Meeting Abstract
90.7 Monday, Jan. 6 15:00 Coordination of abdominal pumping, spiracular valving, and tracheal compression in the Madagascar hissing cockroach GARRETT, J*; SOCHA, J.J.; Virginia Tech; Virginia Tech jfg@vt.edu
In some insect species, respiratory ventilation is thought to occur as the result of three coordinated activities: abdominal pumping, volumetric displacement of the tracheal system, and spiracular valving. The specific coordination pattern that makes ventilation possible is not well understood, and can vary with species as well as with the metabolic demands of developmental stage, body size, activity level, and atmospheric environment. Here, we examined the timing of these three activities using the Madagascar hissing cockroach (Gromphadorhina portentosa), chosen for its relatively large size and unobstructed spiracle anatomy. In experiments at the Advanced Photon Source of Argonne National Laboratory, we recorded synchrotron X-ray video footage of the living animal and synched it with external video of a spiracle and the whole abdomen. This enabled us to quantify the frequencies, durations, and duty cycles of abdominal pumping, spiracle opening and closing, and compression of tracheal tubes and air sacs. In addition, after recording normoxic behaviors we induced higher frequencies of abdominal pumping by reducing the environmental oxygen concentration near the spiracles. In normoxia, abdominal spiracles open briefly (200 – 800 ms) approximately one second after the abdominal pumping sequence begins. As the spiracle opens, some tracheal tubes (typically those of small to medium diameter, approximately 50-300 microns) collapse, which may expel additional air from the system. Our observations suggest that the specific coordination of these movements is fundamental to delivering oxygen throughout the animal’s body. In addition, this new understanding will be used to develop new microfluidic pumping devices based on the respiratory dynamics of the hissing cockroach. Supported by NSF 0938047.
