Fig. 8. (A) The latero-dorsal arches shunt blood from the dorsal vessel to the hearts, with a bias towards the peristaltic heart. Optical recordings are from segment 14 from the left (black line) and right (brown line) heart and from the latero-dorsal arches in the left and right hemisegment. (B) Analysis windows drawn around the vessels and the color code of the optical signals. Initially, the left heart is in the synchronous mode. Systole of the latero-dorsal arches in the left hemisegment (double-headed arrow), coincides with filling of both hearts (rapid downward deflection). After the switch, the now peristaltic left heart fills when the arches on the contralateral (synchronous) side enter systole (double-headed arrow). Conversely, systole of the latero-dorsal arches in the right hemisegment (double-headed arrows) after its switch into the synchronous mode coincides with filling of the contralateral, now peristaltic, heart. Additional filling occurs in the peristaltic heart when the latero-dorsal arch in its own hemisegment enters systole (arrows) but note that systole in the arches on the peristaltic side occurs during systole of the synchronous heart and thus is unable to contribute to its filling.