Meeting Abstract
Hagfishes and moray eels might be the only types of fish that use knotting to apprehend prey. Knotting involves concomitant bending and twisting, which apply a combination of tension, shear, and compression to the body’s core and skin. In hagfish, the stresses on the skin and core are separated by a subcutaneous venous sinus, which gives the skin its slack appearance and provides space for the core to contort as needed without loading the skin in tension or shear. Hagfish skins placed in tension range from being equally to twice as stiff in the longitudinal axis as in the hoop axis. Conversely, the skins of cartilaginous and bony fishes are taut, preclude exaggerated body core deformations, and are often twice as stiff along the hoop axis. Hagfish also benefit from a derived arrangement of body core muscles that power knotting movements. It is unclear if these adaptations are present in species of morays capable of knotting. We address this question by examining the morphology and material properties of the skins from purple mouth morays (Muraenids that knot), and compared these data with those gathered from American eels (non-knotting Anguillids), Asian swamp eels (non-knotting Synbranchids), and hagfishes (Myxinids that knot). Moray eels are like non-knotting eel species in having taut skins that are firmly connected to serially arranged segments of expaxial and hypaxial muscles. However, like Atlantic hagfish skins, moray skins are isotropic and less stiff than non-knotting eel skins. In contrast to hagfish, knotting in moray eels requires neither loose skin nor complex arrangements of core muscles, therefore, the deformations needed for this behavior are likely achieved by different structural and mechanical features of the Muraenid skin and core.
