On the role of the ventilatory wave in dragonfly larvae

Aquatic dragonfly larvae have various methods of ventilation in their modified hindgut chamber. One of these ventilations is chewing ventilation, which is a wavelike motion of the chamber wall. While this mode has been reported by multiple studies, its role remains unclear. In this study, we correlate the chamber wall motion with the internal and external flow to understand the role of the anteriorly propagating chamber wave in the larvae of Libellula sp. The transparency of the species allowed optical access to the internal flow and chamber kinematics. The particulates in the pond water visualized the flow inside the breathing chamber. We observed that soon after the wave motion ends, particles deep within the hindgut rapidly accelerates. This suggests that the function of the anteriorly propagating wave might be to pressurize the back end of the chamber in order to create pressure gradient within. In conjunction with the transmural pressure generated by compression of the abdomen, the axial pressure gradient deep within the chamber might assist in cleaning particulates lodged deep within the breathing chamber.