Simultaneous measurement of oxygen uptake and carbon dioxide emission during discontinuous ventilation in the tok-tok beetle, Psammodes striatus

Abstract

Rates of oxygen uptake and carbon dioxide emission during cycles of discontinuous ventilation by the tok-tok beetle, Psammodes striatus, were measured with computerized flowthrough respirometry. Mean long-term rates of oxygen uptake (LV̇O 2) and carbon dioxide emission (LV̇CO 2) were 0.160 ml g −1 h −1 and 0.130 ml g −1 h −1, respectively (mean of > = 10 discontinuous ventilation cycles in each of 8 beetles, mean mass 2.80 g). RQ over the entire ventilation cycle was 0.83. During the closed-spiracle (closed) phase of the cycle, oxygen and carbon dioxide exchange declined to very low levels. During the fluttering-spiracle (flutter) phase, short-term V̇O 2 (SV̇O 2) increased to ∼ LV̇O 2, thus meeting tissue oxygen requirements, while short-term V̇CO 2 (SV̇CO 2) was only 13% of LV̇CO 2. The flutter phase respiratory exchange ratio was 0.15. During the open-spiracle phase, this ratio increased to 1.27, carbon dioxide emission increased to 228% of LV̇CO 2, and oxygen uptake peaked rapidly and then settled to a second plateau marginally above LV̇O 2. Abdominal pulsations invariably occurred in the open phase, and cost 2% of total oxygen uptake. The flutter phase accounted for 33.9% and the open phase for 63.9% of total oxygen uptake; in terms of carbon dioxide emission, the flutter and open phases accounted for 5.7 and 93.1%, respectively.