Search

BackgroundIn recent years large bibliographic databases have made much of the published literature of biology available for searches. However, the capabilities of the search engines integrated into these databases for text-based bibliographic searches are limited. To enable searches that deliver the results expected by comparative anatomists, an underlying logical structure known as an ontology is required.Development and testing of the ontologyHere we present the Mammalian Feeding Muscle Ontology (MFMO), a multi-species ontology focused on anatomical structures that participate in feeding and other oral/pharyngeal behaviors. A unique feature of the MFMO is that a simple, computable, definition of each muscle, which includes its attachments and innervation, is true across mammals. This construction mirrors the logical foundation of comparative anatomy and permits searches using language familiar to biologists. Further, it provides a template for muscles that will be useful in extending any anatomy ontology. The MFMO is developed to support the Feeding Experiments End-User Database Project (FEED, https://feedexp.org/), a publicly-available, online repository for physiological data collected from in vivo studies of feeding (e.g., mastication, biting, swallowing) in mammals. Currently the MFMO is integrated into FEED and also into two literature-specific implementations of Textpresso, a text-mining system that facilitates powerful searches of a corpus of scientific publications. We evaluate the MFMO by asking questions that test the ability of the ontology to return appropriate answers (competency questions). We compare the results of queries of the MFMO to results from similar searches in PubMed and Google Scholar.Results and significanceOur tests demonstrate that the MFMO is competent to answer queries formed in the common language of comparative anatomy, but PubMed and Google Scholar are not. Overall, our results show that by incorporating anatomical ontologies into searches, an expanded and anatomically comprehensive set of results can be obtained. The broader scientific and publishing communities should consider taking up the challenge of semantically enabled search capabilities.

In studies of mammalian mastication, a possible relationship has been proposed between bilateral recruitment of jaw adductor muscle force during unilateral chewing and the degree of fusion of the mandibular symphysis. Specifically, species that have unfused, mobile mandibular symphyses tend to utilize lower levels of jaw adductor force on the balancing (nonchewing) than the working (chewing) side of the head, when compared to related species with fused symphyses. Here, we compare jaw adductor recruitment levels in two species of musteloid carnivoran: the carnivorous ferret (unfused symphysis), and the frugivorous kinkajou (fused symphysis). During forceful chewing, we observe that ferrets recruit far more working‐side muscle force than kinkajous, regardless of food toughness and that high working‐to‐balancing side ratios are the result of increased working‐side force, often coupled with reduced balancing‐side force. We propose that in carnivorans, high working‐to‐balancing side force ratios coupled with an unfused mandibular symphysis are necessary to rotate the hemimandible for precise unilateral occlusion of the carnassial teeth and to sustain laterally oriented force on the jaw to engage the carnassial teeth during shearing of tough foods. In contrast, the kinkajou's flattened cheekteeth permit less precise occlusion and require medially‐oriented forces for grinding, thus, a fused symphysis is mechanically beneficial. Research Highlights: Ferrets' (unfused mandibular symphyses) use of asymmetrical jaw muscle activity may optimi forces for carnassial shearing. Kinkajous' more nearly equal force may be facilitated by their fused symphysis and flat cheek teeth. [ABSTRACT FROM AUTHOR]

We examined masseter recruitment and firing patterns during chewing in four adult ring-tailed lemurs (Lemur catta), using electromyography (EMG). During chewing of tougher foods, the working-side superficial masseter tends to show, on average, 1.7 times more scaled EMG activity than the balancing-side superficial masseter. The working-side deep masseter exhibits, on average, 2.4 times the scaled EMG activity of the balancing-side deep masseter. The relatively larger activity in the working-side muscles suggests that ring-tailed lemurs recruit relatively less force from their balancing-side muscles during chewing. The superficial masseter working-to-balancing-side (W/B) ratio for lemurs overlaps with W/B ratios from anthropoid primates. In contrast, the lemur W/B ratio for the deep masseter is more similar to that of greater galagos, while both are significantly larger than W/B ratios of anthropoids. Because ring-tailed lemurs have unfused and hence presumably weaker symphyses, these data are consistent with the symphyseal fusion-muscle recruitment hypothesis stating that symphyseal fusion in anthropoids provides increased strength for resisting forces created by the balancing-side jaw muscles during chewing. Among the masseter muscles of ring-tailed lemurs, the working-side deep masseter peaks first on average, followed in succession by the balancing-side deep masseter, balancing-side superficial masseter, and finally the working-side superficial masseter. Ring-tailed lemurs are similar to greater galagos in that their balancing-side deep masseter peaks well before their working-side superficial masseter. We see the opposite pattern in anthropoids, where the balancing-side deep masseter peaks, on average, after the working-side superficial masseter. This late activity of the balancing-side deep masseter in anthropoids is linked to lateral-transverse bending, or wishboning, of their mandibular symphyses. Subsequently, the stresses incurred during wishboning are hypothesized to be a proximate reason for strengthening, and hence fusion, of the anthropoid symphysis. Thus, the absence of this muscle-firing pattern in ring-tailed lemurs with their weaker, unfused symphyses provides further correlational support for the symphyseal fusion late-acting balancing-side deep masseter hypothesis linking wishboning and symphyseal strengthening in anthropoids. The early peak activity of the working-side deep masseter in ring-tailed lemurs is unlike galagos and most similar to the pattern seen in macaques and baboons. We hypothesize that this early activity of the working-side deep masseter moves the lower jaw both laterally toward the working side and vertically upward, to position it for the upcoming power stroke. From an evolutionary perspective, the differences in peak firing times for the working-side deep masseter between ring-tailed lemurs and greater galagos indicate that deep masseter firing patterns are not conserved among strepsirrhines. KEY WORDS jaw adductors; chewing; electromyography; symphyseal fusion

It was proposed that the power stroke in primates has two distinct periods of occlusal contact, each with a characteristic motion of the mandibular molars relative to the maxillary molars. The two movements are called phase I and phase II, and they occur sequentially in that order (Kay and Hiiemae [1974] Am J. Phys. Anthropol. 40:227-256, Kay and Hiiemae [1974] Prosimian Biology, Pittsburgh: University of Pittsburgh Press, p. 501-530). Phase I movement is said to be associated with shearing along a series of crests, producing planar phase I facets and crushing on surfaces on the basins of the molars. Phase I terminates in centric occlusion. Phase II movement is said to be associated with grinding along the same surfaces that were used for crushing at the termination of phase I. Hylander et al. ([1987] Am J. Phys. Anthropol. 72:287-312; see also Hiiemae [1984] Food Acquisition and Processing, London: Academic Press, p. 257-281; Hylander and Crompton [1980] Am J. Phys. Anthropol. 52:239-251, [1986] Arch. Oral. Biol. 31:841-848) analyzed data on macaques and suggested that phase II movement may not be nearly as significant for food breakdown as phase I movement simply because, based on the magnitude of mandibular bone strain patterns, adductor muscle and occlusal forces are likely negligible during movement out of centric occlusion. Our goal is to better understand the functional significance of phase II movement within the broader context of masticatory kinematics during the power stroke. We analyze vertical and transverse mandibular motion and relative activity of the masseter and temporalis muscles during phase I and II movements in Papio anubis. We test whether significant muscle activity and, by inference, occlusal force occurs during phase II movement. We find that during phase II movement, there is negligible force developed in the superficial and deep masseter and the anterior and posterior temporalis muscles. Furthermore, mandibular movements are small during phase II compared to phase I. These results suggest that grinding during phase II movement is of minimal importance for food breakdown, and that most food breakdown on phase II facets occurs primarily at the end of phase I movement (i.e., crushing during phase I movement). We note, however, that depending on the orientation of phase I facets, significant grinding also occurs along phase I facets during phase I. KEY WORDS power stroke; jaw muscles; dentition

A study was conducted to understand how jaw-muscle activity varies with food mechanical properties, as well as the toughness and elastic modulus of the majority of foods used in experimental studies of the nonhuman primate masticatory apparatus. It showed that food toughness ranges from approximately 56.97 Jm(super -2) (apple pulp) to 4355.45 Jm(super -2) (prune pit), while the elastic modulus of the experimental foods ranges from 0.07 MPa for gummy bears to 346 MPa for popcorn kernels.

The major purpose of this study is to analyze anterior and posterior temporalis muscle force recruitment and firing patterns in various anthropoid and strepsirrhine primates. There are two specific goals for this project. First, we test the hypothesis that in addition to transversely directed muscle force, the evolution of symphyseal fusion in primates may also be linked to vertically directed balancing-side muscle force during chewing (Hylander et al. [2000] Am. J. Phys. Anthropol. 112:469-492). Second, we test the hypothesis of whether strepsirrhines retain the hypothesized primitive mammalian condition for the firing of the anterior temporalis, whereas anthropoids have the derived condition (Weijs [1994] Biomechanics of Feeding in Vertebrates; Berlin: Springer-Verlag, p. 282-320). Electromyographic (EMG) activities of the left and right anterior and posterior temporalis muscles were recorded and analyzed in baboons, macaques, owl monkeys, thick-tailed galagos, and ring-tailed lemurs. In addition, as we used the working-side superficial masseter as a reference muscle, we also recorded and analyzed EMG activity of the left and right superficial masseter in these primates. The data for the anterior temporalis provided no support for the hypothesis that symphyseal fusion in primates is linked to vertically directed jaw muscle forces during mastication. Thus, symphyseal fusion in primates is most likely mainly linked to the timing and recruitment of transversely directed forces from the balancing-side deep masseter (Hylander et al. [2000] Am. J. Phys. Anthropol. 112:469-492). In addition, our data demonstrate that the firing patterns for the working- and balancing-side anterior temporalis muscles are near identical in both strepsirrhines and anthropoids. Their working- and balancing-side anterior temporalis muscles fire asynchronously and reach peak activity during the power stroke. Similarly, their working- and balancing-side posterior temporalis muscles also fire asynchronously and reach peak activity during the power stroke. Compared to these strepsirrhines, however, the balancing-side posterior temporalis of anthropoids appears to have a relatively delayed firing pattern. Moreover, based on their smaller W/B ratios, anthropoids demonstrate a relative increase in muscle-force recruitment of the balancing-side posterior temporalis. This in turn suggests that anthropoids may emphasize the duration and magnitude of the power stroke during mastication. This hypothesis, however, requires additional testing. Furthermore, during the latter portion of the power stroke, the late activity of the balancing-side posterior temporalis of anthropoids apparently assists the balancing-side deep masseter in driving the working-side molars through the terminal portion of occlusion. Am J Phys Anthropol 128:35 56, 2005. KEY WORDS temporalis; electromyography; biomechanics; jaw-adductor muscle force; mastication; primates

In American law school classrooms, we have a phenomenon that I expect you experience here in Italy as well. The professor asks a question and the student attempts to avoid [...]

We examined masseter and temporalis recruitment and firing patterns during chewing in five male Belanger's treeshrews (Tupaia belangeri), using electromyography (EMG). During chewing, the working-side masseters tend to show almost three times more scaled EMG activity than the balancing-side masseters. Similarly, the working-side temporalis muscles have more than twice the scaled EMG activity of the balancing-side temporalis. The relatively higher activity in the working-side muscles suggests that treeshrews recruit less force from their balancing-side muscles during chewing. Most of the jaw-closing muscles in treeshrews can be sorted into an early-firing or late-firing group, based on occurrence of peak activity during the chewing cycle. Specifically, the first group of jaw-closing muscles to reach peak activity consists of the working-side anterior and posterior temporalis and the balancing-side superficial masseter. The balancing-side anterior and posterior temporalis and the working-side superficial masseter peak later in the power stroke. The working-side deep masseter peaks, on average, slightly before the working-side superficial masseter. The balancing-side deep masseter typically peaks early, at about the same time as the balancing-side superficial masseter. Thus, treeshrews are unlike nonhuman anthropoids that peak their working-side deep masseters early and their balancing-side deep masseters late in the power stroke. Because in anthropoids the late firing of the balancing-side deep masseter contributes to wishboning of the symphysis, the treeshrew EMG data suggest that treeshrews do not routinely wishbone their symphyses during chewing. Based on the treeshrew EMG data, we speculate that during chewing, primitive euprimates 1) recruited more force from the working-side jaw-closing muscles as compared to the balancing-side muscles, 2) fired an early group of jaw-closing muscles followed by a second group of muscles that peaked later in the power stroke, 3) did not fire their working-side deep masseter significantly earlier than their working-side superficial masseter, and 4) did not routinely fire their balancing-side deep masseter after the working-side superficial masseter. KEY WORDS jaw adductors; chewing; electromyography; primate origins

Many primates habitually feed on tree exudates such as gums and saps. Among these exudate feeders, Cebuella pygmaea, Callithrix spp., Phaner furcifer, and most likely Euoticus elegantulus elicit exudate flow by biting into trees with their anterior dentition. We define this behavior as gouging. Beyond the recent publication by Dumont ([1997] Am J Phys Anthropol 102:187-202), there have been few attempts to address whether any aspect of skull form in gouging primates relates to this specialized feeding behavior. However, many researchers have proposed that tree gouging results in larger bite force, larger internal skull loads, and larger jaw gapes in comparison to other chewing and biting behaviors. If true, then we might expect primate gougers to exhibit skull modifications that provide increased abilities to produce bite forces at the incisors, withstand loads in the skull, and/or generate large gapes for gouging. We develop 13 morphological predictions based on the expectation that gouging involves relatively large jaw forces and/or jaw gapes. We compare skull shapes for P. furcifer to five cheirogaleid taxa, E. elegantulus to six galagid species, and C. jacchus to two tamarin species, so as to assess whether gouging primates exhibit these predicted morphological shapes. Our results show little morphological evidence for increased force-production or load-resistance abilities in the skulls of these gouging primates. Conversely, these gougers tend to have skull shapes that are advantageous for creating large gapes. For example, all three gouging species have significantly lower condylar heights relative to the toothrow at a given mandibular length in comparison with closely related, nongouging taxa. Lowering the height of the condyle relative to the mandibular toothrow should reduce the stretching of the masseters and medial pterygoids during jaw opening, as well as position the mandibular incisors more anteriorly at wide jaw gapes. In other words, the lower incisors will follow a more vertical trajectory during both jaw opening and closing. We predict, based on these findings, that tree-gouging primates do not generate unusually large forces, but that they do use relatively large gapes during gouging. Of course, in vivo data on jaw forces and jaw gapes are required to reliably assess skull functions during gouging. KEY WORDS tree gouging; skull functional morphology; gape; forces; load resistance