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

Notamacropus rufogriseus (red-necked wallaby) are in the family Macropodidae, which is the second largest family of marsupials after the family Didelphidae. This study was conducted with the aim of providing a detailed description of the origin and distribution of the brachial plexus in N. rufogriseus. Two-year-old male and 3-year-old female red-necked wallabies were used for the study. The brachial plexus was formed by ventral rami of C4, C5, C6, C7, C8, and T1 spinal nerves. It is composed of three trunks that give rise to 12 principal nerves. The cranial trunk is formed by the combination of the rami C4–C7; the middle trunk is formed by the combination of the rami C6 and C7; and the caudal trunk is formed by the combination of the rami C8 and T1. Differences between left and right side of the plexus brachialis were not observed. C6 ventral spinal rami contribute the most to brachial plexus nerve formation, while C4 contributes the least. The formation and distribution of the plexus in N. rufogriseus exhibited more resemblance to the patterns observed in marsupial animals rather than placental mammals. Marsupial mammals demonstrate the involvement of C4 in the development of the brachial plexus. The formation and branching of the brachial plexus sequentially adapt in accordance with changes in their thoracic limb activities and innervation points. Anatomical data from brachial plexus studies optimizes thoracic limb clinical and surgical treatments. This work can provide baseline data for future marsupial brachial plexus studies and fill gaps in the scarce literature.

The humerus is central for locomotion in turtles as quadrupedal animals. Osteological variation across testudine clades remains poorly documented. Here, we systematically describe the humerus anatomy for all major extant turtle clades based on 38 species representing the phylogenetic and ecological diversity of crown turtles. Three Late Triassic species of shelled stem turtles (Testudindata) are included to establish the plesiomorphic humerus morphology. Our work is based on 3D models, establishing a publicly available digital database. Previously defined terms for anatomical sides of the humerus (e.g., dorsal, ventral) are often not aligned with the respective body sides in turtles and other quadrupedal animals with sprawling gait. We propose alternative anatomical directional terms to simplify communication: radial and ulnar (the sides articulating with the radius/ulna), capitular (the side bearing the humeral head), and intertubercular (opposite to capitular surface). Turtle humeri show low morphological variation with exceptions concentrated in locomotory specialists. We propose 15 discrete characters to summarize osteological variation for future phylogenetic studies. Disparity analyses comparing non-shelled and shelled turtles indicate that the presence of the shell constrains humerus variation. Flippered aquatic turtles are released from this constraint and significantly increase overall disparity. Ontogenetic changes of turtle humeri are related to increased ossification and pronunciation of the proximal processes, the distal articulation areas, and the closure of the ectepicondylar groove to a foramen. Some turtle species retain juvenile features into adulthood and provide evidence for paedomorphic evolution. We review major changes of turtle humerus morphology throughout the evolution of its stem group.

We present the first description of inspiration-first air breaths in royal knifefish, Chitala blanci, a ray-finned fish known to use four-stroke air breaths. Four-stroke breaths are used by nearly all ray-finned fish species that use their gas bladder to breathe air and are the ancestral breath type of ray-finned fishes. Interestingly, one such species, Amia calva, is known to perform two distinct breath types. Amia use four-stroke breaths when they need more oxygen and performs inspiration-first breaths to restore buoyancy. We observed that C. blanci also performs inspiration-first breaths and tested whether the two breath types are performed for the same functions in C. blanci as they are in Amia. We recorded the frequency of each breath type when exposed to aquatic hypoxia and two conditions of oxygen availability. We found that C. blanci performed more four-stroke breaths (81% ± 15% of total breaths) than inspiration-first breaths when exposed to aerial normoxia but performed more inspiration-first breaths (72% ± 40%) than four-stroke breaths when exposed to aerial hyperoxia. These patterns match those described for Amia and indicate that C. blanci performs four-stroke breaths in response to oxygen depletion and performs inspiration-first breaths to maintain buoyancy. Few studies have examined the role of air-breathing in buoyancy regulation. Decreasing buoyancy, rather than oxygen availability, to stimulate air breaths may reveal that inspiration-first breaths are more common among fishes than we are aware. We consider this possibility and present a new hypothesis for the origin and early evolution of air breathing in vertebrates.

Mammary glands define mammals as a group, yet a comprehensive anatomical description of the mammary gland does not exist for almost any mammalian species. In humans, the anatomical and surgical literature provide conflicting and incomplete descriptions of the gross anatomy of the breast. We dissected 9 male and 15 female human body donors to clarify this gross anatomy. We found that, like other epidermally derived glands of the body, the mammary glandular tissue is constrained to a membrane-bound, central structure referred to as the corpus mammae in the surgical literature, and not dispersed throughout the breast as typically described in the anatomical literature. The major fasciae of the human anterior body wall, including the superficial fatty Camper's fascia and the deeper membranous Scarpa's fascia, both contribute to the structure of the breast. This anatomical arrangement suggests that, as the mammary gland invaginates posteriorly from the integument during embryological development, the mammary fat pad most likely derives from Camper's fascia, and growth of Scarpa's fascia around this fat pad forms the anterior and posterior lamellae of the breast pocket. Anteriorly, Scarpa's fascia becomes a double layer that creates the surface structure of the breast. Posteriorly, Scarpa's fascia forms a circummammary ligament that (1) stabilizes the breast against the thoracic wall and (2) is continuous with Scarpa's fascia on the rest of the anterior body wall. The suspensory ligaments of the breast represent the typical retinaculae cuti found consistently throughout the human body wall, and do not directly attach to the skin. Instead, these retinaculae attach to the anterior or posterior lamella of Scarpa's fascia.

Recent years have seen increasing scientific interest in whether neuron counts can act as correlates of diverse biological phenomena. Lately, Herculano-Houzel (2023) argued that fossil endocasts and comparative neurological data from extant sauropsids allow to reconstruct telencephalic neuron counts in Mesozoic dinosaurs and pterosaurs, which might act as proxies for behaviors and life history traits in these animals. According to this analysis, large theropods such as Tyrannosaurus rex were long-lived, exceptionally intelligent animals equipped with “macaque- or baboon-like cognition”, whereas sauropods and most ornithischian dinosaurs would have displayed significantly smaller brains and an ectothermic physiology. Besides challenging established views on Mesozoic dinosaur biology, these claims raise questions on whether neuron count estimates could benefit research on fossil animals in general. Here, we address these findings by revisiting Herculano-Houzel's (2023) work, identifying several crucial shortcomings regarding analysis and interpretation. We present revised estimates of encephalization and telencephalic neuron counts in dinosaurs, which we derive from phylogenetically informed modeling and an amended dataset of endocranial measurements. For large-bodied theropods in particular, we recover significantly lower neuron counts than previously proposed. Furthermore, we review the suitability of neurological variables such as neuron numbers and relative brain size to predict cognitive complexity, metabolic rate and life history traits in dinosaurs, coming to the conclusion that they are flawed proxies for these biological phenomena. Instead of relying on such neurological estimates when reconstructing Mesozoic dinosaur biology, we argue that integrative studies are needed to approach this complex subject.

Understanding squamate reproductive morphology is crucial for investigating ecological, behavioral, and evolutionary questions. Here, we describe the anatomy and histology of the male genital system of Ameiva ameiva from southeastern Brazil. Ten adult males were dissected to characterize genital macroscopy and collect fragments of the testes, gonadoducts, and kidneys for histological examination. We examined 10 transverse histological sections per individual and measured the epithelial height of the epididymis and ductus deferens. The male reproductive system consists of a pair of yellowish oval testes, the rete testis, ductuli efferentes, epididymis, ductus deferens, ampulla ductus deferentis, sexual segment of the kidney (SSK), cloaca, and hemipenis. The hemipenis is elongated, cylindrical, and unilobed, with a sulcate face and an asulcate face, which has continuous fringes throughout its length. Seminiferous tubules exhibited germ cells at various stages. The epididymis is wider and more coiled than the ductus deferens. The rete testis has a simple squamous epithelium with long stereocilia, while the narrower ductuli efferentes are lined by a simple ciliated cuboidal epithelium. The epididymal epithelium is pseudostratified columnar, with basal and ciliated principal cells, whereas the ductus deferens epithelium is pseudostratified to simple cuboidal. The epididymal epithelium is 1.5 times taller than the ductus deferens epithelium. Here, we observed the SSK present in the cortex of the ventral region of the kidneys due to the hypertrophy of the distal convoluted tubules, as well as its secretory activity. Our findings will contribute to future research into the evolution of squamate reproductive morphology.

Vascular endothelial growth factor (VEGF) family members are responsible for endothelial cells' growth, proliferation, migration, angiogenesis, vascular permeability, and differentiation and proliferation of non-endothelial cell types. VEGF and its receptors are found in mammalian lymphoid organs. The present study was conceived to determine (a) the presence and localization of angiogenic VEGF and its receptors (Fms-like tyrosine kinase 1 [Flt1/fms], fetal liver kinase 1 [Flk1]/kinase insert domain receptor [KDR], Fms-like tyrosine kinase 4 [Flt4]) and vascular endothelial growth inhibitor (VEGI) in the quail spleen; and (b) whether their expressions in the spleen components change during the post-hatching growth of the organ, using immunohistochemistry. Immunohistochemical stainings showed that VEGI, VEGF, and VEGF receptors were expressed in many components, including the vascular endothelial and smooth muscle cells, ellipsoid-associated cells (EACs), and immune cells, of quail spleen and that VEGF and its receptors' immunostaining intensity scores (ISs) varied depending on the post-hatching growth period, while VEGI-IS did not change. In addition, ISs of VEGI, VEGF, Flt1/fms, and Flt4 in EACs were weak to moderate, while flk1/KDR-IS in EACs adjacent to the capsule of Schweigger-Seidel sheaths (ellipsoids) was higher than other proteins, supports a more important and specific role of Flk1/KDR in the EAC function. These specific expressions of VEGI, VEGF, flt1/fms, flk1/KDR, and flt4 proteins in splenic cell types suggest their particular roles, in the functional development of splenic components and thus, are critical to post-hatching maturation of quail spleen. These findings indicate that the expression levels of VEGF, Flt1/fms, and Flt4, except Flk1/KDR, are low in the quail spleen, and only a few components of the spleen express VEGF, Flt1/fms, and Flt4 under normal conditions.