Herpetology (Bio 488), Spring ‘11, Poe & Snell, L03 – Energetics & Performance continued 1

Energetics & Performance:Components of Heat Exchange Work in Concert

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• Behavioral Aspects of Thermoregulation– A large part of thermoregulation in amphibians and reptiles is behaviorally

controlled – Body temperature generally regulated within a narrow, optimum range of

temperatures. • Particularly true of reptiles. • Temperature sensitive region of brain is the hypothalamus (monitors

temperature of blood).

• Cardiovascular Control of Thermoregulation– In many reptiles, the cardiovascular system is also important in regulating

the rate of heating and cooling of the body.

• Heating and cooling rates are not equal. Why?

• 3 ways the cardiovascular system helps regulate these rates: – Higher heart rate during heating. – Intracardiac shunt: Blood transfer in heart that increases proportion of

blood going to skin and body (decrease amount going to lungs). – Vasodilatation in areas of skin that are warm.

Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

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• Development of Our Understanding of Thermoregulation:

Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

However, Skeptics found that:

Herpetology (Bio 488), Spring ‘11, Poe & Snell, L03 – Energetics & Performance continued 4

Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

Australian Bearded Dragon (Poona barbate)

• This Lead to Research Into Physiological Adaptation:

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Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

• And Research Into Behavioral Mechanisms:

Dipsosaurus dorsalis

Upper “Set Point”

Lower “Set Point”

Ameiva festiva

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Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

• As Well As Behavioral Physiology:

Brooding female python

Non-brooding female

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Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

More Behavioral Physiology:

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Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

Then Completely Integrated Field Observational Studies:

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Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

Similar Effects Exist for Water Balance:

Water Effects

Water Impacts Temperature Effects

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Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

So What Does This Do For Reptiles & Amphibians?

TheoreticalReal (Ameiva festiva)

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Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

Which Came First?Evolution of “Preferred” Body Temperature,

or

Convergence of Optimal Levels of Processes?

Natrix maura

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Energetics & Performance:Physics of Heat Exchange & Behavior Yield Thermoregulation

Either Way the Use of Exothermal Energy Partially Explains the Superiority of Reptiles and Amphibians!