Meeting Abstract

P3.20  Friday, Jan. 6  Spiracular activity and respiratory airflow in the Madagascar hissing cockroach (Gromphadorhina portentosa) HEINRICH, EC*; MCHENRY, MJ; BRADLEY, TJ; Univ. of California, Irvine; Univ. of California, Irvine; Univ. of California, Irvine eheinric@uci.edu

Using simultaneous dual-camera video recordings, flow-through respirometry, flow visualization, and gas microanalysis, we have examined spiracular function and respiratory air flow patterns in the Madagascar hissing cockroach (Gromphadorhina portentosa). Synchronized video recordings of individual spiracles demonstrate that all abdominal spiracles (5-9) open and close together. The fourth spiracles are used for hissing, and are otherwise closed at all times. It is more difficult to determine if the thoracic spiracles are open or closed using external visual inspection. Synchronized video and flow through respirometry have been used to provide insight into how spiracular control contributes to different patterns of CO₂ release. At different times, roaches appear to exhibit classic discontinuous respiration, continuous respiration with all spiracles open or continuous respiration with active ventilatory movements, during which the spiracles open and close in time with abdominal pumping. On the basis of neurological data, a previous model suggested that spiracular activity promotes unidirectional airflow through the insect. Using airflow visualization methods we show that during periods of active ventilation, airflow proceeds from the anterior to the posterior end of the insect. These results demonstrate the complexity of respiratory control in insects, in which the respiratory pattern responds to metabolic rate, gas composition, and activity level. This work was supported by the following grants from the National Science Foundation: IOS-0920683 (TJB) and IOS-0952344 (MJM).