Buoyancy

Specific gravity:fresh water 1.0sea water 1.026

fats, oils 0.9-0.93tissues 1.05-1.1cartilage 1.1bone, scales 2.0total fish body 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 1.0sea water 1.026

fats, oils 0.9-0.93tissues 1.05-1.1cartilage 1.1bone, scales 2.0total fish body 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 teleostslipids (specific gravity ~0.90)squalene (especially in the liver) ~0.86

- Mola mola uses ‘fresh’ water (lighter than sea water)

Specific gravity:fresh water 1.0sea water 1.026

fats, oils 0.9-0.93tissues 1.05-1.1cartilage 1.1bone, scales 2.0total fish body 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 teleostslipids (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 bloodallow passive diffusion via rete mirable

Gas bladder:

lactic acid in blood circulating around bladder releases oxygen (Root effect)

Cells convert glucose to lactic acid

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 bloodallow passive diffusion via rete mirabledeepsea fishes – higher pressures – longer capillariesgas 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

endothermstemperature 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 oxygenhigh - protein denaturation

Cold: moderate - slowed molecular/biochemical reactionslow - 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)