P1.225 Wednesday, Jan. 4 Visualization of hemolymph flow in the heart of a cockroach GIARRA, Matthew N. *; VLACHOS, Pavlos P. ; SOCHA, John J. ; Virginia Polytechnic Institute and State University; Virginia Polytechnic Institute and State University; Virginia Polytechnic Institute and State University email@example.com
Insects pump hemolymph (blood) through their bodies using an open circulatory system consisting of numerous pumps that are not interconnected by vascular tissue. One major and highly conserved element in the circulatory system is the dorsal vessel (or heart), which is a long, axially-oriented muscular tube that produces peristaltic-like contractions along its length and pumps hemolymph between the posterior and anterior ends of the animal. Many species of insects exhibit periodic heartbeat reversals, wherein the directions of both the contractile waves in the heart and of the flow of hemolymph alternate between anterograde (anterior to posterior) and retrograde (posterior to anterior). The physical mechanism by which these wave-like contractions produce directional flow, as well as details of the flow kinematics in and around the heart, are unknown. Here, we experimentally measured the flow of hemolymph within the heart of a living cockroach (Periplaneta americana) to gain insight regarding the heart’s pumping capacity. Hemolymph flow in the heart was observed via the injection of fluorescent dye and fluorescent particles into the pericardial sinus. Digital videos of the dye and particle motions were analyzed, and the Reynolds number of the flow was estimated to be of order 1. These preliminary results serve as a starting point for more sophisticated experiments in the future, including 2-D and 3-D in vivo measurements of the velocity fields comprising the hemolymph flow.