Pleopod Rowing Is Used to Achieve High Forward Swimming Speeds During the Escape Response of Odontodactylus havanensis (Stomatopoda)
The escape responses of twelve individuals of the stomatopod Odontodactylus havanensis (35-64 mm body length) were recorded with conventional and high-speed (60 and 500 images per second) video cameras. Unlike the typical pattern of escape swimming seen in most elongate Malacostracan crustaceans in which quick backward swimming is achieved by rapid pleonal flexion (tail-flipping), O. havanensis always swam forward during its escape response. Rowing of the pleopods provided thrust during swimming. The power phase was metachronal and the recovery phase was approximately synchronous. The mean stroke frequency, from high-speed video, was 17 Hz. With this swimming mode, speeds of 1.25 to 1.62 meters per second and 21 to 40 body-lengths per second were attained. The intermittent nature of the rowing propulsive mode led to temporally unsteady kinematics marked by periodicity. Although forward swimming via pleopod rowing is a very common form of locomotion employed by elongate crustaceans, it is typically observed only during relatively slow, “routine” swimming, with escape being driven by tail-flipping. Odontodactylus havanensis breaks this pattern. Further study into how this species is able to achieve such high speeds via rowing locomotion may yield new insights into our knowledge of animal locomotion through fluids.