Meeting Abstract
We compared iliosacral movements and motor patterns during jumping and landing in anurans with “lateral-bender” and “rod-like” pelvic designs. Muscle activity patterns, iliosacral anteroposterior (AP) movements and sagittal bending of the pelvis were quantified in the lateral bending Ascaphus (Leiopelmatidae) and Rhinella (Bufonidae) and the rod-like Lithobates (Ranidae). All species exhibited sagittal extension during take-off; however, trunk elevation occurred significantly earlier in the rod-like pelvis. Piriformis muscles depressed the urostyle whereas longissimus dorsi muscles elevated the trunk during take-off. Coccygeoiliacus muscles produced anterior translation of the sacrum on the ilia. A new model illustrates how AP translation facilitates trunk extension in lateral-benders thought to have limited sagittal bending. During landing, AP translation patterns are similar, as impact forces slide the sacrum from its posterior to anterior limits. Sagittal flexion during landing differs among taxa and AP translation during landing may dampen impact forces, especially in Rhinella in which pelvic function is tuned to forelimb-landing dynamics. The flexibility of the lateral-bender pelvis helps to explain retention of this basal configuration in many anurans. The novel function of the rod-like pelvis may be to increase the rate of trunk elevation relative to faster rates of energy release from the hind limbs, enabling them to jump farther.
