Meeting Abstract

30.6  Wednesday, Jan. 5  Do gut movements induce tracheal collapse in carabid beetles? PENDAR, H.*; SOCHA, J.J.; Virginia Tech hpendar@vt.edu

Some insects actively produce volume changes of the tracheal system to augment gas exchange. Respiratory tracheal structures (tracheae, air sacs, and tracheoles) are chitin-based membranous composites capable of deformation given sufficient pressure or mechanical force. Mechanisms of volume change include collapse by muscle contraction and expansion, abdominal or thoracic pumping, auto-ventilation by leg or wing movement, and hemolymph transport. Here, we test the hypothesis that movements of the digestive system induce collapse by deforming local tracheal tubes via direct displacement. We observed gut movements and tracheal collapse in carabid beetle species using synchrotron x-rays. To increase contrast, beetles were fed cadmium-laced food prior to imaging. X-ray observations revealed two kinds of gut movements: peristaltic movements of the gut wall, and anterior-posterior pulsatory flows within the gut contents. Peristaltic movements did not induce tracheal collapse. In contrast, some pulsatory flows were associated with cycles of tube collapse. These results may suggest a new mechanism of active ventilation; conversely, internal flows in the gut may simply be a consequence of the same anatomical mechanism that produces tube collapse in carabid beetles. Research supported by NSF 0938047 and the Institute for Critical Technology and Applied Science (ICTAS).