Anatomical Record-Advances in Integrative Anatomy and Evolutionary Biology最新文献

We aimed to determine the timing of appearance and the morphologic and morphometric features of the initial human cerebral sulcal formation. Using high-resolution magnetic resonance images obtained from 33 samples between 11 and 16 weeks (w) of gestation (crown-rump length <130 mm), the cerebral surface and internal structures on serial two-dimensional planes and all possible sulci on three-dimensional reconstructions were marked, allowing comparison of the positions of the sulci in the samples and inter-samples. Our method provided accurate conclusions regarding the timing of sulcal formation. Detection timing was as early as and earlier than those in previous studies using anatomical dissection and magnetic resonance imaging (MRI), respectively: <12 w for the callosum, <13 w for the hippocampal, calcarine, and parieto-occipital sulci, and < 15 w for the lateral sulcus. Occasionally, an olfactory sulcus was detected. However, the cingulate sulcus could not be definitely identified. The lateral sulcus gradually appeared and changed shape. The lengths of the left and right sides of the olfactory sulci and the left side of the hippocampal sulcus increased linearly with the CRL. The length of the right side of the hippocampal sulcus and the left and right sides of the calcarine, parieto-occipital, and not determined_a sulci did not increase with the CRL The depth of the all sulci, except for the parieto-occipital sulci, increased linearly with the CRL. The sulci might not arise as if they elongate gradually but arise simultaneously over some distance. We determined the timing of the initial sulcal formation using high-resolution MRI. Our findings may significantly impact prenatal diagnosis and research on neurodevelopmental disorders.

Although the reproduction of some Boidae snakes has been studied through the macroscopic anatomy of the gonads, without microscopic morphology, there is little precision in describing reproductive cycles, especially for males. The relationship between the reproductive cycle-gametogenesis and reproductive seasonality throughout the year-has yet to be detailed for many Boidae species. We present macroscopic and histological data on the reproductive tracts of both male and viviparous female Corallus hortulana (Linnaeus 1758) (Amazon Tree Boa) from the Brazilian Amazon rainforest. Males present spermiogenesis and spermiation mainly during January and June (wet season to beginning-dry season). Contrary to common assumption, we speculate that sperm production in C. hortulana, even in the tropical Amazon, is likely energetically demanding, influenced by rainfall, given that testicular involution occurred between May and November (most of the driest months of the year). Females present ovarian follicles in processes of vitellogenesis from December to August (wet season and part of the dry season). However, newborns are found in the wild mainly in the wet season, characterizing the cycle of female C. hortulana as seasonal. Unprecedentedly, we present the first microscopic description of the pouch and non-glandular uterus in a Boidae species. The cells that compose the epithelial tissue of the non-glandular uterus have been suggested for maintaining and supporting spermatozoa (sperm storage) in snakes, but we found no evidence that sperm storage occurs in this portion of the oviduct in C. hortulana. This study not only improves our understanding of reproductive biology in a boid, but because several aspects of reproductive cycles are conservative in the family (e.g., season of birth of newborn snakes), it aids in the development of effective conservation policies for endangered species such as Corallus cropanii, the rarest Boidae in the Americas.

The human voice is a major signal transmission modality for our species. Accordingly, perception of its quality serves as an intraspecific window into the status of an individual's health, robusticity, and even stature in the group. Diminished quality-as may occur in aging or certain diseases-is a major feature in the lessening of an individual's communication modality. Here, we review the underlying anatomy and function that comprise the voice producing elements-the vocal tract sensu lato-from the lungs through the larynx and supralaryngeal modifying elements. Aspects of the aging larynx and constituent elements such as the vocal folds ("true vocal cords") and intrinsic laryngeal joints, are discussed within the context of how their aging or disease degradation may affect an individual's speech and concomitant perception and interpretation by listeners. The aging voice is considered within the context of the overall effects of aging sensory systems in both humans and other mammals.

Determining the ecology of fossil species presents considerable challenges due to the often fragmentary preservation of specimens. The mammaliaform Hadrocodium wui from the Jurassic of China is known only from the cranium and mandible but may have had a fossorial lifestyle. It shares morphological similarities with talpid moles and soricid shrews and is closely related to other fossorial mammaliaforms. However, the lack of postcranial elements has so far precluded a definitive assessment regarding its fossorial behavior. Using a combination of geometric morphometric analysis of the lower mandible and finite element analyses of the cranium, comparisons between H. wui and extant groups are made. H. wui resembles talpid moles more closely than shrews in mandible shape. However, there are more similarities between H. wui and semi-fossorial/semi-aquatic moles than fully fossorial moles. The skull of H. wui is particularly weak in every tested biomechanical scenario when compared to the related mammaliaform Morganucodon oehleri and talpid moles. This weakness is potentially a result of the reduction in thickness of the zygomatic arch. In contrast, the shrew crania show similar stress magnitudes and distribution. These results imply that H. wui was not fully fossorial and fed on a diet of softer invertebrates. Skull morphology may therefore not be sufficient to infer fossoriality in forelimb-digging species.

Bones of the skull are traditionally categorized as derived from either endochondral or intramembranous bone. In our previous work, we have observed the interaction of different tissue types in growth of the skull. We find the dichotomy of intramembranous and endochondral bone to be too restrictive, limiting our interpretation of sources of biological variation. Here, we advocate for the use of the term ectochondral bone to describe bone that originates from an endochondral model but is directed in its subsequent growth by membranes and other fascial attachments. Growth of the alisphenoid and orbitosphenoid are described as two examples of ectochondral bone, influenced in their shape primarily by the surrounding soft tissues. Ectochondral bone may be an ideal mechanism for rapidly evolving new phenotypes. Instead of evolving novelties by altering morphology of the cartilage template, novel features may be formed by ectochondral ossification, a more direct and rapid mode of osteogenesis than that of the cartilage template.

Megantereon was a widespread saber-toothed felid from the Pliocene and Pleistocene of the Old World and North America, but its rarity in the fossil record makes it complicated to restore its life appearance. Lack of complete specimens makes it necessary to combine information from fossils of different individuals to reconstruct their facial anatomy. In this work, we combine the analysis of skulls and mandibles of Megantereon from various fossil sites with the study of extant carnivorans through dissection, 3D scans, and the observation of live individuals. Megantereon combined very elongated upper canines with mandibular flanges that were not deep enough to match the length of the sabers, as well as a wide maxilla combined with narrow incisor rows and mandibular symphysis. Such features are compatible with the presence of exposed canines in life, because the narrow symphysis allows room to accommodate lips and other soft tissues medial to the sabers, while the protrusion of the tips of the upper canines beyond the mental flanges makes it unlikely that they would be enveloped in soft tissue sheaths, which would dangle with the inherent risk of puncture. Megantereon was transitional between saber-toothed felids with covered upper canines, where saber length fits with mental flange depth, and the derived Smilodon where the upper canines are much longer than the flanges and the lips fit between upper canines and mandible, leaving the upper canine crowns largely exposed in life.

Tusks are ever-growing teeth present in mammals of the clade Paenungulata. Unlike the perpetually growing incisors of rodents, tusks are not used in mastication, and in at least some paenungulatans, the tusk is composed of dentin alone in adults. Few studies have provided tissue-level information on tusks of adult paenungulatans with embedding techniques that identify epithelial and other soft tissues. In order to examine the mineralized tissues as well as the cells that form teeth, we studied a single, subadult rock hyrax (Procavia capensis) using microCT and paraffin histology with traditional staining as well as RUNX2 immunohistochemistry, and compared its teeth to scans of adult hyraxes. Three-dimensional reconstructions from microCT volumes revealed that the tusk of this specimen is the only fully erupted replacement tooth, the first adult premolar (P1) is starting to erupt, and the first permanent molar (M1) is fully erupted, whereas all other replacement teeth and M2 remain in crypts. The tusk has a thin layer of enamel on its dorsal side; this is confirmed by histology. All deciduous premolars still possess roots that are in the process of resorption. Amelogenesis has progressed to maturation or nearly so in P1-P3. Notable histological characteristics of replacement premolars include the lack of a stellate reticulum in all except P4, and expression of RUNX2 in ameloblasts, a marker which is expressed by ameloblasts at all stages of amelogenesis. Since the pulp chambers of replacement premolars are relatively large compared to adults, a lengthy time in crypts may be important for dentin production. The results confirm that the hyrax has thin enamel on tusks, supporting the hypothesis that enamel is of limited importance for non-feeding behaviors.

Complexity and reproductive plasticity are very well-known characteristics of anurans. The group is being continuously explored taxonomically and phylogenetically, which leads to a great potential diversity not yet uncovered. This is particularly evident due to the lack of investigation regarding species-specific traits, even the ones well distributed in the lineages as polyandry. Although the climate and environment affect reproductive variability, each species has unique dynamics, and a deeper understanding of their reproductive cycles is essential for meaningful comparisons and recognition of patterns within the extensive variability observed in anurans. Given this context, the present study examined the reproductive and environmental parameters of the polyandrous species Leptodactylus podicipinus throughout its reproductive cycle over two consecutive years. The objective was to characterize the species' reproductive dynamics and compare them with phylogenetically related species and other polyandrous species, aiming to explore patterns and the influence of polyandry on anuran reproduction. The main reproductive activity of L. podicipinus was during the months with greater rainfall, from October to February. The seminiferous epithelium presented a higher mean of final germinative cells (spermatozoa) in the reproductive period (October-February) and early germinative cells (spermatocytes I and spermatids) in the non-reproductive period (March-September). Among the climatic parameters tested, rainfall was the only one significantly related to reproductive outcomes. Two distinct germinative patterns were identified between polyandric and non-polyandric species compared. Polyandry is certainly a trait that plays a significant role in shaping gametogenesis and the evolution of animals with this reproductive attribute.