Ontogenetic changes in mantle kinematics during escape-jet locomotion in the oval squid, Sepioteuthis lessoniana lesson, 1830

We investigated the kinematics of mantle movement during escape jet behavio r in an ontogenetic series of Sepioteuthis lessoniana, the oval squid. Chan ges in mantle diameter during the jet were measured from digitized S-VHS vi deo fields of tethered animals that ranged in age from hatchlings to 9 week s. The amplitude of both mantle contraction and mantle hyperinflation (expr essed as percent change from the resting mantle diameter) during an escape jet was significantly greater in hatchlings than in older, larger squid (P < 0.05). The maximum amplitude of mantle contraction during the escape jet decreased from an average of -40% in hatchlings to -30% in the largest anim als studied. The maximum amplitude of mantle hyperinflation decreased from an average of 18% in hatchlings to 9% in the largest squid examined. In add ition, the maximum rate of mantle contraction decreased significantly durin g ontogeny (P < 0.05), from a maximum of 8.6 mantle circumference lengths p er second (L/s) in hatchlings to 3.8 L/s in the largest animals studied. Th e ontogenetic changes in the mantle kinematics of the escape jet occurred c oncomitantly with changes in the organization of collagenous connective tis sue fiber networks in the mantle. The alteration in mantle kinematics durin g growth may result in proportionately greater mass flux during the escape jet in newly hatched squid than in larger animals.