Three-dimensional movements of the pectoral fin during yaw turns in the Pacific spiny dogfish,Squalus suckleyi

Abstract

Fish pectoral fins move in complex ways, acting as control surfaces to affect force balance during swimming and maneuvering. Though objectively less dynamic than their actinopterygian relatives, shark pectoral fins undergo complex conformational changes and movements during maneuvering. Asynchronous pectoral fin movement is documented during yaw turning in at least two shark species but the three-dimensional (3D) rotation of the fin about the body axes is unknown. We quantify the 3D actuation of the pectoral fin base relative to the body axes. We hypothesized that Pacific spiny dogfish rotate pectoral fins with three degrees of freedom relative to the body during volitional turning. The pectoral fin on the inside of the turn is consistently protracted, supinated and depressed. Additionally, turning angular velocity increased with increasing fin rotation. Estimated drag on the fin increased and the shark decelerated during turning. Based on these findings, we propose that Pacific spiny dogfish uses drag-based turning during volitional swimming. Post-mortem muscle stimulation revealed depression, protraction and supination of the pectoral fin through stimulation of the ventral and cranial pterygoideus muscles. These data confirm functional hypotheses about pectoral fin musculature and suggest that Pacific spiny dogfish actively rotate pectoral fins to facilitate drag-based turning.

Backing up from negative stimuli: A back‐thrust mechanism during escape‐like response in wild sevengill sharks (Notorynchus cepedianus)

“…In the case of sharks, however, these studies are rare and largely outnumbered by experimental studies on locomotion under controlled conditions in the laboratory that represent a field of study of increased interest (Maia et al., 2012). Experimental studies usually focus on one aspect of the movement, which is analyzed with great accuracy thanks to technological advances (e.g., Camp et al., 2017; Hoffmann et al., 2019). However, natural conditions are hardly replicated in the laboratory, and therefore, the behavior of experimental animals is usually influenced and limited.…”

Body and Pectoral Fin Kinematics During Routine Yaw Turning in Bonnethead Sharks (Sphyrna tiburo)

“…Further, pectoral fin actuation is under muscular control; thus, fin actuation may lead to a finer degree of control during maneuvering ( Maia et al. 2012 ; Hoffmann et al. 2019 ).…”

“…The goals of this study were to describe the body and pectoral fin as they relate to turning performance of bonnethead sharks. We hypothesized that the bonnethead shark would protract, supinate, and depress the fin inside to body curvature, and that increasing fin rotation would correlate with turning performance metrics as previously described for the Pacific spiny dogfish ( Hoffmann et al. 2019 ).…”

Escaped bait: Bull shark Carcharhinus leucas with an intentionally attached harness rig

“…This may explain the robust condition of the bull shark despite its prolonged entanglement. Shark pectoral fins are moveable about the insertion, with musculature that allows them to be elevated, depressed and rotated relative to the body, and are critical for both vertical (rising and sinking) and horizontal (turning) manoeuvrability (Hoffmann et al, 2019;Maia et al, 2012;Wilga & Lauder, 2000), therefore the constant elevation of the pectoral fins caused by the apparatus would likely have affected swimming performance. Sharks have a high capacity for wound healing and recovery following injury (Bird, 1978;Chin et al, 2015;Kessel et al, 2017;Riley et al, 2009).…”