Figure 4.

Examples of bubble movement through presumed ostial openings in the heart wall of the grasshopper Schistocerca americana. Yellow bubbles represent single bubbles tracked through one video sequence (30 Hz), with the start of the sequence indicated in white and bubble positions corrected for whole-body movement. The blue arrows represent the apparent locations of ostia, inferred from the movements of the bubbles. (A) Heart entrance event in which the bubble traveled dorsally and anteriorly in the pericardial sinus, moved through the ostium, then was transported anteriorly within the heart (5th abdominal segment). For corresponding video, see Additional File 6. Scale bar, 200 μm. (B) Entrance event in which the bubble moved posteriorly in the pericardial sinus, dorsally through the ostium, and anteriorly after entering the heart (6th abdominal segment, same individual as above). For corresponding video, see Additional File 7.