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First published online March 8, 2005
Journal of Experimental Biology 208, 907-914 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01479

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The role of the mesothoracic spiracles in respiration in flighted and flightless dung beetles

Frances D. Duncan^1,* and Marcus J. Byrne²

¹ School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, South Africa
² Ecophysiological Studies Research Programme, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, Wits 2050, South Africa

View larger version (27K): [in a new window]   Fig. 1. (A). Relative positions of the anterior and posterior spiracles in dung beetles. (B) Collection localities of the four species of dung beetles used in this study indicating their separated distributions on the subcontinent. x Pachylomerus femoralis; x Scarabaeus gariepinus; x S. striatum; x Circellium bacchus. Climate graphs indicate rainfall in mm (y1 axis, solid bars), and temperature in °C (y2 axis, mean maximum, unbroken line; mean minimum, broken line). Ab, abdominal segment.

View larger version (29K): [in a new window]   Fig. 2. Recordings of CO2 emission from the anterior mesothoracic spiracles and the posterior elytral case in four species of dung beetles. (A) Pachylomerus femoralis (5.53 g), (B) Scarabaeus gariepinus (1.475 g), (C) S. striatum (0.487 g) and (D) Circellium bacchus (4.859 g). Note the different scales on the axes. C, closed period; F, flutter period; B, burst period. These are explained further in the text.

View larger version (18K): [in a new window]   Fig. 3. The CO2 emission rates from the mesothoracic spiracles and elytral case as a function of total CO2 emission in four dung beetle species. The regression equations, for which there is a significant correlation, are given for each species, where: m, mesothoracic spiracular CO2; el, elytral case CO2; and t, total CO2. For P. femoralis: el=0.022+0.88t, r2=0.78, P=0.048. For S. gariepinus: el=–0.003+0.85t, r2=0.96, P=0. For S. striatum: m=–0.058+1.52t, r2=0.78, P=0.02. For C. bacchus: m=–0.021+0.86t, r2=0.98, P=0.002.