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-beetles02572nas a2200289   4500008004100000245011400041210006900155260000800224300001200232490000800244520178000252653002302032653001402055653001402069653001502083653001402098653001702112653001402129653001202143653001402155653001202169653000902181653001502190100002302205700002002228856003402248       2003                        eng d00aUngulate community structure and ecological processes: body size, hoof area and trampling in African savannas0 aUngulate community structure and ecological processes body size   cMar  a560-5680 v1343 aA wide range of bioenergetic, production, life history and ecological traits scale with body size in vertebrates. However, the consequences of differences in community body-size structure for ecological processes have not been explored. We studied the scaling relationships between body mass, shoulder height, hoof area, stride length and daily ranging distance in African ungulates ranging in size from the 5 kg dik-dik to the 5,000 kg African elephant, and the implications of these relationships on the area trampled by single and multi-species herbivore communities of differing structure. Hoof area, shoulder height and stride length were strongly correlated with body mass (Pearson's r >0.98, 0.95 and 0.90, respectively). Hoof area scaled linearly to body mass with a slope of unity, implying that the pressures exerted on the ground per unit area by a small antelope and an elephant are identical. Shoulder height and stride length scaled to body mass with similar slopes of 0.32 and 0.26, respectively; larger herbivores have relatively shorter legs and take relatively shorter steps than small herbivores, and so trample a greater area of ground per unit distance travelled. We compared several real and hypothetical single- and multi-species ungulate communities using exponents of between 0.1 and 0.5 for the body mass to daily ranging distance relationship and found that the estimated area trampled was greater in communities dominated by larger animals. The impacts of large herbivores are not limited to trampling. Questions about the ecological implications of community body-size structure for such variables as foraging and food intake, dung quality and deposition rates, methane production, and daily travelling distances remain clear research priorities.10aAfrican herbivores10aallometry10abody mass10aecosystems10aelephants10ainfiltration10alivestock10amammals10apressures10ascaling10asoil10avegetation1 aCumming, D., H. M.1 aCumming, G., S.  u<Go to ISI>://00018158270001402856nas a2200205   4500008004100000245015400041210006900195300001200264490000700276520206400283653001402347653002902361653002702390653001602417653001202433100002202445700001902467700002602486856013802512       2004                        eng d00aLinear and threshold-dependent expression of secondary sexual traits in the same individual: insights from a horned beetle (Coleoptera: Scarabaeidae)0 aLinear and thresholddependent expression of secondary sexual tra  a473-4800 v833 aElaborate horns or horn-like structures in male scarab beetles commonly scale with body size either (a) in a linear fashion with horn size increasing relatively faster than body size or (b) in a threshold-dependent, sigmoid fashion; that is, males smaller than a certain critical body size develop no or only rudimentary horns, whereas males larger than the threshold size express fully developed horns. The development of linear vs. sigmoid scaling relationships is thought to require fundamentally different regulatory mechanisms. Here we show that such disparate regulatory mechanisms may co-occur in the same individual. Large males of the south-east Asian Onthophagus  ( Proagoderus ) watanabei  (Ochi & Kon) (Scarabaeidae, Onthophagini) develop a pair of long, curved head horns as well as a single thoracic horn. We show that unlike paired head horns in a large number of Onthophagus  species, in O. watanabei  the relationship between head horns and body size is best explained by a linear model. Large males develop dispropor- tionately longer horns than small males, but the difference in relative horn sizes across the range of body sizes is small compared to other Onthophagus  species. However, the scaling relationship between the thoracic horn and body size is best explained by a strongly sigmoid model. Only males above a certain body size threshold express a thoracic horn and males smaller than this threshold express no horn at all. We found a significant positive correlation between head and thoracic horn length residuals, contrary to what would be expected if a resource allocation tradeoff during larval development would influence the length of both horn types. Our results suggest that the scaling rela- tionship between body size and horn length, and the developmental regulation underlying these scaling relation- ships, may be quite different for different horns, even though these horns may develop in the same individual. We discuss our results in the context of the developmental biology of secondary sexual traits in beetles.10aallometry10adevelopmental constraint10adevelopmental tradeoff10aOnthophagus10ascaling1 aMoczek, Armin, P.1 aBruhl, Carsten1 aKrell, Frank-Thorsten  uhttps://scarabnet.myspecies.info/linear-and-threshold-dependent-expression-secondary-sexual-traits-same-individual-insights-horned-be