Comparative Vertebrate Physiology

1
Comparative Vertebrate Physiology

• Temperature relations in animals

2
Temperature variations

• Aquatic extremes
• -2C - 40C
• Terrestrial extremes
• -65C - 70 C

3
Ectotherms in cold climates

• Freezing is lethal
• Strategies
• Freeze tolerant animals - supercooling
• Ca salts, phospholipids restrict ice formation
  to ECF
• Intracellular solutes (glycerol) restricting
  water movement
• Freeze avoidance depress the osmotic freezing
  point
• Antifreeze proteins (sugars and glycerol) disrupt
  ice formation

4
Ectotherms in hot climates

• Critical lethal maximum
• Definition (50 mortality)

Fish 35
Salamanders 29-35.6
Anurans 36-41
Alligators 38
Turtles 41
Lizards 40.1-46.9
Snakes 40.4-41.6
Aquatic
Terrestrial
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Problem with hot climate

• Critical lethal maximum
• Protein denaturing
• Decrease in hemoglobin O2 affinity

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Ectotherm adaptations

• e.g.marine iguana
• Bradycardia
• Peripheral vasoconstriction

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Ectothermy

• Costs
• Cold unless environment permits
• Short duration of activity
• Limited body size
• Benefits
• Niche exploitation
• More energy for growth and reproduction
• Require less water

8
Heterotherms

• Terrestrial environment (e.g. Indian python)

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Heterotherms

• Aquatic environment must produce metabolic heat
• Fishes (rete mirabile)

Ectotherm
Heterotherm
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Heterotherms

• Blue fin tuna

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Endotherms

• Thermal neutral zone

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Endothermy in cold climates

• Strategies
• 1. Decrease rate of heat loss
• Grow larger
• Change shape
• Reduce thermal conductance(huddling, fat,
  migration)

Western pygmy possum
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Endothermy in cold climates

• Reduce thermal conductance(countercurrent heat
  exchange, peripheral vasoconstriction)

Terrestrial
Aquatic
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Endothermy in cold climates

• Strategies
• 2. Increasing heat production
• shivering

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Endothermy in cold climates

• Strategies
• 3. Abandoning homeothermy

Torpor
Hibernation
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Endothermy in hot climates

• Strategies
• Gular fluttering (birds)
• Sweating (mammals)
• Panting (mammals)(evaporative cooling)

Gular
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Endothermy

• Costs
• High rate of food and water consumption
• High rate of respiration (water loss)
• Small amount of energy for growth and
  reproduction
• Benefits
• Active throughout the day and night
• Large body size