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Bite hard: Linking cranial loading mechanics to ecological differences in gnawing behavior in caviomorph rodents
Federico Becerra1, Guido Nicolás Buezas2, Adrián Cisilino3
1Laboratorio de Morfología Funcional y Comportamiento, Instituto de Investigaciones Marinas y Costeras (Universidad Nacional Mar del Plata-Consejo Nacional de Investigaciones Científicas y Técnicas), Mar Del Plata, Argentina.
Journal of Anatomy
|August 1, 2024
Summary
Rodent skulls are robust due to inherited traits, with stress patterns reflecting ecological demands. Powerful jaw muscles, especially in tuco-tucos, create high cranial stress but do not cause structural failure.
Area of Science:
- Comparative biomechanics
- Mammalian evolutionary morphology
- Cranial functional anatomy
Background:
- Mammalian skulls exhibit diverse morphologies adapted to various functions.
- Rodents possess unique masticatory apparatus, enabling significant ecological radiation.
- Previous studies suggest muscle development, not cranial morphology, explains bite force variation in caviomorphs.
Purpose of the Study:
- To investigate how reaction forces from incisor compression and adductor muscle tension affect caviomorph crania.
- To compare cranial stress patterns in species with different ecologies (subterranean, semi-fossorial, saxicolous).
- To assess the mechanical impact of standardized muscle forces across different caviomorph species.
Main Methods:
- Finite element analysis (FEA) was performed on the crania of three caviomorph species: Talas' tuco-tuco (Ctenomys talarum), common degu (Octodon degus), and long-tailed chinchilla (Chinchilla lanigera).
- Simulations included in vivo biting scenarios for all species.
- Rescaled muscle forces were applied to non-ctenomyid models to match those of the tuco-tuco for comparative analysis.
Main Results:
- In vivo simulations showed stress patterns correlating with ecological demands, with the subterranean tuco-tuco exhibiting the highest stress.
- Standardized muscle force simulations revealed significantly increased stress (magnitude and area) in degu and chinchilla models compared to their in vivo states.
- The zygomatic arch and lateral snout sections experienced the greatest stress increase (2.5–5.0 times) in standardized non-ctenomyid models, yet structural failure was not indicated.
Conclusions:
- Caviomorph crania possess a high baseline mechanical strength inherited from a robust 'rodent' model.
- Interspecific cranial differences are primarily linked to masticatory habits and the development of adductor musculature.
- Hypertrophied jaw muscles, particularly masseteric and zygomaticomandibular, are key drivers of cranial strain, enabling subterranean species like tuco-tucos to withstand extreme forces.
