Meeting Abstract

55.5  Sunday, Jan. 5 14:30  Critical oxygen partial pressures during rest and flight in giant scarabaeoid beetles KLOK, CJ*; CAMPBELL, J; DUELL, M; HARRISON, JF; Arizona State University; Arizona State University; Arizona State University; Arizona State University cjklok@asu.edu

Prior studies showed that safety margins for oxygen delivery, or the critical partial pressure of oxygen (CritPO₂), is independent of size during low metabolic demand (‘rest’) in adult insects in size ranges up to 4 grams. In this study we expand the upper size limit by an order of magnitude investigating CritPO₂ in a series of scarabaeoid beetle species ranging from 0.5 to 40 grams, to test whether this size independence remains valid for insects of gigantic proportions. Here we measured low metabolic demand CritPO₂, using flow through respirometry and dynamic oxygen reduction, and (for some species) added high metabolic demand measures by determining CritPO₂ during tethered flight. The flight CritPO₂ was determined using a low friction flight mill, logging air oxygen partial pressures, flight speed, and flight duration during normoxic control flights and dynamic oxygen reduction CritPO₂ flights. Our results indicate that the size independence of CritPO₂ holds for all species in this increased size range with CritPO₂ at rest of <1.5 kPa and flight CritPO₂ values of ~10 kPa. This would suggest that the larger species have to employ various compensatory mechanisms to overcome the distance dependent constraints on oxygen delivery that may include tracheal hypermetry and increased ventilation. This research was partially supported by NSF IOS 1122157 to JFH and CJK.