THOMPSON, J.T.*; LOBO, K.M.; St. Joseph’s University, Philadelphia, PA; St. Joseph’s University, Philadelphia, PA: Kinematics of the escape jet in paralarval squids.

The mantle and funnel of squids are essential in generating and modulating thrust for jet locomotion. Previous research has demonstrated that aspects of the morphology, kinematics, and mechanics of the mantle and funnel differ dramatically between a newly hatched squid (i.e., a paralarva) and an adult. The maximum amplitude and rate of mantle contraction, the average mass flux of the escape jet, and the relative aperture of the funnel are all significantly greater in paralarvae, yet the mass-specific thrust of the escape jet is significantly lower in paralarvae. These ontogenetic differences in the escape jet, which correlate with a significant rearrangement of the muscles and connective tissues of the mantle, imply a tradeoff during ontogeny: paralarvae appear to achieve substantially greater propulsion efficiency than adults (not just for the escape jet but for jetting at all speeds) but at the price of diminished mass-specific thrust. To determine the effects of the hypothesized performance tradeoff during ontogeny, we investigated the kinematics of escape-jet locomotion in the paralarvae of two species of loliginid squids: Sepioteuthis lessoniana and Loligo pealei. We recorded escape-jet behavior using two synchronized high speed digital video cameras running at 250 fps. We tracked the position of each squid in three dimensions and calculated velocities and accelerations using direct linear transformation. The tentative results indicate that, relative to body size, paralarvae generate lower peak velocity during the escape jet than adults. Conversely, the peak acceleration of the escape jet was greatest in paralarvae.