Organismic Biology Bio 207
Lecture 2
Prof. Simchon
Organisms in the aquatic environment; water inside
and outside; Barriers to water and solute movements
Review last week’s lecture
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Biome
Microclimate
Abiotic factors
Adaptation
Homeostasis
Regulators versus conformers
Acclimation/acclimatization/adaptation
Membrane properties
Transport of Water
1
Movement of water and ions through
membranes
• Passive movement:- diffusion
• Water and ions can move passively through
aquapores and ion channels in membranes
whereas larger molecules cannot.
• Active movement:- energy required pumps
Factors Affecting Diffusion Rates - passive
M = PA (C1 – C2)
ΔX
Fick diffusion equation
Membrane
X
C1
Concentration
M= the rate of net movement of a solute; from a
region of high concentration (C1) to low
concentration. (C2); units are moles/sec
U X = distance between C1 and C2; units are cm.
C2
X1
X2
Distance
M = D (c1 - c2)/(X2 - X1)
M = D dC/ dX
(C1-C2): the difference in solute concentration
across the membrane. Units are M or mole/1000
cm3 or
P is the diffusion constant. P depends upon
the permeability of the membrane and the
temperature and has units of cm2/sec
A = the surface area where diffusion is occurring
(units are cm2).
2
Factors affecting diffusion rate:
Membrane
ΔX
M = PA (C1 – C2)
ΔX
Concentration
C1
U
How would increasing
ΔX affect M?
C2
X1
X2
Distance
M = D (c1 - c2)/(X2 - X1)
M = D dC/ dX
Fick Diffusion Equation :
Diffusion equation for moisture migration
M = PA (C1 – C2)
ΔX
M can be measured = transfer/time
A and ΔX can also be measured
C1 and C2 can be measured
Calculate P = permeability constant
3
What is P, Permeability constant?
M = P A(C1 – C2)
ΔX
What is P, permeability constant?
M = P A(C1 – C2)
ΔX
• What would be the result of P = 0?
• What would be the result of P = 1?
• What would cause P > 0 and P < 1?
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Factors Affecting Diffusion Rates - passive
• Fick law
• What about membrane charge?
Electrical effects in simple diffusion
• Positive charges are attracted to negative charges
• Similar charges repel each other
• A large electrical difference may cause a solute to
move in such a direction so as to increase the
concentration difference.
5
Electrical effects in simple diffusion
Comp 1
Comp 1
Comp 2
A
A+
A
Comp 1
A+
- +
- +
Comp 2
A+
Comp 2
A+
Ions and semi-permeable membranes
Equilibrium both sides
Concentrations of
solutes equal and ion
charge balanced
If an ion is too large
to cross the
membrane, other
electrical charges
will move to
maintain a balance
in charge and conc.
6
Ions and semi-permeable membranes
Equilibrium both sides
Concentrations of
solutes equal and ion
charge balanced
If an ion is too large
to cross the
membrane, other
electrical charges
will move to
maintain a balance
in charge and conc.
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What is the role of surface area in total
diffusion per unit time?
• M = the rate of net movement of a solute per unit of cross
sectional area Q = total net diffusion of a solute or solvent
per unit time
• If we know A, we can find the net diffusion per unit time
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Trace the diffusion path
List the structures
crossed as water
and ions diffuse
ΔX
Lung
M = PA (C1 – C2)
ΔX
Barrier between water and blood of gill
• Gill has a lining of pavement
epithelial cells (2 plasma
membranes and the cytosol)
• Capillary has a pillar cell lining it
(also 2 plasma membranes and
cytosol
• In between is a basement
membrane and some
extracellular fluid
Pavement epi.
Epithelium
Blood
(ECF)
Pillar cell
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Barrier between water and blood of
gill
• Gill has a lining of pavement
epithelial cells (2 plasma membranes
and the cytosol)
• Capillary has a pillar cell lining it
(also 2 plasma membranes and cytosol
• In between is a basement membrane
and some extracellular fluid
Pavement epi.
Epithelium
Blood
(ECF)
Pillar cell
Tonicity
Refers to a cells response to different salt solutions
Does it shrink, swell or stay the same shape
Only apply if there are impermeable partice
Isotonic
Hypotonic
Hypertonic
means its volume is unchanged when placed
in that solution
if cells are placed in a hypotonic solution, water
enters the cell and they swell and may burst.
if cells are placed in a hypertonic solution, water
leaves the cell and they may shrink.
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Tonicity
Fresh water
Freshwater
Na+ 0.5mM
K+ 0.1mM
Cl- 0.3mM
Na+ 160 mM
K+
5 mM
Ca ++ 6 mM
Cl120 mM
water
Water flows from a high concentration of watera weaker concentration of solutes into the organism, to equilibrium
Solutes flow along their conc gradient towards lower conc of solutes.
Out of the organism.
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If volume changes get a change in cell volume- swells
Freshwater
water
water
If water flows in and volume increases, solution is
hypotonic to organism
If volume changes get a change in cell volume- shrivels
Salty water
water
water
If water flows out and volume decreases,
solution is hypertonic to organism
It will not shrinkl, since cell is permeable to salt
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Equilibrium
Are all organism in equilibrium with their environment?
What state are we in?
Homeostasis
The tendency to maintain the relatively
constancy of important variable inside cell or
animal, even in the face of significant
environmental changes.
(from Eckert) “The condition of relative internal stability
maintained by physiological control mechanisms”
In this course, we will discuss stability in the context of…
– Osmolarity (solute concentration)
– Temperature
– And… a little about blood pH
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Homeostasis = Control internal environment
Regulate its internal environment to a given value = set-point
Advantages:
Constant internal environment important for many
physiological processes.
Temperature, salinity, ions (Na, Ca, K), water, etc
Disadvantages:
In order to keep constant internal environment
the organism will have to spend energy (active
processes). Does not come for free.
How do we keep steady state?
What we will learn in the course
1. How can an organism regulates its internal
environment?
2. What is the energy needed in order to regulate the
internal environment?
3. How does the organism get this energy?
4. How can you tell if the organism control a parameter?
We will study several parameters that can be regulated
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Course divided into Units (Syllabus P-8)
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Unit I:
Unit II
Unit III:
Unit IV:
The organism and the environment
Transport systems
Energy Acquisition
Energy Usage
Responses to different aquatic concentrations
Osmotic regulation
The first parameter that we will study is regulation
of the organism internal osmolarity
Conformer
Regulator
Euryhaline
Stenohaline
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Responses to different aquatic concentrations
Conformer: change the osmotic concentration of his body
to remain isoosmotic with the medium
Regulator: maintain or regulate its osmotic concentration
in spite of external concentration changes
Euryhaline: can tolerate large variation in concentration of
the medium
Stenohaline: cannot tolerate large variation in concentration
of the medium
Conformers vs. regulators
Some animals regulate some variables within the
internal environment but not others (e.g. salmon have
variable body temp but regulated blood chloride)
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Mode of osmo-regulation
Can be assessed by placing organism in different solutions of
varying concentration and measuring extracellular (ECF)
concentration.
Conformer
800
700
600
ECF concentration
(mOsm)
500
400
Regulator
300
200
100
0
0
100
200
300
400
500
600
700
800
Environment concentration (mOsm)
Mode of osmo-regulation
Can be assessed by placing organism in different solutions of
varying concentration and measuring extracellular (ECF)
concentration.
Conformer
800
Hyper-osmoregulator
700
Regulator-B
600
ECF concentration
(mOsm)
500
400
Regulator-A
300
200
Hypo-osmoregulator
100
0
0
100
200
300
400
500
600
700
800
Environment concentration (mOsm)
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Mode of osmo-regulation
Mode of osmo-regulation
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Transport Across Membrane
Passive
• water depends on osmolarities
• not charged particles depends on concentration gradient (Fick)
• charged particles depends on concentration and electrical
gradients
Active Transport needs energy
Fish in sea water
• passive water out
• passive salt in  water in (remember tonicity)
Active salt out
Passive movement of water and ions through membranes
Freshwater
Na+ 0.5mM
K+ 0.1mM
Cl- 0.3mM
water
Na+ 160 mM
K+
5 mM
Ca ++ 6 mM
Cl120 mM
Diffusion is the movement of material caused by a random motion of
atoms and molecules with the net result of complete mixing.
Substances will move from a high to low concentration until equilibrium
? Direction of water and solute flux?
Water flows from a high concentration of watera weaker concentration of solutes into the organism, to equilibrium
Solutes flow along their conc gradient towards lower conc of solutes.
Out of the organism.
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Sea water
Sea water
Na+ 500mM
K+ 100mM
Cl- 400mM
water
Na+ 160 mM
K+
5 mM
Ca ++ 6 mM
Cl120 mM
Direction of water and solute flux?
Animals lose water passively to the environment
and gain solutes from the environment
Why fish do not swell or shrink?
• The salt is also permeable
• Only impermeable particle will
contribute to osmosis – Water movement
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Osmotic
Refers to the chemical concentration (osmolarity) of
cell compare to environment
Iso-osmotic means its concentration is the same as
compare to a given solution
hyper-osmotic means its concentration is greater as
compare to a given solution
.
hypo-osmotic means its concentration is less as
compare to a given solution
Tonicity: Refer to impermeable particles
Refers to a cells response to different salt solutions
Does it shrink, swell or stay the same shape
Only apply if there are impermeable partice
Isotonic
means its volume is unchanged when placed
in that solution
Hypotonic
if cells are placed in a hypotonic solution,
water enters the cell and they swell and may burst.
Hypertonic if cells are placed in a hypertonic solution,
water leaves the cell and they may shrink.
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Volume Change of Aquatic Organism
Fresh water animals are subject to swelling owing to movement
of water into their bodies down the osmotic gradient.
THEY MUST PREVENT NET GAIN OF WATER
They need mechanism to prevent gain of water.
Homeostasis
The tendency to maintain the relatively
constancy of important variable inside cell
or animal, even in the face of significant
environmental changes.
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Responses to different aquatic
concentrations
Conformer
Regulator
What would these two graphs look like?
Euryhaline
Stenohaline
What do these words mean?
Responses to different aquatic concentrations
Conformer: change the osmotic concentration of his body
to remain isoosmotic with the medium.
Regulator: maintain or regulate its osmotic concentration
in spite of external concentration changes.
Euryhaline: can tolerate large variation in concentration of
the medium
Stenohaline: cannot tolerate large variation in concentration
of the medium
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Balance
Input vs output
Zero balance:
Input = Output
Negative balance: Input < Output
Positive balance: Input > Output
Regulator:
Conformer:
Equilibrium vs Steady state
Equilibrium are not zero balance: They
change their internal environment to be equal
to external environment.
a) Input but no output
b) Output but no input
Most organisms are not in equilibrium
They are in zero balance (input = output) that
is why they are in steady state
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Mode of osmo-regulation
Can be assessed by placing organism in different solutions of
varying concentration and measuring extracellular (ECF)
concentration.
ECF concentration
(mOsm)
Hyperosmoregulator
Conformer
Line of Identity
Regulator
Hypoosmoregulator
Environment concentration (mOsm)
Fish conformer placed in sea water
Sea water
Na+ 400mM
K+ 100mM
Cl- 500mM
water
Na+ 160 mM
K+
5 mM
Ca ++ 6 mM
Cl120 mM
Total = 1,000 mM
Animals lose (output) water passively to the environment
and gain (input) solutes from the environment
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Water and Solute regulation: Conformer
If fish put in hyperosmotic environment:
Fish gains solutes (input) and loses water (output)
passively.
So ECF osmolarity should increase to reach equilibrium
with environment.
Fish conformer placed in sea water
Does this fish change it volume?
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Fish in sea water
• passive water out
• passive salt in  water in
No volume change
Since the membrane is also permeable to
solutes, so no net movement of water will
occur.
Conformer placed in sea water
1,000 mOsm
ECF (organism)
300 mOsm
Passive
Solutes
Animals gain (input) solutes from the environment.
Positive balance till equilibrium is reached
ECF = 1,000 mOsm
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Conformer placed in sea water
1,000 mOsm
ECF (organism)
1,000 mOsm
Passive
Solutes
Animals gain (input) solutes from the environment.
Positive balance till equilibrium is reached
ECF = 1,000 mOsm
Conformer
Fish conformer placed in fresh water
Freshwater
Na+ 0.5mM
K+ 0.1mM
Cl- 0.3mM
Na+ 160 mM
K+
5 mM
Ca ++ 6 mM
Cl120 mM
water
Water flows from a high concentration of water- (weaker
concentration of solutes) into the organism, to reach equilibrium
Solutes flow along their concentration gradient towards lower
concentration of solutes - out of the organism.
Since the membrane is also permeable to solutes, so no net
movement of water will occur. So the fish will not swell…….
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Remember only impermeable particles will
exert tonicity and water will move.
If particle and salt move water will not move
to reach equilibrum
CONFORMERS WLL REACH
EQUILIBRUM WITH THE ENVIROMENT
without any change in volume
Mode of osmo-regulation
Can be assessed by placing organism in different solutions of varying concentration
and measuring extracellular (ECF) concentration.
ECF concentration
(mOsm)
Hyperosmoregulator
Conformer
Line of Identity
Regulator
Hypoosmoregulator
Environment concentration (mOsm)
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Osmoregulation
External Environment vs Internal Environment
External
Environment
Internal
Environment
ECF
Mode of regulator
• Passive process: salt will move in one direction.
• To prevent the organism from reaching equilibrum
• HOMEOSTASIS = STEADY STATE
• Active process in the opposite direction
Zero balance is reached they are not in equilibrium
Active processes = active processes in opposite direction
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Regulate intracellular/extracellular Na and K
K+
K+ = 140 mM
K+ = 5 mM
Na+ = 10 mM
Na+ = 150 mM
ATP
Na+
1. Passive K+ out / Na+ in
2. Active K+ in / Na+ out (Na/K pump)
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Mode of osmo-regulation
Can be assessed by placing organism in different solutions of
varying concentration and measuring ECF concentration.
comformer
hyper-osmoegulator only
C
ECF conc
(mOsm)
hypo-osmoregulator
D
B
hyper-hypo osmoregulator
A
Environment conc (mOsm)
Mode of Osmoregulation
Internal environment (mOsm/kg)
1200
animal is hyperosmotic to environment
line of identity
Osmotic Hyperegulator
800
Osmotic
Hypo/hyperregulator
400
Osmotic Hyporegulator
animal is hypo-osmotic to environment
0
0
200
400
600
800
1000
1200
External environment (mOsm/kg)
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Modes of osmo-regulation
Hyper-osmotic regulator
Osmotic Hyporegulation
How does an organism maintain lower
osmotic pressure than the environment?
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Hyporegulation: Living in water of different
ionic concentrations
Seawater
Na+ 400mM
K+ 100mM
Cl- 500mM
ECF
Na+ 160 mM
K+
5 mM
Ca ++ 6 mM
Cl120 mM\
291 mOsm
1000 mOsm
What happens when this fish whose extracellular fluids
(ECF) contain the ion concentrations indicated, lives in salt
water with its very high ion concentrations?
Hyporegulation: Sea water hyperosmotic to fish ECF
Sea water
Na+ 400mM
K+ 100mM
Cl- 500mM
Na+ 160 mM
K+
5 mM
Ca ++ 6 mM
Cl120 mM
water
Animals lose water passively to the environment
and gain solutes passively from the environment.
• What challenges does the fish have as it maintains water
•
balance?
What challenges does the fish have as it maintains solute
balance?
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Water and Solute regulation:
Hyporegulation
Fish gains solutes and loses water passively.
So ECF osmolarity should increase (conformer)
Regulator: In order to maintain constant ECF
osmolarity, the fish will have to excrete somehow
the extra solutes actively.
Problem: Fish cannot concentrate urine.
So how can they excrete the extra salt that get in
passively?
Hypo-osmoregulators in oceans
Salt get in passively
Chloride cells pump out actively excess chloride
and sodium follows
Chloride cells in gills
Sea water
Hypotonic to environment
Passive water loss and salt gain (input salt)
Actively secrete salts at gills (output salt)
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A fish in salt water: body water
balance?
Osmotic loss
(gills)
Water
containing
salts
Urinary water
• Hyposmotic to environment: always losing water by osmosis
• Large gill surface area: somewhat permeable to water
• Drink sea water: brings with it large amount of solute
Fish in Salt water: solute balance Hypo-osmoregulation
Salt water
Na+, Cl(gill secretion)
Salts from
sea water
Mg2+, SO42(in urine)
•
•
•
•
Drinking sea water adds excess solute
Kidney cannot produce concentrated urine
Gills actively secrete Na+ and Cl-: chloride cells
Kidney secretes divalent ions
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Osmotic Hyporegulation
1,000 mOsm
ECF (organism)
Passive diffusion of
300 mOsm
Active excretion
Solutes
Solutes
OUTPUT
INPUT
Zero balance:
Input = Output
Problem: How can they excrete the extra salt?
Mechanisms of Handling NaCl in sea water
Fish
Specialized chloride cells
Sharks
Specialized rectal gland
Marine Teleost Fish
Gills containing ion pumps
Birds and reptiles Salt secreting glands which empty into
the nostril
Mammals
Thick ascending limb of the loop of Henle of
the kidney tubule
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Chloride and sodium secretion
Chloride cells pump out excess chloride
and sodium follows
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Fish Chloride cell
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SHARK RECTAL GLAND
SHARK RECTAL GLAND
The rectal gland is a highly
specialized salt secreting
organ that secretes a fluid
that is iso-osmotic to
blood plasma but is
almost entirely composed
of sodium and chloride.
Sharks’s osmotic concentration is slightly above
that of seawater but the salt concentration is not.
This results in the diffusional uptake of Na+ and Clthrough the gills and food ingestion.
The elimination of excess salts is carried out
primarily by the kidney and the rectal gland.
The rectal gland is made up of many blind ending
tubules that empty into a duct, which then opens
into the intestine near the rectum.
The rectal gland excretes a fluid essentially
isosmotic with body fluids, but which consists
almost entirely of Na+ and Cl- at a concentration
approximately twice that found in body fluids.
The chloride cells are also a route of salt excretion.
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Avian Nasal Glands
Marine birds need to be able to
rid their bodies of excess salt
or face dehydration and die.
Birds possess a pair of salt
secretion glands located
just above their eyes.
Glands are well developed
in marine birds such
pelicans, albatrosses and
penguins.
Some birds with poorly developed salt glands can
stimulate growth of the glands by the uptake of a salt
load.
Avian Nasal Glands
These glands are found in all
birds except perching birds.
When a bird drinks salt water, venous pressure increases.
This triggers both the heart, and activation of the
acetocholine secreting cholinergic neurons by osmoreceptors in the hypothalamus.
The secretion cells of the salt gland gets stimulated.
The lumen, secretory tubes, and the central
canal, comprise one lobe, and several make
up one of the twined salt glands.
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Life in marine environments- birds
Life in oceans -reptiles
Actively pumps out
salt through salt
glands in nares
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Life in marine environmentsmammals
Responses to different aquatic
concentrations
Conformer
Regulator
What would these two graphs look like?
Euryhaline
Stenohaline
What do these words mean?
43
Equilibrium vs Steady state
Equilibrium are not zero balance: They
change their internal environment to be equal
to external environment.
a) Input but no output
b) Output but no input
Most organisms are not in equilibrium
Regulators are in zero balance (input = output)
that is why they are in steady state
Water and Solute regulation:
Hyper-regulation
Fish loses solutes and gains water passively.
So ECF osmolarity should decrease (conformer)
Regulator: In order to maintain constant
ECF osmolarity, the fish will have to excrete
somehow a diluted solution actively.
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Life in freshwater environments
hyper-osmoregulator
Maintain ECF hyperosmotic to environment
Problem?
Hyper-regulation: Water and Solute
Balance in the Fresh Water
Fresh Water
[Na+] = 0.5 mM
[K+] = 0.1 mM
[Cl -] = 0.3 mM
[Ca 2+] = 0.2 mM
mOsm = 5
ECF
[Na+] = 160 mM
[K+] = 5 mM
[Cl -] = 120 mM
[Ca 2+] = 6 mM
mOsm = 340
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Fish living in fresh water: Hyper-regulation:
Freshwater
water
Na+ 160 mM
K+
5 mM
Ca ++ 6 mM
Cl120 mM
Na+ 0.5mM
K+ 0.1mM
Cl- 0.3mM
Water flows from a high concentration of watera weaker concentration of solutes into the organism, to equilibrium
Solutes flow along their conc gradient towards lower conc of solutes.
Out of the organism.
Osmotic Hyper-regulation
100 mOsm
ECF (organism)
Passive diffusion of
300 mOsm
Active uptake of
Solutes
Solutes
OUTPUT
Zero balance:
INPUT
Input = Output
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Freshwater Fish = hyper-osmoregulator
Active uptake of
monovalent ions (Na+ Cl-)
via the CHLORIDE cells in
the gills
Copious production of
dilute urine leading to
high water loss, but also
results in some loss of
ions
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