Meeting Abstract

35.2  Sunday, Jan. 5 08:15  High-Speed X-Ray Visualization of Blood Flows in the Grasshopper Heart GIARRA, M.N.*; VLACHOS, P.P.; SOCHA, J.J.; Virginia Tech; Virginia Tech; Purdue University matthew.giarra@gmail.com

Insects transport hemolymph (blood) through the body using an open circulatory system and numerous small pumps. The main pump is the dorsal vessel, an axially-oriented tube that produces muscular contractions within its posterior section (the heart). Many species exhibit periodic reversals of flow in the vessel, wherein the directions of contractile waves alternate between anterograde and retrograde on the minute time-scale. Beyond this, the details of the flow kinematics in the heart are unknown. We aimed to understand the details of flows by measuring time-resolved fluid velocities in the hearts of living grasshoppers (Schistocerca americana). To quantify flows, we used synchrotron x-ray imaging to record the motion of 10 μm flow-tracer particles in the hearts of seven animals. The particles were injected into the pericardial sinus and allowed to advect into the heart prior to imaging. In succession, we recorded flows with a high-speed camera (125 fps) and then with a standard camera (30 fps). These cameras captured 6 to 20 seconds and 10 to 30 minutes of data per specimen, respectively. Using the high-speed imagery, we measured time-resolved flow velocities over multiple heartbeats using a custom particle image velocimetry algorithm. The standard-speed videos were used to verify that the high-speed videos were representative of long-term flow patterns. Our data suggest different heart flow characteristics than has been described in previous studies of insects. Specifically, we observed that the flow in the heart alternates direction every few seconds, a time scale an order of magnitude shorter than what others have reported. Such rapid flow reversals may indicate that the insect heart serves some other function besides purely directional pumping. Supported by NSF 0938047.