02643nas a2200301   4500008004100000245013000041210006900171300001200240490000700252520172600259653002301985653003102008653003702039653003102076653001602107653001202123653001302135653001502148653001602163653001702179653002202196653001602218653002202234653001602256653001502272100001902287856003502306       2002                        eng d00aThe role of the subelytral cavity in water loss in the flightless dung beetle, Circellium bacchus (Coleoptera : Scarabaeinae)0 arole of the subelytral cavity in water loss in the flightless du  a253-2580 v993 aCircellium bacchus is a flightless telecoprid (ball-rolling) dung beetle, endemic to the afrotropical region, where it is found in a few restricted populations in the eastern Cape of South Africa. Its apterous condition and large size (mass ranges from 6 to 12 g) are considered to be adaptations to a semi-arid habitat. This beetle is active in the sun for long periods, walking between widely scattered dung pats, thus is under selection pressure to reduce water loss. C bacchus has eight spiracles on each side of the body. The metathoracic spiracle and six abdominal spiracles open into the sub-elytral cavity, which is closed. The mesothoracic spiracle is the largest and most exposed, occurring ventrally in the membrane connecting the prothorax and mesothorax. When at rest a cyclic form of respiration, known as discontinuous gas exchange cycle, is used by C. bacchus, releasing a burst of carbon dioxide approximately once an hour when the spiracles open for about 33 minutes. Flow-through respirometry was used to measure water loss from the thorax (being the head, prothorax and mesothorax) and elytral case (containing the metathorax and abdomen) separately. The total water loss of C. bacchus could be divided up as 65% cuticular water loss from the thorax, 35% cuticular water loss from the elytral case, 4% respiratory water loss from the thorax and no measurable respiratory water loss from the elytral case. 1.51 mug of water is lost for every mul of CO2 emitted during respiration in the thorax. Thus, the main avenue for both respiration and respiratory water loss is via the mesothoracic spiracles, suggesting that the primary function of the subelytral cavity is not to reduce respiratory water loss.10aCircellium bacchus10adesert tenebrionid beetles10adiscontinuous gas exchange cycle10aDiscontinuous gas-exchange10adung beetle10ainsects10apatterns10aphysiology10arespiration10aScarabaeidae10asubelytral cavity10aterrestrial10atrait information10aventilation10awater loss1 aDuncan, F., D.  u<Go to ISI>://000177174200016 02147nas a2200325   4500008004100000245008500041210006900126260000800195300001200203490000800215520124000223653000801463653001501471653003701486653001501523653002401538653001601562653001701578653001601595653001701611653001701628653001701645653001501662653002401677653002401701653002501725100001901750700001801769856003401787       2000                        eng d00aDiscontinuous gas exchange in dung beetles: patterns and ecological implications0 aDiscontinuous gas exchange in dung beetles patterns and ecologic  cMar  a452-4580 v1223 aThis study correlates a distinctive pattern of external gas exchanger referred to as the discontinuous gas exchange cycle (DGC), observed in the laboratory, with habitat associations of five species of telecoprid dung beetles. The beetles were chosen from a variety of habitats that would be expected to present different amounts of water stress. All five species exhibited DGC. Sisyphus fasciculatus has been recorded only in woodland areas, and does not have strict spiracular control during its DGC. Anachalcos convexus and Scarabaeus rusticus are associated with open mesic habitats. Both species exhibit a distinct DGC, previously found in some other insect species, but intermediate within this study group. Sc. flavicornis and Circellium bacchus are typically found in arid regions, and have the most unusual form of DGC with spiracular fluttering during the burst phase. These results support the hypothesis that spiracular fluttering reduces respiratory water loss. From this study we conclude that the DGC is an ancestral adaptation. most probably as a result of anoxic environments in underground burrows, but that spiracular control is enhanced to reduce respiratory water lass in beetle species that live in arid habitats.10aant10aCOLEOPTERA10adiscontinuous gas exchange cycle10aformicidae10ahabitat association10ahymenoptera10anamib desert10arespiration10aScarabaeidae10aScarabaeinae10asouth-africa10atelecoprid10atenebrionid beetles10aterrestrial insects10aventilatory patterns1 aDuncan, F., D.1 aByrne, M., J.  u<Go to ISI>://00008645500000202075nas a2200217   4500008004100000245005000041210005000091300001400141490000800155520142500163653002301588653003701611653001601648653001601664653001701680653001301697653002301710100002401733700002201757856007801779       2002                        eng d00aRespiratory airflow in a wingless dung beetle0 aRespiratory airflow in a wingless dung beetle  a2489-24970 v2053 aThe sealed subelytral cavity of many flightless beetle species is widely acknowledged to be an adaptation to water saving in arid-habitat species. However, this hypothesis relies on the acceptance of two largely untested assumptions: (i) that the movement of respiratory gases is unidirectional from anterior to posterior and (ii) that the coordinated action of the spiracles directs this flow. We tested these assumptions by simultaneously measuring CO2 and O2 exchange at the anterior mesothorax, independently of gas exchange in the posterior body, which included the subelytral cavity, of a large apterous beetle, Circellium bacchus. Flow-through respirometry revealed a marked discontinuous gas-exchange cycle (DGC) pattern from the anterior half of the body. Very little CO2was released from the posterior body, where the DGC was not apparent. Labelled air was shown to flow forwards from the posterior to the anterior body. Individual sampling from the mesothoracic spiracles revealed that the right mesothoracic spiracle, lying outside the elytral cavity, is the primary route for respiratory gas exchange in C. bacchusat rest. This discovery necessitates a reassessment of the currently assumed role of the subelytral cavity in water conservation and is, to our knowledge, the first demonstration of forward airflow associated with the unilateral use of a single thoracic spiracle for respiration in an insect. 10aCircellium bacchus10adiscontinuous gas exchange cycle10adung beetle10arespiration10aScarabaeidae10aspiracle10asubelytral cavity.1 aDuncan, Frances, D.1 aByrne, Marcus, J.  uhttps://scarabnet.myspecies.info/respiratory-airflow-wingless-dung-beetle