Meeting Abstract
P3.136 Sunday, Jan. 6 Respiratory flow control in darkling beetles: Testing the compartmentalization hypothesis AVILES, J.*; PENDAR, H.; SOCHA, J.J.; Virginia Tech; Virginia Tech; Virginia Tech javiles@vt.edu
The tracheal system in some insect species is known to rhythmically collapse and re-inflate, creating bulk flow of air that augments gas exchange in the respiratory system. In darkling beetles, this dynamic compression of tracheal tubes occurs differentially within body regions: more tracheae collapse in the head and thorax than collapse in the abdomen. This pattern of tube collapse may result from the differential application of pressure within the body, enabled by functional compartmentalization of the thorax from the abdomen. Alternatively, if the hemolymph in the coelom is continuous throughout the beetle, the hydrostatic pressure of the hemolymph should be equal throughout, and the coelom can be considered to act as a single compartment. To test if darkling beetles exhibit functional compartmentalization between body regions, we inserted pressure sensors into the third abdominal segment and the thorax of live darkling beetles and recorded changes in pressure at a sampling rate of 100 Hz. Simultaneously, video cameras recorded abdominal pumping and tracheal tube collapse in the outer margins of the thorax. Beetles exhibited significant pressure pulses on the order of 0.2-1.3 kPa roughly every 10 seconds, followed by a period of relatively constant pressure. These pulses occurred simultaneously in both the abdomen and the thorax. However, the peak abdominal pressure was always greater (~30-80%) than that of thoracic pressure, contrary to expectation based on tracheal tube collapse patterns. The concurrency of pressure pulses in different regions of the body suggests that a single mechanism produces tracheal tube collapse, but the differences in peak pressure indicate that the beetle may possess a mechanism that functionally isolates hemolymph between the abdomen and thorax. Support by NSF 0938047 (JJS).
