Underwater propulsion at intermediate Re: Multi-oar biomechanics of mysids

Appendage synchronization of free-swimming aquatic crustaceans can result in different styles of propulsion. Members of the order Mysida have a shrimp-like morphology, with females having oostegites acting as a brood pouch, which is unique to the order. Mysids move through the water by altering body orientation, angles between limb joints, and stroke frequency of their thoracopods (eight sets of limbs on the thorax) and their pleopods (five sets of limbs on their abdomen). Observations of swimming behavior in the mysid Americamysis bahia indicate that there are four different forms of swimming: hovering, slow forward swimming, fast forward swimming, and an inverted caridoid escape response. While hovering and slow forward swimming only require coordination of the thoracopods, fast forward swimming includes a metachronal thrust from the pleopods. For the inverted caridoid response, the mysid bends at its abdomen, bringing its carapace to its telson, and then unflexes to propel itself forward. Body orientation, thoracopod motion, and pleopod motion unique to each swimming mode are analyzed to quantify these differences. Understanding of biomechanics at this scale can be applied to mechanistic designs of robots that will operate in a similar regime.