Structure and function in the tail of the Pumpkinseed sunfish (Lepomis gibbosus)

Patterns of in vivo bone deformation in the caudal skeleton of sunfishes have been studied with rosette strain gauges. An anatomical description of caudal osteology and myology is provided for comparison with other actinopterygian fishes and as an aid in interpreting the bone strain patterns. Peak bone strain during fast‐start acceleration was −3213 µε and the peak strain rate was −296 x 103 µs/s. During steady locomotion, strain rates and magnitudes were considerably lower (10–85 x 103 µε/s and 379–1074 µε, respectively). The main strain peak during fast‐starts occurs during kinematic stage one. Mean principal tensile and compressive angles are aligned parallel and perpendicular to the body axis during fast‐starts, while steady locomotion results in strain axes inclined at a mean angle of −34° to the body axis. These results are compared to strain data from other vertebrates: vertebrate bone is only very rarely subjected to deformations greater than 3100 µε and to strain rates greater than 100 × 103 µε/s. The role of this type of functional analysis in studying actinopterygian locomotor patterns is discussed.