Meeting Abstract

92.1  Saturday, Jan. 7  Evolution of tetrapod rhythmicity ROSS, C.F.*; BLOB, R; CARRIER, D.R.; DALEY, M.A.; DEBAN, S.M.; DEMES, B.; GRIPPER, J.L.; KILBOURNE, B.; LANDBERG, T.; POLK, J.; SCHILLING, N.; VANHOOYDONCK, B.; University of Chicago; Clemson University; University of Utah; Royal Veterinary College; University of South Florida Tampa; Stony Brook University; University of Chicago; University of Chicago; Boston University; University of Illinois Urbana-Champagne; Friedrich-Schiller-Universität; University of Antwerp rossc@uchicago.edu

The period of cyclic, oscillating musculoskeletal systems scales with the size of the system in a manner suggestive of resonant tuning. However, the energetic and control benefits of resonant tuning can only be realized if variance in mean cycle period is low. Chew cycle period is less variable among mammals than among lepidosaurs and scales with jaw length in mammals but not lepidosaurs, suggesting clade-specific differences in degree of resonance tuning of musculoskeletal movements. Rhythmicity of locomotor movements was compared across tachymetabolic (birds, mammals) and bradymetabolic (lizards, alligators, turtles, salamanders) tetrapods. Variance in locomotor cycle periods was shown to be significantly lower in tachymetabolic than in bradymetabolic animals using treadmill data, non-treadmill data, or both. When phylogenetic relationships were taken into account, the non-treadmill analysis remained significant, the treadmill analysis became nonsignificant (but only marginally) and the non-treadmill analysis was not significant. It is hypothesized that high rhythmicity has advantages related to resonance tuning, coordination, and control of complex behaviors. Convergently evolved features of bird and mammal sensorimotor systems plausibly linked to rhythmicity include large Ia-afferent nerve fibers, &gamma-motoneurons, and enlarged, elaborated telencephala