Meeting Abstract
Escape response performance is an important aspect of fitness as it aids in survival. Much of the work on escape responses has focused on fish that undulate their body or caudal fin (BCF swimming) or use their paired pectoral fins during routine locomotion. However, fish that rely on the median fins (e.g., anal or dorsal) during steady swimming have not been well investigated, despite their unique modes of locomotion. Gymnotiform locomotion is of particular interest because these fish hold their body steady, undulate only an elongated anal fin to produce thrust during routine swimming, and often have reduced caudal fins, which are a major thrust-producing structure in an escape response. Only one study has investigated the kinematics of escape in a gymnotiform swimmer, and they demonstrated that Xenomystus nigri uses axial movements to form a “c-bend” and has a high acceleration relative to similarly-sized BCF swimmers. It remains unclear, however, whether these results hold true across species that employ this swimming mode, including intermediate forms that undulate an elongate anal fin with simultaneous (but lower frequency) body undulations. To investigate the kinematics and performance of escape response maneuvers across gymnotiform-swimming species, we filmed and digitized escapes of X. nigri and two other pure gymnotiform swimmers (Eigenmannia virescens and Apteronotus albifrons), two BCF swimmers (Devario malabaricus and Osteoglossum bicirrhosum), and two intermediate forms that utilize both body-caudal fin and anal fin undulations (Chitala ornata and Notopterus notopterus). We found that while body curvatures may differ, phylogenetically-corrected escape performance was unaffected by the distinction between the gymnotiform and BCF swimming modes.
