title: Hydrodynamics and energetics of jumping copepod nauplii and copepodids.
abstract: Within its life cycle, a copepod goes through drastic changes in size, shape and swimming mode. In particular, there is a stark difference between the early (nauplius) and later (copepodid) stages. Copepods inhabit an intermediate Reynolds number regime (between ~1 and 100) where both viscosity and inertia are potentially important, and the Reynolds number changes by an order of magnitude during growth. Thus we expect the life stage related changes experienced by a copepod to result in hydrodynamic and energetic differences, ultimately affecting the fitness. To quantify these differences, we measured the swimming kinematics and fluid flow around jumping Acartia tonsa at different stages of its life cycle, using particle image velocimetry and particle tracking velocimetry. We found that the flow structures around nauplii and copepodids are topologically different, with one and two vortex rings, respectively. Our measurements suggest that copepodids cover a larger distance compared to their body size in each jump and are also hydrodynamically quieter, as the flow disturbance they create attenuates faster with distance. Also, copepodids are energetically more efficient than nauplii, presumably due to the change in hydrodynamic regime accompanied with a well-adapted body form and swimming stroke.
authors.affiliation: Department of Physics and Centre for Ocean Life, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark nawa@fysik.dtu.dk.
authors.forename: Navish
authors.initials: N
authors.lastname: Wadhwa
authors.affiliation: Department of Physics and Centre for Ocean Life, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Andersen
authors.affiliation: National Institute for Aquatic Resources and Centre for Ocean Life, Technical University of Denmark, DK-2920 Charlottenlund, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kiørboe
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D033342:Copepoda / Q000254:growth & development / Q000502:physiology*; D057446:Hydrodynamics; D007814:Larva; D012212:Rheology; D013550:Swimming; D014741:Video Recording; D014783:Viscosity
keywords: Copepodids; Energy dissipation; Nauplii; Reynolds number; Swimming; Velocimetry