Buoyancy and Thermoregulation

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Buoyancy and Thermoregulation Buoyancy (read p.
63-65 in text) Minimizes energy costs
through - large quantities of low density
compounds - lift from fins - swim
bladder Densities of materials - cartilage
and muscle 0.9 g/cm3 - bone
2 g/cm3 - gas
lt0.05 g/cm3 - water 1.0 g/cm3
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Swim bladders physostomous with pneumatic
duct to esophagus physoclistous no duct
Volume of closed swim bladder varies with
depth Surface 1 atmosphere of pressure (30
inches Hg) 10 m deep 2 atmospheres of
pressure 20 m deep 3 atmospheres of pressure
Ideal Gas Law P V n r T Pressure times volume
is a constant
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Physostomous swim bladders air moved in and out
of swim bladder through muscle contractions and
through simple capilary system Physoclistic swim
bladder air moved in and out of swim
bladder through rete mirable
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Rete mirable is a hair pin counter current
system uses Bohr effect
Can multiply O2 partial pressure at depth Only
physoclistic fish occupy deep water environments
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THERMAL REGULATION (read pp. 83-89 in
text) Most fish are cold blooded
poikilothermic ectotherms Environmental
Problems in Warm Water enzymes degrade low
oxygen environments high oxygen demand in
Cold Water cell membranes dont transport
well nerve cells lose ability to
fire metabolism slows
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The freezing point of water and fish Freshwater
freezes at 0C fish bodies freeze at
-0.7C fish can freeze into the ice
Salt water freezes at -1.86C fish freeze at
-0.7C Fish can freeze in water antifreeze
compounds in blood (glycoproteins) antifreeze
compounds in body fluids (glycerol) Fish can
produce these seasonally Some Antarctic fish are
supercooled
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Many fish can behaviorally thermoregulate homeoth
ermic ectotherms guppies and salmon Often
we see ontogenetic shifts in temperature
preferences juvenile fish choose warmer
temperatures allows for increased growth rate
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A few fish are warm-blooded called
poikilothermic endotherms Tuna is an
example Heat from swimming muscles warms blood
flowing into body core
Another example of hair pin counter current
system (rete mirable)
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Allows Tuna to maintain 12C body temperature
over ambient more efficient for muscle movement
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Some fish use counter current system to maintain
brain and eye temperatures above ambient
Use modified muscles as heat generators
(shivering) solves problems associated
with poor nerve function in cold often used by
predators inhabiting cold environments
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No fish are homeothermic endotherms Water is
good conductor of heat (marine mammals have
blubber or fur)
Poikilothermic Homeothermic
Salmon Guppies
Ectotherm Endotherm
Most fishes
Tuna