NSF Award
1354788
Many fish feed by using their jaws to scissor away pieces of flesh and often generate movements with their rigid body skeletons to remove the piece. The poorly understood hagfish can also effectively accomplish this task despite lacking jaws or even a spine. Hagfish rely on complex arrangements of soft muscle and connective tissues to coordinate forceful and dynamic movements of 1) a unique toothplate that can shear off large chunks of food, and 2) flexible bodies with loose skins that can be tied into knots. Body knots are pressed against the surface of the carcass so that hagfish can gain leverage to support toothplate function. This study attempts to describe principles of function associated with generation of force and precision movements using soft tissue mechanisms. In addition, this research will provide training for four undergraduates and one Master of Science student and initiate national and international collaborations. The PIs and their students will work with three local public aquaria to develop exhibits that showcase unique hagfish biomechanics and behaviors. Finally, hagfish body models and simulations may result in the development of practical applications, such as safety ropes with dynamic knotting capabilities and bio-inspiration for deformable material mechanisms.<br/><br/>This project encompasses a three-part analysis. First, the biomechanical analysis of toothplate movement will begin with a morphological analysis based on dissections and two- & three-dimensional X-ray imaging. Resulting postulates of how forces are produced and transmitted will be tested using analyses of high-speed video and muscle activity recordings during feeding bouts. Second, the morphology and material properties of the loose hagfish skin are likely very important to body knot manipulations. Skin morphology will be described using histological reconstructions and material properties will be measured using biaxial tensile tests. These data may then be used as input into a simplified model of the hagfish body, based on a flexible rope model of a sheath/core design, upon which to simulate knot formation and slippage. Third, in order to assess the contribution of body knotting behavior to hagfish 'bite' strength, a custom underwater force platform, to which food will be tethered, will record the magnitude and direction of shearing and body knot reaction forces. Results from the studies will be disseminated through publication in peer-reviewed journals and at scientific meetings.
