Cuttlefish Turn Slowly but Tightly with Directional Flexibility Using Short Vortex Ring Jets

AbstractCephalopods, such as squids and cuttlefishes, play an integral role in food web dynamics as both prey and predator, whereby proficient turning is required for successful predator avoidance and prey capture. However, surprisingly little is known about the turning capabilities of most cephalopods. In this study, body movements and 3D flow fields around adult dwarf cuttlefish, Sepia bandensis, were recorded during a range of maneuvers to quantify turning performance. While significant variation in turning capabilities was observed, S. bandensis, on average, turned tightly (mean length-specific turning radius = 0.14±0.013 [SEM]; minimum length-specific turning radius = 0.013±0.002) but relatively slowly (average angular velocity = 45.85°±2.70° s^-1; maximum angular velocity = 110.34°±7.09° s^-1). Jet properties were not reliable predictors of turn performance, as S. bandensis relied primarily on short vortex ring jets (length-to-diameter ratio of jet vorticity = 2.47±0.18) of moderate velocity (average jet velocity ∼ 14 cm s^-1; maximum jet velocity ∼ 22 cm s^-1) irrespective of turn type. The orientation of the turn (arms-first vs. tail-first) did not have a significant effect on kinematic or hydrodynamic properties, and most turns were performed arms-first (72.6% of turns). Compared to other cephalopods, cuttlefish turned using shorter jets with similar velocity profiles. These results are consistent with the residence of S. bandensis in complex benthic habitats, where tight, controlled turns facilitated by short jet pulses and high turning proficiency in either orientation are needed.