Meeting Abstract
Apteronotus albifrons, or the gymnotiform black ghost knifefish, is known for its ribbon-like motion of the anal fin during swimming. This anal fin contains approximately 150 individual fin rays that allow for full movement of the fin. While these fish possess an elongate anal fin for locomotion, they completely lack a dorsal fin. However, due to inbreeding or relaxed selection, a mutant strain of A. albifrons exhibits an elongate dorsal fin. The presence of the dorsal fin mutation allows for the opportunity to study the effects of the dorsal fin on gymnotiform swimming. This dorsal fin is unique because it does not seem to function like a normal fin; it does not seem that the fish can control the fin. Preliminary internal morphology of the regained dorsal fin suggest that the mutant knifefish regained both the individual fin rays and fin ray supports as seen in the fully functional anal fin. While the swimming kinematics of normal A. albifrons have been previously described, the goal of this project was to determine the effect of a regained dorsal fin in the mutant knifefish on routine swimming kinematics and abilities. Using 5 mutant and 4 normal knifefish of similar size, we compared the swimming kinematics of the anal fin (e.g., amplitude and wavelength) during routine forward, backward and hover swimming. Fish were filmed at 250 Hz and fin kinematics were analyzed in ImageJ. Preliminary results suggest that the reappearance of the dorsal fin does not alter routine swimming kinematics. We discuss these results in the context of knifefish locomotion and dorsal fin function.
