Download St. Francis Xavier University Countercurrent Multiplier

Biology 201
Dr. Edwin DeMont
The Fishes: Vertebrate Success
in Water
St. Francis Xavier University
The Fishes
The locomotor
structure of a fish
functions to propel it
through the water and
helps to reduce the
cost of locomotion.
St. Francis Xavier University
No Slip Condition
Filmed live
No flow exists at the
interface of a solid and a
moving fluid.
Skin Friction Drag
Always exists
Laminar or turbulent
Velocity gradient
Shear forces
Friction
Boundary layer (b.l.)
Surface of fish or Wall of artery
Video
St. Francis Xavier University
Drag Reduction
Aquatic swimmers have
several different mechanisms
to reduce skin friction drag.
- Riblets on scallops
- Riblets on sharks
- Fish Slime
Human swimmers
- Modify b.l.
Laminar ↔ turbulent
St. Francis Xavier University
Pressure drag
Filmed live
High pressure
Low pressure
Image source
Pressure
Drag
Pressure
differences create
a pressure gradient
→ Pressure Drag
Reduce pressure
drag by
streamlining.
St. Francis Xavier University
Total drag
Total Drag = Skin Friction Drag + Pressure Drag
Total Drag → constant × V2
But – drag isn’t
always bad news…
Drag on body slows it down – wastes energy
St. Francis Xavier University
Drag as thrust
Fins oscillate back
and forth creating
drag on the fin.
During the backstroke
(power) the drag force is
directly forward and
becomes the thrust force.
What happens on the
forward (recovery)
stroke?
St. Francis Xavier University
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.
St. Francis Xavier University
Buoyancy Control
Water pressure increases
Volume of s.b. decreases
Density of fish increases
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.
Need to precisely control
volume. Why?
St. Francis Xavier University
Buoyancy Control
Two types of swim bladder: (1) no connection to gut and
(2) direct connection to gut.
1. Physoclistous fishes
2. Physostomous fishes
Another diagram
St. Francis Xavier University
Countercurrent Multiplier
Normal blood flow through rete
O2
Gas gland
O2
Swimbladder
St. Francis Xavier University
Countercurrent Multiplier
Fish wants to move oxygen into
Swimbladder
Produces
lactic acid
O2
Gas gland
O2
O2
O2
Decreases affinity of oxygen to
hemoglobin
Swimbladder
St. Francis Xavier University
Countercurrent Multiplier
Fish wants to move Oxygen into
Swimbladder
Produces
lactic acid
O2
Gas gland
O2O2
O2
O2 O
2
O2 O2
Swimbladder
St. Francis Xavier University
Countercurrent Multiplier
Fish wants to move Oxygen into
Swimbladder
O2
O2
Produces
lactic acid
O2
Gas gland
O2O2
O2
O2 O
2
O2 O2
Swimbladder
St. Francis Xavier University
Countercurrent Multiplier
Fish wants to move Oxygen into
Swimbladder
O2
O2O O2
2
O2
O2O2 O2 O
2
O
2
O2 O2 O2
O2
O2
Swimbladder
St. Francis Xavier University
Sensory Functions
Photo source
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
St. Francis Xavier University
Lateral Line
Image source
The lateral line system is a
set of pits that detect
changes in water pressure.
Shear forces in
b.l. bend cupula
Sense hairs bend and
response initiated.
Why is the lateral line
located here?
St. Francis Xavier University
Sound Production
Picture Source
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)
St. Francis Xavier University
Photo source
Photo source
Atlantic Herring
Communication:
- Reduced lateral line
- Swim bladder connects to
inner ear and gut.
‘Frt’ing Sound (at night)
Contact
Anti-predator
(Fast Repetitive Tick)
St. Francis Xavier University
DVD Video
Wild Moves: Insights into
Animal Physiology
Fish and Marine Mammals:
Swimming and Diving
www.films.com
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.
St. Francis Xavier University
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?
St. Francis Xavier University