Graduate Student Brown University Providence, Rhode Island, United States
Abstract Body :The ability to ingest prey larger than their head (macrostomy) is a widespread, derived trait in snakes that involves distending the skin and metabolic upregulation. However, data remain sparse for how the material properties skin vary: after feeding, among longitudinal locations, and among species. We recorded uniaxial stresses and strains in circumferential loops of skin from four fasted and four recently fed boa constrictors. We also tested skin from different pre-cloacal longitudinal locations in additional fasted snakes including two non-macrostomate genera (Afrotyphlops; Anilius) and a highly specialized macrostomate genus that eats only bird eggs (Dasypeltis). The neck skin of fed boa constrictors had a lower elastic modulus (26.7±8.1 MPa ± s.e.m.) than the neck skin of fasted snakes (60.9±4.2 MPa ± s.e.m.), and both were significantly lower than mid-body and caudal skin values of fasted snakes (p< 0.05). Compared to the other taxa, the longitudinal variation in the skin properties of the non-macrostomates was minimal, whereas the egg-eating snakes had neck skin with much lower stiffness that reached much greater strain before failure than skin from more posterior locations. Hence, the extent of longitudinal variation in skin properties is both species-dependent and affected by feeding. Whether the differences associated with feeding arise from active remodeling of the skin or from damage that needs subsequent repair is an interesting question for future studies.
