03096nas a2200229   4500008004100000245010200041210006900143260000800212300001400220490000800234520233100242653002702573653001602600653001702616653001902633653001202652653001502664653001502679100002202694700002502716856012502741       2003                        eng d00aDiscontinuous gas exchange and the significance of respiratory water loss in scarabaeinae beetles0 aDiscontinuous gas exchange and the significance of respiratory w  cJul  a3547-35560 v2063 aRespiratory water loss in insects is a controversial topic. Whilst earlier studies considered respiratory transpiration a significant component of overall water loss, to the extent that it was thought to be responsible not only for the evolution of discontinuous gas exchange cycles (DGCs) but also for variation in DGC patterns, later work repeatedly questioned its importance. In particular, investigations of the proportional contribution of respiratory transpiration to total water loss in species showing DGCs suggested that respiratory transpiration was unlikely to be important in these species. In turn, these studies have been criticized on analytical grounds. In this study we investigated variation in cuticular and respiratory water loss rates in five Scarabaeus dung beetle species, all of which show discontinuous gas exchange cycles, to ascertain the significance of respiratory water loss using modern analytical techniques. In particular, we determined whether there is variation in water loss rates amongst these beetles, whether both respiratory and cuticular water loss rates contribute significantly to variation in the former, and whether metabolic rate variation and variation in the duration of the DGC periods contribute significantly to variation in respiratory water loss rate. Total water loss rate varied such that species from arid areas had the lowest rates of water loss, and both cuticular and spiracular transpiration contributed significantly to variation in overall water loss rate. Moreover, variation in metabolic rate and in the duration of the DGC periods contributed significantly to variation in respiratory water loss rate. By contrast, examination of proportional water loss revealed little other than that it varies between 6.5% and 21%, depending on the species and the temperature at which it was examined. Cuticular water loss scaled as mass0.721, but did not differ from that expected from geometric considerations alone. By contrast, respiratory water loss scaled as mass0.531, suggesting that gas exchange takes place by diffusion and convection. Our results provide direct evidence that respiratory water loss forms a significant component of water balance, and that changes in both metabolic rate and DGC characteristics contribute to modulation of respiratory water loss. 10adesiccation resistance10adung beetle10agas exchange10ametabolic rate10ascaling10aScarabaeus10awater loss1 aChown, Steven, L.1 aDavis, Adrian, L. V.  uhttps://scarabnet.myspecies.info/discontinuous-gas-exchange-and-significance-respiratory-water-loss-scarabaeinae-beetles00829nas a2200229   4500008004100000245012800041210006900169300001000238490000600248653002700254653001300281653002000294653001500314653001800329653002100347100001800368700002000386700001700406700002000423700001800443856013800461       1995                        eng d00aEcophysiology, range contraction and survival of a geographically restricted African dung beetle (Coleoptera: Scarabaeidae)0 aEcophysiology range contraction and survival of a geographically  a30-390 v910adesiccation resistance10aendemism10aflight activity10aflightless10ascarab beetle10athermoregulation1 aChown, S., L.1 aScholtz, C., H.1 aKlok, C., J.1 aJoubert, F., J.1 aColes, K., S.  uhttps://scarabnet.myspecies.info/ecophysiology-range-contraction-and-survival-geographically-restricted-african-dung-beetle-coleopter02927nas a2200337   4500008004100000245016300041210006900204260000800273300001200281490000700293520190100300653002002201653001602221653002702237653002702264653002802291653001702319653000802336653003002344653001202374653002702386653001702413653002202430653000902452653001502461100002102476700001802497700002002515700002002535856003402555       2000                        eng d00aA comparative analysis of metabolic rate in six Scarabaeus species (Coleoptera : Scarabaeidae) from southern Africa: further caveats when inferring adaptation0 acomparative analysis of metabolic rate in six Scarabaeus species  cApr  a553-5620 v463 aAlterations in VO2 or VCO2 are amongst the more polemical physiological adaptations ascribed to insects. Generally, metabolic rate is thought to be lowered in response to arid conditions, and elevated in species from cold environments compared to their more temperate relatives. However, most studies have rarely addressed the influence of both environmental factors in unison. To this end, standard metabolic rate and its temperature dependence were measured (at 4 degrees C intervals from 16 to 32 degrees C) in six Scarabaeus dung beetle species (three flightless, three volant) from a variety of habitats (warm, arid to cool, mesic) in southern Africa using flow-through respirometry. Mass specific VCO2 varied from 0.0158 mi g(-1) h(-1) at 16 degrees C to 0.1839 ml g(-1) h(-1) at 32 degrees C. The slopes of the rate temperature curves were similar for all species (Q(10)s of 2.14-2.84), although the intercepts differed significantly in the direction (warm arid to cool mesic): S. gariepinus<S. hippocrates<S. striatum<S. galenus<S. rusticus<S. westwoodi. General Linear models were fitted to the VCO2 data with treatment temperature, wing status, mean annual rainfall and mean annual temperature as the independent variables. For all six species, the best fit model included treatment temperature and wing status only. Flightless species had significantly lower VCO(2)s than did winged ones. Amongst the flightless species, S. gariepinus, from the driest area, had the lowest VCO2. Among the winged species it was impossible to determine whether environmental temperature or water availability were most important in influencing VCO2; both were significant. We conclude that investigations of metabolic rate modulation, and especially metabolic cold adaptation, in insects must take both temperature and water availability into account. (C) 2000 Elsevier Science Ltd. All rights reserved.10aacclimatisation10aconsumption10acricket gryllus-firmus10adesiccation resistance10adrosophila-melanogaster10agas-exchange10ains10ametabolic cold adaptation10aoxygen-10arespiratory metabolism10arespirometry10aunselected strain10aVCO210awater-loss1 aDavis, A., L. V.1 aChown, S., L.1 aMcGeoch, M., A.1 aScholtz, C., H.  u<Go to ISI>://000085842500019