Meeting Abstract
Fish are highly diverse in their methods of thrust production and are broadly characterized as either body-caudal fin (BCF) or median/paired fin (MPF) swimmers. Gymnotiform locomotion is a subdivision MPF swimming where fish use an elongated anal fin to produce thrust via ribbon-like undulations. Gymnotiform swimmers are hypothesized to be highly maneuverable but limited in their bursting and sustained swimming abilities. However, a study on the escape response of one gymnotiform species (Xenomystus nigri) suggests that their acceleratory ability is greater than that of similarly sized BCF swimmers. Little is known about the performance of gymnotiform swimmers, and comparative data with other swimming modes is particularly sparse. To better understand the costs and benefits associated with gymnotiform locomotion, as well as the validity of hypothesized tradeoffs, we investigated the sprint performance and sustained swimming costs of two BCF swimmers (Devario malabaricus and Osteoglossum bicirrhosum), three pure gymnotiform swimmers (Apteronotus albifrons, Eigenmannia virescens, and X. nigri), and two knifefish which utilize varying degrees of BCF and anal fin undulations (Chitala ornata and Notopterus notopterus). No differences were detected in maximum sprint speeds across species, suggesting that gymnotiform swimmers are not poor sprinters. Cost of transport analysis showed mixed results across species, but there was no apparent link between locomotor mode and performance. These results demonstrate that variation in swimming mode does not necessarily hinder swimming ability. This study lends support to the proposal that thrust production mechanisms for various types of locomotion (i.e. sprinting, acceleration, and cruising) may be physically decoupled in specialized swimmers, enabling these fish to perform well in all categories.
