Discontinuous gas exchange and the significance of respiratory water loss in scarabaeine beetles

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dc.contributor.authorChown S.L.
dc.contributor.authorDavis A.L.V.
dc.date.accessioned2011-05-15T16:05:04Z
dc.date.available2011-05-15T16:05:04Z
dc.date.issued2003
dc.description.abstractRespiratory 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.
dc.description.versionArticle
dc.identifier.citationJournal of Experimental Biology
dc.identifier.citation206
dc.identifier.citation20
dc.identifier.issn220949
dc.identifier.other10.1242/jeb.00603
dc.identifier.urihttp://hdl.handle.net/10019.1/12954
dc.subjectcarbon dioxide
dc.subjectanimal
dc.subjectarticle
dc.subjectbeetle
dc.subjectcomparative study
dc.subjectenergy metabolism
dc.subjectenvironment
dc.subjectlung gas exchange
dc.subjectmorphometrics
dc.subjectphysiology
dc.subjectSouth Africa
dc.subjectspecies difference
dc.subjectstatistical model
dc.subjecttemperature
dc.subjectthermoregulation
dc.subjecttime
dc.subjectAnimals
dc.subjectBeetles
dc.subjectBody Weights and Measures
dc.subjectCarbon Dioxide
dc.subjectEnergy Metabolism
dc.subjectEnvironment
dc.subjectLinear Models
dc.subjectPulmonary Gas Exchange
dc.subjectSouth Africa
dc.subjectSpecies Specificity
dc.subjectTemperature
dc.subjectTime Factors
dc.subjectWater Loss, Insensible
dc.subjectAnimalia
dc.subjectColeoptera
dc.subjectHexapoda
dc.subjectScarabaeus
dc.titleDiscontinuous gas exchange and the significance of respiratory water loss in scarabaeine beetles
dc.typeArticle
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