Meeting Abstract

P2.94  Sunday, Jan. 5 15:30  A test of functional compartmentalization in the grasshopper Scistocerca americana using internal pressure recordings ADJERID, K*; KENNY, M; PENDAR, H; HARRISON, J.F.; SOCHA, J.J.; Virginia Tech; Virginia Tech; Virginia Tech; Arizona State University; Virginia Tech adjerid@vt.edu

The open circulatory system of insects is often conceived as a single compartment, especially in species that lack a petiole. However, recent work in grasshoppers shows evidence of possible segmental compartmentalization, suggesting that these insects can actively regulate inter-segmental hydrostatic pressures. Here, we test the hypothesis of functional valving in the coelom by directly measuring hemolymph pressures in two regions of the body in the American grasshopper (Schistocerca americana). Pressures were recorded at 100 Hz using two fiber-optic pressure sensors (Samba Preclin 420), separately inserted into the thorax and abdomen of living grasshoppers, while also recording abdominal pumping using an infrared proximity sensor. Our preliminary results indicate substantial variety in pressure patterns. Thorax and abdominal pressures exhibited: 1) near-identical pressure pulses in both segments; 2) correlated pressure pulses of different magnitudes; and 3) completely different pressures. The third pattern suggests that the animal can isolate pressures between segments and perhaps can voluntarily control the onset of pressure release to the other segments. These results lend support to the hypothesis of functional compartmentalization within the grasshopper’s coelom, and further demonstrate that such compartmentalization is flexible. This ability to regulate pressures between segments may result from actions of the intersegmental muscles that can compress the exoskeleton against the gut, or conversely, movements of the gut relative to exoskeleton. Supported by NSF 0938047.