First published online November 2, 2007
Journal of Experimental Biology 210, 3931-3939 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.009548
Unique role of skeletal muscle contraction in vertical lymph movement in anurans
Robert C. Drewes1,*,
Michael S. Hedrick2,
Stanley S. Hillman3 and
Philip C. Withers4
1 Department of Herpetology, California Academy of Sciences, 825 Howard
Street, San Francisco, CA 94013, USA
2 Department of Biological Sciences, California State University, East Bay,
Hayward, CA 94542, USA
3 Department of Biology, Portland State University, Portland, OR 97207-0751,
USA
4 Zoology, School of Animal Biology MO92, University of Western Australia,
Crawley, Western Australia 6009, Australia

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Fig. 1. Stylized models representative of morphological differences in the skeletal
muscle presented in this work. (A,B) Chaunus marinus; (C,D)
Lithobates catesbeiana. A and C represent ventral views; B and D
represent posterior views. Key: A, abdominal crenator; G, gracilis minor; T,
tensor fascia latae; P, piriformis; S, sphincter ani cloacalis; CP, cutaneous
pectoris; CD, cutaneous dorsi.
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Fig. 2. Representative traces of the synchrony between integrated EMG activity of
the skeletal muscles indicated and their synchrony with pressure changes in
the lymphatic sacs in (A) C. marinus and (B) L.
catesbeiana.
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Fig. 3. Examples of correlation between EMG activity in M. piriformis and impedance
change between the urostyle and cloaca in (A) C. marinus and (B)
L. catesbeiana.
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Fig. 4. Pattern of pressure change in the pubic sac during a contractile event. Two
examples of the types of pressure changes recorded from lymph sacs. The first
event illustrates a `decrease only' pattern while the second event illustrates
the more common `biphasic' increase/decrease pressure pattern. Pressure before
(Ppre) and following (Ppost) the
pressure event (shaded area; P) are shown (see text).
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Fig. 5. Frequencies of varying patterns of pressure change for the (A) interfemoral
and (B) pubic lymph sacs of C. marinus. The majority of pressure
events are `biphasic' [increase (+)/decrease (–)] compared with
increase-only (+) or decrease-only (–). Values are means ±
s.e.m.
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Fig. 6. Correlation between the mean event pressure ( P) and the net
change (Ppre–Ppost) for the
intermuscular, iliac, interfemoral and pubic lymph sacs of C.
marinus.
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© The Company of Biologists Ltd 2007