Buoyancy
Specific gravity:
fresh water
sea water
1.0
1.026
fats, oils
tissues
cartilage
bone, scales
total fish body
0.9-0.93
1.05-1.1
1.1
2.0
1.06-1.09
Strategies to deal with sinking:
1.
reduce body weight
- reduce heavy materials
– cartilage in place of bone
– deepsea fishes reduce bone and muscle
Specific gravity:
fresh water
sea water
fats, oils
tissues
cartilage
bone, scales
total fish body
1.0
1.026
0.9-0.93
1.05-1.1
1.1
2.0
1.06-1.09
Strategies to deal with sinking:
1.
reduce body weight
- reduce heavy materials
- add lighter materials
- strategy used by most sharks, a few teleosts
lipids (specific gravity ~0.90)
squalene (especially in the liver) ~0.86
- Mola mola uses ‘fresh’ water (lighter than sea water)
Specific gravity:
fresh water
sea water
fats, oils
tissues
cartilage
bone, scales
total fish body
1.0
1.026
0.9-0.93
1.05-1.1
1.1
2.0
1.06-1.09
Strategies to deal with sinking:
1.
reduce body weight
- reduce heavy materials
- add lighter materials
- strategy used by most sharks, a few teleosts
lipids (specific gravity ~0.90)
squalene (especially in the liver) ~0.86
- Mola mola uses ‘fresh’ water (lighter than sea water)
using fat alone requires ~ 48% of body volume as fat
(e.g., Salmoniformes – siscowet lake trout)
Strategies to deal with sinking:
1.
reduce body weight
2.
add buoyancy compensating organ (gas bladder)
- physostomus (open to the outside)
- physoclistous (sealed)
Strategies to deal with sinking:
1.
reduce body weight
2.
add buoyancy compensating organ (gas bladder)
- physostomus (open to the outside)
- physoclistous (sealed)
BUT: pressure increases 1 atm for every 33’ depth (10 m)
Strategies to deal with sinking:
1.
reduce body weight
2.
add buoyancy compensating organ (gas bladder)
- physostomus (open to the outside)
- physoclistous (sealed)
BUT: pressure increases 1 atm for every 33’ depth (10 m)
fish do not usually change depth to bring about more
than a 25% change in gas bladder volume
- change from 90 to 100m decreases volume by only 10%
- change from 20 to 30 m decreases by about 25%
Strategies to deal with sinking:
1.
reduce body weight
2.
add buoyancy compensating organ (gas bladder)
- physostomus (open to the outside)
- physoclistous (sealed) ~ 2/3 of all teleosts
increase partial pressure of gas in blood
allow passive diffusion via rete mirable
Gas bladder:
Cells convert glucose
to lactic acid
lactic acid in blood circulating around bladder releases oxygen (Root effect)
Strategies to deal with sinking:
1.
reduce body weight
2.
add buoyancy compensating organ (gas bladder)
- physostomus (open to the outside)
- physoclistous (sealed) ~ 2/3 of all teleosts
increase partial pressure of gas in blood
allow passive diffusion via rete mirable
deepsea fishes – higher pressures – longer capillaries
gas resorbed via simple diffusion, expelled via gills
Strategies to deal with sinking:
1.
reduce body weight
2.
add buoyancy compensating organ (gas bladder)
3.
generate lift
- heterocercal tail
- planing surfaces – pectoral fins, entire body
Scorpaeniformes – sea moth, flying gunard
Pleuronectiformes - flounder
Strategies to deal with sinking:
1.
reduce body weight
2.
add buoyancy compensating organ (gas bladder)
3.
generate lift
4.
avoid the problem – live on the bottom, use lift as needed
Scorpaeniformes - sculpin
Respiration
Respiration
availability of O2 in water varies with
- temperature
- productivity
- BOD
origin of fishes in warm Tethys Sea….
Respiration
• lungs – lungfishes (Subclass Dipnoi – Ceratodontiformes, Lepidosireniformes)
- including obligate air breathers
Respiration
• lungs – lungfishes
• modified gas bladder – bichirs, bowfin, gars
(Polypteriformes, Lepisosteiformes, Amiiformes)
Respiration
• lungs – lungfishes
• modified gas bladder – bichirs, bowfin, gars
• “normal” gills – most teleosts
buccopharyngeal
cavity
parabranchial
cavity
Respiration
• lungs – lungfishes
• modified gas bladder – bichirs, bowfin, gars
• “normal” gills
- respiratory pump, or
- ram ventilation
Respiration
• lungs – lungfishes
• modified gas bladder – bichirs, bowfin, gars
• “normal” gills
• modified gills
- gill filaments tend to stick together in air
- tough filaments handle temporary exposure to air
e.g. walking catfish
Respiration
• lungs – lungfishes
• modified gas bladder – bichirs, bowfin, gars
• “normal” gills
• modified gills
• skin
- reedfish – skin supplies 32% of O2 need despite ganoid scales
- mudskipper (Periopthalmus) – 48%
- eels (Anguilla) – 30-66%
“eel fields”….
Respiration
• lungs – lungfishes
• modified gas bladder – bichirs, bowfin, gars
• “normal” gills
• modified gills
• skin
- reedfish – skin supplies 32% of O2 need despite ganoid scales
- mudskipper (Periopthalmus) – 48%
- eels (Anguilla) – 30-66%
• mouth – electric eel, carp
• gut – Plecostomus
Respiration
• lungs – lungfishes
• modified gas bladder – bichirs, bowfin, gars
• “normal” gills
• modified gills
• skin
- reedfish – skin supplies 32% of O2 need despite ganoid scales
- mudskipper (Periopthalmus) – 48%
- eels (Anguilla) – 30-66%
• mouth – electric eel, carp
• gut – Plecostomus
• surface water - killifish
Cyprinodontiformes
Thermoregulation
are fish “cold-blooded”?
poikilotherms
internal temperature varies
homeotherms
internal temperature remains stable
ectotherms
temperature is controlled externally
endotherms
temperature is controlled internally
thermal strategies
ectotherms – thermoregulate behaviorally
- switch different forms of enzymes on and off
- tend to have limited thermal ranges
- alter cell membrane saturated:unsaturated
fat ratio to maintain fluidity
thermal strategies
ectotherms – thermoregulate behaviorally
- switch different forms of enzymes on and off
- tend to have limited thermal ranges
- alter cell membrane saturated:unsaturated
fat ratio to maintain fluidity
endotherms – thermoregulate physiologically
- use rete mirable to conserve heat
- red muscle next to spinal column to insulate heat
thermal strategies
ectotherms – thermoregulate behaviorally
- switch different forms of enzymes on and off
- tend to have limited thermal ranges
- alter cell membrane saturated:unsaturated
fat ratio to maintain fluidity
endotherms – thermoregulate physiologically
- use rete mirable to conserve heat
- red muscle next to spinal column to insulate heat
thermogenesis – use of eye muscle in scombrids (mackerel)
no contractile elements, many mitochondria
Extreme thermal conditions
Heat: moderate - insufficient oxygen
high - protein denaturation
Cold: moderate - slowed molecular/biochemical reactions
low - ice crystals form in tissues
- solutes in remaining fluid increase concentration
Extreme thermal conditions
(1) ice insulates water
(2) salt water freezes at -1.86 (below freezing point of tissues)
(3) solutes in tissue depress freezing temp of body fluids to ~ -0.7
Extreme thermal conditions
Solutions to cold:
- produce antifreeze glycoproteins w. genes turned on at low temp
Notothenioid kidneys lack glomeruli which would remove
antifreeze glycoproteins
Ice fishes
Perciformes
Suborder Notothenioidei
Extreme thermal conditions
Solutions to cold:
- produce antifreeze glycoproteins w. genes tuned on at low temps
Notothenioid kidneys lack glomeruli which would remove
antifreeze glycoproteins
- increase concentrations of osmolytes (ions)
smelt use glycerol - metabolically costly to produce
(smelt known as ‘sweet fish’ in winter fishing)