Movie 2.

Jerking behavior, buccal cavity compression, membrane rupture, and exit from the egg. A. callidryas embryos 6 days of age display jerking behavior and a buccal cavity compression while flooded. The first embryo moves quickly, but does not change position, using a strong and abrupt axial muscle contraction (jerk). The second embryo moves its lower jaw, briefly changing the shape of its snout, but does not gape open its mouth or jerk its body (buccal cavity compression). This behavior is followed by rupture of the egg membrane and exit from the egg capsule. The videos were recorded using a Canon DSLR and MPE-65 mm macro lens and play in real time.