18.2 Wednesday, Jan. 4 Dynamics of the sucking pump in fluid feeding butterflies ROBERTS, C.*; SOCHA, J.J.; Virginia Tech; Virginia Tech firstname.lastname@example.org
Butterflies feed by means of a sucking pump in the head, which creates a pressure gradient to drive food through the proboscis. Although the functional morphology of internal food transport of Lepidoptera has been widely studied, the exact timing of movements in the sucking pump system are unknown. Using synchrotron x-ray imaging, we visualized the internal food transport within the head of living cabbage white butterflies, Pieris rapae. Experiments were conducted at the 32-ID beamline at Argonne National Laboratory’s Advanced Photon Source. Fasted butterflies were mounted by the wings and allowed to feed on 40% sugar water mixed with an iodine compound (Isovue), as a contrast agent. Using ImageJ to analyze the video records, we quantified timing of events within a sucking pump cycle. Feeding in P. rapae involves three main components: the sucking pump, the oral valve, and the esophageal valve. In the dilation phase, food is drawn into the lumen of the sucking pump by expansion of the dorsal wall. Just prior to ejection, the oral valve closes as the pump reaches its maximum fluid volume. In the ejection phase, compressor muscles of the sucking pump contract rapidly, pushing the fluid out of the lumen through the open esophageal valve and into the esophagus. The oral valve then re-opens. The total pump cycle duration was 1.72 ± 0.74 seconds per pump cycle. Our results show that the dilation phase is consistently longer than the compression phase, with a ratio of 4.9 : 1 (SD, 0.4). Our results determine a dynamic model of P. rapae feeding, confirming suggested hypotheses developed from anatomical studies. This study will contribute to the development of new analytical models of feeding that aim to understand the functional performance of single-pump fluid feeding systems in insects.