biology 201 dr. edwin demont st. francis xavier university the fishes: vertebrate success in water
TRANSCRIPT
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The Fishes
The locomotor structure of a fish
functions to propel it through the water and
helps to reduce the cost of locomotion.
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No Slip Condition
No flow exists at the interface of a solid and a
moving fluid.
Filmed live
Surface of fish or Wall of artery
Velocity gradientShear forces
FrictionBoundary layer (b.l.)
Video
Skin Friction Drag
Always exists
Laminar or turbulent
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Drag Reduction
Aquatic swimmers have several different mechanisms to reduce skin friction drag.
- Riblets on scallops
- Fish Slime
- Riblets on sharks
- Modify b.l. Laminar ↔ turbulent
Human swimmers
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Pressure drag
Filmed live
Imag
e so
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Low pressureHigh pressure
Pressure Drag
Pressure differences create a pressure gradient → Pressure Drag
Reduce pressure drag by
streamlining.
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Total drag
Total Drag = Skin Friction Drag + Pressure Drag
Total Drag → constant × V2
Drag on body slows it down – wastes energy
But – drag isn’t always bad news…
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Drag as thrust
Fins oscillate back and forth creating drag on the fin.
What happens on the forward (recovery)
stroke?
During the backstroke (power) the drag force is
directly forward and becomes the thrust force.
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Whole Body
Whole body (or caudal fin) undulations also generate thrust.
Tail interacts with water to form
‘vortexes’ that move downstream and ‘push’ the fish
forward.
Volume of s.b. decreases
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Buoyancy Control
Several mechanisms aid in vertical regulation and
include fins to create lift, changing body density by the
addition of oils.
Swim bladders (s.b.) are also used for
buoyancy.
Water pressure increases
Density of fish increasesNeed to precisely control
volume. Why?
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Buoyancy Control
Two types of swim bladder: (1) no connection to gut and (2) direct connection to gut.
2. Physostomous fishes 1. Physoclistous fishesAnother diagram
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Countercurrent Multiplier
Swimbladder
Gas gland
Normal blood flow through rete
O2
O2
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Countercurrent Multiplier
Swimbladder
Gas gland
Fish wants to move oxygen into Swimbladder
Produces lactic acid
O2 O2
O2
O2
Decreases affinity of oxygen to hemoglobin
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Countercurrent Multiplier
Swimbladder
Gas gland
Fish wants to move Oxygen into Swimbladder
Produces lactic acid
O2 O2
O2 O2O2
O2O2
O2
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Countercurrent Multiplier
Swimbladder
Gas gland
Fish wants to move Oxygen into Swimbladder
Produces lactic acid
O2 O2
O2 O2O2
O2O2
O2 O2O2
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Countercurrent Multiplier
Swimbladder
Fish wants to move Oxygen into Swimbladder
O2 O2
O2 O2O2
O2O2
O2 O2
O2
O2
O2
O2
O2 O2
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Sensory FunctionsP
hoto
sou
rce
Sensory receptors are widely distributed and used for
olfaction, vision, hearing, equilibrium and for detecting
water movements.
Schooling may be controlled by sensing water movement
generated by nearby fish.
Collision-free Driving by Mimicking Fish Behavior
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Lateral Line
The lateral line system is a set of pits that detect
changes in water pressure.
Why is the lateral line located here?
Imag
e so
urce
Shear forces in b.l. bend cupula
Sense hairs bend and response initiated.
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Sound Production
Audio communication is not obvious in fishes, but may be used extensively.
Low frequency sounds can be detected by lateral line
receptors.White Grunt (Haemulon
plumieri)
Pic
ture
Sou
rce
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Atlantic HerringP
hoto
sou
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Pho
to s
ourc
e
‘Frt’ing Sound (at night)
ContactAnti-predator
(Fast Repetitive Tick)
Communication:- Reduced lateral line
- Swim bladder connects to inner ear and gut.
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DVD Video
Wild Moves: Insights into Animal Physiology
Fish and Marine Mammals:Swimming and Diving
Several questions will be raised during the video. By the end of the video, you should be able to answer the questions listed on the next slide.
www.films.com
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DVD Video
1. What determines the locomotor styles of fishes?
2. How do fish change their locomotor style with speed?
3. Why do fish have two types of muscles?
4. Why do large fish swim the fastest?
5. What mechanisms do aquatic animals use to maintain themselves in the water column?