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First published online May 13, 2004
Journal of Experimental Biology 207, 2115-2131 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00995

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The effects of surface diameter and incline on the hindlimb kinematics of an arboreal lizard (Anolis sagrei)

Lawrence C. Spezzano, Jr^* and Bruce C. Jayne

Department of Biological Sciences, University of Cincinnati, PO Box 210006, Cincinnati, OH 45221-0006, USA

View larger version (15K): [in a new window]   Fig. 1. An anterior, schematic view of potential effects of perch diameter on limb posture showing a sprawling limb (A) and a more upright limb posture on a wide (B) and narrow perch (C). The pelvic width, and lengths of the femur and tibia, are anatomically correct for A. sagrei. The transverse axis of the pelvis, femur and tibia, are all in the plane of the illustration. (D) The expected effects of perch diameter on hip height (*), and the clearance between the top of the perch and the ventral surface of the lizard when the limbs have the posture shown in A. The horizontal broken line indicates the length of the tibia.

View larger version (118K): [in a new window]   Fig. 2. Right lateral and dorsal views of A. sagrei (snout–vent length 5.5 cm, mass 5.0 g) moving on level 1 cm (A–D) and 10 cm (E–H) diameter perches at footfall (A,E), midstance (B,F), endstance (C,G) and midswing (D,H). The elapsed times after footfall of successive images for the 1 cm and 10 cm are 32, 60 and 88 ms and 36, 72 and 108 ms, respectively. The vertical lines on the perches are 5 cm apart. The forward speeds of the strides on the 1 cm and 10 cm perches were 52 and 55 cm s–1, respectively. See http://www.biology.uc.edu/faculty/jayne/videos.htm for digital videos of Anolis locomotion.

View larger version (26K): [in a new window]   Fig. 3. Mean values for the positions of the right hindlimb relative to the right hip (x=0, y=0, z=0, where x, y and z indicate anterior, dorsal and lateral, respectively) for each combination of incline (0°, 45° and 90°; columns) and locomotor surface (rows) at footfall (A) and midstance (B) on different diameter perches (1 cm, 3 cm, 6 cm, 10 cm and flat). From proximal to distal the endpoints of the line segments represent the hip, knee, ankle, distal end of the metatarsals and tip of the fourth toe. Sample sizes range from 10 to 16 strides (from four individuals per species) for each combination of the two factors. The projections onto the y–z and y–x planes correspond to anterior view and right lateral views, respectively.

View larger version (23K): [in a new window]   Fig. 4. Lateral (A,B) and dorsal (C,D) views of the positions for the right knee, ankle, metatarsal and toe tip relative to the hip (0, 0, 0) during one stride on a level 1 cm (A,C) and 10 cm (B,D) diameter perch. Positive values of x, y and z indicate anterior, dorsal and lateral movement, respectively. Open symbols, stance; filled symbols, swing portions of the stride; the overall direction of movement is clockwise. The time between successive points is 4 ms, and the strides are from the same individual.

View larger version (40K): [in a new window]   Fig. 5. Angles of the knee, ankle, femur rotation, femur retraction and femur depression, versus time for one stride of a single individual on a 1 cm (A–C) and 10 cm (D–F) diameter perch inclined at 0° (A,D), 45° (B,E) and 90° (C,F). Footfall occurred at 0%, and the vertical broken line represents the end of stance.

View larger version (14K): [in a new window]   Fig. 6. Mean values of stride (black symbols) and step (white symbols) length (A), stride frequency (B), hip height at footfall (C) and three-dimensional effective limb lengths at footfall (D) for each perch diameter and incline. Table 1 summarizes statistical comparisons of these variables among all surfaces.

View larger version (15K): [in a new window]   Fig. 7. Mean values of the minimum (black symbols) and maximum (white symbols) during the entire stride cycle for the longitudinal (A), vertical (B) and lateral (C) position of the tip of the fourth metatarsal relative to the hip for each perch diameter and incline. Tables 2 and 3 summarize the statistical comparisons of these variables.

View larger version (21K): [in a new window]   Fig. 8. Anterior view of the cumulative y and z (dorsal and lateral, respectively) positions of the right hip (black), knee (red), ankle (yellow), tip of the fourth metatarsal (green) and tip of the fourth toe (blue) of all the strides of one individual for each diameter on the level incline. For overlapping data, the more proximal points are layered on top of the more distal points. The horizontal line represents the top of the perch.

View larger version (19K): [in a new window]   Fig. 9. Mean values of knee (A) and ankle (B) angles at footfall (black symbols) and end of stance (white symbols) and pelvic rotation (C) for each perch diameter and incline. Table 4 summarizes the statistical comparisons of these variables.

View larger version (19K): [in a new window]   Fig. 10. Mean values of the minimum (black symbols) and maximum (white symbols) angles of femur retraction (A), depression (B) and long-axis rotation (C) for each perch diameter and incline during the entire stride cycle. Table 4 summarizes the statistical comparisons of these variables.

View larger version (16K): [in a new window]   Fig. 11. Mean values of angular excursions for the femur during retraction (A), depression (B) and long-axis rotation (C) for each perch diameter and incline during the entire stride cycle. Table 4 summarizes the statistical comparisons of these variables.

View larger version (22K): [in a new window]   Fig. 12. Principle component 2 (PC2) versus principle component 1 (PC1) from a single analysis of 15 kinematic variables of A. sagrei for all strides observed on each perch diameter and incline. Each point is an individual stride (N=185), and the points are separated by incline: level (A), uphill 45° (B) and 90° (C). Red circles, yellow squares, green triangles, blue inverted-triangles and black hexagons represent strides on 1, 3, 6, 10 cm and flat surfaces, respectively. Table 5 provides the loadings for the principle components.