title: Gas exchange pattern transitions in the workers of the harvester termite.
abstract: The evolutionary genesis and the current adaptive significance of the use of the discontinuous gas exchange cycle (DGC) for respiration by insects is the subject of intense debate. Years of research have resulted in several leading hypotheses, one of which is the emergent-property hypothesis. This hypothesis states that DGC is an emergent property or consequence of interactions between the O2 and CO2 set points that regulate spiracular function, i.e. opening and closing. Workers of the harvester termite, Hodotermes mossambicus were selected as a model to test this hypothesis. The respiratory patterns of major workers, investigated using flow-through respirometry, were obtained at 100% relative humidity (RH) under varying temperature to evaluate the assumptions of the emergent-property hypothesis. Metabolic rate, measured as VCO2 increased significantly after 15 °C. As VCO2 increased in response to increasing temperature and activity, the gas exchange pattern displayed by workers transitioned to a continuous gas exchange. A true DGC, defined as showing all three phases and a coefficient of variation value close to 2, was not expressed under the experimental conditions. The conclusion drawn from this study of termite workers is that changes in respiratory patterns are most likely an emergent property of the insects' nervous and respiratory system.
authors.affiliation: School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Johannesburg WITS 2050, South Africa.
authors.forename: Isabelle M
authors.initials: IM
authors.lastname: Inder
authors.affiliation: School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Johannesburg WITS 2050, South Africa. Electronic address: frances.duncan@wits.ac.za.
authors.forename: Frances D
authors.initials: FD
authors.lastname: Duncan
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D004734:Energy Metabolism; D020049:Isoptera / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D012119:Respiration; D012143:Respiratory Physiological Phenomena; D013696:Temperature
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen
keywords: Discontinuous gas exchange; Flow-through respirometry; Hodotermes mossambicus; Temperature; Termites