Mastication in the little brown bat, <i>Myotis lucifugus</i>

Kallen, Frank C.; Gans, Carl

doi:10.1002/jmor.1051360402

Cited by 111 publications

(48 citation statements)

References 31 publications

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“…The tendency of the human medial pterygoid muscles to alternate their activity in all phases of the masticatory stroke other than early closing (when both are active although unequally) and sometimes late in the intercuspal position, is reminiscent of that reported by Kallen and Gans (1972) for Myotis. Their data differ slightly in that ipsilateral activity begins a little later (as the jaw swings medially into intercuspation) and lasts a little longer (as the jaw moves out of intercuspation); another small difference is the apparent consistent absence of a late burst from the contralateral muscle in the intercuspal position, a feature which appeared in some of our subjects.…”

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confidence: 85%

Medial pterygoid muscle activity during the closing and compressive phases of human mastication

Hannam

Wood

1981

American J Phys Anthropol

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The lack of specific data correlating activity in the human medial pterygoid muscle with displacement of the jaw during mastication, and the hint of possible differences in function between certain mammalian species, prompted a study of unilateral mastication in six adult subjects. Muscle activity in the medial pterygoid, masseter, and anterior temporal muscles was recorded simultaneously with three-dimensional movement of an incisor point on the mandible. Signals from muscles and displacement transducer were sampled by a disc-based computer system programmed to analyze data averaged over 30 chewing cycles on each side and in some instances over 30 open-close and clench cycles. Patterns of medial pterygoid activity were consistent for the group as a whole, demonstrating activation of both muscles early in the closing cycle with strong ipsilateral muscle activity before and throughout the intercuspal phase of the cycle, reappearing in some subjects just before the end of intercuspation. Medial pterygoid activity mirrored masseter and anterior temporal activity only during certain phases of the closing cycle, suggesting that these muscles should be considered as being selectively coactivated with, rather than synergists of, the major elevators of the jaw. The muscles were active during horizontal components of movement of the incisor teeth in chewing, but were inactive during the open-close and clench task despite vigorous contraction of the masseter muscles. Overall, the observations complement previous reports of medial pterygoid muscle activity in humans. They also confirm, for these muscles at least, a general similarity between man and the little brown bat, a relationship hitherto suspected but unsubstantiated.

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confidence: 85%

Medial pterygoid muscle activity during the closing and compressive phases of human mastication

Hannam

Wood

1981

American J Phys Anthropol

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“…Published electromyographic data suggest that all jaw closer muscles are indeed maximally or near maximally recruited during biting on hard or tough foods (Kallen and Gans, 1972;De Gueldre and De Vree, 1988). Note, however, that maximal activation does not necessarily imply force generation.…”

Section: A Herrel and Othersmentioning

confidence: 98%

Morphological and mechanical determinants of bite force in bats: do muscles matter?

Herrel

Smet

Aguirre

et al. 2008

Journal of Experimental Biology

146

183

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SUMMARYBats are one of the most diverse groups of mammals and have radiated into a wide variety of trophic niches. Accordingly, the cranial structure in bats is unusually variable among mammals and thought to reflect specializations for feeding and echolocation. However, recent analyses of cranial structure, feeding behavior and bite force across a wide range of bats suggest that correlations between morphology and performance and/or ecology are not as clearcut as previously thought. For example, most of the variation in bite force across a wide range of phyllostomid bats was explained by differences in body size rather than specific cranial traits. However, remarkably little is known about the muscular components that are responsible for generating the actual bite forces. We have tested which aspects of the cranial muscular system are good predictors of bite force across a wide range of species using a modeling approach. Model calculations of bite force show good correspondence with in vivo data suggesting that they can be used to estimate performance of the cranial system. Moreover, our data show that bite force is strikingly well explained by differences in temporalis muscle mass, temporalis fiber length and masseter muscle mass. Moreover, our data show that evolutionary changes in bite force capacity in bats are associated with evolutionary changes in relative m. temporalis mass and absolute skull length.

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“…However, as already mentioned, galagos have ratios well in excess of 1:1, and similarly high W/B superficial masseter ratios occur in dogs (which also lack fusion; Dessem, 1989). Likewise, EMG analyses of bats have shown that Myotis, a vespertilionid with a patent symphysis, appears to exhibit higher W/B ratios than Pteropus, a pteropodid with an ossified symphysis (Kallen and Gans, 1972;de Gueldre and de Vree, 1984, 1988, 1990. Therefore, the extent to which any of these species are typical of mammals with unfused symphyses remains unclear, and will require comparable in vivo data for additional taxa.…”

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confidence: 97%

Transverse masticatory movements, occlusal orientation, and symphyseal fusion in selenodont artiodactyls

Hogue

Ravosa

2001

Journal of Morphology

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Based on extensive experimental work on primates, two masticatory loading regimes have emerged as the likely determinants of mandibular symphyseal fusion-dorsoventral shear and lateral transverse bending (wishboning) (Ravosa and Hylander, 1994; Hylander et al., 1998, 2000). Recently, however, it has been argued that, rather than functioning to strengthen the symphysis during mastication, fusion serves to stiffen the symphyseal joint so as to facilitate increased transverse jaw movements during occlusion (Lieberman and Crompton, 2000). As part of this transverse stiffness model, it has been suggested that taxa with fused symphyses should also exhibit more horizontally oriented occlusal wear facets. Using a series of univariate and bivariate analyses, we test predictions of these three models in a sample of 44 species of selenodont artiodactyls. Consistent with the wishboning and transverse stiffness models, taxa with fused symphyses (camelids) have more horizontally oriented M(2) and M(2) occlusal wear facets, anteroposteriorly (AP) elongate symphyses, and relatively wider corpora. Contrary to the dorsoventral shear model, camelids do not have relatively deeper corpora (due to greater parasagittal bending). While taxa with ossified symphyses have relatively larger symphysis cross-sectional areas, this appears to be the byproduct of an increase in AP symphysis length due to greater lateral transverse bending of the mandible. Theoretical consideration of the biomechanics of mastication further suggests that strength, not stiffness, is the critical factor in determining symphyseal ossification. Thus, like anthropoid primates, fusion in selenodont artiodactyls appears to function in resisting increased wishboning stresses arising from an emphasis on transverse occlusal/mandibular movements and loads.

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Mastication in the little brown bat, Myotis lucifugus

Cited by 111 publications

References 31 publications

Medial pterygoid muscle activity during the closing and compressive phases of human mastication

Medial pterygoid muscle activity during the closing and compressive phases of human mastication

Morphological and mechanical determinants of bite force in bats: do muscles matter?

Transverse masticatory movements, occlusal orientation, and symphyseal fusion in selenodont artiodactyls

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