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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.