Meeting Abstract

P3.118  Jan. 6  The Respiratory Patterns of Insects BRADLEY, TJ; Univ. of California, Irvine tbradley@uci.edu

Three respiratory patterns have been described in insects: Discontinuous, Cyclic and Continuous. The Discontinuous Gas Exchange Cycle (DGC) is characterized by an open phase in which the spiracular valves are fully open, a closed phase which serves to reduce oxygen concentrations at the tissues and thus reduce oxidative damage, and a flutter phase in which the spiracles regulate internal oxygen levels at a physiologically safe level. In the Cyclic pattern, although the spiracles appear never to fully close, a rhythmic pattern of carbon dioxide release is observed. In the Continuous pattern, carbon dioxide release is relatively constant and no rhythmicity can be discerned. I suggest that the three patterns are not distinct, but rather are a continuum. When oxygen delivery greatly exceeds oxygen consumption, a closed phase, and thus a Discontinuous pattern is observed. If oxygen delivery is reduced or metabolic rate increases, the closed phase is reduced and the Discontinuous pattern transforms into a Cyclic pattern. Finally, if the metabolic consumption of oxygen roughly matches the rate of oxygen entry, the Continuous pattern is employed, and the spiracles regulate gas exchange to meet demand without closing. The critical parameters influencing the pattern are 1) the partial pressure of oxygen in the surrounding atmosphere, 2) the rate of oxygen use (i.e. the aerobic metabolic rate) and 3) the carbon dioxide concentration in the atmosphere which can influence the length of the open phase. Insects exhibit the DGC when the tracheal system is capable of delivering oxygen during the open phase at a rate faster than it is consumed by oxidative metabolism. The minute to minute balance between these two processes, one delivering oxygen the other removing it, determines the pattern of respiration exhibited by the insect at any given time.