Jaw-muscle fiber architecture and skull form facilitate relatively wide jaw gapes in male cercopithecoid monkeys.

In primates and other mammals, the capacity to generate a wide maximum jaw gape is an important performance variable related to both feeding and nonfeeding oral behaviors, such as canine gape display and clearing the canines for use as weapons during aggressive encounters. Across sexually dimorphic catarrhine primates, gape is significantly correlated with canine height and with musculoskeletal features that facilitate wide gapes. Given the importance of canine gape behaviors in males as part of intrasexual competition for females, functional relationships between gape, canine height, and musculoskeletal morphology can be predicted to differ between the sexes.

Concerns of osteopathic medical students during the COVID-19 pandemic.

Objectives: This study aims to quantify the areas of most concern in medical students in relation to their residency application in the setting of the COVID-19 pandemic and to identify risk factors for all that cause concern and specific areas of concern in a population with well-established high rates of anxiety at baseline. The COVID-19 pandemic introduced sweeping changes to medical education that had wide-ranging effects on medical students and their applications for medical residencies.

Methods: In August 2020, we utilized a cross-sectional study to quantify student's areas of concern related to residency application related to the COVID-19 pandemic.

Developmental milestones in captive Galago moholi.

Systems of the body develop in a modular manner. For example, neural development in primates is generally rapid, whereas dental development varies much more. In the present study, we examined development of the skull, teeth, and postcrania in a highly specialized leaping primate, Galago moholi.

The impact of measurement technique and sampling on estimates of skeletal muscle fibre architecture.

Skeletal muscle fibre architecture provides important insights into performance of vertebrate locomotor and feeding behaviours. Chemical digestion and in situ sectioning of muscle bellies along their lengths to expose fibres, fibre orientation and intramuscular tendon, are two classical methods for estimating architectural variables such as fibre length (L) and physiological cross-sectional area (PCSA). It has recently been proposed that L estimates are systematically shorter and hence less accurate using in situ sectioning.

Comparing age- and bone-related differences in collagen fiber orientation: A case study of bats and laboratory mice using quantitative polarized light microscopy.

As bones age in most mammals, they typically become more fragile. This state of bone fragility is often associated with more homogenous collagen fiber orientations (CFO). Unlike most mammals, bats maintain mechanically competent bone throughout their lifespans, but little is known of positional and age-related changes in CFO within wing bones.

Genetics of evolved load resistance in the skeletons of unusually large mice from Gough Island.

A primary function of the skeleton is to resist the loads imparted by body weight. Genetic analyses have identified genomic regions that contribute to differences in skeletal load resistance between laboratory strains of mice, but these studies are usually restricted to 1 or 2 bones and leave open the question of how load resistance evolves in natural populations. To address these challenges, we examined the genetics of bone structure using the largest wild house mice on record, which live on Gough Island (GI).

Trends in mandibular fractures in the USA: A 20-year retrospective analysis.

Background/aim: The mandible is one of the most fractured bones in the maxillofacial region. This study analyzes trends in mandibular fracture patterns, demographics, and mechanisms since the early 2000s.

Material And Methods: Mandibular fractures were reviewed from the 2007, 2011, and 2017 National Trauma Data Bank including 13,142, 17,057, and 20,391 patients by year, respectively.

A complex genetic architecture underlies mandibular evolution in big mice from Gough Island.

Some of the most compelling examples of morphological evolution come from island populations. Alterations in the size and shape of the mandible have been repeatedly observed in murid rodents following island colonization. Despite this pattern and the significance of the mandible for dietary adaptation, the genetic basis of island-mainland divergence in mandibular form remains uninvestigated.

Grit your teeth and chew your food: Implications of food material properties and abrasives for rates of dental microwear formation in laboratory (Primates).

Dental microwear analysis has been employed in studies of a wide range of modern and fossil animals, yielding insights into the biology/ecology of those taxa. Some researchers have suggested that dental microwear patterns ultimately relate back to the material properties of the foods being consumed, whereas others have suggested that, because exogenous grit is harder than organic materials in food, grit should have an overwhelming impact on dental microwear patterns. To shed light on this issue, laboratory-based feeding experiments were conducted on tufted capuchin monkeys [] with dental impressions taken before and after consumption of different artificial foods.

Anatomical and physiological variation of the hyoid musculature during swallowing in infant pigs.

The function of a muscle is impacted by its line of action, activity timing and contractile characteristics when active, all of which have the potential to vary within a behavior. One function of the hyoid musculature is to move the hyoid bone during swallowing, yet we have little insight into how their lines of action and contractile characteristics might change during a swallow. We used an infant pig model to quantify the contractile characteristics of four hyoid muscles during a swallow using synchronized electromyography, fluoromicrometry and high-speed biplanar videofluoroscopy.

Cranial synchondroses of primates at birth.

Cranial synchondroses are cartilaginous joints between basicranial bones or between basicranial bones and septal cartilage, and have been implicated as having a potential active role in determining craniofacial form. However, few studies have examined them histologically. Using histological and immunohistochemical methods, we examined all basicranial joints in serial sagittal sections of newborn heads from nine genera of primates (five anthropoids, four strepsirrhines).

Linking gene expression and phenotypic changes in the developmental and evolutionary origins of osteosclerosis in the ribs of bowhead whales (Balaena mysticetus).

Bowhead whales are among the longest-lived mammals with an extreme lifespan of about 211 years. During the first 25 years of their lives, rib bones increase in mineral density and the medulla transitions from compact to trabecular bone. Molecular drivers associated with these phenotypic changes in bone remain unknown.

Sauce it up: influence of condiment properties on oral processing behavior, bolus formation and sensory perception of solid foods.

Condiments are rarely consumed on their own. Although addition of condiments to carrier foods is known to affect oral processing behavior and sensory perception, an understanding of how different condiment properties impact oral processing behavior and sensory perception of solid carrier foods is lacking. This study aimed to understand the role of condiments varying in composition and/or rheological properties in bolus formation facilitation, and how they influence oral processing behavior and sensory perception of solid carrier foods.

What smells? Developing in-field methods to characterize the chemical composition of wild mammalian scent cues.

Olfactory cues play an important role in mammalian biology, but have been challenging to assess in the field. Current methods pose problematic issues with sample storage and transportation, limiting our ability to connect chemical variation in scents with relevant ecological and behavioral contexts. Real-time, in-field analysis portable gas chromatography-mass spectrometry (GC-MS) has the potential to overcome these issues, but with trade-offs of reduced sensitivity and compound mass range.

Getting Humans Off Monkeys' Backs: Using Primate Acclimation as a Guide for Habitat Management Efforts.

Wild primates face grave conservation challenges, with habitat loss and climate change projected to cause mass extinctions in the coming decades. As large-bodied Neotropical primates, mantled howling monkeys (Alouatta palliata) are predicted to fare poorly under climate change, yet are also known for their resilience in a variety of environments, including highly disturbed habitats. We utilized ecophysiology research on this species to determine the morphological, physiological, and behavioral mechanisms howlers employ to overcome ecological challenges.

Callitrichid responses to dead and dying infants: the effects of paternal bonding and cause of death.

Many primates show responses to dead infants, yet testing explanations for these behaviors has been difficult. Callitrichids present a unique opportunity to delineate between hypotheses, since unlike most species, male caretakers form closer social bonds with infants than mothers. Callitrichids are also known to commit infanticide, leaving obvious wounds that may enable them to more readily recognize death.

Masticatory Loading and Ossification of the Mandibular Symphysis during Anthropoid Origins.

An ossified or 'fused' mandibular symphysis characterizes the origins of the Anthropoidea, a primate suborder that includes humans. Longstanding debate about the adaptive significance of variation in this jaw joint centers on whether a bony symphysis is stronger than an unfused one spanned by cartilage and ligaments. To provide essential information regarding mechanical performance, intact adult symphyses from representative primates and scandentians were loaded ex vivo to simulate stresses during biting and chewing - dorsoventral (DV) shear and lateral transverse bending ('wishboning').

Mandibular symphyseal fusion in fossil primates: Insights from correlated patterns of jaw shape and masticatory function in living primates.

Objectives: Variation in primate masticatory form and function has been extensively researched through both morphological and experimental studies. As a result, symphyseal fusion in different primate clades has been linked to either the recruitment of vertically directed balancing-side muscle force, the timing and recruitment of transversely directed forces, or both. This study investigates the relationship between jaw muscle activity patterns and morphology in extant primates to make inferences about masticatory function in extinct primates, with implications for understanding the evolution of symphyseal fusion.

The dental microwear of hard-object feeding in laboratory Sapajus apella and its implications for dental microwear formation.

Objectives: This study seeks to determine if (a) consumption of hard food items or a mixture of food items leads to the formation of premolar or molar microwear in laboratory capuchin monkeys (Sapajus apella) in one feeding session and (b) rates of microwear formation are associated with the number of food items consumed.

Materials And Methods: Five adult male capuchins were used in two experiments, one where they were fed unshelled Brazil nuts, and the other where they were fed a mixture of food items. Dental impressions were taken before and after each feeding session.

Comparative dental anatomy in newborn primates: Cusp mineralization.

Previous descriptive work on deciduous dentition of primates has focused disproportionately on great apes and humans. To address this bias in the literature, we studied 131 subadult nonhominoid specimens (including 110 newborns) describing deciduous tooth morphology and assessing maximum hydroxyapatite density (MHD). All specimens were CT scanned at 70 kVp and reconstructed at 20.

Morphological and masticatory performance variation of mouth behavior groups.

Food texture preference and product acceptance are hypothesized to be influenced by mouth behavior. Recent work identified four mouth behavior (MB) groups that describe most consumers in the United States: Chewers, Crunchers, Smooshers, and Suckers. While these behavioral preferences are thought to play a significant role in food selection and purchasing decisions, it is unknown how closely they relate to body and oral cavity measures as well as masticatory apparatus performance.

The influence of masseter and temporalis sarcomere length operating ranges as determined by laser diffraction on architectural estimates of muscle force and excursion in macaques (Macaca fascicularis and Macaca mulatta).

Objective: Determine sarcomere length (L) operating ranges of the superficial masseter and temporalis in vitro in a macaque model and examine the impact of position-dependent variation on L and architectural estimates of muscle function (i.e., fiber length, PCSA) before and after L-normalization.

Masticatory Apparatus Performance and Functional Morphology in the Extremely Large Mice from Gough Island.

Since their arrival approximately 200 years ago, the house mice (Mus musculus) on Gough Island (GI) rapidly increased in size to become the largest wild house mice on record. Along with this extreme increase in body size, GI mice adopted a predatory diet, consuming significant quantities of seabird chicks and eggs. We studied this natural experiment to determine how evolution of extreme size and a novel diet impacted masticatory apparatus performance and functional morphology in these mice.

Monkey business: Collaborating to grow an ecological physiology of primates.

The lab and field provide differing approaches to studying primate biology. We outline the challenges and benefits of these approaches and demonstrate how collaboration can help bridge these perspectives to provide complementary insight into primate adaptive pathways. With this aim, our collaboration has made tangible insights into the ecological physiology of several primate species, and also yielded more subtle, intangible professional benefits.