Jaw Protrusion Research Articles

How to surprise a copepod: Strike kinematics reduce hydrodynamic disturbance and increase stealth of suction‐feeding fish

To capture prey with suction, fish must get sufficiently close to their prey to allow the suction flow to overwhelm the prey and draw it into the mouth. Both swimming towards the prey and suction flow create a hydrodynamic disturbance, which can elicit an escape response by the prey. Using particle image velocimetry, we measured flow speeds and derived fluid deformation rates at the location of the prey as bluegill sunfish fed. In front of the mouth, flows had a composite time‐dependent nature. First, the bow wave pushed water away from the fish, but when the mouth opened and suction commenced, flow reversed and water deformation rates increased rapidly. Our inferences indicate that, at the prey, the approaching bluegill is detected primarily based on its suction‐induced disturbance, rather than its bow wave‐induced disturbance. A comparison of suction‐induced disturbance with the signal produced by active suspension feeders indicated that fish are able to produce a more subtle disturbance than expected based on their flow speeds and mouth size alone. Jaw protrusion and the rapid opening of the mouth during the strike both help to minimize the signal available to the prey. We propose that the temporally quick strikes and high jaw protrusion that are seen in many zooplanktivorous teleosts represent adaptations that minimize the time available to prey for executing an escape response.

A Comparison of Wilson Sum Score and Combination Mallampati, Tiromental and Sternomental Distances for Predicting Difficult Intubation

Aim. Our goal is to find the best predicting test for difficult intubation. Material and method. The present study is a double-blind, prospective one that has been made during the period of 2006-2008. It was perfomed in the Department of Surgery by the Service Of Anesthesiology and Intensive Care of the University Hospital Center “Mother Theresa” in Tirana, Albania. There were 426 ASA 1-2 adult patients involved in this study all of whom underwent general anesthesia for urologic and general surgery. All of the following parameters, i. e Mallampati score, tyromental sternomental and interincisive distances, Delilkan test , lower jaw protrusion and length , neck movement, body masss index, morfology of teeths, use of gidewire and Wilson score, were recorded for every patient. The dates were presented in absolute and relative mode, calculating also OD ratio and confidence interval of 95%. For each parameter were calculated the following: sensitivity, specificity, predictive positive value, and predictive negative value, with a significant P value < 0.05 (5%). Results. The total number of patients with difficult intubations was 40. Thirty seven patients had difficult intubations and 3 patients failed to be intubated. The specificity of all parameters was low, nevertheless the sensitivity was high. The combination of the parameters improved the predictive model, thus increasing the specificity. Wilson score predicted 33 patients with difficult intubations instead of 9 patients predicted by the combination of Mallampati-sternomental- tiromental distances. Conclusion. We concluded that the Wilson score was the best predictive test. OPEN ACCESS

Effects of Jaw, Head and Body Positions on Upper Airway Dimensions and Maximum Forced Inspiratory Airflow

The purpose of this study was to evaluate jaw, head and body position-related changes in upper airway dimensions and maximum forced inspiratory airflow. Fifteen male normal subjects were selected and underwent magnetic resonance imaging in the following five different jaw, head and body positions: (1) supine with no jaw protrusion; (2) supine with jaw protrusion; (3) lateral decubitus with jaw protrusion; (4) supine, head rotation with jaw protrusion; (5) pronation, head rotation with jaw protrusion. The dimensional changes of the upper airway were measured according to the magnetic resonance images. To assess the changes in ventilation, the maximum forced inspiratory airflow was tested using a spirometer. This was accomplished with the subjects placed in the positions previously described. Data of airway dimensions and inspiratory velocity were reported using descriptive statistics. The results showed that upper airway dimensions and maximum forced inspiratory airflow changed by the changes of jaw, head and body positions. Jaw protrusion and head rotation could enlarge the upper airway dimensions and provided more maximum forced inspiratory airflow. These positions may prove beneficial for alleviating the symptoms of patients with obstructive sleep apnea syndrome.

Masticatory muscle activity during deliberately performed oral tasks

The aim of this study was to investigate masticatory muscle activity during deliberately performed functional and non-functional oral tasks. Electromyographic (EMG) surface activity was recorded unilaterally from the masseter, anterior temporalis and suprahyoid muscles in 11 subjects (5 men, 6 women; age = 34.6 ± 10.8 years), who were accurately instructed to perform 30 different oral tasks under computer guidance using task markers. Data were analyzed by descriptive statistics, repeated measurements analysis of variance (ANOVA) and hierarchical cluster analysis. The maximum EMG amplitude of the masseter and anterior temporalis muscles was more often found during hard chewing tasks than during maximum clenching tasks. The relative contribution of masseter and anterior temporalis changed across the tasks examined (F ⩾ 5.2; p ⩽ 0.001). The masseter muscle was significantly (p ⩽ 0.05) more active than the anterior temporalis muscle during tasks involving incisal biting, jaw protrusion, laterotrusion and jaw cupping, the difference being statistically significant (p ⩽ 0.05). The anterior temporalis muscle was significantly (p ⩽ 0.01) more active than the masseter muscle during tasks performed in intercuspal position, during tooth grinding, and during hard chewing on the working side. Based upon the relative contribution of the masseter, anterior temporalis, and suprahyoid muscles, the investigated oral tasks could be grouped into six separate clusters. The findings provided further insight into muscle- and task-specific EMG patterns during functional and non-functional oral behaviors.

Morphology of a picky eater: A novel mechanism underlies premaxillary protrusion and retraction within cyprinodontiforms

Upper jaw protrusion is hypothesized to improve feeding performance in teleost fishes by enhancing suction production and stealth of the feeding event. However, many cyprinodontiform fishes (mid-water feeders, such as mosquitofish, killifish, swordtails, mollies and pupfish) use upper jaw protrusion for “picking” prey out of the water column or off the substrate; this feeding mode may require improved jaw dexterity, but does not necessarily require increased stealth and/or suction production. We describe functional aspects of the bones, muscles and ligaments of the anterior jaws in three cyprinodontiform genera: Fundulus (Fundulidae), Gambusia and Poecilia (Poeciliidae). All three genera possess a premaxillomandibular ligament that connects the premaxilla of the upper jaw to the mandible. The architecture of this ligament is markedly different from the upper–lower jaw connections previously described for basal atherinomorphs or other teleosts, and this loose ligamentous connection allows for more pronounced premaxillary protrusion in this group relative to closely related outgroup taxa. Within poeciliids, a novel insertion of the second division of the adductor mandibulae (A2) onto the premaxilla has also evolved, which allows this jaw adductor to actively retract the premaxilla during mouth closing. This movement is in contrast with most other teleosts, where the upper jaw is retracted passively via pressure applied by the adduction of the lower jaw. We postulate that this mechanism of premaxillary protrusion mediates the cyprinodontiforms’ ability to selectively pick specific food items from the water column, surface or bottom, as a picking-based feeding mechanism requires controlled and coordinated “forceps-like” movements of the upper and lower jaws. This mechanism is further refined in some poeciliids, where direct muscular control of the premaxillae may facilitate picking and/or scraping material from the substrate.

Jaw protrusion enhances forces exerted on prey by suction feeding fishes

The ability to protrude the jaws during prey capture is a hallmark of teleost fishes, widely recognized as one of the most significant innovations in their diverse and mechanically complex skull. An elaborated jaw protrusion mechanism has independently evolved multiple times in bony fishes, and is a conspicuous feature in several of their most spectacular radiations, ultimately being found in about half of the approximately 30000 living species. Variation in jaw protrusion distance and speed is thought to have facilitated the remarkable trophic diversity found across fish groups, although the mechanical consequences of jaw protrusion for aquatic feeding performance remain unclear. Using a hydrodynamic approach, we show that rapid protrusion of the jaws towards the prey, coupled with the spatial pattern of the flow in front of the mouth, accelerates the water around the prey. Jaw protrusion provides an independent source of acceleration from that induced by the unsteady flow at the mouth aperture, increasing by up to 35% the total force exerted on attached, escaping and free-floating passive prey. Despite initiating the strike further away, fishes can increase peak force on their prey by protruding their jaws towards it, compared with a 'non-protruding' state, where the distance to prey remains constant throughout the strike. The force requirements for capturing aquatic prey might have served as a selective factor for the evolution of jaw protrusion in modern fishes.

Coordinated mechanics of feeding, swimming, and eye movements in Tautoga onitis, and implications for the evolution of trophic strategies in fishes

Fish feeding behavior results from successful coordination of the fins, jaws, and sensory systems, and the organization of this behavior may affect the fish’s foraging abilities and trophic ecology. Using quantitative kinematic methods, movements of the jaws, fins and eyes of Tautoga onitis (Teleostei: Labridae) were analyzed during feeding events. Tautog feeding events consisted of three phases: approach, strike, and recovery, each defined by a combination of kinematic events. The approach was characterized by changes in fin movements and in body position, with the eyes directed forward at the food item. The strike began with the onset of jaw opening and protrusion, then cranial elevation, with the eyes no longer looking at the food item. The end of the strike and the beginning of the recovery involved a braking maneuver with the pectoral fins; the fish turns and swims away from the original food location item after prey capture. The coordination performance variables of tautog were quantitatively compared to published data from closely related cheiline wrasses and parrotfishes, which represent different feeding ecologies within a monophyletic assemblage. Fishes feeding on molluscs and benthic invertebrates (Cheilinus fasciatus and Tautoga onitis) represented an intermediate coordination condition, with herbivores (the parrotfishes, Scarus quoyi and Sparisoma radians) at one extreme, and fishes feeding on elusive prey (Epibulus insidiator and Oxycheilinus digrammus) at the other extreme. The analysis suggests that the biomechanical demands of coordination for feeding on benthic invertebrates may represent a generalized, and perhaps ancestral behavior in the wrasses, whereas more specialized trophic niches have evolved divergent, more specialized demands. Examining the movement and coordination of the jaws, fins, and eyes during fish feeding provides a detailed mechanistic basis for behavior, and comparison of coordination patterns during feeding among different taxa can measure how these trophic strategies differ. Understanding the evolution of feeding ecologies in these demersal fishes may have implications for understanding their role within their shallow water reef community.

Tooth reorientation affects tooth function during prey processing and tooth ontogeny in the lesser electric ray, Narcine brasiliensis

The dental anatomy of elasmobranch fishes (sharks, rays and relatives) creates a functional system that is more dynamic than that of mammalian dentition. Continuous dental replacement (where new teeth are moved rostrally to replace older ones) and indirect fibrous attachment of the dentition to the jaw allow teeth to reorient relative to the jaw over both long- and short-term scales, respectively. In this study, we examine the processing behavior and dental anatomy of the lesser electric ray Narcine brasiliensis (Ölfers, 1831) to illustrate that the freedom of movement of elasmobranch dentition allows a functional flexibility that can be important for complex prey processing behaviors. From static manipulations of dissected jaws and observations of feeding events in live animals, we show that the teeth rotate during jaw protrusion, resulting in a secondary grasping mechanism that likely serves to hold prey while the buccal cavity is flushed free of sediment. The function of teeth is not always readily apparent from morphology; in addition to short-term reorientation, the long-term dental reorientation during replacement allows a given tooth to serve multiple functions during tooth ontogeny. Unlike teeth inside the mouth, the cusps of external teeth (on the portion of the tooth pad that extends past the occlusal plane) lay flat, such that the labial faces act as a functional battering surface, protecting the jaws during prey excavation.

Diversification of coordination patterns during feeding behaviour in cheiline wrasses

Successful fish feeding often requires the coordination of several complex motor and sensory systems to ensure that food is accurately detected, approached, acquired, and consumed. In the present study, we address feeding behaviour as a coordinated set of multiple, facultatively independent, anatomical systems. We sought to determine whether the patterns of interaction between trophic, locomotor, and oculomotor systems are associated with changes in morphology and ecology within a closely-related, but trophically divergent, group of fishes. We present a quantitative kinematic analysis of skull motion, locomotor behaviour, and oculomotor responses during feeding to assess coordination in three functional systems directly involved in feeding. We use coordination profiles to depict the feeding behaviours of three carnivorous coral reef fishes of the tribe Cheilinini in the family Labridae (the wrasses): Cheilinus fasciatus (a slow-swimming predator of benthic invertebrates), Epibulus insidiator (a slow-stalking predator with extraordinary jaw protrusion), and Oxycheilinus digrammus (a fast-attack predator). Differences were detected in several variables relating to jaw, body, fin, and eye movements. Overall patterns of coordination were more similar between E. insidiator and O. digrammus, which are capable of capturing elusive prey, than between C. fasciatus and E. insidiator, which are the two most closely-related species among the three. Evidence for the evolution of coordination patterns among cheiline fishes suggests that the sensory-motor systems involved in processing stimuli and coordinating a physical response during feeding have changed considerably, even among closely-related species. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 93, 289–308. ADDITIONAL KEYWORDS: biomechanics – Cheilinini – coral reef fish – functional morphology – kinematics – Labridae – swimming – vision.

Vocal tract and register changes analysed by real-time MRI in male professional singers—a pilot study

Changes of vocal tract shape accompanying changes of vocal register and pitch in singing have remained an unclear field. Dynamic real-time magnetic resonance imaging (MRI) was applied to two professional classical singers (a tenor and a baritone) in this pilot study. The singers sang ascending scales from B3 to G#4 on the vowel /a/, keeping the modal register throughout or shifting to falsetto register for the highest pitches. The results show that these singers made few and minor modifications of vocal tract shape when they changed from modal to falsetto and some clear modifications when they kept the register. In this case the baritone increased his tongue dorsum height, widened his jaw opening, and decreased his jaw protrusion, while the tenor merely lifted his uvula. The method used seems promising and should be applied to a greater number of singer subjects in the future.

The long-term effect of craniotomy on temporalis muscle function

The objective of this study was to evaluate jaw movements and the masticatory muscle in patients who underwent craniotomy for treatment of cerebral aneurysm. Descriptive study. There were 71 patients evaluated between 4 and 6 months after craniotomy, by means of a systematized approach. Their mean age was 45.3 years. Thirty-four (47.9%) patients complained of headache during dental evaluation. Twenty (28.2%) patients reported pain during normal jaw movements. There was a correlation between pain complaints and jaw movements during dental examinations (P = .03). Patients with postcraniotomy headache had more masticatory muscle tenderness on palpation than those without post-craniotomy headache (P < .02). Jaw protrusion was worse than the reference values (P < .01). Headache was the complaint in 47.9% of the sample. Jaw movement was statistically a pain-precipitating factor. Patients who suffered from postcraniotomy headache had more masticatory muscle tenderness. There were functional jaw limitations.

Incidence and Predictors of Difficult and Impossible Mask Ventilation

Mask ventilation is an essential element of airway management that has rarely been studied as the primary outcome. The authors sought to determine the incidence and predictors of difficult and impossible mask ventilation. A four-point scale to grade difficulty in performing mask ventilation (MV) is used at the authors' institution. They used a prospective, observational study to identify cases of grade 3 MV (inadequate, unstable, or requiring two providers), grade 4 MV (impossible to ventilate), and difficult intubation. Univariate and multivariate analyses of a variety of patient history and physical examination characteristics were used to establish risk factors for grade 3 and 4 MV. During a 24-month period, 22,660 attempts at MV were recorded. 313 cases (1.4%) of grade 3 MV, 37 cases (0.16%) of grade 4 MV, and 84 cases (0.37%) of grade 3 or 4 MV and difficult intubation were observed. Body mass index of 30 kg/m or greater, a beard, Mallampati classification III or IV, age of 57 yr or older, severely limited jaw protrusion, and snoring were identified as independent predictors for grade 3 MV. Snoring and thyromental distance of less than 6 cm were independent predictors for grade 4 MV. Limited or severely limited mandibular protrusion, abnormal neck anatomy, sleep apnea, snoring, and body mass index of 30 kg/m or greater were independent predictors of grade 3 or 4 MV and difficult intubation. The authors observed the incidence of grade 3 MV to be 1.4%, similar to studies with the same definition of difficult MV. Presence of a beard is the only easily modifiable independent risk factor for difficult MV. The mandibular protrusion test may be an essential element of the airway examination.

MICRO- AND MACROEVOLUTIONARY DECOUPLING OF CICHLID JAWS: A TEST OF LIEM'S KEY INNOVATION HYPOTHESIS

The extent to which elements of functional systems can change independently (modularity) likely influences the diversification of lineages. Major innovations in organismal design, like the pharyngeal jaw in cichlid fishes, may be key to a group's success when they relax constraints on diversification by increasing phenotypic modularity. In cichlid fishes, pharyngeal jaw modifications that enhanced the ability to breakdown prey may have freed their oral jaws from serving their ancestral dual role as a site of both prey capture and prey processing. This functional decoupling that allowed the oral jaws to become devoted solely to prey capture has been hypothesized to have permitted the two sets of cichlid jaws to evolve independently. We tested the hypothesis that oral and pharyngeal jaw mechanics are evolutionarily decoupled both within and among Neotropical Heroine cichlids. In the trophically polymorphic species Herichthys minckleyi, molariforms that exhibit enlarged molarlike pharyngeal jaw teeth were found to have approximately 400% greater lower jaw mass compared to H. minckleyi with the alternative papilliform pharyngeal morphology. However, oral jaw gape, lower jaw velocity ratios, anterior jaw linkage mechanics, and jaw protrusion did not differ between the morphotypes. In 40 other Heroine species, there was a weak correlation between oral jaw mechanics and pharyngeal jaw mass when phylogenetic history was ignored. Yet, after expansion of the cytochrome b phylogeny for Heroines, change in oral jaw mechanics was found to be independent of evolutionary change in pharyngeal jaw mass based on independent contrasts. Evolutionary decoupling of oral and pharyngeal jaw mechanics has likely played a critical role in the unparalleled trophic diversification of cichlid fishes.

Prey capture behavior and kinematics of the Atlantic cownose ray, Rhinoptera bonasus

The structurally reinforced jaws of the cownose ray, Rhinoptera bonasus testify to this species’ durophagous diet of mollusks, but seem ill-suited to the behaviors necessary for excavating such prey. This study explores this discordance by investigating the prey excavation and capture kinematics of R. bonasus. Based on the basal suction feeding mechanism in this group of fishes, we hypothesized a hydraulic method of excavation. As expected, prey capture kinematics of R. bonasus show marked differences relative to other elasmobranchs, relating to prey excavation and use of the cephalic lobes (modified anterior pectoral fin extensions unique to derived myliobatiform rays). Prey are excavated by repeated opening and closing of the jaws to fluidize surrounding sand. The food item is then enclosed laterally by the depressed cephalic lobes, which transport it toward the mouth for ingestion by inertial suction. Unlike in most sharks, upper jaw protrusion and mandibular depression are simultaneous. During food capture, the ray's spiracle, mouth, and gill slit movements are timed such that water enters only the mouth (e.g., the spiracle closes prior to prey capture and reopens immediately following). Indigestible parts are then hydraulically winnowed from edible prey portions, by mouth movements similar to those used in excavation, and ejected through the mouth. The unique sensory/manipulatory capabilities of the cephalic lobes, as well as the cownose ray's hydraulic excavation/winnowing behaviors and suction feeding, make this species an effective benthic predator, despite its epibenthic lifestyle.

Assessing the laryngeal view by conventional laryngoscopy after awake fibreoptic tracheal intubation

A male patient who presented for surgery for vocal cord tumour was assessed in the pre-operative anaesthesia clinic. He had previously undergone C 2–4 cervical laminectomy. A difficult airway was predicted [1] as neck extension and jaw protrusion were very limited, he had a bull neck, was overweight and was Mallampati grade 3 [2]. His trachea was intubated using an awake fibreoptic technique, which proved difficult due to the laryngeal tumour. Conventional laryngoscopy was performed after the patient was anaesthetised. Minimal leverage with a size four Macintosh laryngoscope blade brought the larynx into full view, providing a Grade 1 view of the larynx [3]. This case highlights the importance of performing laryngoscopy by the conventional technique under general anaesthesia, after tracheal intubation using an awake fibreoptic technique. The view provided by conventional laryngoscopy can be graded and the ease or difficulty of subsequent attempts at intubation can therefore be predicted. In this case, it was reassuring to know that in the unlikely event of urgent re-intubation being required postoperatively, it would probably be achieved with ease using the conventional method. If this patient were to require anaesthesia in future, awake fibreoptic intubation would probably still be the best option, as airway maintenance using a facemask and airway might prove difficult. Possible distortion of the anatomy of the airway by radiotherapy would be further reason to proceed with an awake fibreoptic technique.

Videoendoscopic surgery for inaccessible glottic lesions

Lesions in the anterior segment of the vocal fold are sometimes difficult to access by means of conventional suspension microlaryngoscopy under general anaesthesia because of anatomical factors such as short, stout and inflexible necks, reduced jaw protrusion, and long incisors. Various techniques have recently been proposed for the management of inaccessible glottic lesions, most of which are performed under general anaesthesia. The use of flexible videoendoscopic surgery under topical anaesthesia in two cases of anterior glottic lesions that could not be treated by means of conventional suspension laryngoscopy is described. Case report. A flexible videobronchoscope with an instrument channel was inserted transnasally on an out-patient basis. While the examiner carried out the endoscopy, an assistant maneuvered the biopsy forceps through the instrument channel, and removed the lesion. Both patients underwent successful removal of an anterior glottic polyp, and the one-year follow-up evaluation revealed normal anatomy of the vocal folds and normal vocal function. Flexible videoendoscopic surgery under topical anaesthesia is a safe, simple and minimally invasive procedure that can be considered as an alternative to traditional endoscopic surgery for inaccessible anterior glottic lesions.

Coordination of feeding, locomotor and visual systems in parrotfishes(Teleostei: Labridae)

Fishes require complex coordinated motions of the jaws, body and fins during feeding in order to successfully execute the strike or bite and then move away from the predation site. In conjunction with locomotor systems, sensory modalities guide coordinated feeding behavior, with vision playing an important role in many fishes. Although often studied separately, the locomotor, feeding and visual systems have not previously been examined together during fish feeding. To explore feeding coordination, we examined the kinematics of feeding behavior in two species of herbivorous parrotfish, Sparisoma radians and Scarus quoyi, which exhibit different single bite and repetitive bite strategies. Kinematic data on pectoral fin movements and body position show distinctive differences in strategies for the approach and post-strike motion between these species. Sparisoma and Scarus exhibited significant differences in the magnitude of jaw protrusion, time to maximum jaw protrusion, cranial elevation, and order of events in the feeding sequence. Oculomotor data show that both species orient the pupil forward and downward directed at the site of jaw contact until 100 ms before the bite, at which point the visual field is rotated laterally. Combinations of kinematic variables show repeated patterns of synchrony (onset and duration) for the approach to the food (distance, velocity, eye movement), prey capture (eye movement, jaw movement, fin movement) and post-capture maneuvering (fin movement, distance). Kinematic analyses of multiple functional systems reveal coordination mechanisms for detecting and approaching prey and executing the rapid opening and closing of the jaws during acquisition of food. Comparison of the coordination of feeding, swimming and sensory systems among fish species can elucidate alternative coordination strategies involved in herbivory in coral reef fishes.

FEEDING FRENZY

As any diver knows, hungry fish roaming the oceans display an astonishing array of ways to fill their stomachs. `How can we explain the tremendous variation we see in the oceans?' Aaron Rice at the University of Chicago wondered. He decided to take a closer look at the dining habits of two vegetarian parrotfish species, the bucktooth parrotfish (Sparisoma radians) and Quoy's parrotfish (Scarus quoyi). Working with Mark Westneat, Rice investigated how parrotfish coordinate the movements of their jaws, fins and eyes as they munch on their dinners(p. 3503).We know a lot about visual, locomotor and feeding systems in isolation,Rice explains, but a fish really needs to coordinate all three systems to ensure that it doesn't go hungry. `You need jaws to eat your food,' Rice says,`but a set of jaws can't get to food on its own.' To understand how a fish feeds, we need to understand how its jaws, fins and eyes operate in relation to each other.So Rice and Westneat set out to study how parrotfish coordinate these systems.Luckily, parrotfish aren't too fussy about eating in the lab. Bucktooth parrotfish found the small lettuce pieces Rice anchored to the bottom of their tanks a tasty enough substitute for their usual fare of sea grasses. And Quoy's parrotfish happily feasted on algae that Rice spread onto a coral skeleton dinner plate, as they are accustomed to in the ocean.Satisfied that the fish would eat in the lab, Rice and Westneat prepared to film them. But they hadn't counted on parrotfishes' bashful nature. The fish were `perpetually nervous', Rice recalls, especially with bright lights and the large eye of a high-speed digital camera trained on them. It took Rice months to coax the fish to eat in front of the camera. When they finally had some good footage, Rice traced the exact movements of each fish's jaws, fins and eyes as it lunged towards its meal by plotting 19 landmarks onto a frame of the video and meticulously recording the landmarks' positions in successive frames.What Rice and Westneat found surprised them. Despite both being herbivores,the two species had quite different coordination patterns. Quoy's parrotfish showed much earlier cranial elevation and a lot more jaw protrusion as they approached their food than bucktooth parrotfish did. The pair suspects that these differences reflect the algae-munching habit of Quoy's parrotfish;scraping algae off coral may require more force than grazing on sea grass, and perhaps these differences help Quoy's parrotfish generate a more powerful bite. But they also spotted similarities; both species peered down at their food as they approached it, and glanced upwards just before taking a bite. Rice isn't sure why they do this, but it might be to spot lurking predators. Both species also braked sharply just before reaching their mouthful. This makes a lot of sense for Quoy's parrotfish; if your head is on a collision course with an unforgiving lump of coral, you'd better make sure that you slam on the brakes fast enough to avoid a concussion.The complex feeding kinematics that Rice and Westneat describe for these herbivores illustrate how important it is to consider both what an animal sees and how it moves. `The future of feeding ecology lies in understanding how these different systems operate together', Rice concludes.

Analysis of the bite force and mechanical design of the feeding mechanism of the durophagous horn shark Heterodontus francisci

Three-dimensional static equilibrium analysis of the forces generated by the jaw musculature of the horn shark Heterodontus francisci was used to theoretically estimate the maximum force distributions and loadings on its jaws and suspensorium during biting. Theoretical maximum bite force was then compared with bite forces measured (1) voluntarily in situ, (2) in restrained animals and (3) during electrical stimulation of the jaw adductor musculature of anesthetized sharks. Maximum theoretical bite force ranged from 128 N at the anteriormost cuspidate teeth to 338 N at the posteriormost molariform teeth. The hyomandibula, which connects the posterior margin of the jaws to the base of the chondrocranium, is loaded in tension during biting. Conversely, the ethmoidal articulation between the palatal region of the upper jaw and the chondrocranium is loaded in compression, even during upper jaw protrusion, because H. francisci's upper jaw does not disarticulate from the chondrocranium during prey capture. Maximum in situ bite force averaged 95 N for free-swimming H. francisci, with a maximum of 133 N. Time to maximum force averaged 322 ms and was significantly longer than time away from maximum force (212 ms). Bite force measurements from restrained individuals (187 N) were significantly greater than those from free-swimming individuals (95 N) but were equivalent to those from both theoretical (128 N) and electrically stimulated measurements (132 N). The mean mass-specific bite of H. francisci was greater than that of many other vertebrates and second highest of the cartilaginous fishes that have been studied. Measuring bite force on restrained sharks appears to be the best indicator of maximum bite force. The large bite forces and robust molariform dentition of H. francisci correspond to its consumption of hard prey.

Inter‐observer agreement of tests used for prediction of difficult laryngoscopy/tracheal intubation

Guidelines recommend pre-operative airway evaluation for the prediction of airway management difficulties. Combining tests for evaluation increases the accuracy of the assessment. One model including seven parameters transformed into a simplified airway risk index (SARI) has been proven to be valid. We determined the inter-observer agreement of the specific test combinations included in SARI as well as of the total score. Four observers assessed 136 patients, 120 without and 16 with a difficult airway history. Two residents and two specialists in anaesthesia performed the airway assessment consisting of the measurement of the mouth opening, the thyromental distance (TMD), the ability to protrude the mandible and an evaluation of the Mallampati class and head and neck mobility. Body weight was also recorded. Inter-observer agreement between specialists and residents, separately, was analysed using kappa statistics and Spearman's correlation analysis and the limits of agreement were evaluated using the 95% confidence interval. The agreement between pairs of assessors was also evaluated. The inter-observer agreement was good to excellent for both specialists and residents when measuring mouth opening (Spearman's correlation coefficient R=0.88-0.97) and the horizontal distance between the upper and lower incisors during jaw protrusion (R=0.56-0.97). The Mallampati classification assessment demonstrated satisfactory to complete inter-observer agreement (kappa=0.41-1). The assessment of TMD and neck mobility showed considerable discrepancies between observers. We demonstrated good inter-observer agreement using three tests from SARI and recommend the Mallampati classification, mouth opening and ability of jaw protrusion for pre-operative airway evaluation. A simplification of the assessment of TMD and neck mobility is warranted.