Structure and function in swimming

  1. General considerations
    1. Diversity of locomotion abilities
      1. walking, flying, jumping, gliding, climbing, burrowing, wriggling, crutching, sucking along, flipping forward
      2. But most swim.
    2. water is dense, viscous, incompressible
      1. 800 X denser than air
      2. Unlike in air, design for support not a problem
      3. But movement through takes great deal of energy
        1. design for efficiency of propulsion
  2. Structure of swimming mechanism
    1. Skeleton: the levers. Do schematic drawing. this is for bony fish.
      1. Axial skeleton
        1. skull
          1. the leading end in swimming
          2. attachment site for muscles
          3. support for paired fins
        2. Vertebral column in bony fish. (figs 3.11, 3.12, hand out a vert.)
          1. withstands compression.

            2. Without, muscle contraction would cause collapse

          2. One vertebra per segment.
          3. Different types of vertebrae:
            1. Precaudal and caudal vert.
          4. Structures of a vertebra
            1. centrum
            2. neural spine, neural arch, neural canal
            3. hemal spine, hemal arch, hemal canal
            4. ribs: attach to vertebrae
        3. caudal skeleton (fig. 3.13, 3.14)
          1. functions of tail
            1. forward thrust
            2. rudder, steering
          2. skeleton provides support for fin rays
      2. appendicular skeleton
        1. median fins: dorsal, anal (quick drawing)
          1. vanes (maintain direction)
          2. keels (keep from rolling)
        2. pectoral fins
          1. functions:
            1. brakes
            2. stabilizers, lift in sharks
          2. pectoral girdle (fig. 3.15)
            1. skeletal base
            2. attached to posterior skull
        3. pelvic fins
          1. function as brakes
          2. pelvic girdle
  3. Power supply: the body muscles
    1. Myomeres or myotomes
      1. One myomere per segment
      2. Formed intoW-shapes. (fig. 8.1, see also handout)
        1. Cross section: cuts through multiple myomeres
        2. nested cones
      3. Separated by fibers of collagen, myosepta
        1. made of collagen
        2. Multiple horizonal septa
          1. Separates blocks of epaxial and hypaxial muscle
        3. a single median septum
        4. attach muscles to backbone and skin
    2. Red and white muscle fibers
      1. anatomical, physiological differences (table)
        1. Red: aerobic metabolism
        2. White: anaerobic metabolism
      2. Functional differences
        1. measured with electrodes
        2. Red: cruise swimming, sustained for at least hours
        3. White: burst swimming
        4. Two different motor systems
      3. In different fishes:
        1. Inactive, with brief bursts of activity: all white
        2. Constant swimmers: 10%-25% red
      4. Location in swimming muscle
        1. may be intermingled: salmon
        2. red may be superficial lateral mass: stripers and bluefish
        3. red may be deep lateral mass: tuna, swordfish, mako shark
      5. Fiber orientations
        1. red fibers parallel to body axis
        2. white fibers in successive myomeres form spiral tracks (drawing)

    Efficiency: all fibers contract same, regardless of distance from vertebrae.

  4. Swimming
    1. Swimming diversity (Table 8.1)
      1. Some swim with fins
      2. Here, focus on trunk and tail swimming
    2. Generation of thrust
      1. Undulation
        1. Muscles contract locally, on one side
        2. body flexes there
        3. more posterior myomeres contract
        4. wave of flexion passes down body
        5. push on water along body, and medial fins
      2. Forces (fig. 8.1)
        1. Part of push on water translates into thrust
        2. some will be 'slippage' or lift, like sailboat without keel
        3. Wave speed: faster than is moving through water
        4. wave amplitude: widens head to tail
      3. Different swimming modes (table and handout)
        1. Anguilliform
          1. 1 or more wave (book says 0.5 and up) contained in body
          2. thrust at medial fins
          3. Tail not needed
          4. Some practitioners benthic, some pelagic and have to swim constantly
          5. Slow; lots of drag at flexes
        2. Subcarangiform, carangiform, thunniform
          1. 0.5 wave and less in body
          2. thrust is more posterior, tails more impt
          3. faster swimming possible, more streamlining
        3. Ostraciform
          1. Only caudal fin oscillates; slow sculling motion
    3. Swimming performance measurement
      1. Devices such as flumes
      2. Clocking natural swimming
      3. Sustained swimming speeds , 1-4 body l/sec
      4. Burst swimming, 10 body l/sec. Thunniform swimmers have been clocked at 75-100 km/hour
      5. Note from Goolish figure: larvae appear to be capable of sustained speeds of 10-12 bl/sec.

 

 

Red

White

Fiber morphology

slender

fat

vascularization

well

poorly

myoglobin

yes

no

mitochondria

many large

few small

energy storage

lipid

mostly glycogen