BRC-BIO: Trade-offs in locomotor performance: comparing hoppers and jumpers in variable environments

About This Grant

The way an organism navigates an environment or habitat can be influenced by an individual’s physiology and the physical properties of its environment. More specifically, the substrate an organism interacts with can pose various challenges during locomotor movements that can impact performance. Adaptations in movement require a dynamic interplay between an organisms’ nervous system, anatomy, and muscle physiology, which together drive whole-body movements. However, the physiological strategies that one animal uses may not be ideally suited for a different habitat or substrate type. This research aims to understand how specialized ways of movement, more specifically, how hopping and jumping may constrain how an organism responds to instantaneous changes in the environment. Frogs and toads provide a unique model to understand variation in movement strategies. This project will investigate whole-body movement and nervous system control of muscle recruitment in response to changes in substrate stiffness. In addition, the project will investigate the mechanics and organization of tendon tissue to better understand the role of tendon stiffness in specialized forms of movement. Such unique adaptations in muscle and tendon physiology can inform the impacts of changing environments across habitats on locomotion, as well as design parameters in engineered systems dealing with environmental disturbance. The broader impacts of this research will increase research opportunities and mentorship of undergraduate students historically underrepresented in STEM, as well as enable the development of educational workshop-based trainings and resources to increase access to STEM research opportunities across the home institution. Throughout history the emergence of new modes of locomotion has played a crucial role in an animal’s ability to navigate new habitats. For example, behavioral transitions between microhabitats may result in more subtle shifts in an animal’s locomotor strategy. In some cases, the locomotor system may be flexible enough to accommodate changes in the physical properties of the environment. The proposed work aims to understand how specialized ways of movement have uniquely constrained motor control strategies and muscle-tendon properties. To address this, the first aim will quantify and compare interspecific kinematic variation between the long distance, endurance hopping of Cane toads, and the fast, powerful jumps of Cuban tree frogs, in response to environmental perturbations in substrate stiffness. The second aim measures in vivo hindlimb muscle length and motor patterns in response to substrate stiffness to characterize the motor control mechanisms used by long distance endurance hoppers. The third aim seeks to characterize tendon ultrastructure by quantifying collagen fibril organization using techniques in transmission electron microscopy and serial block-face scanning electron microscopy. Lastly, tendon material properties will be quantified using in vitro tendon tissue stress and strain tests to determine the role of tissue stiffness across species specialized for differing modes of locomotion and power output. The proposed research will advance understanding of how specialization in different locomotor modes can provide robust benefits or limitations at various levels of physiological organization. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.