BRADLEY, TJ*; GRAY, EM; Univ.of California, Irvine: Mosquitoes Respire Using the Discontinuous Gas Exchange Cycle.

Larval stages of the mosquito Culiseta inornata were collected and reared in the laboratory at 20oC and 12:12 L:D. Adult female mosquitoes aged between 2 and 6 days post-emergence and with access to 10% sucrose were used for the experiments. Measurements of respiratory patterns were performed using flow-through respirometry in a temperature-controlled room. The respirometry equipment consisted of an 8-channel multiplexor, a LiCor CO2 infrared gas analyzer (LiCor 6251, Lincoln, NB) and a computer running the program Expedata (Sable Systems software) which simultaneously, via a UI-2, controls the multiplexor and acquires data from the gas analyzer. We performed measurements at a variety of flow rates between 20 and 1000 ml/min. Each series of measurements consisted of recording the respiratory pattern of a mosquito at multiple flow rates. We performed the experiments at different temperatures in order to affect the metabolic rate of the mosquitoes. The temperatures chosen for the measurements were 10, 20 and 30oC. Between each series of experiments we changed the temperature and waited 12 hours for the room and equipment to adjust to the new temperature before performing another series of experiments. We found that under the experimental conditions in which insects are normally examined, the mosquitoes appeared to using a cyclic respiratory pattern. Lowering the temperature and/or increasing the rate of air flow revealed that the mosquitoes were actually using the discontinuous gas exchange cycle (DGC). The importance of the rate of air flow in respirometry of small insects will be discussed. The DGC has profound implications for the water conservation and avoidance of oxygen toxicity in these insects.