Anatomical Record最新文献

The length of the snout in mammals has important evolutionary consequences for the functional systems housed within the rostrum. However, whether increased snout lengths lead to expanded olfactory performance has rarely been examined. Here, we investigate inner rostral function among 10 species of myrmecophagous (ant- and/or termite-eating) placental mammals and 10 closely related species. We use nondestructive computed tomography scanning methods to characterize inner rostral function based on the underlying morphology of the turbinal bones in the nasal cavity. Three approaches were chosen to address this question, including the quantification of functional turbinal surface area, the quantification of functional turbinal three-dimensional complexity, and geometric morphometrics. By including non-model species from several different mammalian orders, we were able to extend the discussion surrounding turbinal homologies to comparisons across mammals. Our results show no increased olfactory function in all myrmecophagous species relative to their sister taxa, which suggests that there is no trade-off for increased olfactory capabilities in myrmecophagous species with elongated snouts. We found no evidence of convergence in turbinal morphology among all five myrmecophagous lineages. However, we found evidence of morphological convergence in the turbinals between the giant armadillo and the aardvark, suggesting a more complex interplay between the evolution of turbinal morphology and ecological correlates. While myrmecophagy alone may not be a strong enough ecological signal to overcome phylogenetic and developmental constraints, we suggest that this might be the case at the intersection of this dietary specialization with a primarily underground lifestyle where odorants may be difficult to detect.

Whales (cetaceans, including dolphins and porpoises) are superbly adapted to life in water, but retain vestiges of their terrestrial ancestry, particularly the need to breathe air. Their respiratory tract exhibits many differences from their closest relatives, the terrestrial artiodactyls (even toed ungulates). In this review, we describe the anatomy of cetacean respiratory adaptions. These include protective features (e.g., preventing water incursions during breathing or swallowing, mitigating effects of pressure changes during diving/ascent) and unique functions (e.g., underwater sound production, regulating gas exchange during the dive cycle).

Dental microwear texture analysis (DMTA) is widely applied for inferring diet in vertebrates. Besides diet and ingesta properties, factors like wear stage and bite force may affect microwear formation, potentially leading to tooth position-specific microwear patterns. We investigated DMTA consistency along the upper cheek tooth row in young adult female rats at different growth stages, but with erupted adult dentitions. Bite forces for each molar (M) position were determined using muscle cross-sectional areas and lever arm mechanics. Rats were categorized into three size classes based on increasing skull length. Maximum bite force increased with size, while across all size classes, M3 bite force was almost 1.4 times higher than M1 bite force. In size class 1, M1 and M2 showed higher values than M3 for DMTA complexity, height, and volume parameters, while in size class 3, M1 had the lowest values. Comparing the same tooth position between size classes revealed opposing trends: M1 and M2 showed, for most parameters, decreasing roughness and complexity from size class 1-3, while M3 displayed the opposite trend, with size class 1 showing lowest, and either size class 2 or 3 the highest roughness and complexity values. This suggests that as rats age and M3 fully occludes, it becomes more utilized during mastication. DMTA, being a short-term diet proxy, is influenced by eruption and occlusion status changes. Our findings emphasize the importance of bite force and ontogenetic stage when interpreting microwear patterns and advise to select teeth in full occlusion for diet reconstruction.

Extensive research into bat flight mechanisms has highlighted the complex functional and evolutionary dynamics of their wing structures, yet the anatomical details of certain wing muscles remain elusive. In particular, the intramembranous plagiopatagiales proprii muscles, located within the plagiopatagium-an area of the wing lacking direct joint connections-exhibit remarkable variation across bat families. These muscles, which extend anteroposteriorly in macroscopic bundles, play a crucial role in wing stiffening, modulating membrane tension, and reducing wing curvature during flight. Since larger bats tend to have higher wing loading (WL; the ratio of body mass [BMa] to wing area) and may therefore experience increased patagial curvature and resultant drag, we hypothesized that body size significantly influences the evolutionary development of the plagiopatagiales proprii muscles. This study investigates the relationship between BMa and the morphology of the plagiopatagiales proprii in New World leaf-nosed bats (Phyllostomidae), employing bivariate allometry, multivariate analysis, and comparative phylogenetic methods across 24 species from eight phyllostomid subfamilies. Our findings reveal a significant phylogenetic signal in muscle architecture, along with positive evolutionary allometry in muscle area. This suggests an adaptive increase in muscle size in larger species, likely to counterbalance the increased WL, reduce wing curvature, and minimize drag. This research enhances our understanding of the functional and adaptive morphological evolution of intramembranous wing muscles in phyllostomid bats, underscoring their evolutionary significance.

Employing immunohistochemical procedures with antibodies raised against tyrosine hydroxylase (TH) and choline acetyltransferase we identified and mapped the locus coeruleus complex (LoC) and the pontine laterodorsal tegmental (LDT) and pedunculopontine tegmental (PPN) cholinergic nuclei in the brains of a Congo gray parrot, a timneh gray parrot, and a pied crow. The LoC and LDT/PPN are centrally involved in the regulation and generation of different sleep states, and as all birds studied to date show both REM and non-REM sleep states, like mammals, we investigated whether these noradrenergic and cholinergic nuclei in the avian pons shared anatomical features with those in the mammalian pons. The LoC was parcellated into 3 distinct nuclei, including the locus coeruleus (A6), subcoeruleus (A7), and the fifth arcuate nucleus (A5), while distinct LDT and PPN nuclei were revealed. Several similarities that allow the assumption of homology of these nuclei between birds and mammals were revealed, including their location relative to each other and other structures within the pontine region, as well as a specific degree of topographical overlap of the noradrenergic and cholinergic neurons. Despite this, some differences were noted that may be of interest in understanding the differences in sleep between birds and mammals. Further anatomical and physiological studies are needed to determine whether these pontine nuclei in birds play the same role as in mammals, as while the homology is apparent, the functional analogy needs to be revealed.

Rhynchosauria is a group of extinct, exclusively Triassic, terrestrial, and herbivorous archosauromorphs, characterized by a peculiar maxillary-mandibular apparatus. They reached global distribution during the Carnian, with the Hyperodapedontinae clade. The rhynchosaurian record from South America is included in the Ladinian-?earliest Carnian Dinodontosaurus Assemblage Zone (Pinheiros-Chiniquá Sequence, Brazil) and Tarjadia Assemblage Zone (Chañares Formation, Argentina), and for strictly Carnian Hyperodapedon Assemblage Zone (Lower Candelária Sequence, Brazil) and Ischigualasto Formation (Argentina). Here, we present the first record of Hyperodapedontinae from the Brazilian Early Carnian Santacruzodon Assemblage Zone (Santa Cruz Sequence). The most diagnostic elements belong to a nearly complete left pes, which presents a combination of hyperodapedontine traits. The presence of a second individual of cf. Hyperodapedontinae is based on a fragmentary, isolated left metatarsal IV. An isolated fragment of premaxilla could belong to the second specimen (based on preservation mode) or to a third individual. This new report fills a gap within the South American rhynchosaurian distribution, strengthening biostratigraphic correlation with other regions from Gondwana (i.e., Madagascar), where similar and coeval faunas are known. The inclusion of these specimens in a phylogenetic dataset resulted in low resolution results, due to missing data because postcranial characters for rhynchosaurs are still poorly explored.

We here provide a detailed description of the vertebral morphology of the African arboreal viperid snakes of the genus Atheris. Vertebrae of three different species of the genus, i.e., Atheris desaixi, Atheris hispida, and Atheris katangensis, were investigated via the aid of μCT (micro-computed tomography) scanning. We describe several vertebrae from different regions of the vertebral column for all three species, starting from the atlas-axis complex to the caudal tip, in order to demonstrate important differences regarding the intracolumnar variation. Comparison of these three species shows an overall similar general morphology of the trunk vertebrae among the Atheris species. We extensively compare Atheris with other known viperids. As the sole arboreal genus of Viperinae the prehensile nature of the tail of Atheris is reflected in its caudal vertebral morphology, which is characterized by a high number of caudal vertebrae but also robust and anteroventrally oriented pleurapophyses as a skeletal adaptation, linked with the myology of the tail, to an arboreal lifestyle. We anticipate that the extensive figuring of these viperid specimens will also aid identifications in paleontology.

Domestic dogs (Canis familiaris) are descended from gray wolf (Canis lupus) populations that inhabited Western Europe and Siberia. The specific timing of dog domestication is debated, but archeological and genetic evidence suggest that it was a multi-phase process that began at least 15,000 years ago. There are many morphological differences between dogs and wolves, including marked divergence in facial muscle morphology, but we know little about the comparative physiology of these muscles. A better understanding of comparative facial muscle physiology between domestic dogs and gray wolves would improve our conceptual framework for the processual mechanisms in dog domestication. To address these issues, we assessed the myosin profiles (type I and type II) from the zygomaticus and orbicularis oris muscles of 6 domestic dogs and 4 gray wolves. Due to small sample sizes, statistical analyses were not done. Results reveal that sampled domestic dogs have almost 100% fast-twitch (type II) muscle fibers while gray wolves have less than 50%, meaning that dog faces can contract fast while wolf faces are able to sustain facial muscle contraction. Sample sizes are limited but the present study indicates that dog domestication is associated with not only a change in facial muscle morphology but a concomitant change in how these muscles function physiologically. Selective pressures in the development of communication between dogs and humans using facial expression may have influenced this evolutionary divergence, but the paedomorphic retention of barking in adult dogs may have also played a role.

The present study reexamined the immunolocalization of membranous serotonin transporter (SERT) in the rat carotid body, and demonstrated SERT-immunoreactive cells of unreported morphology. SERT was immunohistochemically localized in a very small population of cell clusters or single type I cells (2.8%) immunoreactive for synaptophysin, the marker of these cells. Intense SERT immunoreactivity outlined the perinuclear cytoplasm and multiple cytoplasmic processes of type I cells. Of SERT-immunoreactive type I cells, 14.6% and 32.6% were immunoreactive for tyrosine hydroxylase (TH) and dopamine beta-hydroxylase, respectively, while 75.9% were immunoreactive for serotonin (5-HT). 5-HT-immunoreactive products were localized in cell bodies rather than cytoplasmic processes. SERT-immunoreactive type I cells were composed of an oval cell body with multiple threads and spherical or elongated cytoplasmic processes. Clusters or single SERT-immunoreactive type I cells were localized between or attached to other TH-immunoreactive type I cells by cell bodies or variform cytoplasmic processes. SERT-immunoreactive type I cells mainly contained bassoon-immunoreactive products in their cell bodies rather than their variform cytoplasmic processes. These results demonstrated the characteristic morphology of SERT-immunoreactive type I cells, which extend multiple cytoplasmic processes with variform terminal parts. Their morphology might be suitable for uptake of 5-HT to control the serotonergic modulation in the carotid body.

Despite detailed descriptions of cranial anatomy in representatives of most major chondrichthyan groups, the inner ear has been described infrequently and most often from the soft tissue of the membranous labyrinth. However, skeletal labyrinth morphology has been linked with ecology in several groups of vertebrates, and shark skeletal labyrinths bear several specializations for detecting low frequency sounds. Without description of these structures across a broad sample of taxa, future exploration of the ecomorphology of ear shape is not possible. We used high-resolution CT scanning to generate three-dimensional models of the endocranial anatomy in four elasmobranchs: the Nurse Shark (Ginglymostoma cirratum), the Japanese Tope Shark (Hemitriakis japanica), the Horn Shark (Heterodontus francisci), and the Zebra Shark (Stegostoma tigrinum). Major differences are apparent between the skeletal labyrinths of these taxa, which might be ascribed to either phylogenetic history or lifestyle. In particular, the size of the skeletal labyrinth relative to the cranium dramatically differs among these chondrichthyans, as does the diameter and angle of the semicircular canals and the size of the canals relative to the vestibule. Based on the separation of the anterior and posterior semicircular canals, and the lack thereof in S. tigrinum, the degree of specialization for low frequency sound detection may also vary.