Meeting Abstract
S3-2.4 Saturday, Jan. 5 How is a morphology that is under strong selection for swimming performance “repurposed” for terrestrial locomotion? GIBB, A.C.*; ASHLEY-ROSS, M.A.; HSIEH, S.T.; Northern Arizona University; Wake Forest University; Temple University alice.gibb@nau.edu
Non-amphibious teleost fish spend the vast majority of their lives in the water. Yet, individuals may become stranded during efforts to evade predators or colonize new habitats and must produce effective movements on land to return to the water. How is a morphology that is under strong selection for swimming performance “repurposed” to produce terrestrial locomotion? On a slope, a fish can produce head and/or tail oscillations that overcome inertia, enabling it to tumble or slide downhill. However, to effectively traverse overland, a fish cannot simply recapture potential energy, but must produce propulsive ground-reaction forces. To this end, many small, fully-aquatic teleosts employ a “tail-flip” jump when stranded on a flat surface. In this behavior, a fish, lying on its side, peels the head off the substrate, rolls the anterior body over the tail, and then straightens the body to launch into the air. We note that both down-slope and overland-transit behaviors in fully-aquatic fishes are markedly different from locomotor behaviors exhibited by many amphibious fishes; in amphibious fishes, the ventral (rather than lateral) surface of the body is in contact with the substrate, and bending movements are primarily parallel to the substrate. In addition, in several amphibious species, the body-bending component of the locomotor behavior is reversed, such that the tail curls towards the head (rather than the head toward the tail) with subsequent axial extension plus rotation contributing to effective thrust production. Thus, from observations of extant teleosts that represent a gradient of “terrestriality”, we hypothesize that the transition to a “prone” position may be a key component of the evolution of a terrestrial habit.
