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Published byChristiana Morrison Modified over 7 years ago
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Movement in water
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Aim nfloating or sinking njet propulsion nswimming u slow u fast nmechanics and shape of an optimal design nhow fish move forwards
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References nSchmidt – Nielsen K (1997) Animal physiology nMcNeill Alexander R (1995) CD Rom How Animals move nWeb links: see: http://biolpc22.york.ac.uk/632/movelectures/water/
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In water ndensity of flesh similar to that of water u Skeletal support not so important nSwimming more efficient than running! nmajor cooling effect
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density n= mass / volume nair 1 kg /m 3 ndistilled water 1000 kg / m 3 nsea water 1030 kg / m 3 nbut tissues denser than water u muscle 1060 kg / m 3 u bone 1500-2000 kg / m 3
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Floating ndensity of fish > water nless dense than water u jellyfish : jelly u shark liver : squalene nswim to generate lift u sharks ngas store u Physalia u Nautilus oxygen u teleost swimbladder
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Sharks have to swim… nlift from aerofoil shape of pectoral fins nasymmetric tail moves more water on top u forces water down and shark up
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Floating with CO n Physalia u makes carbon monoxide
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Floating with gas nNautilus oxygen nrigid chamber u x-ray mostly gas u last still water filled
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Swimbladders nfull of oxygen nX-ray of butterfly fish
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Swimbladders at depth nPressure increases with depth u 1 atm = 10 m u Swimbladders get smaller, u give less buoyancy nfish unstable with depth
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How fill swimbladder 1.secrete lactic acid into blood n forces hb to release O 2 [Root effect] 2.run a counter-current exchanger n keep O2 in blood of rete mirabile
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Blood flow in rete flow lactic acid
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Oxygen flow in rete ncounter current u can fill swimbladder at 100 atm bladder
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Summary so far nbuoyancy can be solved u low density u active gas secretion u swimming ncarry a cost u larger (more drag from wider body) u difficult to stay stable nwhat is the optimal solution?
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Jet propulsion nconservation of momentum = m*v nmass of fish * velocity of fish = mass of water * velocity of water u squid F contract mantle u dragonfly larvae
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Paddling / rowing u ducks u beetle larvae u frogs swimming
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Paddling / rowing ndepends on conservation of momentum u ducks u beetle larvae u frogs swimming
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Drag nReynolds number gives an estimate of drag nRe = length * speed * density / viscosity u for air, density / viscosity = 7*10 4 s / m 2 u for water; density/ viscosity = 10 6 s/m 2 nfriction nturbulence
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Reynolds number nRe < 1 no wake u e.g. protozoan nRe < 10 6 flow is laminar u e.g. beetle nRe > 10 6 flow is turbulent u e.g. dolphin nDrag depends on shape nDrag reduced by up to 65% by mucus
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Swimming nUndulations u side to side (fish) u up down (whales, dolphins) nhow do undulations propel you forwards? nRowing u fins (reef fish) u legs (insects e.g. beetle larvae & birds)
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How does a fish move?
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How are swimming movements produced? nMyomere arrangement
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Myomere cross-section nWhite muscle contracts anaerobically, u using glucose for fuel and producing lactate. nRed muscle contracts aerobically, u using lipid for fuel and producing CO 2.
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Design for minimal drag ntuna or swordfish: u highly efficient for high-speed cruising in calm water ntorpedo-shaped body nnarrow caudal peduncle nlunate, rigid fins
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Why don’t all fish look like that? nThe design is highly inefficient: u In naturally turbulent water (streams, tidal rips, etc.) u for acceleration from stationary u for turning u for moving slowly u & especially for lying still
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Size and shape easy to turn – rigid slow – fast head moves – head still power from whole – power from tail muscles pull via tendons on tail fin
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Ambush predators nkeep head still u long body/dorsal fins nrapid start u flexible body, plenty of muscle u large tail fin nbarracuda npike
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Design for manoeuvrability nSmall items don’t move fast, but require delicate, focused movements for capture. nA short, rounded body with sculling or undulating fins. nCompressing the body laterally provides a wide surface to exert force on the water
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Optimal design? nNo one optimal design nefficient energetics isn’t all nmaximum speed isn’t all
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How is thrust generated? nthrust = momentum / time nanguilliform
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How else is thrust generated? ntail movement nCarangiform u tail generates symmetric vortex street note rotation
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How else is thrust generated? ntail movement acts like a hydrofoil u thunniform u cetaceans u penguins
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Flying not swimming ntail movement acts like a hydrofoil ngenerates lift and drag u drag acts in line of motion u lift acts perpendicular (normal) to drag drag lift total
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Summary ngravity less important nbuoyancy can be solved nthrust from u paddles [fins] u body u tail nno one optimal solution? npoint to ponder: swimming in protozoa
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