A Comparison of the Cortical Structure of the Bowhead Whale (Balaena mysticetus), a Basal Mysticete,with Other Cetaceans

Few studies exist of the bowhead whale brain and virtually nothing is known about its cortical cytoarchitecture or how it compares to other cetaceans. Bowhead whales are one of the least encephalized cetaceans and occupy a basal phylogenetic position among mysticetes. Therefore, the bowhead whale is an important specimen for understanding the evolutionary specializations of cetacean brains. Here, we present an overview of the structure and cytoarchitecture of the bowhead whale cerebral cortex gleaned from Nissl-stained sections and magnetic resonance imaging (MRI) in comparison with other mysticetes and odontocetes. In general, the cytoarchitecture of cetacean cortex is consistent in displaying a thin cortex, a thick, prominent layer I, and absence of a granular layer IV. Cell density, composition, and width of layers III, V, and VI vary among cortical regions, and cetacean cortex is cell-sparse relative to that of terrestrial mammals. Notably, all regions of the bowhead cortex possess high numbers of von Economo neurons and fork neurons, with the highest numbers observed at the apex of gyri. The bowhead whale is also distinctive in having a significantly reduced hippocampus that occupies a space below the corpus callosum within the lateral ventricle. Consistent with other balaenids, bowhead whales possess what appears to be a blunted temporal lobe, which is in contrast to the expansive temporal lobes that characterize most odontocetes. The present report demonstrates that many morphological and cytoarchitectural characteristics are conserved among cetaceans, while other features, such as a reduced temporal lobe, may characterize balaenids among mysticetes. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:745–760, 2019. © 2018 Wiley Periodicals, Inc.     

Slick,Stretchy Fascia Underlies the Sliding Tongue of Rorquals

The tongue of rorqual (balaenopterid) whales slides far down the throat into the expanded oral pouch as an enormous mouthful of water is engulfed during gulp feeding. As the tongue and adjacent oral floor expands and slides caudoventrally, it glides along a more superficial (outer) layer of ventral body wall musculature, just deep to the accordion-like ventral throat pleats. We hypothesize that this sliding movement of adjacent musculature is facilitated by a slick, stretchy layer of loose areolar connective tissue that binds the muscle fibers and reduces friction: fascia. Gross anatomical examination of the gular region of adult minke, fin, and humpback whales confirms the presence of a discrete, three-layered sublingual fascia interposed between adhering fasciae of the tongue and body wall. Histological analysis of this sublingual fascia reveals collagen and elastin fibers loosely organized in a random feltwork along with numerous fibroblasts in a watery extracellular matrix. Biomechanical testing of tissue samples in the field and laboratory, via machine-controlled or manual stretching, demonstrates expansion of the sublingual fascia and its three layers up to 250% beyond resting dimensions, with slightly more extension observed in anteroposterior (rather than mediolateral or oblique) stretching, and with the most superficial of the fascia's three layers. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:735–744, 2019. © 2018 Wiley Periodicals, Inc.     

Scaling of Anatomically Derived Maximal Bite Force in Primates

By combining muscle architectural data with biomechanical variables relating to the jaw, we produce anatomically derived maximum bite force estimations for 23 species of catarrhine and platyrrhine primates. We investigate how bite force scales across the sample as a whole (and within each parvorder) relative to two size proxies, body mass and cranial geometric mean, and the effect of diet upon bite force. Bite force is estimated at three representative bite points along the dental row: the first maxillary incisor, canine, and third-most mesial paracone. We modeled bite force by combining calculated physiological cross-sectional area of the jaw adductors from Hartstone-Rose et al. [Anat Rec 301 (2018) 311–324] with osteological measurements of lever- and load-arm lengths from the same specimens [Hartstone-Rose et al., Anat Rec 295 (2012) 1336–1351]. Bite force scales with positive allometry relative to cranial geometric mean across our entire sample and tends toward positive allometry relative to body mass. Bite force tends toward positive allometry within platyrrhines but scales isometrically within catarrhines. There was no statistically significant scaling difference with diet. Our findings imply an absence of a dietary signal in the scaling of bite force, a result that differs from the scaling of physiological cross-sectional area alone. That is, although previous studies have found a dietary signal in the muscle fiber architecture in these species, when these are combined with their leverages, that signal is undetectable. On the parvorder level, our data also demonstrate that the platyrrhine masticatory system appears more mechanically advantageous than that of catarrhines. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:2026–2035, 2020. © 2019 American Association for Anatomy     

Development and Assessment of Fully Automated and Globally Transitive Geometric Morphometric Methods,With Application to a Biological Comparative Dataset With High Interspecific Variation

Automated geometric morphometric methods are promising tools for shape analysis in comparative biology, improving researchers’ abilities to quantify variation extensively (by permitting more specimens to be analyzed) and intensively (by characterizing shapes with greater fidelity). Although use of these methods has increased, published automated methods have some notable limitations: pairwise correspondences are frequently inaccurate and pairwise mappings are not globally consistent (i.e., they lack transitivity across the full sample). Here, we reassess the accuracy of published automated methods—cPDist (Boyer et al. Proc Nat Acad Sci 108 ( 2011 ) 18221–18226) and auto3Dgm (Boyer et al.: Anat Rec 298 ( 2015b ) 249–276)—and evaluate several modifications to these methods. We show that a substantial percentage of alignments and pairwise maps between specimens of dissimilar geometries were inaccurate in the study of Boyer et al. (Proc Nat Acad Sci 108 ( 2011 ) 18221–18226), despite a taxonomically partitioned variance structure of continuous Procrustes distances. We show these inaccuracies are remedied using a globally informed methodology within a collection of shapes, rather than relying on pairwise comparisons (c.f. Boyer et al.: Anat Rec 298 ( 2015b ) 249–276). Unfortunately, while global information generally enhances maps between dissimilar objects, it can degrade the quality of correspondences between similar objects due to the accumulation of numerical error. We explore a number of approaches to mitigate this degradation, quantify their performance, and compare the generated pairwise maps (and the shape space characterized by these maps) to a “ground truth” obtained from landmarks manually collected by geometric morphometricians. Novel methods both improve the quality of the pairwise correspondences relative to cPDist and achieve a taxonomic distinctiveness comparable to auto3Dgm. Anat Rec, 301:636–658, 2018. © 2017 Wiley Periodicals, Inc.     

The First Record of Incidences of Ankylosis in Seven Triplefin Fishes (Pisces: Tripterygiidae) from New Zealand

Different cases of vertebral ankylosis were examined in seven tripterygiid species obtained from waters around New Zealand. The skeletal deformities observed are located in the caudal region of the vertebral column. Those occurred in Forsterygion nigripenne, Matanui bathytaton and in one specimen of Ruanoho whero were severe cases. The mechanism of the formation of vertebral ankylosis and the causes behind such anomaly were discussed. Further studies are needed to relate specific pollutants with the observed types of deformities. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:39–45, 2018. © 2017 Wiley Periodicals, Inc.     

Sensory Hairs in the Bowhead Whale,Balaena mysticetus (Cetacea,Mammalia)

We studied the histology and morphometrics of the hairs of bowhead whales (Balaena mysticetus). These whales are hairless except for two patches of more than 300 hairs on the rostral tip of the lower lip and chin, the rostral tip of the upper lip, and a bilateral row of approximately ten hairs caudal to the blowhole. Histological data indicate that hairs in all three of these areas are vibrissae: they show an outermost connective tissue capsule, a circumferential blood sinus system surrounding the hair shaft, and dense innervation to the follicle. Morphometric data were collected on hair diameters, epidermal recess diameters, hair follicle length, and external hair lengths. The main difference between the hairs in the different regions is that blowhole hairs have larger diameters than the hairs in the chin and rostrum regions. We speculate that the hair shaft thickness patterns in bowheads reflect functional specializations. Anat Rec, 298:1327–1335, 2015. © 2015 Wiley Periodicals, Inc.     

Experimentally Induced Biliary Atresia by Means of Rotavirus-Infection Is Directly Linked to Severe Damage of the Microvasculature in the Extrahepatic Bile Duct

Vascular damage has been reported to contribute to atresia formation in several diseases including biliary atresia. This study focused on the extrahepatic biliary plexus in experimental biliary atresia. Newborn BALB/cAnNCrl-pups were infected with rhesus rotavirus within 24 hr after birth to induce experimental biliary atresia. The extrahepatic biliary plexus was examined by confocal microscopy on whole-mount preparations, scored by three independent researchers, and further evaluated at the subcellular level with transmission electron microscopy. Imaging results revealed a progressive destruction of the extrahepatic biliary vascular plexus in the course of experimental biliary atresia induced by rotavirus infection. Endothelial cell damage was already visible as cell swelling and necrosis in the first days after infection and a damaged microcirculation that rapidly deteriorated with progression of obliterative cholangiopathy, was observed in the infected mice as early as 72 hr after birth. In experimental biliary atresia, the destruction of the extrahepatic biliary vascular plexus starts already in the first days postinfection and clearly precedes the morphological symptoms of atresia. The deterioration of the vascular bed architecture continues with disease progression. Therefore, we conclude that the (ultra)structural changes in the extrahepatic biliary microvasculature occurring before the visible onset of atresia has a predictive diagnostic value and this impairment in blood supply to the extrahepatic bile duct may be an important contributing factor to the pathogenesis of acquired biliary atresia. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:818–824, 2019. © 2018 Wiley Periodicals, Inc.     

RETRACTED: Physcion 8-O-β-Glucopyranoside Exerts Anti-Tumor Activity Against Non-Small Cell Lung Cancer by Targeting PPARγ

Lung cancer is one of the most common causes of cancer related mortality. The present study is designed to investigate whether a naturally occurring anthraquinone compound, physcion 8-O-β-glucopyranoside (PG) could exert anti-cancer activity against non-small cell lung cancer (NSCLC). Cell viability was determined by Cell Counting Kit-8 (CCK-8) assay. Cell cycle distribution and cell apoptosis were determined by flow cytometry. Expressions of marker proteins were assessed by western blot analysis. To examine the role of PPARγ (peroxisome proliferator-activated receptor γ) in PG-induced apoptosis and cell cycle arrest, PPARγ was knockdown using siRNA. In addition, a xenograft model was established to investigate the effect of PG in vivo. The results showed that PG markedly induced cell cycle arrest and apoptosis in human NSCLC cell lines A549 and H358. The anti-tumor effect of PG in NSCLC cells was mediated by upregulation of PPARγ. Besides, in NSCLC cell lines, the anti-cancer activity of PG was also examined in the xenograft mice model, which showed that PG could significantly reduce tumor burden and activate apoptotic signaling. Our results demonstrated that PG can be regarded as a candidate chemotherapeutic agent for lung cancer. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:785–793, 2019. © 2018 Wiley Periodicals, Inc.     

Effective Mechanical Advantage Allometry of Felid Elbow and Knee Extensors

Larger terrestrial mammals have generally been found to use more extended limb postures, a mechanism which maintains muscular requirements at larger sizes by improving the effective mechanical advantage (EMA) of limb musculature. Felids, however, have been documented to maintain joint angles across body sizes. If felid morphology scales isometrically, it would mean larger felids have relatively weaker muscles, compromising locomotor activities. Here, we examine the allometric relationships between the EMA of the elbow and knee extensors and body mass, finding that the EMA of the triceps brachii and quadriceps muscles scale with positive allometry. When species-specific joint angles were used rather than felid-average joint angles, EMA scales to body mass with more positive allometry. When the scaling of the muscle and ground reaction force (GRF) lever arms were investigated individually the allometric signal was lost; however, the muscle lever arms generally have allometric slope coefficients that are consistent with positive allometry, while the GRF lever arms demonstrate negative allometric slope coefficients. This suggests there are subtle alterations to limb morphology allowing different felid species to achieve an increased EMA via distinctive mechanisms. The quadriceps EMA was found to scale with sufficient positive allometry to compensate for increases in size without alteration in muscular anatomy; however, this is not the case for the triceps brachii EMA. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:775–784, 2019. © 2018 Wiley Periodicals, Inc.     

Natural development of dermal ectopic bone in the american alligator (Alligator mississippiensis) resembles heterotopic ossification disorders in humans

Heterotopic ossification (HO) occurs when soft tissues are inappropriately converted to bony tissue. Several human diseases result in HO with few reliable treatment options. Animal models that naturally produce dermal ectopic bone (i.e., osteoderms), such as crocodilians, have never been utilized as models for studying these disorders in humans. Here, a histological evaluation and staging criteria for osteoderm development is described for the first time in the American alligator (Alligator mississipiensis). Differential staining and immunohistochemistry of alligator scales depict a progressive change during development, where woven bone forms from the differentiated dermis. Bone formation proceeds via intramembranous ossification, which is initiated in part by endothelial cell precursors that undergo endothelial‐to‐mesenchymal transition and eventually acquire an osteoblast phenotype. As such, the development of osteoderms in the American alligator bears morphological and mechanistic similarities to HO in humans, presenting a potential model for future study of soft tissue mineralization pathologies and providing insight into the morphological and molecular development of osteoderms in other vertebrate lineages. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:56–76, 2018. © 2017 Wiley Periodicals, Inc.     

Morphometric Variations in the Skin Layers of Frogs: An Exploration Into Their Relation With Ecological Parameters in Leptodactylus (Anura,Leptodactylidae), With an Emphasis on the Eberth‐Kastschenko Layer

Leptodactylus is a genus of frogs known to live in diverse habitats and to show both aquatic and terrestrial breeding habits. We studied 21 species of Leptodactylus to explore whether skin structure specialization relates to habitats and habit variation. Morphometric analyses of the skin thickness revealed that phylogeny has a strong influence on variations in the thickness of the epidermis, stratum spongiosum, Eberth‐Kastschenko layer, and stratum compactum, while habitat and habits display no significant correlation. The optimization of the phylogenetic hypothesis suggested that a pattern of intermediate values for skin layer thickness are plesiomorphic for this group. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1895–1909, 2017. © 2017 Wiley Periodicals, Inc.     

An Analysis of Extraocular Muscle Forces in the Piked Dogfish (Squalus acanthias)

Vertebrates utilize six extraocular muscles that attach to a tough, protective sclera to rotate the eye. The goal of the study was to describe the maximum tetanic forces, as well as the torques produced by the six extraocular muscles of the piked dogfish Squalus acanthias to understand the forces exerted on the eye. The lateral rectus extraocular muscle of Squalus acanthias was determined to be parallel fibered with the muscle fibers bundled into discrete fascicles. The extraocular muscles attach to the sclera by muscular insertions. The total tensile forces generated by the extraocular muscles ranged from 1.18 N to 2.21 N. The torques of the extraocular muscles ranged from 0.39 N to 2.34 N. The torques were greatest in the principal direction of movement for each specific muscle. The lateral rectus produced the greatest total tensile force, as well as the greatest torque force component, while the medial rectus produced the second greatest. This is likely due to the constant rotational movement of the eye anteriorly and posteriorly to stabilize the visual image, as well as increase the effective visual field during swimming. Rotational forces in dimensions other than the primary direction of movement may contribute to motion in directions other than the principal direction during multi-muscle contraction that occurs in the vertebrate eye. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:837–844, 2019. © 2018 Wiley Periodicals, Inc.     

Adaptations of the Marsupial Newborn: Birth as an Extreme Environment

At birth a mammalian neonate enters an extreme environment compared to the intrauterine environment in which it has grown. This transition may be particularly extreme in marsupials because they are born at an exceedingly altricial state, after an exceptionally short gestation. Their stage of development must be considered embryonic by almost any criteria. Yet at this very early stage of development marsupials must travel to the teat, attach and suckle, and have basic functioning of all major physiological systems. In this article, we review the adaptations of the marsupial neonate for survival at an embryonic state, showing that the neonate exhibits a mosaic of accelerations and delays of various tissues and organs as well as several special adaptations to produce the functioning newborn. We then discuss the development of the craniofacial region, the body axis and limbs in order to detail some of the major changes to development leading to this uniquely configured neonate. We show that marsupial development arises out of a variety of heterochronies (changes in relative timing of events) and heterotopies (changes in location of specific developmental events) at the genetic, cellular and organ level. We argue that these data support hypotheses that many of the specific patterns seen in marsupial development arise from the basic constraint of embryonic energetic and tissue resources. Finally ideas on the evolutionary context of the marsupial developmental strategy are briefly reviewed. Anat Rec, 2019. © 2018 Wiley Periodicals, Inc. Anat Rec, 303:235–249, 2020. © 2018 American Association for Anatomy     

Designing multimedia instruction in anatomy: An evidence-based approach

This paper summarizes 10 research-based principles for how to design effective multimedia instruction in medical education involving anatomy. Clin. Anat. 32:2–11, 2019. © 2018 Wiley Periodicals, Inc.     

From Anomalous Arteries to Selective Brain Cooling: Parallel Evolution of the Artiodactyl Carotid Rete

Terrestrial artiodactyls (even-toed ungulates) inhabit some of the world's most extreme environments, including arid deserts and high elevations. As medium-to-large-bodied mammals, artiodactyls have a suite of specialized physiologies to facilitate occupation of regions unavailable to other large mammals. One such physiology is selective brain cooling, wherein reduction of brain temperature below core body temperature has been demonstrated to reduce evaporative water loss. This physiology is enabled by an arterial heat-exchanger called the carotid rete. The ubiquity of the carotid rete throughout the clade, as well as its evolutionary history, is currently uninvestigated. Here, I use osteological correlates to survey clade-wide presence and morphology of the carotid rete, prior to conducting a preliminary evolutionary analysis. Nearly all living artiodactyls possess a carotid rete and are capable of selective brain cooling; however, major arteries supplying the rete are derived from different embryonic aortic arches on a suborder-specific basis. Ancestral character estimation infers this pattern of variation to be the result of independent evolutionary processes, suggesting carotid rete homoplasy arising via parallelism. This is a surprising finding given the role this structure plays in driving a physiology that has been implicated in mitigating artiodactylan responses to extreme environmental conditions. Future studies should incorporate extinct species represented in the fossil record to better parse between parallel and convergent mechanisms, as well as to better understand the relationship between the carotid rete, selective brain cooling, and survivorship of climate perturbation. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 303:308–317, 2020. © 2018 American Association for Anatomy     

Evolution of Hindlimb Muscle Anatomy Across the Tetrapod Water-to-Land Transition,Including Comparisons With Forelimb Anatomy

Tetrapod limbs are a key innovation implicated in the evolutionary success of the clade. Although musculoskeletal evolution of the pectoral appendage across the fins-to-limbs transition is fairly well documented, that of the pelvic appendage is much less so. The skeletal elements of the pelvic appendage in some tetrapodomorph fish and the earliest tetrapods are relatively smaller and/or qualitatively less similar to those of crown tetrapods than those of the pectoral appendage. However, comparative and developmental works have suggested that the musculature of the tetrapod forelimb and hindlimb was initially very similar, constituting a “similarity bottleneck” at the fins-to-limbs transition. Here, we used extant phylogenetic bracketing and phylogenetic character optimization to reconstruct pelvic appendicular muscle anatomy in several key taxa spanning the fins-to-limbs and water-to-land transitions. Our results support the hypothesis that transformation of the pelvic appendages from fin-like to limb-like lagged behind that of the pectoral appendages. Compared to similar reconstructions of the pectoral appendages, the pelvic appendages of the earliest tetrapods had fewer muscles, particularly in the distal limb (shank). In addition, our results suggest that the first tetrapods had a greater number of muscle-muscle topological correspondences between the pectoral and pelvic appendages than tetrapodomorph fish had. However, ancestral crown-group tetrapods appear to have had an even greater number of similar muscles (both in terms of number and as a percentage of the total number of muscles), indicating that the main topological similarity bottleneck between the paired appendages may have occurred at the origin of the tetrapod crown group. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 303:218–234, 2020. © 2018 American Association for Anatomy     

Pedro Ramón y Cajal: The Legacy of a Neurohistologist,a Medical Doctor,and a Pathologist

The work of Santiago Ramón y Cajal is difficult to understand without knowing the personalities of Justo, his father, and his brother Pedro. His father practically forced the two brothers to study medicine. Thanks to that, Santiago was able to combine his artistic talent with histology and wonderfully describe cerebral architecture. Pedro was a faithful brother and above all a friend of Santiago, and they worked together for years. Pedro was able to demonstrate the theories of his brother in nonmammalian amniotes, concluding that the basic elements of the nervous system are common to these animals and he provided images that served Santiago to formulate the theory of dynamic polarization. Pedro, who decided to remain in the shadow of his brother, was a very complete doctor, pathologist and gynecologist, who made interesting contributions in all these fields and above all was a great humanist who left an important personal and scientific legacy. Anat Rec, 2019. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists. Anat Rec, 303:1189–1202, 2020. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.