title: Cyclic gas exchange in the giant burrowing cockroach, Macropanesthia rhinoceros: effect of oxygen tension and temperature.
abstract: The giant burrowing cockroach, Macropanesthia rhinoceros, is endemic to north-eastern Australia and excavates a permanent burrow up to 1m deep into soil. Using flow-through respirometry, we investigated gas exchange and water loss at three different oxygen tensions (21%, 10% and 2% at 20 degrees C) and temperatures (10, 20 and 30 degrees C at 21% oxygen). M. rhinoceros employ cyclic gas exchange (CGE) making the species by far the largest insect known to engage in discontinuous ventilation. CGE featured rhythmic bursts of CO(2) dispersed among inter-burst periods of reduced output. CGE was most commonly observed at 20 degrees C and degraded at <10% oxygen. Mild hypoxia (10% oxygen) resulted in a lengthening of the burst period by approximately two-fold; this result is complementary to oxygen consumption data that suggests that the burst period is important in oxygen uptake. When exposed to severe hypoxia (2% oxygen), CGE was degraded to a more erratic continuous pattern. Also, during severe hypoxia, total water loss increased significantly, although CO(2) release was maintained at the same level as in 21% oxygen. During CGE, an increase in temperature from 10 to 20 degrees C caused both water loss and CO(2) output to double; from 20 to 30 degrees C, CO(2) output again doubled but water loss increased by only 31%.
authors: CSIRO Entomology, GPO Box 1700, Canberra ACT 2601, Australia. james.woodman@csiro.au
authors: James D
authors: JD
authors: Woodman
authors: Paul D
authors: PD
authors: Cooper
authors: Victoria S
authors: VS
authors: Haritos
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D003058:Cockroaches / Q000378:metabolism / Q000502:physiology*; D005260:Female; D008297:Male; D009068:Movement / Q000502:physiology; D010100:Oxygen / Q000378:metabolism / Q000502:physiology*; D015657:Respiratory Transport / Q000502:physiology*; D013696:Temperature; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water; D002245:Carbon Dioxide; D010100:Oxygen