Jumping and kicking in the false stick insect Prosarthria teretrirostris: kinematics and motor control
Malcolm Burrows1,* and
Harald Wolf2
1 Department of Zoology, University of Cambridge, Cambridge CB2 3EJ,
UK
2 Abteilung Neurobiologie, Universität Ulm, Ulm D-89069,
Germany
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Fig. 1 . The body shapes of (A) Prosarthria teretrirostris, (B)
Cuniculina impigra, a stick insect, and (C) Schistocerca
gregaria, a locust. Scale bars, 25 mm.
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Fig. 2 . Movements of the femoro-tibial joint and body during a jump by a freely
moving adult male captured by high-speed images at 1000 frames s-1.
(A) Plot of hind-leg femoro-tibial angle and femur/body joint movements,
changes in height of the body and angle of the body relative to the ground.
Time zero was taken as the point when the hind legs left the ground and the
insect became airborne. Tibial extension takes 40 ms. The inset diagrams are
tracings from single frames, at the times indicated, to show body posture, leg
movements and the way the various measurements were made. The vertical lines
show when the front and hind legs are lifted from the ground. (B) Bending of
the tibia of a hind leg during the jump plotted in A at the times (in ms)
indicated. Horizontal lines indicate ground level. The degree of bending is
measured as the distance from the centre of the tibia to a line (chord)
joining the femoro-tibial and tibio-tarsal joints. The values (in mm) are
given in the right-hand column. The drawings are tracings from single images
in the jump.
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Fig. 3. Movements of the femoro-tibial joint during a kick by a restrained adult
female captured by high-speed images at 1000 frames s-1. The
angular changes of the tibia about the femur are plotted against time, with
the point of maximum extension designated as zero. The tibia extends fully in
7 ms. Oscillations in movements occur when the tibia reaches its maximum
excursion. Three single frames are shown from this kick at the times
indicated. The femur as a whole moved slightly in the Plasticine during the
rapid extension of the tibia, but no distortions are apparent in the
semi-lunar process (see Fig.
4A) when the tibia is flexed in advance of the kick or when it is
extending rapidly.
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Fig. 4. The femoro-tibial joint of the left hind leg of an adult female
Prosarthria teretrirostris. (A) View from the anterior surface. The
anterior semi-lunar process is a thin curved structure forming a dark groove
in the femur. The coverplate is sculpted so that the pivot of a tibial horn
with the incurving part of the anterior semi-lunar process is visible. The
extensor tibiae muscle inserts on the dorsal rim of the tibia and the flexor
tibiae muscle around a ventral U-shaped rim of tibial cuticle. (B) Ventral
view with the tibia extended. The ventral femur has infoldings that form an
internal lump over which the tendon of the flexor tibiae muscle slides (see
Fig. 5B). The membrane
surrounding the tendon is folded to form a pocket. Hair rows on the proximal
tibia can be seen. (C) Dorsal view of the tibia and its articulation with the
femur with the joint flexed. The pivot between the femur and the tibia is seen
as a pair of close appositions between the two semi-lunar processes of the
femur and the horns of the tibia.
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Fig. 5. Movements of the insertions of the flexor and extensor tibiae muscles
relative to the pivot of the femoro-tibial joint as the tibia moves about the
femur. (A) Drawing of the femoro-tibial joint of a left hind leg viewed
anteriorly. The distributed insertion of the tendon of the extensor tibiae
muscle is shown. The outline of the femur and tibia are colour-coded in orange
and red, respectively, and the pivot of the joint is represented by a black
dot. The tendon of the extensor tibiae muscle is blue and that of the flexor
is green. (B) Six diagrams made from scale drawings of the femoro-tibial joint
angles from 163° (extended) to 21.5° (flexed). The outline of the
joint is drawn only for the most extended position of the tibia, but the lump
over which the flexor tibiae tendon slides is drawn in each. At the most
flexed angle, which was never observed during natural movements of the joint,
the action of the extensor tendon is over centre. (C) Graphs of the extensor
and flexor lever arms (expressed as fractions of tibial length) at different
joint angles measured from the forces that have to be applied to the tendons
to effect joint movements. The lever arms of the flexor and extensor are equal
(lever ratio=1) at a joint angle of 55°.
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Fig. 6. Actions of the extensor and flexor tibiae muscles during kicking and
jumping. (A) A kick by a restrained female. The flexor muscle is active first
and moves the tibia to a flexed position. The flexor and extensor muscles then
co-contract. The large spikes in the extensor have been distorted by the
amplifier. The flexor muscle spikes stop just before the tibia extends
rapidly, while those of the extensor continue for another 15-20 ms. (B) A jump
by an unrestrained female. The pattern of muscle action is similar to that
during kicking, with a period of co-contraction followed by cessation of
flexor activity before the tibia extends and the insect takes off. The jump
propels the insect beyond the limits of the tibial movement detector so that
the movement trace is lost.
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© The Company of Biologists Ltd 2002
