METAMORPHIC AND SPEED EFFECTS ON HINDLIMB KINEMATICS DURING TERRESTRIAL LOCOMOTION IN THE SALAMANDER DICAMPTODON TENEBROSUS

The kinematics of the hindlimb during terrestrial treadmill locomotion in Dicamptodon tenebrosus were compared between larval and metamorpho sed individuals at different speeds. Coordinates of marker points on t he salamander's midline, pelvic girdle and left hindlimb were digitize d from high-speed videos (200 fields s(-1)). These yielded kinematic v ariables describing trunk flexion, pelvic girdle rotation, femoral pro traction/retraction and knee flexion/extension. A three-way analysis o f variance tested for mean differences among individuals, speeds and m etamorphic stages for each variable. No significant overall effects of metamorphosis were found, although several variables showed significa nt stage X individual effects. Multivariate analyses revealed that the variance in kinematics of the larvae was significantly greater than t hat of the metamorphosed salamanders. Several variables showed signifi cant speed effects or strong trends, among them stride length (increas es with speed), cycle duration (decreases), contact interval (decrease s) and phase variables describing the relative timing between minimum/ maximum angles and the beginning of stance/swing phase. Such changes w ith speed are consistent with those shown for diverse arthropods and t etrapods and suggest that changes in stride length and timing events d uring a stride represent a general mechanism for effecting an increase in locomotor speed.