Movie 2

Initial heart beats in O. insularis. A Naef stage XV embryo. In this lateral view, two different heartbeats could be detected. We believe these to be the branchial hearts. These hearts do not beat synchronously; the one at the top beats approximately every 2 seconds, while the other beats erratically. There is some movement between the two branchial hearts; however, at this developmental stage is not clear to us if this is the systemic heart.