Meeting Abstract
Swim performance in fishes is influenced by body morphology, which is often reflective of the natural environment. For example, fish living in high-flow environments (e.g., river rapids) typically have streamlined bodies and fins designed for steady swimming, while fish from low-flow, structurally complex environments (e.g., swamps) typically have maneuverable bodies and large fins that aid in unsteady swimming. These factors can also be influenced by phylogenetic relationships among species. To obtain a comprehensive understanding of the influence of natural habitat on morphology and swimming performance, we investigated the relationship between morphology and swimming performance among three closely related species of wild-caught elephant nose mormyrid fishes from divergent habitats. Geometric morphometrics was used to characterize differences in body and fin shapes among a high-flow species (Campylomormyrus spp.), an open-water species (Gnathonemus petersii), and a swamp species (Gnathonemus victoriae). We also determined the swimming capabilities of each species at four swim speeds (0.5-2.0 body lengths/sec). While our results indicate that morphological differences among species are reflective of their natural environments (e.g., high-flow species are more streamlined than swamp species), our swim performance findings are contrary to our predictions. The high-flow species, Campylomormyrus spp., spent significantly more time swimming unsteadily at every speed compared to both Gnathonemus species. This can be explained, in part, by differences in the head and snout shape among the three species, which may have a greater influence on swimming patterns than overall body shape.
