Meeting Abstract

P2.87  Sunday, Jan. 5 15:30  A 3D kinematic analysis of abdominal motion in darkling beetles PENDAR, H*; SOCHA, JJ; Virginia Tech; Virginia Tech hpendar@vt.edu

Although abdominal pumping in insects is well known to be involved in respiration, it is unclear how specific movements of the abdomen produce airflows. Some motions may cause a volumetric displacement of the tracheal system, but it is also possible that the abdomen induces hemolymph flow or that no net volumetric change occurs. To better understand the relationship between abdominal movements and their internal effects, a comprehensive geometrical analysis of the abdomen concurrent with internal measurements is needed. In this study, we construct a real-time 3D model of abdominal cuticle in the darkling beetle (Zophobas morio) based on computational stereo techniques. After removing the elytra and soft wings and marking the surface with paint dots (size, ~50-200 µm), we used two synchronized cameras to record abdominal movements. In addition, we simultaneously recorded two other physiologically-relevant behaviors: 1) A third camera captured movements of tracheal tubes through the transparent metathoracic cuticle, revealing tracheal compression without the use of x-rays; 2) Internal pressures of the hemolymph in the prothorax were recorded using a fiber optic pressure transducer. Videos were analyzed using a custom Matlab program to quantify the 3D motion of the abdomen including volume displacement. A principal component analysis on the geometrical shape of the abdomen revealed that the beetle employs three major types of abdominal movements. In the most commonly observed type of abdominal motion, all tergites synchronously compressed in the ventral direction; concurrent to this compression, there was a substantial increase in hemolymph pressure, and tracheal tubes collapsed. The observed variation in behavior demonstrates that the abdominal pump likely serves multiple physiological functions. Supported by NSF 0938047.