Facial musculature in naked mole‐rats ( Heterocephalus glaber )

Naked mole‐rats ( Heterocephalus glaber ) are fossorial rodents with an unusually long‐life span and eusocial niche. They are from the Bathyergidae family and their unusual anatomical and physiological traits, including several adaptations to their fossorial and eusocial niche, have been relatively under‐studied compared to other rodent species. Their adaptations to a subterranean niche and eusociality are demonstrated by their large incisors, oral folds, and highly developed tactile system (incisors and tactile hairs covering their body). Naked mole‐rats utilize their large incisors for social interacting, defense, navigation, object manipulation, feeding, and digging. Their oral folds close caudal to their incisors to prevent dirt from entering their oral cavity while digging. Their well‐developed tactile system compensates for their reduced visual (functionally blind) and auditory systems (reduced pinnae). Naked mole‐rat facial musculature would also be expected to have evolved and express neotenic features as an adaption to a fossorial niche. There are few studies that have characterized facial musculature in naked mole‐rats. Therefore, we performed detailed facial muscle dissections of adult naked mole‐rats, which included the presence and attachment sites. We compared our dissections with comparative anatomical studies. Our dissections showed subterranean adaptations to face musculature in naked mole‐rates, including reduced musculature associated with ear and eye movements. Further, our findings provide insight into the ecological and evolutionary adaptations of naked mole‐rat facial musculature to a subterranean niche.