Meeting Abstract
Many benthic fishes move along the bottom with a bipedal or punting gait of the paired pelvic or pectoral fins. We examined the benthic gaits of flatfishes (six species, total n=34) which use the dorsal and anal fin to move along the substrate to (1) better understand the functional and evolutionary morphology of this system and (2) compare flatfish gaits to those based on paired appendages and cilia. All flatfish species employed one or more benthic gaits, which we termed “walking” and “bounding”. Two flatfish species, the Pacific sand sole, Psettichthys melanostictus (N=5) and the English sole, Parophrys vetulus (N=5) were selected for additional gait analyses. We found that walking is consistently used as a form of benthic locomotion in Psetticthys melanostictus, while bounding is preferred by Parophrys vetulus. We tracked points on the head and leading edge of the fin wave from videos (120 fps) using the DLTdv5 Digitizing Tools for MATLAB and the Manual Tracking plugin for ImageJ. During bounding, a single wave of median fin propulsion is assisted by lateral undulations of the body and tail, producing rapid but intermittent acceleration of the body. During walking, flatfishes use sequential portions of their median fins as “feet” that move in parallel waves to propel their bodies across the substrate at a constant velocity. To complete a walk cycle, a fin ray swings up off of the substrate, protracts and converges with neighboring fin rays to form a functional “foot”. The fin ray “foot” then pushes down and back, and the wave progresses posteriorly to produce forward movement of the body. The waves of the median fin rays appear broadly similar to the metachronal waves observed in millipede legs and the cilia of paramecium; to our knowledge this is the first example of metachronal waves producing a vertebrate walking gait.
