The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Aye-aye jaw adductors: anatomy, architecture, and allometry


1Center for Functional Anatomy and Evolution, The Johns Hopkins University, 2Department of Biology, Pennsylvania State University, Altoona

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With its specialized foraging style and distinctive craniodental complex, the aye-aye (Daubentonia madagascariensis) is a most unusual strepsirrhine primate. During extractive foraging, aye-ayes employ wide gapes and perhaps generate large incisive bite forces, two functional requirements that typically might be predicted to produce conflicting morphological demands in an evolutionary trade-off. Given these functional requirements, the jaw adductors of Daubentonia are expected to have long fascicles to accommodate wide gapes and/or great physiological cross-sectional areas (PCSA) to produce large bite forces. Thus far, the only published data on chewing muscle fascicle length and PCSA in Daubentonia are from a subadult specimen. The chewing muscles in that specimen had very long fascicles and unremarkable PCSA, supporting gape adaptation in the masticatory complex, but not force adaptation. Here we report the first data from an adult aye-aye. Relative to both body mass and jaw length, its total chewing muscle PCSA (2067 mm2) is significantly greater (three standard deviations) than the mean of a broad sample of strepsirrhines. Mean fascicle length (9.9mm) relative to both body mass or jaw length for the adult specimen is also high relative to the strepsirrhine mean, but within the second standard deviation. Taken together with the data from the subadult Daubentonia specimen, this suggests that aye-ayes might shift foraging mechanics through development, based on changing functional constraints, with juveniles using a wide-gape strategy and adults using large bite forces.

Travel funded by Johns Hopkins University and Pennsylvania State University.

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