Meeting Abstract

57.2  Jan. 6  Effects of substrate on the terrestrial locomotion of the ropefish. PACE, C. M.*; GIBB, A. C.; Northern Arizona University; Northern Arizona University Cinnamon.Pace@nau.edu

The ropefish, Erpetoichthys calabaricus, is an elongate polypterid that makes terrestrial excursions. Because ropefish rely on body-substrate interactions to produce forward thrust, the nature of the substrate likely affects locomotor efficacy. Ropefish were imaged (Redlake PCI 10005) moving across a moisture gradient of dry sand, moist sand, and wet sand substrates. Velocity and kinematics were quantified across all substrates. On all substrates the body was the propulsive organ and the pectoral fins played little or no role (in contrast to aquatic locomotion). During dry sand trials, sand adhered to the fish�s slime layer, movement was discontinuous, and body movements were relatively uncoordinated. During wet sand trials there was little or no adhering of sand particles, movement was typically continuous, and movement was coordinated and sinusoidal. During the moist sand trials, which were intermediate in water content between the dry sand trials and wet sand trials, movement parameters were also intermediate between those of the dry sand and the wet sand trials. For example, the average velocity for the trials occurring across wet sand (0.81�.16 cm/s) was slightly faster than the average velocity for the trials occurring across moist sand (0.72 � .38 cm/s), but both were faster than the average velocity of the trials occurring across dry sand (0.12 � .03 cm/s). These results imply that substrate impacts terrestrial locomotion and that ropefish possibly require both a wet and somewhat non-yielding surface to effectively move on land. It is important to determine the effects of substrate on locomotion in order to both increase our understanding of the dynamic nature of movement and to better evaluate the methods by which we assess animal locomotion in the laboratory setting.