal growth.

The goal of this study was to examine if in utero cannabis exposure predicted reduced birth size and if these effects were evident in specific growth parameters as early as the second trimester. Eligible women had an initial prenatal visit between January 1, 2010, and March 31, 2020, completed an anatomy ultrasound between 18-24 weeks' gestation, and had no self-reported alcohol, tobacco, or other biochemically verified drug use. The two primary study groups were cannabis users (n = 109) identified through self-report and urine toxicology screens, and a randomly selected control group of non-substance users (n = 171). Medical records were manually reviewed for background and medical information, anatomy ultrasound results, and birth size parameters. After controlling for significant confounders, regression results indicated significant (p < .05) deficits in birth weight associated with cannabis exposure, with a trend for increasing weight effects beginning in the second trimester. A significant decrease in head circumference was evident as early as the second trimester, with differences remaining significant until birth. Significant overall length and specific bone length deficits were not predicted by cannabis exposure, at birth or earlier in gestation, after control for confounding. Cannabis exposure predicted growth deficits at birth, with some effects evident as early as the second trimester. The biggest and earliest effects were seen for cranial size, with an adjusted deficit of more than 14 percentile points by birth. Overall weight was not impacted until at or near delivery.

Can Cranium Size be Predicted from Orbit Dimensions?

Aim: The morphometry of skeletal remains is of importance to anatomists, forensic experts, and anthropologists. One of the most preferred skeletal remains is the cranium. Orbital morphometry in the cranium and cranium allows us to have information about parameters such as age, gender and lineage. This study was carried out to seek an answer to the question of whether cranium sizes can be estimated from orbital sizes. &#x0D; Material and Methods: In the study, 21 dry skulls belonging to the were used. Length and width measurements of the cranium and orbit were made. A precision digital caliper was used for measurements. &#x0D; Results: The ratio of the diameters of the cranium and orbit was calculated as 4.56 on the sagittal axis and 3.35 on the transverse left axis and these ratios were accepted as a related ratio (RR). OrbitRR values were calculated by converging the orbit to the cranium in RR ratios. Statistical validity (Bland Altman Plot) and reliability (Intraclass Correlation Coeffidency) analyzes were performed to evaluate the agreement between the measurements. There was no statistically significant difference between OrbitRR and cranium diameters (p&gt;0.05). Since there was no statistical difference, validity and reliability analysis was performed. It was observed that there was statistical validity between OrbitRR and cranium diameter in the sagittal and transverse axis. In the reliability analysis results, low agreement (r=0.405) was detected in the sagittal (r=0.391) and transverse axis (0.30

Reed bamboos drive skull shape evolution in bush frogs of the Western Ghats, Peninsular India.

Reed bamboo is a major ecological and economic resource for many animals, including humans. Nonetheless, the influence of this plant's evolutionary role on the morphology of animal species remains unexplored. Here, we investigated the significance of bamboo habitats as ecological opportunities in shaping the skull morphology of bush frogs (Raorchestes) from the Western Ghats, Peninsular India. We applied a three-dimensional (3D) geometric morphometric approach to capture the skull shape of 55 species of bush frogs. We visualized the skull shape variables in phylomorphospace with principal component analysis and performed phylogenetic generalized least-squares analysis to assess the impact of cranial size (evolutionary allometry) and habitat (bamboo or non-bamboo) on cranial shape. We quantified the morphological disparity between bamboo and non-bamboo bush frogs' skull shape, and employed RRphylo, a phylogenetic ridge regression method, to access the evolutionary rate and rate shifts of skull shape change. The phylomorphospace delineated bamboo and non-bamboo bush frogs. While cranial shape exhibited a significant but smaller association with size, its association with habitat type was non-significant. We detected, however, significant differences in skull shape between the two frog groups, with bamboo frogs showing higher morphological disparity and a remarkable shift in the evolutionary rate of skull shape diversification. These findings underscore the role of reed bamboo in the evolution of skull shape in the radiation of frogs, endemic to the Western Ghats. We demonstrate that the association between the members of two distinct endemic clades (bamboo reeds and bamboo frogs) is the outcome of a deep-time ecological opportunity that dates back to the Miocene.

Neurocranial growth in the OIM mouse model of osteogenesis imperfecta.

Osteogenesis imperfecta (OI) is a disorder of type I collagen characterized by abnormal bone formation. The OI craniofacial phenotype includes midfacial underdevelopment, as well as neurocranial changes (e.g., macrocephaly and platybasia) that may also affect underlying nervous tissues. This study aims to better understand how OI affects the integrated development of the neurocranium and the brain. Juvenile and adult mice with OI (OIM) and unaffected wild type (WT) littermates were imaged using in vivo micro-computed tomography (microCT). Virtual endocast models were used to measure brain volume, and 3D landmarks were collected from the cranium and brain endocasts. Geometric morphometric analyses were used to compare brain shape and integration between the genotypes. OIM mice had increased brain volumes (relative to cranial centroid size) only at the juvenile stage. No significant difference was seen in cranial base angle (CBA) between OIM and WT mice. However, CBA was higher in juvenile than in adult OIM mice. Brain shape was significantly different between OIM and WT mice at both stages, with OIM mice having more globular brains than WT mice. Neurocranial and brain morphology were strongly integrated within both genotypes, while adult OIM mice tended to have lower levels of skull-brain integration than WT mice. These results suggest that neurocranial dysmorphologies in OI may be more severe at earlier stages of postnatal development. Decreased skull-brain integration in adult mice suggests that compensatory mechanisms may exist during postnatal growth to maintain neurological function despite significant changes in neurocranial morphology.

Cranial asymmetry in odontocetes: a facilitator of sonic exploration?

Directional cranial asymmetry is an intriguing condition that has evolved in all odontocetes which has mostly been associated with sound production for echolocation. In this study, we investigated how cranial asymmetry varies across odontocete species both in terms of quality (i.e., shape), and quantity (magnitude of deviation from symmetry). We investigated 72 species across all ten families of Odontoceti using two-dimensional geometric morphometrics. The average asymmetric shape was largely consistent across odontocetes – the rostral tip, maxillae, antorbital notches and braincase, as well as the suture crest between the frontal and interparietal bones were displaced to the right, whereas the nasal septum and premaxillae showed leftward shifts, in concert with an enlargement of the right premaxilla and maxilla. A clear phylogenetic signal related to asymmetric shape variation was identified across odontocetes using squared-change parsimony. The magnitude of asymmetry was widely variable across Odontoceti, with greatest asymmetry in Kogiidae, Monodontidae and Globicephalinae, followed by Physeteridae, Platanistidae and Lipotidae, while the asymmetry was lowest in Lissodelphininae, Phocoenidae, Iniidae and Pontoporiidae. Ziphiidae presented a wide spectrum of asymmetry. Generalized linear models explaining magnitude of asymmetry found associations with click source level while accounting for cranial size. Using phylogenetic generalized least squares, we reconfirm that source level and centroid size significantly predict the level of cranial asymmetry, with more asymmetric marine taxa generally consisting of bigger species emitting higher output sonar signal, i.e. louder sounds. Both characteristics theoretically support foraging at depth, the former by allowing extended diving and the latter being adaptive for prey detection at longer distances. Thus, cranial asymmetry seems to be an evolutionary pathway that allows odontocetes to devote more space for sound-generating structures associated with echolocation and thus increases biosonar search range and foraging efficiency beyond simple phylogenetic scaling predictions.

An economic model and evidence of the evolution of human intelligence in the Middle Pleistocene: Climate change and assortative mating.

A main objective of this paper is to provide the first model of how climate change, working through sexual selection, could have led to dramatic increases in hominin brain size, and presumably intelligence, in the Middle Pleistocene. The model is built using core elements from the field of family economics, including assortative mating and specialization and complementarities between mates. The main assumptions are that family public goods (e.g., conversation, shelter, fire) were particularly cognitively intensive to produce and became increasingly important for child survival during glacial phases. Intermediate climates (e.g., not the depths of severe glacial phases) create the largest gains from specialization, encouraging negative assortative mating. In contrast, severe glacial phases encourage positive assortative mating because of the rising importance of family public goods. One testable hypothesis is that absence of severe glacial phases should have led to stasis in brain size. Two other testable hypotheses are that severe glacial phases should have led to speciation events, as well as increases in brain size. The evidence shows that there was a million-year stasis in cranial size prior to the start of the severe glacial phases. This stasis is broken by a speciation event (Homo heidelbergensis), with the oldest fossil evidence dated near the close of the first severe glacial phase. In the next 300 kyr, there are two additional severe glacial phases, accompanied by considerable increases in cranial capacity. The last speciation event is Homo sapiens, with the earliest fossils dated near the end of the last of these two glacial phases.

Comparison of the transverse cranial base dimension in different craniofacial skeletal relationships: A cone-beam computed tomography study

Background/purposeIn comparing the cranial base's size, most cephalometric studies focused on the length and angle in the anteroposterior direction. However, investigating the anterior, middle, and posterior cranial base's transverse dimensions is challenging. This study aimed to investigate the transverse dimensions of the cranial base in different craniofacial skeletal patterns and sexes using cone-beam computed tomography (CBCT). Materials and methodsA total of 210 adults (105 males and 105 females), including three different skeletal relationships, were included in the study. The cranial base dimensions were measured on a three-dimensional image structure rendered by CBCT. Statistical methods included the Kappa statistic for analysis of consistency and reproducibility and the independent t-test for differences in cranial base dimensions between sexes. A general linear model (GLM) was used to compare the transverse size of the cranial base among skeletal Class I, II, and III groups. The Pearson correlation coefficient explored the correlation among the cranial base dimensions. ResultsThe cranial base dimensions did not differ significantly between skeletal Class I, II, and III. The more prominent cranial base size was found in males than females, except for the crista galli length (CGL) and cribriform ethmoid plate width (CEPW). The cranial base dimensions did not differ significantly between different skeletal relationships. Most dimensions have significant correlations in the middle and the posterior cranial base. ConclusionThe cranial base's transverse dimensions in Taiwanese adults show no significant differences between craniofacial skeletal relationships. In the middle and posterior cranial base, transverse measurements reveal significant sexual dimorphism.

Cranial morphology of Balkan and West Asian livestock guardian dogs.

Several large "shepherd" or livestock guardian dog (LGD) breeds were historically selectively bred to protect sheep and goat flocks in the Balkans, Anatolia, and the Caucasus regions. Although these breeds exhibit similar behavior, their morphology is different. Yet, the fine characterization of the phenotypic differences remains to be analyzed. The aim of this study is to characterize cranial morphology in the specific Balkan and West Asian LGD breeds. We use a 3D geometric morphometric in order to assess morphological differences regarding both shape and size between LGD breeds and compare this phenotypic diversity to close relative wild canids. Our results indicate that Balkan and Anatolian LGDs form a distinct cluster within a relatively large dog cranial size and shape diversity. Most LGDs display a cranial morphology that could be described as intermediate to the mastiff breeds and large herding dogs, except for the Romanian Mioritic shepherd which has a more brachycephalic cranium strongly resembling the bully-type dog cranial morphotype. Although often considered to represent an ancient type of dog, the Balkan-West Asian LGDs are clearly distinguishable from wolves, dingoes, and most other primitive and spitz-type dogs and this group displays a surprising cranial diversity.

SP28. The Risk Analysis Index Has Superior Frailty Discrimination Than the Modified Frailty Index-5 for Predicting Poor Cranioplasty Outcomes

PURPOSE: Cranioplasty is a common surgical procedure where autologous or synthetic materials are used to repair cranial defects and although considered simple and low-risk, it is surprisingly associated with significant morbidity and mortality. Although increased patient age has been shown to be a predictor of poor postoperative outcomes, no studies have evaluated frailty’s impact on cranioplasty outcomes. This study examined the association between frailty and cranioplasty by comparing effect sizes of the Risk Analysis Index-Administrative (RAI-A), Modified Frailty Index-5 (mFI-5), and increasing patient age on the primary outcome of 30-day mortality and secondary outcomes of non-home discharge rates and postoperative complications, as measured by the Clavien-Dindo (CD) complication classification system: (CD I: surgical site infection, CD II: postoperative bleeding or transfusion(s), CD IIIb: reoperation under general anesthesia, CD IV: sepsis, septic shock, pulmonary embolism, myocardial infraction, ventilator status, 30-day mortality). METHODS: The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) was queried for all patients undergoing cranioplasty between 2012-2020. Data for baseline demographics, comorbidities, operative characteristics, and postoperative outcomes were evaluated. Statistical analysis was performed on IBM SPSS Statistics ver. 28.0 (IBM Co., Armonk, NY, USA). The discriminatory thresholds of RAI-A, mFI-5, and increasing patient age on 30-day mortality were evaluated using receiver operating characteristics (ROC) curve analysis. The area under the curve (AUC) is represented as a C-statistic with a 95% confidence interval (CI). Two distinct multivariable analyses were conducted for RAI-A and mFI-5 to measure the independent relationships between frailty and outcomes. Covariates controlled for included race, BMI, primary procedure, cranial defect size, and material type. Additionally, the mFI-5 model was age-adjusted, allowing for direct comparison of effect sizes between age and frailty. We excluded age from the model for RAI-A to prevent any collinearity, since age contributes to the total RAI-A score. RESULTS: There were 2,864 included study patients with a median age of 57 years (IQR, 44-67), and a higher proportion of patients were female (57.0%), and white (68.5%). The RAI-A demonstrated better predictive ability for 30-day mortality (C-Statistic: 0.741, 95% CI: 0.678-0.804) compared to mFI-5 (C-Statistic: 0.574, 95% CI: 0.489-0.659) and increasing patient age (C-Statistic: 0.671, 95% CI: 0.610-0.732). On multivariable analyses, RAI-A demonstrated superior independent associations with mortality, NHD, CDII, and CDIII when compared to mFI-5 and increasing patient age. (p<0.05). CONCLUSIONS: The RAI-A demonstrated superior discrimination than the mFI-5 and increasing patient age in predicting poor outcomes following cranioplasty. The high rates of operative morbidity (5.0-36.5%) and mortality (0.4-3.2%) after cranioplasty highlight the importance of being able to predict which patients are at increased risk for poor cranioplasty outcomes, so that shared decision making regarding the potential risk and benefits of treatment can occur. Multivariable Analyses for Postoperative Outcomes

A global assessment of the ‘island rule’ in bats based on functionally distinct measures of body size

AbstractAimThe ‘island rule’ postulates that on islands large continental animals become smaller, and small continental animals become larger. Its generality has been supported by some studies but contested by others. Bats are cosmopolitan and speciose mammals thus are ideal to test ecogeographic patterns. Based on three functionally distinct measures of body size, I compare mainland and island variation in bats at the order to subspecies level.LocationGlobally.TaxonChiroptera.MethodsI compiled information from literature on the skull length, forearm length, and body mass of 251 bat species in 840 locations. For conspecific bats from different locations, I calculated size divergences, and categorized them as within‐mainland (M–M), mainland‐to‐island (M–I), or island‐to‐island (I–I). I used a modified size ratio to quantify divergences, analysis of variance, non‐parametric tests, and effect sizes to complement statistical significances.ResultsOn islands, cranial size increases, wing length becomes more uniform, and body mass decreases more often than not. The first trend would support the island rule, but had a small effect size. Families differ considerably in how they vary geographically. Species are ranked very differently based on functionally distinct size measures. Divergences are uniform across M–M, M–I, and I–I ranges, and large between bats of different subspecies.Main ConclusionsLikely owing to limitations imposed by flight and echolocation, bats do not follow the island rule. The absence of correlation between how bats are ranked based on them indicates that functionally distinct size measures are not necessarily coadaptive. High vagilities may lead to low local differentiation, but interfamilial variation shows this differentiation to also depend on other factors. Body sizes converge to species‐specific optima, not to supraspecific optima as predicted by theoretical studies. Size differences are reflected in taxonomy more often if observed across M–I ranges.

The Olfactory Bulb in Companion Animals-Anatomy, Physiology, and Clinical Importance.

The Olfactory Bulb is a component of the Olfactory System, in which it plays an essential role as an interface between the peripheral components and the cerebral cortex responsible for olfactory interpretation and discrimination. It is in this element that the first selective integration of olfactory stimuli occurs through a complex cell interaction that forwards the received olfactory information to higher cortical centers. Considering its position in the organizational hierarchy of the olfactory system, it is now known that changes in the Olfactory Bulb can lead to olfactory abnormalities. Through imaging techniques, it was possible to establish relationships between the occurrence of changes secondary to brain aging and senility, neurodegenerative diseases, head trauma, and infectious diseases with a decrease in the size of the Olfactory Bulb and in olfactory acuity. In companion animals, this relationship has also been identified, with observations of relations between the cranial conformation, the disposition, size, and shape of the Olfactory Bulb, and the occurrence of structural alterations associated with diseases with different etiologies. However, greater difficulty in quantitatively assessing olfactory acuity in animals and a manifestly smaller number of studies dedicated to this topic maintain a lack of concrete and unequivocal results in this field of veterinary sciences. The aim of this work is to revisit the Olfactory Bulb in companion animals in all its dimensions, review its anatomy and histological characteristics, physiological integration in the olfactory system, importance as a potential early indicator of the establishment of specific pathologies, as well as techniques of imaging evaluation for its in vivo clinical exploration.

The skull variation of the olive field mouse Abrothrix olivacea (Cricetidae: Abrotrichini) is localized and correlated to the ecogeographic features of its geographic distribution.

The relationship between phenotypic variation and landscape heterogeneity has been extensively studied to understand how the environment influences patterns of morphological variation and differentiation of populations. Several studies had partially addressed intraspecific variation in the sigmodontine rodent Abrothrix olivacea, focusing on the characterization of physiological aspects and cranial variation. However, these had been conducted based on geographically restricted populational samples, and in most cases, the aspects characterized were not explicitly contextualized with the environmental configurations in which the populations occurred. Here, the cranial variation of A. olivacea was characterized by recording twenty cranial measurements in 235 individuals from 64 localities in Argentina and Chile, which widely cover the geographic and environmental distribution of this species. The morphological variation was analyzed and ecogeographically contextualized using multivariate statistical analyses, which also included climatic and ecological variation at the localities where the individuals were sampled. Results indicate that the cranial variation of this species is mostly clustered in localized patterns associated to the types of environments, and that the levels of cranial differentiation are higher among the populations from arid and treeless zones. Additionally, the ecogeographical association of cranial size variation indicate that this species does not follow Bergmann's rule and that island populations exhibit larger cranial sizes compared to their continental counterparts distributed at the same latitudes. These results suggest that cranial differentiation among the populations of this species is not homogeneous throughout its geographic distribution, and that the patterns of morphological differentiation are also not completely consistent with the patterns of genetic structuring that have been described recently. Finally, the analyses performed to ponder morphological differentiation among populations suggest that the contribution of genetic drift in the formation of these patterns can be ruled out among Patagonian populations, and that the selective effect imposed by the environment could better explain them.