Water & heat balance, Thermoregulation

Herp metabolism focus

Water balance and temperature control in amphibians and reptiles.

Importance of water balance

Critical for nearly all living organisms.

Barriers to water movement

Mucus glands, lipid glands, and multiple keratinized skin layers.

Alpha keratin

Soft keratin contributing to flexibility and water resistance.

Beta keratin

Harder keratin that greatly reduces water loss in reptiles.

Water intake in amphibians

Absorbed through the skin rather than drinking.

Typical amphibian habitats

Moist or aquatic environments.

Dry-habitat amphibian strategies

Use moist microhabitats and burrowing.

Spadefoot toad adaptation

Burrowing to avoid desiccation.

Water intake in reptiles

Most non-avian reptiles drink water.

Arid-adapted reptiles

Specialized for water collection and conservation.

Namib Desert moisture source

Fog from the ocean.

Fog harvesting in reptiles

Collect droplets on body surfaces.

Lizard fog collection

Droplets collected from vegetation and scales.

Capillary action in scales

Channels water along scales to the mouth.

Horned lizard water collection

Channels water via specialized scale structure.

Moloch lizard adaptation

Convergent water-harvesting scale system.

Bitis peringueyi behavior

Flattens body to drink droplets from scales.

Massasauga rattlesnake behavior

Flattens body to drink water off scales.

Arid-adapted tortoise behavior

Channels water from shell to mouth.

Tortoise shell gutter

Carapace edge directs water to head.

Psammobates geometricus

Example of arid-adapted tortoise.

Kinixys erosa

Example of water-channeling tortoise.

Desert tortoise habitat

Arid regions with unpredictable rainfall.

Desert tortoise water strategy

Excavates catchment basins for rainwater.

Role of water in waste removal

Transport and dilution of metabolic wastes.

Amniote kidneys

Reclaim water and excrete nitrogenous waste.

Nitrogen waste in eggs

All amniotes produce uric acid in eggs.

Ureotelic animals

Mammals and turtles excrete nitrogen as urea.

Water cost of urea excretion

Requires large amounts of water.

Uric acid excretion in turtles

Used especially by arid-land tortoises.

Uricotelic animals

Squamates, tuatara, crocodilians, and birds.

Advantage of uric acid

Conserves water.

Crocodilian nitrogen excretion

Mostly ammonia, diluted in aquatic environments.

Dietary water source

Eating other animals provides 70–80% water.

Salt balance from vertebrate prey

Major ions remain balanced.

Insect diet ion imbalance

Excess potassium.

Plant diet ion imbalance

Excess sodium, potassium, and bicarbonate.

Salt glands function

Remove excess ions with minimal water loss.

Sea turtle salt glands

Lacrimal glands near the eyes.

Crying turtle phenomenon

Salt secretion visible during nesting on land.

Lizard salt glands

Nasal glands expelling salts via sneezing.

Herbivorous iguanian lizards

Especially reliant on salt glands.

Sea snake salt glands

Posterior sublingual gland.

Crocodilian salt glands

Lingual glands under the tongue.

Desert tortoise salt glands

Absent; relies on diet and water balance.

Evidence of desert tortoise ancestry

May not have evolved in deserts.

Metabolic water production

Water produced during cellular metabolism.

Water yield from fat

1 g fat produces ~1.07 g water.

Water yield from starch

1 g starch produces ~0.56 g water.

Water yield from protein with urea

~0.4 g water per gram protein.

Water yield from protein with uric acid

~0.5 g water per gram protein.

Amphibian water loss

Lost primarily through skin.

Amphibian water conservation

Mucus, frequent shedding, burrowing, humid refuges.

Reptile water conservation

Underground shelter and scaly skin.

Reptile skin advantage

Beta keratin greatly reduces evaporation.

Thermoregulation processes

Conduction, convection, radiation, evaporation.

Conduction

Heat transfer through direct contact.

Convection

Heat transfer via moving air or water.

Radiation

Heat transfer via electromagnetic waves.

Evaporation

Heat loss when liquid turns to gas.

Calorie definition

Energy needed to raise 1 g water by 1°C.

Calorie to Calorie conversion

1000 calories equals 1 dietary Calorie.

Body size and heat exchange

Smaller animals gain and lose heat faster.

Surface area to volume ratio

Higher ratio increases heat exchange.

Postural thermoregulation

Changing body position to gain or lose heat.

Behavioral thermoregulation

Movement between sun and shade.

Color change in thermoregulation

Melanin movement alters heat absorption.

Dark coloration effect

Absorbs more radiant heat.

Light coloration effect

Reflects more radiant heat.

Desert iguana absorption

Dark individuals absorb more visible light.

Scale texture and heat

Rough dorsal scales absorb infrared radiation.

Ventral scale adaptation

Smooth scales reflect heat from substrate.

Teiid lizards example

Dorsal roughness and ventral reflectivity.

Evaporative cooling in amphibians

Common in warm aquatic environments.

Panting in reptiles

Used by desert lizards to cool.

Chuckawalla cooling

Panting behavior.

Desert iguana cooling

Panting behavior.

Gular fluttering

Rapid throat movement for cooling.

Species using gular fluttering

Varanid lizards.

Cardiovascular shunting

Redirects blood flow to regulate temperature.

Shunting to skin

Increases heat loss.

Shunting away from skin

Conserves heat.

AV shunt function

Controls blood flow to skin capillaries.

Thermoregulation cost

Higher in closed, shaded habitats.

Open habitat advantage

More thermal options available.

Thermal conformity

Matching body temperature to environment.

Tropical lizard adaptation

Easier thermal conformity.

Anolis sagrei habitat

Open tree trunk environments.

Anolis sagrei body temperature

Approximately 32.3°C.

Anolis lineatopus habitat

Shaded forest.

Anolis lineatopus body temperature

Approximately 26–29°C.

Anolis grahami

Intermediate habitat and temperature.

Basking warming rate

Rapid temperature increase.

Cooling rate in refuge

Slower temperature decrease.

Preferred body temperature stability

Small daily variation.

Importance of optimal temperature

Essential for health and immunity.

Behavioral fever

Animals raise body temperature to fight infection.

Thermoregulation in pet reptiles

Often inadequate, causing illness or death.

Metabolic heating in ectotherms

Possible in large species.