Figure 2.

Relationship between heart movements and hemolymph flow (3rd abdominal segment) in the grasshopper Schistocerca americana. (A) Side view x-ray video image indicating the color conventions used in (B). Anterior is to the right; dorsal is to the top. (B) Time series from one video sequence showing the relationship between pericardial sinus depth (blue) and hemolymph flow direction (green, yellow, white). Decrease in pericardial sinus depth corresponds to compression. Green represents net forward (anterograde) flow, yellow represents backflow, and white indicates zero flow. Average compression frequency was 55 cycles/min (0.92 Hz). In most instances, forward flow occurred only during compressive movements of the pericardial sinus, and presumably of the heart itself. Backflow did not occur with each forward flow event, but when it did, it occurred directly after the forward flow event. Note that there was no observable hemolymph movement for roughly half the time.