Meeting Abstract
Hagfish possess a relatively rare flexibility that allows them to tie their bodies into knots. These knots can be worked along the length of their bodies to clean off mucous, escape tight spaces, pull prey from burrows, and possibly replace the leverage commonly generated by an opposing jaw. Knotting supports these crucial functions because the loops may be pressed against a surface to create leverage. A first step in understanding the knotting behavior is to characterize knot formation. In this study, we describe the kinematics of how hagfish form, and then manipulate, the body knot. Preliminary results showed that knotting may be stereotyped, however the low-resolution frame-by-frame kinematic analysis only weakly supported this assertion. To more robustly describe how hagfish tie body knots, we have developed an enhanced kinematic analysis. We employed a custom restraint device to consistently and controllably induce knotting in 20 individuals of Eptatretus stoutii (Pacific hagfish) and 4 individuals of E. springerii (Gulf hagfish). We used two high-speed cameras (200Hz) to capture the right-lateral and ventral views. Using custom software, we automatically isolated the body of the hagfish in each frame of the video for both camera views. Careful calibration of the camera and tank geometry allowed us to create a point cloud. This was used to create a surface mesh of the body that depended on semi-automatic user guidance to make sense of noise in the point cloud. The resultant mesh animation allowed us to quickly generate a high-resolution kinematic analysis that included body deformations resulting from formation and manipulation of knots. We are currently working on fully automated methods of surface mesh creation.
