Meeting Abstract
The insect circulatory system is “open”, with flow of hemolymph produced by the dorsal vessel, a long tubular heart that pumps fluid from posterior to anterior. Tubular pumps are found throughout the animal kingdom, yet specific mechanisms of flow production in many taxa are not well understood. The insect heart pumps in wave-like contractions by helically-wound muscles around the tubes circumference. In addition, fan-like alary muscles may function to provide tension or aid in expansion of the heart lumen. Flow in the heart may also be aided by pressure differences resulting from internal compartmentalization or abdominal contractions. In the context of these complex factors, our aim is to understand the kinematics of heart contraction for biomechanical models of hemolymph flow production. We developed a non-invasive technique using infrared (IR) sensors to observe and record pumping movements in the heart of the tenebrionid beetle Zophobas morio. To measure the propagation of contraction waves of the dorsal vessel, the beetle was first gently restrained with wings splayed and pinned to either side. Two IR sensors positioned above the abdomen captured dorsal vessel movement by sending and receiving IR light using two fiber-optic cables. Because changes in IR signals result from any change in light reflectance, specific patterns of IR signals were interpreted by comparison with synchronized video recordings of the abdominal surface. The use of IR to measure heart kinematics is a new non-invasive technique that can be used to quantify how tubular pumps in insects contribute to overall internal hemolymph flow.
