Meeting Abstract
Here, we present a comprehensive dataset on the scaling of musculoskeletal architecture in varanids, providing information about the phylogenetically constrained adaptations that allow functional diversification across locomotor muscles in sprawling tetrapods. The effects of size and the fundamental selective pressures associated with it has been recognized for nearly 4 centuries. If animals were geometrically scaled up versions of themselves, increases in body size would result in an increase in musculoskeletal stresses, a result of the geometric scaling of mass and area. This becomes a problem for large animals, where stresses come dangerously close to failure points. In this study, we quantified the architectural properties of 22 lower limb muscles in 27 individuals from 9 species of varanid lizards (from 7.6g Varanus brevicauda to 40000g Varanus komodoensis). Results suggest that larger varanids increase the relative force-generating capacity of the femur abductors and adductors, and ankle extensors with greater scaling exponents than geometric similarity predicts for muscle mass, PCSA or pennation. In addition, muscle mass in the swing phase knee flexors scale with values > M1, which may reflect additional muscle mass required to move a heavier limb. Thus varanids mitigate the size-related increases in stress by increasing muscle mass and PCSA rather than adopting a more upright posture with size as shown in other animals.
