Investigating onychophoran gas exchange and water balance as a means to inform current controversies in arthropod physiology

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dc.contributor.authorClusella-Trullas, Susanaen_ZA
dc.contributor.authorChown, Steven L.en_ZA
dc.date.accessioned2011-05-15T16:05:03Z
dc.date.available2011-05-15T16:05:03Z
dc.date.issued2008-08
dc.descriptionThe original publication is available at http://www.biologists.com/journals.htmlen_ZA
dc.description.abstractSeveral controversies currently dominate the fields of arthropod metabolic rate, gas exchange and water balance, including the extent to which modulation of gas exchange reduces water loss, the origins of discontinuous gas exchange, the relationship between metabolic rate and life-history strategies, and the causes of Palaeozoic gigantism. In all of these areas, repeated calls have been made for the investigation of groups that might most inform the debates, especially of taxa in key phylogenetic positions. Here we respond to this call by investigating metabolic rate, respiratory water loss and critical oxygen partial pressure (Pc) in the onychophoran Peripatopsis capensis, a member of a group basal to the arthropods, and by synthesizing the available data on the Onychophora. The rate of carbon dioxide release (V̇ CO2) at 20°C in P. capensis is 0.043 ml CO2 h -1, in keeping with other onychophoran species; suggesting that low metabolic rates in some arthropod groups are derived. Continuous gas exchange suggests that more complex gas exchange patterns are also derived. Total water loss in P. capensis is 57 mg H2O h-1 at 20°C, similar to modern estimates for another onychophoran species. High relative respiratory water loss rates (∼34%; estimated using a regression technique) suggest that the basal condition in arthropods may be a high respiratory water loss rate. Relatively high Pc values (5-10% O2) suggest that substantial safety margins in insects are also a derived condition. Curling behaviour in P. capensis appears to be a strategy to lower energetic costs when resting, and the concomitant depression of water loss is a proximate consequence of this behaviour.en_ZA
dc.description.versionPost-printen_ZA
dc.format.extent18 p. : ill.
dc.identifier.citationClusella_Trullas, S & Chown, S. L. 2008. Investigating onychophoran gas exchange and water balance as a means to inform current controversies in arthropod physiology. Journal of Experimental Biology, 211(19):3139-3146, doi:10.1242/jeb.021907.en_ZA
dc.identifier.issn1477-9145 (online)
dc.identifier.issn0022-0949 (print)
dc.identifier.otherdoi:10.1242/jeb.021907
dc.identifier.urihttp://hdl.handle.net/10019.1/12947
dc.publisherThe Company of Biologistsen_ZA
dc.rights.holderThe Company of Biologistsen_ZA
dc.subjectHistologyen_ZA
dc.subjectArthropod physiologyen_ZA
dc.subjectBehavior, Animalen_ZA
dc.subjectPeripatopsis capensis
dc.titleInvestigating onychophoran gas exchange and water balance as a means to inform current controversies in arthropod physiologyen_ZA
dc.typeArticle
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