Meeting Abstract

S1-3.16  Jan. 5  The Poise that refreshes: dynamics of internal food transport in a butterfly SOCHA, J.J.**; WATERS, J.S.; WESTNEAT, M.W.; LABARBERA, M.; COOK, S.; FEZZAA, K.; LEE, W.K.; Argonne National Laboratory; Arizona State University; Field Museum; University of Chicago; University of Utah; Argonne National Laboratory; Argonne National Laboratory jjsocha@midway.uchicago.edu

Butterflies feed by sucking fluids through a long, cylindrical proboscis using a cibarial pump in the head. Although much is known about feeding rates and anatomy involved in digestion, little is known about the dynamics of food transport due to the previous inability to see inside the living animal. In this study, we use synchrotron x-rays to visualize internal food transport in living butterflies. Experiments were conducted at the 32-ID beamline at Argonne National Laboratory�s Advanced Photon Source. Fasted cabbage white butterflies (Pieris rapae, N=40) were mounted by the wings and allowed to feed on a radio-opaque sugar water / iodine compound (Isovue) mixture. Effects of fluid viscosity were tested by varying the percentage of both solutions. To visualize the food, we used 33.3 keV monochromatic x-rays tuned for the K-edge absorption band of iodine. During feeding, butterflies moved food into the head using a two-stage pumping mechanism. In the first stage, food is drawn into the cibarium by suction, with the cibarial chamber expanding dorsally; in the second stage, the chamber contents are emptied into the esophagus by positive displacement. Fluid was transported in boluses that remained discrete, discontinuously filling the foregut. A typical bolus of 5 nl volume expanded the esophagus to a diameter of 90 �m and traveled at a speed of 2.8 mm/s through the thorax, implying that bolus transport was dominated by viscous forces (Re ~0.5). Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. W-31-109-Eng-38.