Meeting Abstract
The hemocoel of insects is often considered as an open compartment in which hemolymph is free to flow, particularly in insects lacking a petiole (narrowed waist). However, recent work using synchrotron x-ray imaging has shown indirect evidence of compartmentalization in the American locust (Schistocerca americana). Here, we tested the hypothesis of compartmentalization by simultaneously measuring hemolymph pressures in the thorax and abdomen using two fiber-optic pressure sensors recording at 100 Hz (n = 11 locusts). Pressures were recorded continuously for two hours per trial. Comparing the signals from the two body segments, we observed 80% or greater correlation of patterns and magnitudes in 17.5 ±4.9% of the trial duration. However, for the majority of the trial duration (>82%), there was far less correlation between the two pressure signals (45.5±4.8%). We also recorded baseline pressures as the insects were re-oriented from horizontal to head-up or head-down positions in order to test potential effects of gravity on hemolymph pressure. We observed an average of 0.119 kPa and 0.122 kPa difference from expected values for change in hydrostatic pressures in the thorax and abdomen, respectively. These large variations in pressure patterns between abdomen and thorax suggest a functional compartmentalization within the locust that affects the flow of hemolymph between segments. Functional compartmentalization may result from movements of the gut wall or changes in the orientation of internal anatomical features; alternatively, the gut may expand or contract to allow or impede flow. These observations suggest that hemolymph circulation in locusts is more complex than previously understood. Supported by NSF 0938047.
