Meeting Abstract
Without a vertebral column, hagfish are flexible enough to tie body knots. They do this to avoid predation, clean off slime, and enhance toothplate forces during feeding. These behaviors rely on a large range of bending and twisting motions. We developed a virtual MATLAB simulation to further understand the flexibility constraints of these motions. This virtual hagfish physics simulation was composed of 50 rigid links connected serially using spherical joints with movement-resistant springs. However, the simulated movements were not realistic because we lacked basic estimates of whole body flexibility. In this study, we provided the model with realistic estimates of range of motion and degrees of freedom by measuring the tightest loop radius that the body was able to hold passively. We formed and photographed loops along the bodies of freshly euthanized Pacific hagfish (Eptatretus stoutii) at points corresponding to 20%, 40%, 60%, & 80% body length. We then skinned the hagfish and performed these same experiments to identify the contribution of the loose skin to whole body flexibility. Photographs were then analyzed with NIH ImageJ to measure average loop radii. E. stoutii showed a larger range of lateral movements compared to ventral and especially dorsal movements. We were able to longitudinally twist the bodies between 900o and 1440o depending on the specimens’ length/diameter ratios. Range of motion generally increased towards the posterior portion of the body, and skin did not greatly affect range of motion. These passive flexibility measurements, when incorporated into our simulation, produced more realistic movement. To further improve these measurements, we are analyzing loop radii in actively knotting hagfish and in hagfish of different species.
