The scaling of acceleratory aquatic locomotion: Body size and tail-flip performance of the California spiny lobster Panulirus interruptus

Tail-flipping is a crucial escape locomotion of crustaceans which has been predicted to be limited by increased body mass (M-b). Given isometric growt h, one may predict that with growth event duration will decrease as M-b(-1/ 3), translational distances will increase as M-b(1/3) translational velocit y will be independent of M-b, translational acceleration will decrease as M -b(-1/3), angular displacement will be independent of Mb and angular veloci ty and angular acceleration will decrease as M-b(-1/3) We tested these hypo theses by examining the scaling of 12 morphological variables, five kinemat ic variables and six performance variables of tail-flipping by the Californ ia spiny lobster Panulirus interruptus. Growth approximated isometry, which validated the use of the proposed scali ng hypotheses. For animals from 1 to 1000 g Mb, the predicted scaling relat ionships for tail-flip duration and translational distance and velocity var iables were supported; however, translational acceleration performance was much better than predicted. Predictions for rotation and rotational velocit y variables were not supported, while the rotational acceleration data clos ely matched the predicted relationship. The increase in tail-flip duration as predicted suggests that muscle shorte ning velocity decreases with growth; the sustained acceleration performance (similar to findings for shrimp and fish fast-starts) suggests that muscle force output may increase at a greater rate than predicted by isometry, Th e scaling of rotational acceleration indicates that the torque produced dur ing the tap-hip scales with a mass exponent greater than 1. Comparison of t he tail-flip performance of Panulirus interruptus with those of other crust acean species reveals a wide range in performance by animals of similar bod y size, which suggests that the abdominal muscle mag show interesting diffe rences in contractile properties among different species.