Locomotor flexibility of Polypterus senegalus across various aquatic and terrestrial substrates.

Amphibious fishes show wide variation in form and function. Examination of terrestrial locomotion in fishes has largely focused on highly specialized taxa. From an evolutionary perspective we are interested in how relatively unspecialized fishes locomote when exposed to different terrestrial environments. In this study, we explore the locomotory repertoire of the basal actinopterygian Polypterus senegalus. We describe its terrestrial locomotory strategies on different surfaces and compare them with steady aquatic locomotion. Our study is the first to describe axial and appendicular-based terrestrial locomotion across a range of substrates in this species and shows two distinct terrestrial gaits in P. senegalus, each with substantial variation. One uses body undulation against complex surfaces and the other incorporates alternating, supportive pectoral fins to achieve a tetrapod-like gait. Gait use is correlated with substrate. P. senegalus uses body and pectoral fins in diverse ways, showing opportunistic and flexible strategies of navigating novel environments.