S1-1.12 Jan. 4 Ontogenetic differences in squid jet structure BARTOL, I.K.*; STEWART, W.J.; Old Dominion University, Norfolk, VA; Old Dominion University, Norfolk, VA email@example.com
Squids rely heavily on a pulsed jet for locomotion throughout ontogeny, but the jet is used in very different flow regimes depending on life history stage. Squid hatchlings (paralarvae) may operate at a Reynolds number (Re) = 1, whereas some large squid adults operate at a Re = 108. Over this wide Re range, the physics of fluids play an important role in development of jet features integral to propulsive swimming performance, and consequently swimming strategy may correlate closely with Re. We investigated whether jet structure and swimming behavior change as a function of life history stage. Using a customized holding chamber and a zoom lens with a 0.8 x 0.8 cm field of view, we performed digital particle image velocimetry (DPIV) experiments with free-swimming long-finned squid Loligo pealei paralarvae (dorsal mantle lengths (DML) ~ 0.2 cm). Older life history stage experiments were conducted using brief squid Lolliguncula brevis (2.0 – 9.0 cm DML) swimming in a water tunnel equipped with a multi-camera motorized traverse system and laser guide arm for kinematic and DPIV data recording. Vortex rings were a conspicuous jet feature in all life history stages and jet plug length (L) to funnel diameter (D) ratios were useful indices for predicting vortex ring structure. Paralarvae generally exhibited higher pulsing rates, higher relative jet velocities, and more rapid vortex dissipation rates than the adult squid. Vortex rings with and without trailing jets were observed in all life history stages, but large adults swimming at high speeds had the largest L/D ratios and vortex rings with the longest trailing jets. The implications of these findings for swimming efficiency will be discussed.