Locomotion 1: Form and Locomotion through Ontogeny

Reynolds Number and Body size
1. The ratio of the density of a medium in relation to 1) inertia 2) Fluid Viscosity
2. Low Reynolds Number is a dominance in viscosity making the animal limited by the presence of drag
  1. As the Reynolds Number increases the forces within the water alter to more turbulent flow
    1. Importance in Streamlining of organisms
  2. Organism experience Laminar Flow at Low RN
3. Reynolds number also includes factors such as the speed the organism is travelling and the overall size of an organism
  1. As speed increases so does the RN = Inertia Dominance
  2. As size increases so does Reynolds Number
4. Drag vs Inertia
  1. This switch occurs around 2000-2500 RN
Swimming with Paddles
1. Williams (1994) looked at the ontogeny of Artemia as the animal grows
  1. Artemia go through gradual but dramatic changes throughout their lifecycles
    1. As the animal grows it adds segments to its body (extra swimming legs)
      1. In Late development the Artemia have 11 Trunk limbs to help glide
  2. As the Artemia grew they were within a drag dominated lifestyle
    1. This then changed to a more inertia based lifestyle
  3. Developed Trunk limbs which allowed it to glide through the water (using inertia)
    1. Arms started to beat in a metachronal rhythm
Jet Propulsion (plasticity)
1. Feitl et al (2009) looked at how morphology of Aurelia aurita changed throughout lifecycle
  1. Shows a very different shape to the common bell shape early on (star shaped)
    1. In early stages organism is dominated by drag, Reynolds Number change exponentially with as it grows (inertia)
    2. this star shape has dead zones between Lappets where no water flows, drag is filling these areas
      1. Cleverly utilizing the forces of drag before the structure becomes ineffective
2. Nawroth et al (2010) Looked at how density of water at different temperatures affected devlopment of lappets
  1. 2 different temperatures were experimented 13 degree and 21
    1. At high temperatures the bell shape was filled out more - coped with high temp through morphological plasticity
    2. When brought up in 13 degree water and placed in higher temp water, They showed a lower efficiency in swimming
      1. Negatively altered their plasticity
Cilial Vs. Muscular driven movement
1. Stokes (1997) looked at how the morphology of the Lancelet changed over time
  1. Small larvae were dominated by drag, with these showing mainly cilial based movements (Vicous flow)
  2. Later stages have higher Reynolds numbers and swim using an undulating motion
    1. See a change in the level of musculature = larger dominance in musculature for muscular based swimming
  3. pre-metamorphoses organisms experienced intermediate RN and intermediate viscosity levels
    1. in the transitional phase choose to hover and not to swm
      1. Why??
        Possibly too costly to use muscles to swim
        So as to not highlight to predators where they are
        Better for filter feeding?

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Locomotion 1: Form and Locomotion through Ontogeny

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