Hard Food Research Articles

Eel heads shaped by what they eat

Arriving at the mouths of northern Europe's cold rivers, minute eel larvae are on the verge of a major life transition. Jens De Meyer from Ghent University, Belgium, explains that when the tiny creatures leave the sea, they transform into transparent glass eels ready to embark on the tough journey upstream, where they spend the next 3–12 years and develop into sub-adult yellow eels. However, by the time they are fully grown and ready to begin the gruelling return journey to the Sargasso Sea, some of the eels have developed long narrow heads, while others have broad heads. ‘It is very interesting to find out how and when this dimorphism develops during the eels’ life cycle', says De Meyer. Speculating that the animals' head shapes could be influenced by their diet, De Meyer and Joachim Christiaens headed to sluice gates at the mouth of the Leopold Canal in Belgium to capture glass eels in order to find out how diet affects the animals' heads.Dividing the eels into three groups, the duo put each on a strict diet; one received hard food, the second had a soft diet and the third group received a mixture of the two. ‘Selecting the diet was the most difficult part’, recalls De Meyer, explaining that it had to be varied enough to give the animals on the hard diet a good workout whereas the eels on the soft diet would consume the same nutrients while having an easier time. After searching the literature, De Meyer and Dominique Adriaens selected several species for the animals to dine on: ‘Then we observed their feeding behaviour’, De Meyer recalls, adding, ‘When they required biting or spinning behaviour, we considered it to be “hard food”; however, when the prey could be sucked in, we considered it “soft prey”’. Finally, they photographed the glass eels' heads once a month over 5 months and analysed the growth to see whether diet altered head development.Amazingly, by the end of the test period, the team could see clear differences in the small eels' head shapes. The animals on the hard diet had wider heads that could accommodate larger jaw muscles for biting hard, while the eels that had been fed a soft diet had slender heads. ‘We did not expect such a rapid and pronounced diversification in head shape’, says De Meyer, adding that the differences had been thought to emerge after the animals had transformed into growing yellow eels. And when De Meyer investigated the eels that had been provided with a mixed diet, some of the animals had broad heads while others had narrow ones. ‘This suggests that when eels are given the choice, some prefer hard prey and others soft. This difference in prey preference could decrease the competition for food in eels and thus increase their survival’ he says.However, De Meyer adds that there are concerns for the welfare of eel populations in Europe's rivers and he warns that the broad-headed animals may be at greater risk from pollution than the narrow-headed animals, because they are further up the food chain and consume a diet that has already accumulated more pollutants. He says, ‘Our study shows that this difference in the position in the food chain can be present very early in the eels’ life cycle', and he hopes that a better understanding of how diet affects these animals could be vital in re-establishing eel populations in Europe's depleted rivers.

EMG Activity of Masseter Muscles in the Elderly According to Rheological Properties of Solid Food.

ObjectiveTo assess the impact of aging on masticatory muscle function according to changes in hardness of solid food.MethodsEach of fifteen healthy elderly and young people were selected. Subjects were asked to consume cooked rice, which was processed using the guidelines of the Universal Design Foods concept for elderly people (Japan Care Food Conference 2012). The properties of each cooked rice were categorized as grade 1, 2, 3 and 4 (5×103, 2×104, 5×104, and 5×105 N/m2) respectively. Surface electromyography (sEMG) was used to measure masseter activity from food ingestion to swallowing of test foods. The raw data was normalized by the ratio of sEMG activity to maximal voluntary contraction and compared among subjects. The data was divided according to each sequence of mastication and then calculated within the parameters of EMG activities.ResultsIntraoral tongue pressure was significantly higher in the young than in the elderly (p<0.05). Maximal value of average amplitude of the sequence in whole mastication showed significant positive correlation with hardness of food in both young and elderly groups (p<0.05). In a comparisons between groups, the maximal value of average amplitude of the sequence in whole mastication and peak amplitude in whole mastication showed that mastication in the elderly requires a higher percentage of maximal muscle activity than in the young, even with soft foods (p<0.05).ConclusionsEMG data of the masseter can provide valuable information to aid in the selection of foods according to hardness for the elderly. The results also support the necessity of specialized food preparation or products for the elderly.

Impact of dental neglect score on oral health among patients receiving fixed orthodontic treatment: A cross-sectional study

Objective:Maintenance of meticulous oral health practices is critical for patients who are under orthodontic treatment as failure to do so can result in deterioration of periodontal health. Thus, the present study was commenced to assess dental negligence and oral health status among patients undergoing orthodontic treatment using dental neglect scale (DNS) questionnaire.Materials and Methods:The present cross-sectional study was planned and carried out among the 40 patients undergoing fixed orthodontic treatment. The study comprised of two questionnaires, one was close-ended questionnaire which consisted of questions regarding patient practice in maintenance of oral health and other questionnaire comprised of DNS followed by examination of oral hygiene status using Oral Hygiene Index Simplified. Data so obtained were subjected to analysis using SPSS version 20 and Chi-square test was used to statistically analyze data with P < 0.05 regarded as a statistically significant value.Results:The present study revealed that 63% among the studied orthodontic patients brushed once daily, 26% brushed twice daily, and 11% brushed thrice. About one-fourth was using brush with soft bristles and only 9% among the respondents used interdental aids. Data revealed positive correlation between DNS and oral hygiene index-simplified score with P < 0.05.Conclusion:The present study found that less frequency of brushing, rinsing mouth, and eating sticky and hard food can be attributed to self-neglect of the orthodontic patients.

Stress Distribution under Commercial Denture Liners- A Finite Element and Clinical Analysis.

Previous studies have shown that 20-30% of denture users have been dissatisfied with their dentures. To evaluate the stress pattern under elastic and viscoelastic denture liners using 3-Dimensional Finite Element Analysis (FEA) and its clinical correlation using a questionnaire. The study had both in-vitro and in-vivo phases. In in-vitro phase fabrication of a virtual parametric model of edentulous maxilla and dentures with overlying mucosa was made. A virtual load of 166N was analyzed at three points (Point A=anterior ridge, Point B=right posterior ridge and Point C=left posterior ridge). For the in-vivo phase, 20 edentulous patients were provided conventional complete dentures (Group-I). The dentures were lined with silicone (elastic) liners (Group-II) and acrylic resins (viscoelastic) liners (Group-III) at regular (2 months) intervals. After each reline, the patients were evaluated using food eating ability and denture assessment questionnaires. The results were statistically analyzed. The statistical analysis was done using SPSS (Statistical Package for Social Sciences) version 15.0 statistical analysis software. Other than standard statistical test Analysis of Variance (ANOVA) and Post-Hoc tests (Tukey-HSD) were used. At loading, the in-vitro result for Groups-II and III revealed pressures of 0.074231N and 0.0678364N at Point A, 0.098764N and 0.093642N at Point B, and 0.099876N and 0.093746N at Point C respectively. The in-vivo study revealed that the mean quality of life score for different groups ranged from 23.65±4.00 (Group I) to 33.10±6.15 (Group III). The mean quality of life score for Group II was 29.50±5.08. The viscoelastic liner provided the most uniform stress distribution and performed better than an elastic liner with hard, firm and soft foods.

Electromyography of Swallowing with Fine Wire Intramuscular Electrodes in Healthy Human: Amplitude Difference of Selected Hyoid Muscles

Few studies have examined the intensity of muscle activity during swallowing in healthy humans. We examined selected hyoid muscles using fine wire intramuscular electromyography (EMG) during swallowing of four food consistencies. Thirteen healthy adults were studied using videofluorography and EMG of the anterior belly of digastric (ABD), geniohyoid (GH), sternohyoid (SH), and masseter (MA; surface electrodes) while ingesting thin liquid (three trials) and solid food of three consistencies (banana, tofu, and cookie, three trials each). After rectification, integration, and normalization, peak EMG amplitudes for each muscle in each trial were measured. Hyoid displacements were measured in two dimensions. Data were analyzed using repeated measures ANOVA with Bonferroni correction. GH had the highest adjusted amplitude for both solids and liquid. For MA and ABD, amplitude was highest with triturated cookie. For ABD, amplitude was lowest with liquid. There were no significant food consistency effects for GH or SH. Hyoid displacements were greatest for cookie and the lowest for liquid. EMG amplitude varied with initial food consistency. The high peak EMG amplitude of GH is consistent with its essential role in opening the upper esophageal sphincter. High MA amplitude with hard solid foods is likely due to the higher tongue-palate pressure with triturated solids. The higher ABD amplitude with solid food is associated with greater hyoid displacement. These findings support the existence of a central pattern generator that modifies the level of muscle activity during pharyngeal swallowing in response to input from mechanoreceptors in the oral cavity.

Changes in jaw muscle activity and the physical properties of foods with different textures during chewing behaviors

This study aimed to investigate how the activity of the masseter (Mas) and suprahyoid (Hyoid) muscles is influenced by the physical properties of food, how changes in the rheological properties of food differ between different foods during the process of food reduction, and how different salivary flow rates affect bolus-making capability during masticatory behavior in healthy humans. Ten healthy adults participated in this study. Electromyographic (EMG) recordings were obtained from the Mas and Hyoid muscles, and 15g of steamed rice and rice cake was prepared as test foods. In the ingestion test, the subjects were asked to eat each food in their usual manner. The chewing duration, number of chewing cycles before the first swallow, Mas and Hyoid EMG activity, and chewing cycle time were compared between the foods. Total chewing duration was divided into three substages: early, middle, and late; chewing cycle time and EMG activity per chewing cycle of each substage were compared between the foods and among the substages. In the spitting test, the rheological properties of the bolus at the end of each substage were compared between the foods and among the substages. Finally, stimulated salivary flow rates were measured and the relationships between salivary flow rate and chewing duration, EMG activity, and changes in physical food characteristics were investigated. There were significant differences in total chewing duration and the number of chewing cycles, but not in chewing cycle time, between the foods, which had similar hardness values. The EMG activity levels of the Mas and Hyoid per chewing cycle for the rice cake were significantly greater than for the steamed rice throughout the recording periods. While Mas activity did not change among the substages during chewing, Hyoid EMG activity decreased as chewing progressed. Chewing cycle time also gradually decreased as chewing progressed. The hardness of both foods initially increased, then gradually decreased back to baseline. The adhesiveness of the rice cake initially increased, and did not fall throughout the recording period; the adhesiveness of the steamed rice did not significantly change. Cohesiveness barely changed in either of the two foods during chewing, but was significantly greater for the rice cake than for the steamed rice. Finally, a correlation between the stimulated salivary flow rate and chewing performance was evident only in a change in Mas EMG activity. The current results demonstrate that the activities of the Mas and Hyoid muscles changed as chewing progressed, and were affected by hardness, adhesiveness, and cohesiveness. Salivary flow rate may affect the changes in Mas activity during the process of bolus formation.

Diet and Implant Complications.

A hard or coarse diet may impart a substantial off-axial load to dental implant-supported prostheses and may induce a component, implant midbody fracture or late loss of integration. This may be especially true when there is a large crown to implant ratio. A patient who is able to generate an excessive bite force along with chronic cyclic loading with hard or coarse foods may have implant body or component fractures. There are no established parameters for crown to implant ratio or for detrimental bite loads. Implant longevity may be dependent on many factors, including the supporting bone quality and volume, crown to implant ratio, implant width and length, the prosthetic occlusal scheme and bite force/arch location, and the patient's dietary load.

Effects of Electromagnetic Heating on Quick Freezing

Purpose: Quick freezing is widely used in commercial food storage. Well-known freezing techniques such as individual quick freezing require a low-temperature coolant and small cuts for the heat-transfer efficiency. However, the freezing method for bulk food resembles techniques used in the 1970s. In this study, electromagnetic (EM) heating was applied to improve the quick freezing of bulk food. Methods: During freezing, the surface of food can be rapidly cooled by an outside coolant, but the inner parts of the food cool slowly owing to the latent heat from the phase change. EM waves can directly heat the inner parts of food to prevent it from freezing until the outer parts finish their phase change and are cooled rapidly. The center temperature of garlic cloves was probed with optical thermo sensors while liquid nitrogen (LN) was sprayed. Results: When EM heating was applied, the center cooling time of the garlic cloves from freezing until -10°C was 48 s, which was approximately half the value of 85 s obtained without EM heating. For the white radish cubes, the center cooling time was also improved, from 288 to 132 s. The samples frozen by LN spray with EM heating had a closer hardness to the unfrozen samples than the samples frozen by LN only. Conclusions: The EM heating during quick freezing functions to maintain the hardness of fresh food by reducing the freezing time from 0 to -10°C.

Effect of Estrogen and Food Hardness on Metabolism and Turnover of Condylar Cartilage

To clarify the effect of estrogen and food hardness on condylar cartilage and the cartilage-bone interface. A total of 56 rats were divided into four groups: (1) ovariectomized rats fed a normal (pressed pellet) food, (2) ovariectomized rats fed a soft (powder) food, (3) control rats fed a normal (pressed pellet) food, and (4) control rats fed a soft (powder) food. Some rats (n = 29) were sacrificed at the age of 67 days and others (n = 27) at the age of 87 days, and then 5-μm-thick sagittal paraffin sections were prepared from each temporomandibular joint (TMJ). Toluidine blue staining, in situ hybridization with type X collagen, terminal deoxynucleotidyl transferase and deoxyuridine triphosphate nick end labeling (TUNEL-assay), and tartrate-resistant acid phosphatase (TRAP) histochemistry were performed. Immunohistochemical analyses included cathepsin K, adiponectin, proliferating cell nuclear antigen (PCNA), and type X collagen staining. Analysis of variance and appropriate post-hoc tests were used in all analyses. Ovariectomy and normal food consistency increased the thickness of condylar cartilage (P < .001), PCNA expression (P < .001) and type X collagen expression (P < .001). Ovariectomy decreased the number (P < .05) and size of osteoclasts (P < .01). Soft food increased the number of cartilage cells stained positively against adiponectin (P < .01). Decreased estrogen level and normal food hardness increase the thickness of condylar cartilage by various mechanisms.

A randomized controlled trial of self-perceived pain, discomfort, and impairment of jaw function in children undergoing orthodontic treatment with fixed or removable appliances.

To compare patients' perceptions of fixed and removable appliance therapy for correction of anterior crossbite in the mixed dentition, with special reference to perceived pain, discomfort, and impairment of jaw function. Sixty-two patients with anterior crossbite and functional shift were recruited consecutively and randomized for treatment with fixed appliances (brackets and archwires) or removable appliances (acrylic plates and protruding springs). A questionnaire, previously found to be valid and reliable, was used for evaluation at the following time points: before appliance insertion, on the evening of the day of insertion, every day/evening for 7 days after insertion, and at the first and second scheduled appointments (after 4 and 8 weeks, respectively). Pain and discomfort intensity were higher for the first 3 days for the fixed appliance. Pain and discomfort scores overall peaked on day 2. Adverse effects on school and leisure activities were reported more frequently in the removable than in the fixed appliance group. The fixed appliance group reported more difficulty eating different kinds of hard and soft food, while the removable appliance group experienced more speech difficulties. No significant intergroup difference was found for self-estimated disturbance of appearance between the appliances. The general levels of pain and discomfort were low to moderate in both groups. There were some statistically significant differences between the groups, but these were only minor and with minor clinical relevance. As both appliances were generally well accepted by the patients, either fixed or removable appliance therapy can be recommended.

Recognition of Nutrition Intake Using Time-Frequency Decomposition in a Wearable Necklace Using a Piezoelectric Sensor

Food intake levels, hydration, ingestion rate, and dietary choices are all factors known to impact the risk of obesity. This paper presents a novel wearable system in the form of a necklace, which aggregates data from an embedded piezoelectric sensor capable of detecting skin motion in the lower trachea during ingestion. The skin motion produces an output voltage with varying frequencies over time. As a result, we propose an algorithm based on time-frequency decomposition, spectrogram analysis of piezoelectric sensor signals, to accurately distinguish between food types, such as liquid and solid, hot and cold drinks, and hard and soft foods. The necklace transmits data to a smartphone, which performs the processing of the signals, classifies the food type, and provides visual feedback to the user to assist the user in monitoring their eating habits over time. We compare our spectrogram analysis with other time-frequency features, such as matching pursuit and wavelets. Experimental results demonstrate promise in using time-frequency features, with high accuracy of distinguishing between food categories using spectrogram analysis and extracting key features representative of the unique swallow patterns of various foods.

MODALITATE DE EVALUARE A STATUSULUI ORAL LA PACIENŢII CU BOLI RENALE CRONICE

Aim. Designing a complex assessment questionnaire of oral status and quality of life in terms of oral health in patients with chronic kidney disease (CKD). Material and method. This study is required because there are lacks of information in Romania, related to oral status of patients with chronic kidney disease – chronic renal failure, with or without nephritic syndrome, with or without dialysis. Rationale study was conducted by internationally indexed database query. The design study consists to finally obtain a questionnaire to collect medical information related to: the stage of kidney disease, main cardiac, liver, skeletal system diseases and also diabetes. All these are related with specific medication and its influence on oral cavity. There has been collected biochemistry data with relevance in chronic renal failure related to the oral status, oral symptomatology – the presence or absence of roots, toothless, the xerostomia. Also we obtain data about denture presence or absence, quality of life trough prosthetic efficiency – chewing efficiency – for hard and soft foods, esthetic satisfaction, sanitization effectiveness, necessity and effectiveness of dental treatment. The questionnaire is applied to a group of patients with renal impairment and, by comparison, to a group of patients without renal impairment. Results and conclusions. The final form of a pre-test questionnaire has been obtained. After applying the two groups of patients: were correct errors of form and were subsequently excluded sections with insufficient data, were optimize application time, readjusted methodology subjects inclusion/exclusion.

Symptoms Reported by Head and Neck Cancer Patients during Radiotherapy and Association with Mucosal Ulceration Site and Size: An Observational Study.

BackgroundSelf-reported pain and impairment of oral functions varies markedly and often in spite of extensive oral mucositis (OM). The aim of the current study was to appraise how patient-reported debilitation caused by OM is influenced by the extent and possibly location of the OM lesions.MethodsPatients with head and neck cancer undergoing radiotherapy were examined before treatment, twice weekly during 6-7 weeks of therapy, and 3-4 weeks after therapy completion. OM signs of 33 participants were evaluated using the Oral Mucositis Assessment Scale (OMAS), while OM symptoms were recorded using Patient-Reported Oral Mucositis Symptom (PROMS)-questionnaires. Changes in OM experience as a function of OM signs was undertaken by comparing the aggregated and individual PROMS scale values at the point of transition of OMAS ulceration scores between 0 to 1, 1 to 2 and 2 to 3, respectively in the nine intra-oral locations designated in the OMAS. ANOVA with pairwise contrasts using the LSD procedure was applied for comparisons of mean changes of PROMS scale values for the participants who experienced an OMAS score of 2 or more during therapy (n=24).ResultsImpairment of eating hard foods was more when the OMAS score for ulceration anywhere in the mouth or in the soft palate changed from 1 to 2, compared to between score 0 and 1 (p=.002 and p=.05) or between score 2 and 3 (p=.001 and p=.02). Mouth pain increased more upon transition of OMAS score anywhere in the mouth from 1 to 2 compared to 0 to 1 (p=.05).ConclusionThe relationship between patient-reported impairment of oral function and pain caused by OM ulceration is not linear, but rather curvilinear. Our findings should prompt investigators of future interventional trials to consider using a less severe outcome than maximum OM scores as the primary study outcome.

Dental root size in bats with diets of different hardness.

The relationship between tooth roots and diet is relatively unexplored, although a logical relationship between harder diets and increased root surface area (RSA) is suggested. This study addresses the interaction between tooth morphology, diet, and bite force in small mammals, phyllostomid bats. Using micro computed tomography (microCT), tooth root morphology of two fruit-eating species (Carollia perspicillata and Chiroderma villosum) and two insect-eating species (Mimon bennettii and Macrotus californicus) was compared. These species did not differ in skull or estimated body size. Food hardness, rather than dietary classification, proved to be the strongest grouping factor, with the two insectivores and the seed-processing frugivore (C. villosum) having significantly larger RSAs. Bite force was estimated using skull measurements; bite force significantly correlated with tooth RSA but not with body size. Although the three durophagous species did exhibit larger crowns, the area of the occlusal surface did not vary among the four species. There was a linear relationship between root size and crown size, indicating that the roots were not expanded disproportionately; instead the entire tooth was larger in the hard diet species. MicroCT allows the nondestructive quantification of previously difficult-to-access tooth morphology; this method shows the potential for tooth roots to provide valuable dietary, behavioral, and ecological information in small mammals. J. Morphol. 276:1065-1074, 2015. © 2015 Wiley Periodicals, Inc.

Differences in chewing behaviors between healthy fully dentate young and older adults assessed by electromyographic recordings

To characterize changes in chewing behaviors associated with healthy aging, 10 young and 10 older fully dentate healthy participants were enrolled in this study. They chewed carrot samples that differed in hardness until their normal swallowing threshold. Their chewing behaviors were assessed using an electromyographic recording device. Adjusting for gender and body mass index, older adults had a higher number of chewing cycles (p = 0.020), a longer chewing duration (p < 0.001), a slower chewing rate (p = 0.002), a greater maximal electromyographic voltage (p = 0.003) and a greater muscle activity (p = 0.002) before they could comfortably swallow the food bolus. A statistically significant main effect of food hardness on the number of chewing cycles, chewing duration, chewing rate and muscle activity was also observed (p < 0.001 for all). These results suggest that reduced mastication efficiency is associated with healthy aging in fully dentate adults. This ingestive behavior may contribute to aging-related reduction in appetite in older adults.

The main occluding area in normal occlusion and mandibular prognathism.

To clarify whether the concept of main occluding area, where hard food is initially crushed, exists in patients who have a jaw deformity. Nineteen subjects with normal occlusion, 18 patients with mandibular prognathism, and 11 patients with mandibular prognathism who had undergone orthognathic surgery participated in this study. The main occluding area was identified by clenching Temporary Stopping. The coincidence, location of the main occluding area, and distance from the first molars to main occluding area were examined. High coincidence of the main occluding area was obtained in all groups, signifying that the main occluding area exists even in these patients. Mandibular main occluding area was located on the first molar in all groups. Maxillary main occluding area in subjects with normal occlusion was located on the first molar. However, it was located on the second premolar and first molar in patients with mandibular prognathism, and on the first and second molars in patients with mandibular prognathism who had undergone orthognathic surgery. There was a statistically significant difference in distance from the maxillary first molar to the main occluding area among groups, but there was no difference in the distance from the mandibular first molar among groups. The main occluding area is more stable on the mandibular first molar than the maxilla in all groups.

Genetic and Environmental Control on Mandibular Form and Function in Mice

Bone modelling and remodelling is a means by which organisms may be able to plastically modify the external morphology and internal structure of their skeletal tissues. We have shown previously that lab mice of the C56BL/6 strain that were fed either hard or soft foodstuffs with the same nutritional value have significantly different shaped jaws. The shape differences manifest as difference in function, with the mandibles of hard food eaters possessing a higher mechanical advantage (MA) of the temporalis and masseter adductor musculature than the soft food eaters. Here we compare the magnitude of difference in MA between the C56BL/6 hard and soft food eaters to the difference in MA between C56BL/6 hard food eaters and BALB/c hard food eaters. We also compare the difference between strains and between plastically generated morphotypes in resistance to bending and torsion from second moment of area measurements from CT scans and in simulated functional bony stress and strain deduced from finite element models. Hard food eaters have increased resistance to bending, torsion (n=39) and loading induced stress and strain (n=4) compared to soft food eaters. C56BL/6 and BALB/c mice have significantly different shaped jaws with BALB/c mice having more gracile jaws with a less developed masseteric ridge (n = 20). Comparative finite element (FE) models show that BABL/c mice also experience consistently greater deformation when subject to functional feeding‐induced loads (n=4). Environmentally driven plasticity leads to functional differences that favour the efficiency of food processing in the hard food eaters. Difference in performance between hard and soft food eaters exceed the difference in performance between lab strains, suggesting plasticity as a mechanism to provide morphological variation on which natural selection may act.

English

The fundamental pattern of chewing induced by the network of neurons called central pattern generator has been reported to be modified by the information arising from the various oro-facial sensory receptors including muscle spindles of jaw closing muscles. The cell bodies of primary afferent neurons from these muscle spindles lie in mesencephalic trigeminal nucleus (MTN) in the brainstem. The aim of the study was to understand whether muscle spindles from jaw-closing muscles play any role in hard food chewing. Single neuronal discharge of muscle spindle afferents was recorded from the MTN simultaneous with jaw-movement and electromyograpic (EMG) activities of the left masseter (jaw-closing) muscle during chewing soft and hard foods (apple and pellet) in awake rabbits. Ten consecutive chewing cycles were taken for analysis. Discharge of nineteen muscle spindles from seven rabbits was successfully recorded. Muscle-spindle discharge was significantly higher during the closing phase of jaw-movement for the hard food chewing than for the soft food. The jaw-closing muscle EMG activity was significantly higher during hard food chewing compared to soft food. The spindle discharge was higher when the masseter muscle activity was greater for chewing hard food. Significant positive (r=0.822, p=<0.001) correlation was found between the difference of muscle activity between apple and pellet and the difference of spindle discharge between apple and pellet. Above findings suggest that the increase of spindle discharge during hard food chewing may play a role for facilitating jaw-closing muscle activities and thereby provides servo-assistance to jaw-closing muscles to compensate the hardness of food.

Effects of seed traits on the potential for seed dispersal by fish with contrasting modes of feeding

Summary For aquatic and riparian plants, the important role of fish in seed dispersal is increasingly recognised. While the propensity of seeds to disperse is known to be a function of morphological, physical and chemical traits of the seed, in the case of fish‐mediated seed dispersal (ichthyochory), it is largely unknown how seed traits modulate the potential for seed ingestion and their subsequent survival through the gut. Furthermore, which seed traits are important may vary among fish species. To evaluate the role of both seed and fish traits in ichthyochory, we fed seeds of 19 aquatic and riparian plant species to fish with differing feeding mechanisms. Cyprinus carpio (common carp) has a pharyngeal ‘mill’, which it uses physically to crush hard food, while Oreochromis mossambicus (Mozambique tilapia) has only tiny oral and pharyngeal teeth and instead relies more on chemical digestion. A number of seed traits, including hardness, size and shape, were important determinants of the potential of seeds for ichthyochory. Certain traits (e.g. seed dimensions) were more important during ingestion, whereas other traits were more important for seed survival and subsequent germination (e.g. seed hardness, mucilaginous coat). Compared to controls, germination of retrieved seeds in carp was lower in 10 and higher in two plant species, whereas for tilapia, it was lower in seven and higher in three species. Overlap between these plant species was low, indicating clear difference between the fish studied in their potential for seed dispersal. Carp increased in size during the experiment and concomitant decreases in seed survival and retrieval were found, suggesting that body size and the correlated bite force is an important fish trait in ichthyochory. Overall, seed hardness, size and shape appear crucial for the survival of seeds passing through the guts of carp and tilapia. Beyond this general pattern, a greater complexity of trait‐performance relationships appeared: different seed traits are involved during each of the stages of ichthyochory. Moreover, the importance of seed traits differed between carp and tilapia, with some traits having interactive and contrasting effects in both fish species. Aquatic plants with floating seeds adapted to hydrochorous dispersal were less likely to be dispersed by tilapia than plants with non‐floating seeds, suggesting a dispersal trade‐off between ichthyochory and hydrochory. Thus, depending on their seed characteristics, fish may offer an additional dispersal route to aquatic and riparian plants.

Cricetid rodents: Is molar root morphology an indicator of diet?

The relationship between tooth roots and diet is largely unexplored, although a logical relationship between harder diets and increased root surface area is suggested. Existing studies of primates, carnivorans and phyllostomid bats have indicated a relationship between diet hardness, bite force and tooth root surface area. The goal of this study was to determine whether root surface area can act as a potential surrogate for bite force and diet in cricetid rodents. Using microcomputed tomography (microCT), tooth root morphology from six species of rodents, two grass eaters (Calomys callosus and Reithrodon auritus), two seed eaters (Phyllotis darwini and Ochrotomys nuttalli) and two insect eaters (Akodon azarae and Oxymycterus hispidus) were compared. Similar to other studies, these rodents did exhibit differences in tooth root surface area based on diet classification, but food hardness did not seem to be a factor. Grass-eating species showed significantly larger roots relative to the other diet groups (p = 0.001). Bite force was estimated using skull measurements. Seed eaters were found to have a larger bite force, followed by grass and insect eaters, though the trend did not reach statistical significance (p = 0.058). No strong relationship was found between estimated bite force and tooth root surface area. In this study, the mechanics of grass eating seem to have a stronger effect on tooth root surface area than bite force. microCT allows the nondestructive quantification of previously difficult-to-access tooth morphology; this method shows the potential for tooth roots to provide valuable dietary, behavioral and ecological information in rodents.