The role of the subelytral spiracles in respiration in the flightless dung beetle Circellium bacchus
Marcus J. Byrne1,* and
Frances D. Duncan2
1 Ecophysiological Studies Research Programme, School of Animal, Plant and
Environmental Sciences, University of the Witwatersrand, Johannesburg, Wits
2050, South Africa
2 School of Physiology, Faculty of Health Sciences, University of the
Witwatersrand, Parktown 2193, South Africa
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Fig. 1. Position of the spiracles in Circellium bacchus, dorsal view,
elytra removed. Note that the anterior mesothoracic spiracles are actually
between the prothorax and abdomen and are not visible in this view.
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Fig. 2. Experimental set-up used in flow-through respirometry. A, anterior chamber;
P, posterior chamber; I, route for gases to sample the contents of the
posterior chamber during intermittent sampling; see text for details.
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Fig. 3. The relationship between body mass and volume of the subelytral cavity of
Circellium bacchus (regression equation:
y=0.063x-0.013; r2=0.56,
P=0.08, N=7). Error bars represent S.D.
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Fig. 4. Recordings of CO2 emissions of Circellium bacchus
(mass, 7.122 g) from (A) the posterior and anterior spiracles when air was
drawn through the respirometer chamber and over the elytral case (route I; see
Fig. 2) and (B) the posterior
and anterior spiracles when air was drawn through the subelytral cavity, i.e.
over the subelytral spiracles.
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Fig. 5. Results of intermittent sampling of CO2, O2 and water
emissions from the posterior and anterior spiracles of Circellium
bacchus (mass, 8.539 g) from outside the elytral case and inside the
subelytral cavity (SEC). (A) CO2 emission from the anterior
respirometer chamber. (B—D) Gas emissions from the posterior
respirometer chamber.
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© The Company of Biologists Ltd 2003
