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

ABSTRACT: 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. We measured maximum bite force and jaw opening (i.e., gape) along with several musculoskeletal dimensions functionally linked to these performance measurements to test the hypotheses that GI mice evolved larger bite forces and jaw gapes as part of their extreme increase in size and/or novel diet. GI mice can bite more forcefully and open their jaws wider than a representative mainland strain of house mice. Similarly, GI mice have musculoskeletal features of the masticatory apparatus that are absolutely larger than WSB mice. However, when considered relative to body size or jaw length, as a relevant mechanical standard, GI mice show reduced performance, suggesting a size-related decrease in these abilities. Correspondingly, most musculoskeletal features are not relatively larger in GI mice. Incisor biting leverage and condylar dimensions are exceptions, suggesting relative increases in biting efficiency and condylar rotation in GI mice. Based on these results, we hypothesize that evolutionary enhancements in masticatory performance are correlated with the extreme increase in body size and associated musculoskeletal phenotypes in Gough Island mice. Anat Rec, 2019. © 2018 American Association for Anatomy.

SUBMITTER: Parmenter MD

PROVIDER: S-EPMC6565519 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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

Parmenter Michelle D MD Nelson Jacob P JP Weigel Sara E SE Gray Melissa M MM Payseur Bret A BA Vinyard Christopher J CJ

Anatomical record (Hoboken, N.J. : 2007) 20190113 1

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. We m ...[more]

PMID: 30548803

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Project description:BackgroundPrevious masticatory studies have focused on a variety of measurements of foods and boluses or kinematic parameters and sound during mastication. To date, the masticatory sound research of has been limited due to the difficulties of sound collection and accurate analysis. Therefore, significant progress in masticatory sound has not been made. Meanwhile, the correlation between acoustic parameters and mastication performance remains unclear. For the purpose of exploring the acoustic parameters in measuring mastication performance, the bone-conduction techniques and sound analysis were used, and a statistical analysis of acoustic and occlusal parameters were conducted.MethodsThe gnathosonic and chewing sounds of fifty-six volunteers with healthy dentate were recorded by a bone-conduction microphone and further analyzed by Praat 5.4.04 when intercuspally occluding natural foods (peanuts) were consumed. The granulometry of the expectorated boluses from the peanuts was characterized by the median particle size of the whole chewing sequence (D50a) and the median particle size during the fixed chewing strokes (D50b). The chewing time of the whole chewing sequence (CTa), the chewing time of the fixed chewing strokes (CTb), the chewing cycles (CC), and the chewing frequency (CF) were recorded and analyzed by the acoustic software. The acoustic parameters, including gnathosonic pitch, gnathosonic intensity, mastication sound pitch of the whole chewing sequence (MPa), mastication sound pitch of the fixed chewing strokes (MPb), mastication sound intensity of the whole chewing sequence (MIa) and mastication sound intensity of the fixed chewing strokes (MIb), were analyzed. Independent sample t-test, Spearman and Pearson correlation analyses were used where applicable.ResultsSignificant difference in parameters CC, MIa, CF and D50a were found by sex (t-test, p < 0.01). The masticatory degree of the test foods was higher in women (CC, 24.25 ± 5.23; CF, 1.70 ± 0.21 s-1; D50a, 1655.07 ± 346.21 μm) than in men (CC, 18.14 ± 6.38; CF, 1.48 ± 0.18 s-1; D50a, 2159.21 ± 441.26 μm). In the whole chewing sequence study, a highly negative correlation was found between MIa and D50a, and a highly positive correlation was found between MIa and CF (r = - 0.94, r = 0.82, respectively, p < 0.01). No significant correlation was found between the remaining acoustic parameters and mastication parameters. In the fixed chewing strokes study, a highly negative correlation was found between MIb and D50b (r = - 0.85, p < 0.01). There was no significant correlation between the rest of the acoustic parameters and the mastication parameters.ConclusionsMastication sound intensity may be a valuable indicator for assessing mastication. Acoustic analysis can provide a more convenient and quick method of assessing mastication performance.

Dataset Information

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

Publications

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

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