marine mammal thermoregulation - university of...

4/24/2012

1

Announcements

• Meetings by appointment….

– Patrick: 148A

– Lisa: 148B

• 1st midterm exam is in one week!

– (we will be in touch with DRC students)

Pop Quiz!

4/24/2012

2

(fake) Pop Quiz!

No points… just for practice

Chat with your neighbor!

Style of questions you will see on exam

Pop Quiz!

Fill out the following blanks for your favorite phocid:

Kingdom:________

Phylum:_________

Class:__________

Order:__________

Family:__________

Genus and Species:__________

Common Name:__________

4/24/2012

3

Pop Quiz!

Fill out the following blanks for the gray whale:

Kingdom:________

Phylum:_________

Class:__________

Order:__________

Family:__________

Genus and Species:__________

Pop Quiz!

Balaenidae is a taxonomic group composed of:

A. Rorquals

B. Right whales

C. Beaked whales

D. Sperm whales

4/24/2012

4

Pop Quiz!

• Which one of these families is NOT a river

dolphin?

a) Platanistidae

b) Pontoporiidae

c) Lipotidae

d) Monodontidae

Pop Quiz!

• Provide two identifying characteristics of

phocids and two of otariids.

• Provide two identifying characteristics of

odontocetes and two of mystecetes.

4/24/2012

5

Pop Quiz!

True or False:

Odontocetes store a greater proportion of oxygen in

their blood than phocids?

Leopard seals live in the Arctic?

Pop Quiz!

Short essay:

Name 3 species in the sub-order archaeoceti and

indicate how they fit into the evolutionary

progression from terrestrial to aquatic body forms.

4/24/2012

6

Exam Philosophy

• We’re not out to trick you!

• (but we do want you to learn the material)

• All important topics are covered in lecture

• Readings are supplementary and will help

your understanding (but we will not pull

tiny details from them)

Marine Mammal

Thermoregulation

4/24/2012

7

Definitions

• Poikilotherm – temperature conformer: Tb ≈ Ta

• Homeotherm – temperature regulator: Tb ≈ constant

• Endotherm – body temperature derived from metabolism

• Ectotherm – body temperature derived from environment

• Thermoregulation – maintaining a constant body temperature

Definitions

• Poikilotherm – temperature conformer: Tb ≈ Ta

• Homeotherm – temperature regulator: Tb ≈ constant

• Endotherm – body temperature derived from metabolism

• Ectotherm – body temperature derived from environment

• Thermoregulation – maintaining a constant body temperature

4/24/2012

8

Thermoregulation Challenges

• Marine environment generally

much colder than Tb

• Water conducts heat ~25x

faster than air

• Amphibious marine mammals

(pinnipeds) must

thermoregulate in air & water

Maintaining Thermal Balance

Heat loss = Heat production

Heat production

Metabolism Food + O2 = Heat + H2O + CO2

4/24/2012

9


Heat loss

• Convection = heat transfer to a fluid (movement of air or water)

• Conduction = heat transfer to a solid

• Radiation = transfer of radiant energy

• Evaporation = heat transfer by changing water from liquid to gas (respiratory water loss)




convection conduction radiation evaporation

4/24/2012

10

Heat Transfer

Hot reservoir

at TH

Cold reservoir

at TC

L

Q

k

Heat loss (Q)= k A (TH – TC) / L

Heat transfer associated with:

• Surface area

– varies with Mass2/3

• Temperature differential

- b/n environment (Ta) & body (Tb)

Heat loss = Conductance * Surface area * (Tb - Ta)

4/24/2012

11

Thermal Conductivity Material k (W/m C)

Silver 428

Aluminum 235

Iron 80

Otariid blubber 0.17-0.39

Human fat 0.21

Whale blubber 0.18-0.21

Phocid blubber 0.18-0.20

Dolphin blubber 0.10-0.20

Wood (white pine) 0.11

Animal fur 0.038

Air 0.024

Conductors

Insulators

• Lower temperature differential – Tb

– Typical Mammalian Tb = 36-38 oC

– Cetaceans Tb = 35.5 oC

Marine Mammal Strategies

for Thermoregulation

4/24/2012

12

Lowering Body Temperature (Tb)

• Generally occurs while diving

• May lower body temp to reduce O2

consumption

– Hypometabolism

• Promotes longer dive times

cADL = O2 stores

O2 consumption

• Lower temperature differential – Tb

• Increase body size – surface area to volume ratio



4/24/2012

13

Surface Area : Volume Ratio

Surface area = 6 (3x )2

Volume = (3x )3

• Lower temperature differential – Tb = 36-38 oC


• Increase metabolism – heat production



4/24/2012

14

Mass (kg)

10 100 1000

Re

sti

ng

me

tab

oli

c r

ate

(W

)

10

100

1000

10000

2 X Predicted

Predicted

Otariidae

Sirenia

Phocidae

Odontoceti

E. lutris

Metabolic Rates Seem To Be

Elevated In Some Species

Mass 0.75 (Kleiber)

Mass (kg)

10 100 1000

Re

sti

ng

me

tab

oli

c r

ate

(W

)

10

100

1000

10000

2 X Predicted

Predicted

Otariidae

Sirenia

Phocidae

Odontoceti

E. lutris



4/24/2012

15

Mass (kg)

10 100 1000

Re

sti

ng

me

tab

oli

c r

ate

(W

)

10

100

1000

10000

2 X Predicted

Predicted

Otariidae

Sirenia

Phocidae

Odontoceti

E. lutris



Mass (kg)

10 100 1000

Re

sti

ng

me

tab

oli

c r

ate

(W

)

10

100

1000

10000

2 X Predicted

Predicted

Otariidae

Sirenia

Phocidae

Odontoceti

E. lutris



4/24/2012

16

Mass (kg)

10 100 1000

Re

sti

ng

me

tab

oli

c r

ate

(W

)

10

100

1000

10000

2 X Predicted

Predicted

Otariidae

Sirenia

Phocidae

Odontoceti

E. lutris

Mass (kg)

10 100 1000

Re

sti

ng

me

tab

oli

c r

ate

(W

)

10

100

1000

10000

2 X Predicted

Predicted

Otariidae

Sirenia

Phocidae

Odontoceti

E. lutris

4/24/2012

17

Thermal Neutral Zone (TNZ)

• Range of environmental temperatures

over which an animal can maintain

constant Tb without increasing metabolism


4/24/2012

18



4/24/2012

19



(Morrison et al., 1974; Costa & Kooyman, 1984; Williams et al., 1998)

Sea lion

Dolphin

(Morrison et al., 1974; Costa & Kooyman, 1984;

Williams et al., 1998; Mostman-Liwanag et al., in prep)

Sea otter

4/24/2012

20




• Increase insulation – conductance



Two Ways to Increase Insulation

• blubber layer

• density or length of hair

– Sea otters: 125,000 hairs per cm2

Type of insulation depends on the

species & habitat

4/24/2012

21

Insulation

Fur:

• Traps air

among the hairs

• Air provides the

insulation!

Hair Cuticle Shape

Antarctic fur seal

guard hair

underhair

California sea lion

guard hair

underhair

Coyote

guard hair

underhair

River otter

guard hair

underhair

Scales are elongated in species using fur for insulation in water.

(Liwanag et al., in press)

4/24/2012

22

0

2

4

6

8

10

12

14

16S

cale

elo

ngatio

n (

length

/ w

idth

)

A A A A A A A

B

C

a a a a a a a

b

c

Hair Cuticle Shape

Scales are elongated in species using fur for insulation in water.

Guard hairs

Underhairs


Hair Circularity

0.0

0.2

0.4

0.6

0.8

1.0

Gu

ard

hair c

ircula

rity

A A A

B

C

D

D

E

B

C C

more

circular

more

flattened

Guard hairs are flatter in more aquatic species.


4/24/2012

23

0

200

400

600

800

1000

Fur Density

Fu

r density (

hairs ·

mm

-2)

Fur density is greater in species using fur for insulation in water.


0

1

2

3

4

Implications for function of fur in water

Heig

ht of air layer

in fur

(mm

)

SAT SAT SAT SAT (SAT = saturated)

Fur seals maintain an air layer in the fur while immersed…


4/24/2012

24

0

1

2

3

4

Implications for function of fur in water

Heig

ht of air layer

in fur

(mm

)

SAT SAT SAT SAT (SAT = saturated)

Fur seals maintain an air layer in the fur while immersed and diving.


Insulation

Blubber:

• continuous sheet

of adipose tissue

• reinforced by

collagen & elastic

fibers

4/24/2012

25

Blubber Thickness

Fur

density

(hairs ·

mm

-2)

Blu

bber

thic

kness (

mm

)

Blubber thickness increases

as fur density decreases.

Blubber thickness also

increases with body size.

(Liwanag et al., in revision)

Implications for the quality of insulation

Thermal Conductivities Observed

Terrestrial pelts: 0.034 – 0.069 W·m-1·°C-1

Otariid pelts: 0.111 ± 0.034 W·m-1·°C-1

(terrestrial values from Scholander et

al., 1950)

Phocid pelts: 0.158 ± 0.104 W·m-1·°C-1

→ Loss of thermal function in air for pinniped pelts.

4/24/2012

26

Implications for the quality of insulation

Thermal Conductivities Observed

Terrestrial pelts: 0.034 – 0.069 W·m-1·°C-1

Otariid pelts: 0.111 ± 0.034 W·m-1·°C-1

(terrestrial values from Scholander et

al., 1950)

Phocid pelts: 0.158 ± 0.104 W·m-1·°C-1

→ Loss of thermal function in air for pinniped pelts.

Otariid blubber: 0.280 ± 0.069 W·m-1·°C-1

Phocid blubber: 0.192 ± 0.040 W·m-1·°C-1

→ Phocid blubber is of better quality.

0 5 10 15 20

2

4

6

8

10

12

14Adult1

Adult2

Adult3

Adult4

Adult5

Adult sea lion thermal capabilities

Restin

g M

eta

bolic

Rate

(m

LO

2·m

in-1

·kg

-1)

Water Temperature (°C)

TLC = 6.4 ± 2.2 °C

Adult sea lions are thermally neutral at routine water temperatures.

(Liwanag et al., 2009, JEB)

4/24/2012

27

0 5 10 15 20

2

4

6

8

10

12

14Juv1

Juv2

Juv3

Juv4

Juvenile sea lion thermal capabilities

Restin

g M

eta

bolic

Rate

(m

LO

2·m

in-1

·kg

-1)


TLC > 12 °C

Juveniles experience thermal costs during rest at routine water temps.


0 5 10 15 20 25

4

6

8

10

12

14

Swimming thermogenesis


Meta

bolic

Rate

(m

LO

2·m

in-1

·kg

-1)

Rest

Swim @ 1 m/s

Swimming mitigates thermal costs for juvenile sea lions at low water temps.


4/24/2012

28

0 5 10 15 20 25

5

10

15

20

25

Northern fur seal pup thermal capabilities

Restin

g M

eta

bolic

Rate

(m

LO

2·m

in-1

·kg

-1)


TLC = 8.3 ± 2.5 °C

Fur seal pups may experience thermal costs while resting at sea.

(Liwanag, 2010, PBZ)

Mammalian

Phylogeny

4/24/2012

29

Mammalian

Phylogeny

Mammalian

Phylogeny

4/24/2012

30

Mammalian

Phylogeny

Insulation:

Fur seal vs. Sea lion vs. Phocid

4/24/2012

31

Cross Section of Seal Carcass

Fur

Blubber Advantages • Can withstand

fouling

• Does not compress with depth

• Able to dump heat

• Energy store

Disadvantages • Live tissue at low

temps

• Difficult to grow or divide at low temps

• Must haul out to molt & heal

4/24/2012

32

Temperature

differential

between skin &

tissue

Temperature Differential of the Skin

in Water vs. in Air

4/24/2012

33

Catastrophic Molt

Crabeater Seal (Lobodon carcinophaga)

Healing

4/24/2012

34

Advantages • Lighter

• Better insulation for given amount

• Skin is maintained at or near body temp

– Ability to repair skin, molt, etc.

Disadvantages

• Requires air layer

• Needs to be kept

clean

• Insulation declines

with depth

Fur

Blubber Advantages • Can withstand

fouling

• Does not compress with depth

• Able to dump heat

• Energy store

Disadvantages • Live tissue at low

temps

• Difficult to grow or divide at low temps

• Must haul out to molt & heal

Diving with fur

• Loss of air = loss of insulation

• Requires extensive time

grooming at surface

4/24/2012

35

0-5 5-10 10-15 15-20 20-25 HIF

0

20

40

60

80

100

Behavioral thermoregulation

Perc

ent tim

e s

pent gro

om

ing


Post-

prandial

(20 °C)

Grooming behavior increases at colder water temperatures.


0

5

10

15

20

25

30

Metabolism by behavior

Meta

bolic

Rate

(m

LO

2·m

in-1

·kg

-1)

Resting Post-

prandial

Resting

Jug-

handling

Sedentary

Grooming

Active

Grooming

(N=22) (N=4) (N=18) (N=11) (N=29)

A

BC

B

B

C

Jughandling, grooming, and food processing increase metabolic rate.


4/24/2012

36

Thermal Windows

Poorly insulated areas through which heat dissipates

Thermal Windows

4/24/2012

37





• Vascular control – counter-current heat exchange



Counter Current

Heat Exchanger

How do you keep heat loss low to periphery

yet still keep blood flowing to it?

4/24/2012

38

Countercurrent arrangements

4/24/2012

39

Peripheral Blood Vessels

Tongue

Heat flow

Gray Whale Tongue

(a cool meal)

Arteries transport blood to tongue

Veins return blood to body

4/24/2012

40

Cross Section

Through

Dolphin At

The Level Of

The Testes

Problem:

Internal

Testes

Why don’t the dolphin testes “fry”?

Cool temperatures important

for spermatogenesis

4/24/2012

41



for spermatogenesis

Cool blood from fins

& fluke



for spermatogenesis

Cool blood from fins

& fluke

Cools core blood before

reaching testes

4/24/2012

42

Temperature Regulation for Testes





• Vascular control – counter-current heat exchange



• Behavioral thermoregulation

4/24/2012

43

Clump together when cool or to save heat

Behavioral Thermoregulation

Clump together when cool or to save heat


4/24/2012

44

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

% Huddled

Group Size

Pro

po

rtio

n s

ea

lio

ns h

ud

dlin

g

Ave

rag

e g

rou

p s

ize

winter summer

Tair=14.8 ± 1.1 Tair=22.8 ± 4.2

80%

53%


Huddling behavior in California sea lions


Haul out when warm in polar regions

4/24/2012

45


Lie in water when warm


Sand Flipping

4/24/2012

46

How do these animals acclimate to

seasonal changes?

• Dolphins change their blubber

• Quantity – seasonal changes in thickness

Seasonal Changes

4/24/2012

47

Seasonal change in thickness

Seasonal change in thickness

4/24/2012

48

• Dolphins change their blubber

• Quantity – seasonal changes in thickness

• Quality – seasonal changes in composition:

straight chain

(saturated) fats

• Better insulation

bent chain

(unsaturated) fats

• Poorer insulation

Seasonal Changes

California Sea Otter –

smallest marine mammal

4/24/2012

49

Mass (kg)

10 100 1000

Re

sti

ng

me

tab

oli

c r

ate

(W

)

10

100

1000

10000

2 X Predicted

Predicted

Otariidae

Sirenia

Phocidae

Odontoceti

E. lutris

Metabolic Rate In Relation To

Water Temperature

4/24/2012

50

Sea otter allows body temperature to

change Te

mp

era

ture

(°C

)

Uses feeding to keep warm

What about pups?

Born with lanugo & brown fat

4/24/2012

51

• Lanugo: “birth coat”

– Dense coat of very fine hair

– Works in air (not waterproof)

What about pups?

harp seal pup gray seal pup

• Brown fat

– Specialized adipose tissue

– Non-shivering thermogenesis

What about pups?

marine mammal thermoregulation - university of...

Documents