ANSC 3180 Lecture Notes - Lecture 9: Poikilotherm, Thermoregulation, Eutheria
2 May 2018
School
Department
Course
Professor
DEE = (BMR + activity + thermoregulation + heat increment of
feeding)
○
Part of maintenance energy/ daily energy expenditure
•
Birds -40C
!
Placentals (eutherian) -38C
!
Marsupials (therian) -34C
!
Monotremes (protherian) -30C
!
An animal which maintains a relatively constant body temperature,
despite wide fluctuations in environmental temperature (ex. Death
Valley, Ca vs. Antarctica)
○
Homiotherm/homeotherm (warm-blooded)
•
An animal with labile body temperature, which follows changes in
ambient environmental temperature (amphibians and reptiles)
○
'behavioural homiotherms' maintain a fiarly constant elevated body
temperature by moving between sun and shade
○
E.g. naked mole rat
○
Poikilotherm (cold-blooded)
•
Endotherm -animal whose body temperature is determined by heat
derived from body metabolic activity (aka homeotherm)
•
Ectotherm -an animal whose body temperature is determined by heat
sources external to body (aka poikilotherm)
•
ex. Moose: < -40C
!
Lower Critical Temperature -may be very low
○
ex. Moose: winter -0C; summer -+14C
!
Upper Critical Temperature -may also be low
○
*Recall: definitions of LCT and UCT
•
See ways to respond to cooling and warming
○
Thermoneutral Zone: UCT -LCT
•
Without increasing metabolic heat production above maintenance
metabolism AND without employing any behavioural strategy to
conserve or dissipate heat
○
Thermocomfort Zone: smaller range than TNZ
•
There is a slower response to change in core body temp when below
LCT -many ways to maintain temp
○
Young animals -have an every larger allowance for cold past LCT
○
*there is a quick response at end of TNZ (above UCT)
•
Maintenance Energy: Thermoregulation
The metabolic heat produced in the body WITH heat gained
from (or lost to) the external environment to maintain its core
body temp THEN energy must be used to increase or decrease
body temp (--> more food)
!
If a homeothermic mammal/bird cannot balance:
○
Basal metabolism, activity
!
To estimate maintenance energy requirements (/DEE) -to
determine how much food needs to be eaten
!
Thermoregulatory energy must be added to:
○
A Balancing Act
•
Celcius: C = (F -32) * 5/9 0 -100C
○
*C=F=-40
!
Fahrenheit: = (C * 9/5) + 32 32-212 F
0 K --> absolute zero, no thermal energy
!
Kelvin: K= C + 273 273-373 K
○
Temperature Scales: Freezing -boiling
•
Hm -metabolic heat
!
Qr -heat lost/gained by radiation
!
Qc -heat lost by convection
!
Qk -heat lost/gained by conduction
!
Qe -heat lost by evaporation
!
Hm +/-Qr -Qc +/-Qk -Qe = Heat Stored
○
--> infrared thermal radiation from vegetation
!
--> infrared thermal radiation from atmosphere
!
--> reflected sunlight
!
--> direct sunlight
!
--> dust and particles
!
--> scattered sunlight
!
--> wind
!
<-- evaporation
!
<-- infrared thermal radiation from animal
!
Ex. Heat Exchange between animal and the environment -Rhino
○
Direct1)
Diffused2)
Reflected3)
Solar/short wave radiation i.
Thermal/long waveii.
Convection (air/water)iii.
Conduction (direct contact between animal and environment) iv.
Skin1)
Respiratory2)
Metabolic 3)
Evaporationv.
Ex. Heat Exchange with Elephant
○
Depends on a temperature gradient (sensible heat flow)
•
Cannot lose heat if environment is hotter than animal
•
By radiation, convection, conduction1.
Depends on vapor pressure gradient (latent heat flow)
•
Can't lose heat at 100% relative humidity
•
By evaporation2.
Heat gained/lost…
○
Basal metabolism
!
Digestion
!
Movement
!
Growth
!
Gestation
!
Lactation
!
Metabolic heat gained from:
○
All animal and birds radiate heat (infrared/ long wave)
•
The sun (>1500C) radiates heat (some UV wavelengths,
visible light, infrared)
•
Transfer of heat energy from a hotter to a cooler body (by the
passage of electromagnetic waves, can occur slowly through a
vacuum)
!
increasing wavelengths: X-rays -UV -visible -
infrared -microwaves
•
Solar/shortwave: 0.3-3.0 um
•
Thermal/longwave: 3.0-50.0 um
•
Electromagnetic spectrum:
!
All animals, birds, plants, inanimate objects in the
environment radiate heat (longwave/thermal) warmer
than -273C (0K)
•
Sun radiates heat (solar/shortwave)
!
Animals and birds absorbs ~95% of longwave/thermal
radiation
•
Black animals/birds absorb up to 90% of
solar/shortwave radiation
•
White animals/birds only absorb up to 50% of
solar/shortwave radiation
•
All radiation can be absorbed or reflected
!
Radiation:
○
Aka layer of air/water next to warm body
!
The transfer of heat energy through moving air/water
!
When air (or water) are heated, they expand, become less
dense, and rise while cooler, denser air (or water) sinks
!
Animals and birds seek shelter when they are cold or
seek windy locations when they are hot
•
Wind (or moving water) increases heat loss by 'forced
convection'
!
Convection:
○
The transfer of heat energy through solids when oscillating
molecules exchange energy without appreciable changing
their position
!
Transfer of heat between animals/birds and solid surfaces
which they are in contact with ground/snow/vegetation
!
On land -standing (feet), lying (lateral/ventral),
perching (feet), incubating eggs
•
In water -aquatic animals/birds
•
When:
!
Conduction:
○
Becomes the dominant means of heat loss and air
temperature approaches body temperature
•
Wind increases evaporative heat loss
•
The transfer of heat when heat energy is required as water
changes from a liquid to a vapour or gas without change in
temperature
!
Sweating -cattle, horses, camels, humans
!
Panting (evaporation from respiratory tract) -dogs, cats, many
birds
!
Sweating and panting -kangaroos
!
Gular fluttering (in some birds instead of panting) -floor of
mouth and uper oesophagus
!
Saliva-spreading (rats) -some marsupials lick their wrists
!
Water evaporates from plant leaves
!
Cooler to sit on grass than on bare ground
!
Cooler under trees than under wooden shelter
!
Evaporation:
○
Heat Gain & Loss
•
Thermoregulation -
Air temperature + humidity -humidex
○
Air temperature + wind -wind chill
○
Effective Environmental Temperature
•
Different humidex and wind chill values for different animals
•
How hot/cold does it feel?
All 4 methods of heat gain/loss depend on animal/bird SA
•
Measure flattened skin, but larger area than area exposed to
environment (underwings)
○
Surface area may be difficult to measure
•
Surface area changes with posture
•
Thermoregulation and Surface Area:
Pelage (hair/fur) and Plumage (feathers) offer insulation
•
Air is a very poor heat conductor
○
Fluffing
○
Piloerection
○
Pelage/plumage traps a still layer of air next to the skin and reduces heat
loss by convection
•
Summer pelage may provide less insulation than winter pelage
○
Ex. Bears, muskoxen
○
Shrew -weasel -rabbit -dog -reindeer -arctic fox -grizzly -
wolf -polar bear
!
Insulation increases with fur thickeness
○
Highest insulation in birds and arctic mammals
•
Dense, long wool absorbs solar radiation at surface and re-
radiates heat from wool tips
!
Wool surface -85C; skin -42C; core -39C
!
Merino sheep -ambient temperature of 40C and sunny
○
Water and oil reduce insulation of pelage and plumage to decrease
air lost
○
Pelage/plumage may also insulate against environmental heat when
ambient temperature is hot or there is high incident solar radiation
•
African/Asian elephant, white/black/Sumatran/Javan rhinoceros,
river hippopotamus
○
Megaherbivores (mammals) > 1 ton mature weight
•
Pangolins (giant pangolin -~6ft long)
○
Armadillos (giant armadillo -~3ft long, 32 kg)
○
Scaly mammals
•
Fur or Feathers:
PART 2
Boundary layer -air (affected by air movement)1)
Cover layer -pelage or plumage trap still air (insulation is decreased by
wind -ruffling)
2)
Tissue layer, body shell -muscles, blood vessels, fat and skin (insulation
is affected by blood flow)
3)
Body core -visceral organs, major metabolic heat production 4)
Animal's thermal insulation layers:
Animal/bird must also be still (resting/sleeping)
○
~0.35 cm thick (all species, all body sizes)
○
This layer of still air provides as much insulation as tissue layer
insulation during max vasoconstriction
○
A layer of still air next to animal's skin/cover layer in an environment with
little/no air movement
•
Boundary Layer
Some are specialized, insulatic air cells in the medulla of the hair
shaft -hollow hair shafts
○
Guard hairs vs. underfur (muskox)
○
Contour feathers vs. down (eider duck)
○
Type of Hair or Feather1.
More dense -greater insulation
○
Numbers are determined at birth -skin grows but no increase in the
number of hair follicles
○
Horse -1290
!
Cow -700
!
Pigs -37
!
Differs with species:
○
Merino -5000 fibers/cm2
!
Lincoln -1400 fibers/cm2
!
Differs with breed:
○
Smallest sea mammals in NA -very dense fur >150,000 hairs/cm2
○
Number of hairs/cm2
2.
Longer traps more still air (poitou donkey)
○
Length of Cover3.
Animals may be at risk or heat or cold stress during transition
seasons, when changes in pelage/plumage incomplete
○
Shedding, moulting, usually in response to seasonal day length
changes (not ambient temperature)
○
Winter coat in some species -hairs stop falling out and grow longer
○
Shedding and Moulting4.
Under autonomic control (not voluntary) by dermal muscles (traps
or eliminates air)
○
Piloerection/pteroerection5.
Can reduce cover depth by disrupting the hair or feathers -ruffling
○
Air speed as low as >0.9 m/s can reduce cover insulation
○
Wind6.
Reduces depth of the pelage/plumage and replaces air with water
○
Therefore, water cools animal down
!
Air 0.000059 vs. water 0.0014 cal/cm2/s/C --> increased
conductivity (x100)
○
Water7.
Cover Layer Insulation (plumage/pelage)
Visceral organs in the body core have high metabolic rate --> high
heat production
○
Very small amount of core body heat --> skin via conduction
○
Most core body heat --> skin (carried by blood through arteries -
circulatory convection)
○
Heat in body core --> tissue layer --> skin
•
Surface vessels constrict to decrease heat loss via conduction
from skin to environment
!
Occurs with low ambient temperatures
!
Vasoconstriction:
○
Surface vessels dilate to allow high heat transfer via
conduction from skin to environment
!
Occurs with high ambient temperatures
!
Vasodilation:
○
Blood Flow to Skin:
•
High ambient temperature -less trapped air
○
Sub-cutaneous fat:
•
About 3C higher than normal core body temperature
○
Poultry (most birds) ULBT -45C
○
Eutherian ULBT -42C
○
Monotremes ULBT -33C
○
Marsupials ULBT -39C
○
Upper lethal body temperature:
•
High humidity -no evaporative cooling
!
They have no way to remove heat
!
Animals can't survive long with EET (how hot it feels) 5C above
core body temperature
○
But, animals can survive for a long time at 20-60C below core body
temperature
○
Effective Environemental Temperature (EET)
•
When air is inhaled, it gains warmth and moisture from respiratory
tract/lungs
○
Dry desert environments -water loss
!
Cold environments -heat loss
!
When this moist warm air is exhaled, both heat and moisture can be
lost from body
○
Heat and moisture lost when animal breathes out:
•
A lot of moisture and heat are loss
○
Ex. Red-winged blackbird and moose
○
Hot breath in cold air -nasal turbinates
•
Body Shell/Tissue layer (muscles, blood vessels, fat and skin)
Decrease in appetite (decrease in metabolic heat), eat at night when
cooler
○
Use shade (decrease in solar heat), go to windy area (increase
convective cooling), flap elephant ears (increase convective
cooling)
○
Stand in rain, water pool/lake/river (increase in evaporative cooling)
○
Lie down on cool and/or wet ground (increase in conductive
cooling)
○
Help prevent heat stress:
•
*pigs have sweat glands that don’t function
!
Sweating (primates, perissodactyls, artiodactyls have sweat glands
but number glands and rate of sweating varies)
○
Panting (most carnivores, birds)
○
Kangaroos sweat (exercising) and pant (standing in sun)
○
Reduce heat stress:
•
Increase in appetite (increase in metabolic heat)
○
Use of shelter from wind (decrease in convective cooling), shelter
from rain/snow (decrease in evaporative cooling)
○
Stand in sun (increase in solar heat)
○
Help prevent cold stress:
•
Shivering (increase internal body heat)
○
Increase in metabolic rate (increase in heat production)
○
Reduce cold stress:
•
Animal's Body Core (visceral organs)
Highland cow -long fur, cold environments
•
Ankole-Watusi Cattle -short fur, hot environments
•
*different domestic cattle breeds live in different environments -different
thermoregulatory mechanisms
Energy: Thermoregulation
Wednesday,* February*15,*2017
12:25*PM
DEE = (BMR + activity + thermoregulation + heat increment of
feeding)
○
Part of maintenance energy/ daily energy expenditure
•
Birds -40C
!
Placentals (eutherian) -38C
!
Marsupials (therian) -34C
!
Monotremes (protherian) -30C
!
An animal which maintains a relatively constant body temperature,
despite wide fluctuations in environmental temperature (ex. Death
Valley, Ca vs. Antarctica)
○
Homiotherm/homeotherm (warm-blooded)
•
An animal with labile body temperature, which follows changes in
ambient environmental temperature (amphibians and reptiles)
○
'behavioural homiotherms' maintain a fiarly constant elevated body
temperature by moving between sun and shade
○
E.g. naked mole rat
○
Poikilotherm (cold-blooded)
•
Endotherm -animal whose body temperature is determined by heat
derived from body metabolic activity (aka homeotherm)
•
Ectotherm -an animal whose body temperature is determined by heat
sources external to body (aka poikilotherm)
•
ex. Moose: < -40C
!
Lower Critical Temperature -may be very low
○
ex. Moose: winter -0C; summer -+14C
!
Upper Critical Temperature -may also be low
○
*Recall: definitions of LCT and UCT
•
See ways to respond to cooling and warming
○
Thermoneutral Zone: UCT -LCT
•
Without increasing metabolic heat production above maintenance
metabolism AND without employing any behavioural strategy to
conserve or dissipate heat
○
Thermocomfort Zone: smaller range than TNZ
•
There is a slower response to change in core body temp when below
LCT -many ways to maintain temp
○
Young animals -have an every larger allowance for cold past LCT
○
*there is a quick response at end of TNZ (above UCT)
•
Maintenance Energy: Thermoregulation
The metabolic heat produced in the body WITH heat gained
from (or lost to) the external environment to maintain its core
body temp THEN energy must be used to increase or decrease
body temp (--> more food)
!
If a homeothermic mammal/bird cannot balance:
○
Basal metabolism, activity
!
To estimate maintenance energy requirements (/DEE) -to
determine how much food needs to be eaten
!
Thermoregulatory energy must be added to:
○
A Balancing Act
•
Celcius: C = (F -32) * 5/9
0 -100C
○
*C=F=-40
!
Fahrenheit: = (C * 9/5) + 32
32-212 F
0 K --> absolute zero, no thermal energy
!
Kelvin: K= C + 273
273-373 K
○
Temperature Scales:
Freezing -boiling
•
Hm -metabolic heat
!
Qr -heat lost/gained by radiation
!
Qc -heat lost by convection
!
Qk -heat lost/gained by conduction
!
Qe -heat lost by evaporation
!
Hm +/-Qr -Qc +/-Qk -Qe = Heat Stored
○
--> infrared thermal radiation from vegetation
!
--> infrared thermal radiation from atmosphere
!
--> reflected sunlight
!
--> direct sunlight
!
--> dust and particles
!
--> scattered sunlight
!
--> wind
!
<-- evaporation
!
<-- infrared thermal radiation from animal
!
Ex. Heat Exchange between animal and the environment -Rhino
○
Direct1)
Diffused2)
Reflected3)
Solar/short wave radiation
i.
Thermal/long waveii.
Convection (air/water)iii.
Conduction (direct contact between animal and environment) iv.
Skin1)
Respiratory2)
Metabolic 3)
Evaporationv.
Ex. Heat Exchange with Elephant
○
Depends on a temperature gradient (sensible heat flow)
•
Cannot lose heat if environment is hotter than animal
•
By radiation, convection, conduction1.
Depends on vapor pressure gradient (latent heat flow)
•
Can't lose heat at 100% relative humidity
•
By evaporation2.
Heat gained/lost…
○
Basal metabolism
!
Digestion
!
Movement
!
Growth
!
Gestation
!
Lactation
!
Metabolic heat gained from:
○
All animal and birds radiate heat (infrared/ long wave)
•
The sun (>1500C) radiates heat (some UV wavelengths,
visible light, infrared)
•
Transfer of heat energy from a hotter to a cooler body (by the
passage of electromagnetic waves, can occur slowly through a
vacuum)
!
increasing wavelengths: X-rays -UV -visible -
infrared -microwaves
•
Solar/shortwave: 0.3-3.0 um
•
Thermal/longwave: 3.0-50.0 um
•
Electromagnetic spectrum:
!
All animals, birds, plants, inanimate objects in the
environment radiate heat (longwave/thermal) warmer
than -273C (0K)
•
Sun radiates heat (solar/shortwave)
!
Animals and birds absorbs ~95% of longwave/thermal
radiation
•
Black animals/birds absorb up to 90% of
solar/shortwave radiation
•
White animals/birds only absorb up to 50% of
solar/shortwave radiation
•
All radiation can be absorbed or reflected
!
Radiation:
○
Aka layer of air/water next to warm body
!
The transfer of heat energy through moving air/water
!
When air (or water) are heated, they expand, become less
dense, and rise while cooler, denser air (or water) sinks
!
Animals and birds seek shelter when they are cold or
seek windy locations when they are hot
•
Wind (or moving water) increases heat loss by 'forced
convection'
!
Convection:
○
The transfer of heat energy through solids when oscillating
molecules exchange energy without appreciable changing
their position
!
Transfer of heat between animals/birds and solid surfaces
which they are in contact with ground/snow/vegetation
!
On land -standing (feet), lying (lateral/ventral),
perching (feet), incubating eggs
•
In water -aquatic animals/birds
•
When:
!
Conduction:
○
Becomes the dominant means of heat loss and air
temperature approaches body temperature
•
Wind increases evaporative heat loss
•
The transfer of heat when heat energy is required as water
changes from a liquid to a vapour or gas without change in
temperature
!
Sweating -cattle, horses, camels, humans
!
Panting (evaporation from respiratory tract) -dogs, cats, many
birds
!
Sweating and panting -kangaroos
!
Gular fluttering (in some birds instead of panting) -floor of
mouth and uper oesophagus
!
Saliva-spreading (rats) -some marsupials lick their wrists
!
Water evaporates from plant leaves
!
Cooler to sit on grass than on bare ground
!
Cooler under trees than under wooden shelter
!
Evaporation:
○
Heat Gain & Loss
•
Thermoregulation -
Air temperature + humidity -humidex
○
Air temperature + wind -wind chill
○
Effective Environmental Temperature
•
Different humidex and wind chill values for different animals
•
How hot/cold does it feel?
All 4 methods of heat gain/loss depend on animal/bird SA
•
Measure flattened skin, but larger area than area exposed to
environment (underwings)
○
Surface area may be difficult to measure
•
Surface area changes with posture
•
Thermoregulation and Surface Area:
Pelage (hair/fur) and Plumage (feathers) offer insulation
•
Air is a very poor heat conductor
○
Fluffing
○
Piloerection
○
Pelage/plumage traps a still layer of air next to the skin and reduces heat
loss by convection
•
Summer pelage may provide less insulation than winter pelage
○
Ex. Bears, muskoxen
○
Shrew -weasel -rabbit -dog -reindeer -arctic fox -grizzly -
wolf -polar bear
!
Insulation increases with fur thickeness
○
Highest insulation in birds and arctic mammals
•
Dense, long wool absorbs solar radiation at surface and re-
radiates heat from wool tips
!
Wool surface -85C; skin -42C; core -39C
!
Merino sheep -ambient temperature of 40C and sunny
○
Water and oil reduce insulation of pelage and plumage to decrease
air lost
○
Pelage/plumage may also insulate against environmental heat when
ambient temperature is hot or there is high incident solar radiation
•
African/Asian elephant, white/black/Sumatran/Javan rhinoceros,
river hippopotamus
○
Megaherbivores (mammals) > 1 ton mature weight
•
Pangolins (giant pangolin -~6ft long)
○
Armadillos (giant armadillo -~3ft long, 32 kg)
○
Scaly mammals
•
Fur or Feathers:
PART 2
Boundary layer -air (affected by air movement)1)
Cover layer -pelage or plumage trap still air (insulation is decreased by
wind -ruffling)
2)
Tissue layer, body shell -muscles, blood vessels, fat and skin (insulation
is affected by blood flow)
3)
Body core -visceral organs, major metabolic heat production 4)
Animal's thermal insulation layers:
Animal/bird must also be still (resting/sleeping)
○
~0.35 cm thick (all species, all body sizes)
○
This layer of still air provides as much insulation as tissue layer
insulation during max vasoconstriction
○
A layer of still air next to animal's skin/cover layer in an environment with
little/no air movement
•
Boundary Layer
Some are specialized, insulatic air cells in the medulla of the hair
shaft -hollow hair shafts
○
Guard hairs vs. underfur (muskox)
○
Contour feathers vs. down (eider duck)
○
Type of Hair or Feather1.
More dense -greater insulation
○
Numbers are determined at birth -skin grows but no increase in the
number of hair follicles
○
Horse -1290
!
Cow -700
!
Pigs -37
!
Differs with species:
○
Merino -5000 fibers/cm2
!
Lincoln -1400 fibers/cm2
!
Differs with breed:
○
Smallest sea mammals in NA -very dense fur >150,000 hairs/cm2
○
Number of hairs/cm2
2.
Longer traps more still air (poitou donkey)
○
Length of Cover3.
Animals may be at risk or heat or cold stress during transition
seasons, when changes in pelage/plumage incomplete
○
Shedding, moulting, usually in response to seasonal day length
changes (not ambient temperature)
○
Winter coat in some species -hairs stop falling out and grow longer
○
Shedding and Moulting4.
Under autonomic control (not voluntary) by dermal muscles (traps
or eliminates air)
○
Piloerection/pteroerection5.
Can reduce cover depth by disrupting the hair or feathers -ruffling
○
Air speed as low as >0.9 m/s can reduce cover insulation
○
Wind6.
Reduces depth of the pelage/plumage and replaces air with water
○
Therefore, water cools animal down
!
Air 0.000059 vs. water 0.0014 cal/cm2/s/C --> increased
conductivity (x100)
○
Water7.
Cover Layer Insulation (plumage/pelage)
Visceral organs in the body core have high metabolic rate --> high
heat production
○
Very small amount of core body heat --> skin via conduction
○
Most core body heat --> skin (carried by blood through arteries -
circulatory convection)
○
Heat in body core --> tissue layer --> skin
•
Surface vessels constrict to decrease heat loss via conduction
from skin to environment
!
Occurs with low ambient temperatures
!
Vasoconstriction:
○
Surface vessels dilate to allow high heat transfer via
conduction from skin to environment
!
Occurs with high ambient temperatures
!
Vasodilation:
○
Blood Flow to Skin:
•
High ambient temperature -less trapped air
○
Sub-cutaneous fat:
•
About 3C higher than normal core body temperature
○
Poultry (most birds) ULBT -45C
○
Eutherian ULBT -42C
○
Monotremes ULBT -33C
○
Marsupials ULBT -39C
○
Upper lethal body temperature:
•
High humidity -no evaporative cooling
!
They have no way to remove heat
!
Animals can't survive long with EET (how hot it feels) 5C above
core body temperature
○
But, animals can survive for a long time at 20-60C below core body
temperature
○
Effective Environemental Temperature (EET)
•
When air is inhaled, it gains warmth and moisture from respiratory
tract/lungs
○
Dry desert environments -water loss
!
Cold environments -heat loss
!
When this moist warm air is exhaled, both heat and moisture can be
lost from body
○
Heat and moisture lost when animal breathes out:
•
A lot of moisture and heat are loss
○
Ex. Red-winged blackbird and moose
○
Hot breath in cold air -nasal turbinates
•
Body Shell/Tissue layer (muscles, blood vessels, fat and skin)
Decrease in appetite (decrease in metabolic heat), eat at night when
cooler
○
Use shade (decrease in solar heat), go to windy area (increase
convective cooling), flap elephant ears (increase convective
cooling)
○
Stand in rain, water pool/lake/river (increase in evaporative cooling)
○
Lie down on cool and/or wet ground (increase in conductive
cooling)
○
Help prevent heat stress:
•
*pigs have sweat glands that don’t function
!
Sweating (primates, perissodactyls, artiodactyls have sweat glands
but number glands and rate of sweating varies)
○
Panting (most carnivores, birds)
○
Kangaroos sweat (exercising) and pant (standing in sun)
○
Reduce heat stress:
•
Increase in appetite (increase in metabolic heat)
○
Use of shelter from wind (decrease in convective cooling), shelter
from rain/snow (decrease in evaporative cooling)
○
Stand in sun (increase in solar heat)
○
Help prevent cold stress:
•
Shivering (increase internal body heat)
○
Increase in metabolic rate (increase in heat production)
○
Reduce cold stress:
•
Animal's Body Core (visceral organs)
Highland cow -long fur, cold environments
•
Ankole-Watusi Cattle -short fur, hot environments
•
*different domestic cattle breeds live in different environments -different
thermoregulatory mechanisms
Energy: Thermoregulation
Wednesday,* February*15,*2017 12:25*PM
DEE = (BMR + activity + thermoregulation + heat increment of
feeding)
○
Part of maintenance energy/ daily energy expenditure
•
Birds -40C
!
Placentals (eutherian) -38C
!
Marsupials (therian) -34C
!
Monotremes (protherian) -30C
!
An animal which maintains a relatively constant body temperature,
despite wide fluctuations in environmental temperature (ex. Death
Valley, Ca vs. Antarctica)
○
Homiotherm/homeotherm (warm-blooded)
•
An animal with labile body temperature, which follows changes in
ambient environmental temperature (amphibians and reptiles)
○
'behavioural homiotherms' maintain a fiarly constant elevated body
temperature by moving between sun and shade
○
E.g. naked mole rat
○
Poikilotherm (cold-blooded)
•
Endotherm -animal whose body temperature is determined by heat
derived from body metabolic activity (aka homeotherm)
•
Ectotherm -an animal whose body temperature is determined by heat
sources external to body (aka poikilotherm)
•
ex. Moose: < -40C
!
Lower Critical Temperature -may be very low
○
ex. Moose: winter -0C; summer -+14C
!
Upper Critical Temperature -may also be low
○
*Recall: definitions of LCT and UCT
•
See ways to respond to cooling and warming
○
Thermoneutral Zone: UCT -LCT
•
Without increasing metabolic heat production above maintenance
metabolism AND without employing any behavioural strategy to
conserve or dissipate heat
○
Thermocomfort Zone: smaller range than TNZ
•
There is a slower response to change in core body temp when below
LCT -many ways to maintain temp
○
Young animals -have an every larger allowance for cold past LCT
○
*there is a quick response at end of TNZ (above UCT)
•
Maintenance Energy: Thermoregulation
The metabolic heat produced in the body WITH heat gained
from (or lost to) the external environment to maintain its core
body temp THEN energy must be used to increase or decrease
body temp (--> more food)
!
If a homeothermic mammal/bird cannot balance:
○
Basal metabolism, activity
!
To estimate maintenance energy requirements (/DEE) -to
determine how much food needs to be eaten
!
Thermoregulatory energy must be added to:
○
A Balancing Act
•
Celcius: C = (F -32) * 5/9 0 -100C
○
*C=F=-40
!
Fahrenheit: = (C * 9/5) + 32 32-212 F
0 K --> absolute zero, no thermal energy
!
Kelvin: K= C + 273 273-373 K
○
Temperature Scales: Freezing -boiling
•
Hm -metabolic heat
!
Qr -heat lost/gained by radiation
!
Qc -heat lost by convection
!
Qk -heat lost/gained by conduction
!
Qe -heat lost by evaporation
!
Hm +/-Qr -Qc +/-Qk -Qe = Heat Stored
○
--> infrared thermal radiation from vegetation
!
--> infrared thermal radiation from atmosphere
!
--> reflected sunlight
!
--> direct sunlight
!
--> dust and particles
!
--> scattered sunlight
!
--> wind
!
<-- evaporation
!
<-- infrared thermal radiation from animal
!
Ex. Heat Exchange between animal and the environment -Rhino
○
Direct
1)
Diffused
2)
Reflected
3)
Solar/short wave radiation
i.
Thermal/long wave
ii.
Convection (air/water)
iii.
Conduction (direct contact between animal and environment)
iv.
Skin
1)
Respiratory
2)
Metabolic
3)
Evaporation
v.
Ex. Heat Exchange with Elephant
○
Depends on a temperature gradient (sensible heat flow)
•
Cannot lose heat if environment is hotter than animal
•
By radiation, convection, conduction
1.
Depends on vapor pressure gradient (latent heat flow)
•
Can't lose heat at 100% relative humidity
•
By evaporation
2.
Heat gained/lost…
○
Basal metabolism
!
Digestion
!
Movement
!
Growth
!
Gestation
!
Lactation
!
Metabolic heat gained from:
○
All animal and birds radiate heat (infrared/ long wave)
•
The sun (>1500C) radiates heat (some UV wavelengths,
visible light, infrared)
•
Transfer of heat energy from a hotter to a cooler body (by the
passage of electromagnetic waves, can occur slowly through a
vacuum)
!
increasing wavelengths: X-rays -UV -visible -
infrared -microwaves
•
Solar/shortwave: 0.3-3.0 um
•
Thermal/longwave: 3.0-50.0 um
•
Electromagnetic spectrum:
!
All animals, birds, plants, inanimate objects in the
environment radiate heat (longwave/thermal) warmer
than -273C (0K)
•
Sun radiates heat (solar/shortwave)
!
Animals and birds absorbs ~95% of longwave/thermal
radiation
•
Black animals/birds absorb up to 90% of
solar/shortwave radiation
•
White animals/birds only absorb up to 50% of
solar/shortwave radiation
•
All radiation can be absorbed or reflected
!
Radiation:
○
Aka layer of air/water next to warm body
!
The transfer of heat energy through moving air/water
!
When air (or water) are heated, they expand, become less
dense, and rise while cooler, denser air (or water) sinks
!
Animals and birds seek shelter when they are cold or
seek windy locations when they are hot
•
Wind (or moving water) increases heat loss by 'forced
convection'
!
Convection:
○
The transfer of heat energy through solids when oscillating
molecules exchange energy without appreciable changing
their position
!
Transfer of heat between animals/birds and solid surfaces
which they are in contact with ground/snow/vegetation
!
On land -standing (feet), lying (lateral/ventral),
perching (feet), incubating eggs
•
In water -aquatic animals/birds
•
When:
!
Conduction:
○
Becomes the dominant means of heat loss and air
temperature approaches body temperature
•
Wind increases evaporative heat loss
•
The transfer of heat when heat energy is required as water
changes from a liquid to a vapour or gas without change in
temperature
!
Sweating -cattle, horses, camels, humans
!
Panting (evaporation from respiratory tract) -dogs, cats, many
birds
!
Sweating and panting -kangaroos
!
Gular fluttering (in some birds instead of panting) -floor of
mouth and uper oesophagus
!
Saliva-spreading (rats) -some marsupials lick their wrists
!
Water evaporates from plant leaves
!
Cooler to sit on grass than on bare ground
!
Cooler under trees than under wooden shelter
!
Evaporation:
○
Heat Gain & Loss
•
Thermoregulation -
Air temperature + humidity -humidex
○
Air temperature + wind -wind chill
○
Effective Environmental Temperature
•
Different humidex and wind chill values for different animals
•
How hot/cold does it feel?
All 4 methods of heat gain/loss depend on animal/bird SA
•
Measure flattened skin, but larger area than area exposed to
environment (underwings)
○
Surface area may be difficult to measure
•
Surface area changes with posture
•
Thermoregulation and Surface Area:
Pelage (hair/fur) and Plumage (feathers) offer insulation
•
Air is a very poor heat conductor
○
Fluffing
○
Piloerection
○
Pelage/plumage traps a still layer of air next to the skin and reduces heat
loss by convection
•
Summer pelage may provide less insulation than winter pelage
○
Ex. Bears, muskoxen
○
Shrew -weasel -rabbit -dog -reindeer -arctic fox -grizzly -
wolf -polar bear
!
Insulation increases with fur thickeness
○
Highest insulation in birds and arctic mammals
•
Dense, long wool absorbs solar radiation at surface and re-
radiates heat from wool tips
!
Wool surface -85C; skin -42C; core -39C
!
Merino sheep -ambient temperature of 40C and sunny
○
Water and oil reduce insulation of pelage and plumage to decrease
air lost
○
Pelage/plumage may also insulate against environmental heat when
ambient temperature is hot or there is high incident solar radiation
•
African/Asian elephant, white/black/Sumatran/Javan rhinoceros,
river hippopotamus
○
Megaherbivores (mammals) > 1 ton mature weight
•
Pangolins (giant pangolin -~6ft long)
○
Armadillos (giant armadillo -~3ft long, 32 kg)
○
Scaly mammals
•
Fur or Feathers:
PART 2
Boundary layer -air (affected by air movement)1)
Cover layer -pelage or plumage trap still air (insulation is decreased by
wind -ruffling)
2)
Tissue layer, body shell -muscles, blood vessels, fat and skin (insulation
is affected by blood flow)
3)
Body core -visceral organs, major metabolic heat production 4)
Animal's thermal insulation layers:
Animal/bird must also be still (resting/sleeping)
○
~0.35 cm thick (all species, all body sizes)
○
This layer of still air provides as much insulation as tissue layer
insulation during max vasoconstriction
○
A layer of still air next to animal's skin/cover layer in an environment with
little/no air movement
•
Boundary Layer
Some are specialized, insulatic air cells in the medulla of the hair
shaft -hollow hair shafts
○
Guard hairs vs. underfur (muskox)
○
Contour feathers vs. down (eider duck)
○
Type of Hair or Feather1.
More dense -greater insulation
○
Numbers are determined at birth -skin grows but no increase in the
number of hair follicles
○
Horse -1290
!
Cow -700
!
Pigs -37
!
Differs with species:
○
Merino -5000 fibers/cm2
!
Lincoln -1400 fibers/cm2
!
Differs with breed:
○
Smallest sea mammals in NA -very dense fur >150,000 hairs/cm2
○
Number of hairs/cm2
2.
Longer traps more still air (poitou donkey)
○
Length of Cover3.
Animals may be at risk or heat or cold stress during transition
seasons, when changes in pelage/plumage incomplete
○
Shedding, moulting, usually in response to seasonal day length
changes (not ambient temperature)
○
Winter coat in some species -hairs stop falling out and grow longer
○
Shedding and Moulting4.
Under autonomic control (not voluntary) by dermal muscles (traps
or eliminates air)
○
Piloerection/pteroerection5.
Can reduce cover depth by disrupting the hair or feathers -ruffling
○
Air speed as low as >0.9 m/s can reduce cover insulation
○
Wind6.
Reduces depth of the pelage/plumage and replaces air with water
○
Therefore, water cools animal down
!
Air 0.000059 vs. water 0.0014 cal/cm2/s/C --> increased
conductivity (x100)
○
Water7.
Cover Layer Insulation (plumage/pelage)
Visceral organs in the body core have high metabolic rate --> high
heat production
○
Very small amount of core body heat --> skin via conduction
○
Most core body heat --> skin (carried by blood through arteries -
circulatory convection)
○
Heat in body core --> tissue layer --> skin
•
Surface vessels constrict to decrease heat loss via conduction
from skin to environment
!
Occurs with low ambient temperatures
!
Vasoconstriction:
○
Surface vessels dilate to allow high heat transfer via
conduction from skin to environment
!
Occurs with high ambient temperatures
!
Vasodilation:
○
Blood Flow to Skin:
•
High ambient temperature -less trapped air
○
Sub-cutaneous fat:
•
About 3C higher than normal core body temperature
○
Poultry (most birds) ULBT -45C
○
Eutherian ULBT -42C
○
Monotremes ULBT -33C
○
Marsupials ULBT -39C
○
Upper lethal body temperature:
•
High humidity -no evaporative cooling
!
They have no way to remove heat
!
Animals can't survive long with EET (how hot it feels) 5C above
core body temperature
○
But, animals can survive for a long time at 20-60C below core body
temperature
○
Effective Environemental Temperature (EET)
•
When air is inhaled, it gains warmth and moisture from respiratory
tract/lungs
○
Dry desert environments -water loss
!
Cold environments -heat loss
!
When this moist warm air is exhaled, both heat and moisture can be
lost from body
○
Heat and moisture lost when animal breathes out:
•
A lot of moisture and heat are loss
○
Ex. Red-winged blackbird and moose
○
Hot breath in cold air -nasal turbinates
•
Body Shell/Tissue layer (muscles, blood vessels, fat and skin)
Decrease in appetite (decrease in metabolic heat), eat at night when
cooler
○
Use shade (decrease in solar heat), go to windy area (increase
convective cooling), flap elephant ears (increase convective
cooling)
○
Stand in rain, water pool/lake/river (increase in evaporative cooling)
○
Lie down on cool and/or wet ground (increase in conductive
cooling)
○
Help prevent heat stress:
•
*pigs have sweat glands that don’t function
!
Sweating (primates, perissodactyls, artiodactyls have sweat glands
but number glands and rate of sweating varies)
○
Panting (most carnivores, birds)
○
Kangaroos sweat (exercising) and pant (standing in sun)
○
Reduce heat stress:
•
Increase in appetite (increase in metabolic heat)
○
Use of shelter from wind (decrease in convective cooling), shelter
from rain/snow (decrease in evaporative cooling)
○
Stand in sun (increase in solar heat)
○
Help prevent cold stress:
•
Shivering (increase internal body heat)
○
Increase in metabolic rate (increase in heat production)
○
Reduce cold stress:
•
Animal's Body Core (visceral organs)
Highland cow -long fur, cold environments
•
Ankole-Watusi Cattle -short fur, hot environments
•
*different domestic cattle breeds live in different environments -different
thermoregulatory mechanisms
Energy: Thermoregulation
Wednesday,* February*15,*2017 12:25*PM
Document Summary
Dee = (bmr + activity + thermoregulation + heat increment of feeding) An animal which maintains a relatively constant body temperature, despite wide fluctuations in environmental temperature (ex. An animal with labile body temperature, which follows changes in ambient environmental temperature (amphibians and reptiles) "behavioural homiotherms" maintain a fiarly constant elevated body temperature by moving between sun and shade. Endotherm - animal whose body temperature is determined by heat derived from body metabolic activity (aka homeotherm) Ectotherm - an animal whose body temperature is determined by heat sources external to body (aka poikilotherm) Lower critical temperature - may be very low ex. Upper critical temperature - may also be low ex. See ways to respond to cooling and warming. Without increasing metabolic heat production above maintenance metabolism and without employing any behavioural strategy to conserve or dissipate heat. *there is a quick response at end of tnz (above uct)
