1. Comparative Vertebrate Physiology
Temperature relations in animals

2. Temperature variations
Aquatic extremes
-2°C - +40°C
Terrestrial extremes
-65°C °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
Anurans
36-41
Alligators 38
Turtles 41
Lizards
Snakes
Aquatic
Terrestrial

5. Problem with hot climate
Critical lethal maximum
Protein denaturing
Decrease in hemoglobin O2 affinity

6. Ectotherm adaptations
e.g.marine iguana
Bradycardia
Peripheral vasoconstriction

7. Ectothermy Costs Benefits 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)

9. Heterotherms Aquatic environment: must produce metabolic heat
Fishes (rete mirabile)
Ectotherm
Heterotherm

10. Heterotherms
Blue fin tuna

11. Endotherms
Thermal neutral zone

12. Endothermy in cold climates
Strategies
1. Decrease rate of heat loss
Grow larger
Change shape
Reduce thermal conductance (huddling, fat, migration)
Western pygmy possum

13. Endothermy in cold climates
• Reduce thermal conductance (countercurrent heat exchange, peripheral vasoconstriction)
Terrestrial
Aquatic

14. Endothermy in cold climates
Strategies
2. Increasing heat production
shivering

15. Endothermy in cold climates
Strategies
3. Abandoning homeothermy
Torpor
Hibernation

16. Endothermy in hot climates
Strategies
Gular fluttering (birds)
Sweating (mammals)
Panting (mammals) (evaporative cooling)
Gular

17. Endothermy Costs Benefits 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