Meeting Abstract
The killifishes (Cyprinodontiformes) usually respond to a negative aquatic stimulus by performing an aquatic escape, or C-start, but some species will jump onto land when threatened. Once on land, fish often perform a tail-flip jump to return to the water. During the tail-flip jump, a fish raises its head from the substrate and bends towards the tail, forming a “C”, then straightens its body while pushing off of the substrate with the caudal peduncle to launch into ballistic flight. This behavior shares key similarities with the aquatic escape response, including large-amplitude lateral bending, followed by axial straightening. However, a jump must be performed against the forces of gravity and over a longer time interval, relative to the aquatic C-start. Because the mechanical demands on the musculoskeletal system are different on water vs. land, we hypothesized that there would be functional tradeoffs between the C-start and tail-flip jump. We predicted fishes that perform better (longer) terrestrial jumps would perform worse (slower) aquatic C-starts. To test this prediction, we examined three species of killifish: Gambusia affinis, Poecilia mexicana, and Jordanella floridae. We filmed individuals (n=10) of all three species performing the C-start in water (recorded at 800 fps) and tail-flip jump on land (600 fps). In contrast with our original prediction, we found no functional tradeoff between C-start and tail-flip jumping performance. Fishes that performed faster C-starts also tended to perform longer tail-flip jumps. This suggests that the selection pressures that underlie the evolution of both of behaviors may generate a body shape that is capable of producing effective movements in both environments, despite the drastic physical differences between the aquatic and terrestrial realms.
