Hydrodynamics of forward and upside-down locomotion in mysid shrimp

Mysid shrimp, Americamysis bahia, are essential to many benthic and pelagic ecosystems. Due to their abundance and sensitivity to environmental changes, they are a well-established tool for aquatic toxicology studies. But, like many planktonic crustaceans, they are also agile, efficient swimmers. Propulsion is achieved via metachronal paddling of either appendages near their mouth region, the thoracopods, or both thoracopods and pleopod appendages, which are located along their abdomen. Mysid species, A. bahia, are more efficient metachronal swimmers than other species, which makes them an attractive candidate for investigating propulsion hydrodynamics. In this study, a high-speed tomographic particle image velocimetry (PIV) system was used to visualize and quantify a time-resolved 3D velocity field around a free-swimming, A. bahia and its wake for both thoracopod and thoracopod+pleopod swimming. When A. bahia swims with both pleopods and thoracopods, it produces a robust, well-developed 3D multi-jet system in its wake that is not seen when using only its thoracopods. The data provide novel insight into both the flow behavior at intermediate Reynolds number, in which many aquatic species reside, and the intricacies of the bio-locomotion of free-swimming zooplankton.