Oxygen, Metabolism, Gas Transport

Oxygen, Metabolism Oxygen, Metabolism & &

EnergeticsEnergetics

ZOO 1450ZOO 1450IchthyologyIchthyologyChapter 5Chapter 5

IntroductionIntroduction

• Most terrestrial vertebrates have Most terrestrial vertebrates have internal lungsinternal lungs that must that must be ventilated through be ventilated through bidirectionalbidirectional movement of air to movement of air to replenish the oxygen (Oreplenish the oxygen (O22) supply) supply

• Most fish have Most fish have external gillsexternal gills that are ventilated by a that are ventilated by a unidirectionalunidirectional flow of water, by pumping or swimming flow of water, by pumping or swimming

• Fine sieve structure of gills very efficiently extracts OFine sieve structure of gills very efficiently extracts O22 from water. from water.

• Efficient OEfficient O22 uptake is vital to fish because of its low water uptake is vital to fish because of its low watersolubility. solubility.

• Solubility Solubility decreasesdecreases with with increasedincreased temperature & salinity! temperature & salinity!

• Also, metabolic rate (demand for OAlso, metabolic rate (demand for O22 ) increases as ) increases as temperature rises. temperature rises. (How does this affect nutrition?)(How does this affect nutrition?)

• What does this mean to fish??What does this mean to fish??

Introduction (cont.)Introduction (cont.)

Oxygen solubility determined by Oxygen solubility determined by temperaturetemperature

Temp (C) O2 con. at sat. (mg/l) – Fresh

O2 con. at sat. (mg/l) – Salt

0 10.3 8.0

10 8.0 6.3

20 6.5 5.3

30 5.6 4.6

In warm water...fish need to extract MORE O2 from LESS!

• GillsGills are the main are the main site of gas exchangesite of gas exchange in almost all fishes.in almost all fishes.

• The gills consist of bony or The gills consist of bony or stiffened stiffened archesarches (cartilage) that (cartilage) that anchor pairs of anchor pairs of gill filamentsgill filaments..

NumerousNumerous lamellaelamellae protrude from protrude from both sides of each filament and both sides of each filament and are the primary sites of gas are the primary sites of gas exchange.exchange.

Microscopic gill structure: Microscopic gill structure: showing gill filament and showing gill filament and lamellae (Red blood cells lamellae (Red blood cells

evident.)evident.)

How can fish remove 80 - How can fish remove 80 - 90% of O90% of O22 available from available from

water?water?

1)1) Short diffusion distanceShort diffusion distance at gill at gill sitesite

2)2) Large surface areaLarge surface area for for diffusion at gill sitediffusion at gill site

3)3) Counter current exchangeCounter current exchange of of gases at gill sitegases at gill site

4)4) Large volume of waterLarge volume of water passes passes over gillsover gills

1. Fill mouth cavity a. open mouthb. expand volume of mouthc. expand volume of gill chamber with

operculum closed

2. Fill gill cavity a. close mouth b. squeeze mouth cavity c. expand gill cavity with operculum closed

3. Expel water from gill cavity a. squeeze mouth b. squeeze gill cavities open operculum

4. Reset for next cycle

Oxygen Exchange in Oxygen Exchange in FishFish

• Fish employ the Fish employ the countercurrent countercurrent systemsystem to extract O to extract O22 from the water.from the water.

• This system moves This system moves water flowing across water flowing across the gills, in an the gills, in an opposite opposite direction to direction to the blood flow the blood flow creating the creating the maximum efficiency maximum efficiency of gas exchange. of gas exchange.

• Blood flow through Blood flow through lamellae is from posterior lamellae is from posterior to anteriorto anterior((back to frontback to front).).

• Water flow over lamellae Water flow over lamellae is from anterior to is from anterior to posteriorposterior((front to backfront to back).).

• Counter-current allows Counter-current allows for diffusion from high Ofor diffusion from high O22 in water to low Oin water to low O22 in in blood across entire length blood across entire length of lamella.of lamella.

Countercurrant Countercurrant Close-up!Close-up!

When he blood and water flows in the same direction, theWhen he blood and water flows in the same direction, the co-current co-current systemsystem, it will , it will initially diffuses large amounts of oxygen but the efficiency reduces when the initially diffuses large amounts of oxygen but the efficiency reduces when the fluids start to reach equilibrium.fluids start to reach equilibrium.

In the counter-current system, equilibrium is never reached! Result: Oxygen In the counter-current system, equilibrium is never reached! Result: Oxygen flow is always directed into the gills.flow is always directed into the gills.

% O2 in water

% O2 in gills

% O2 in water

% O2 in gills

Let’s Do the Math...Let’s Do the Math...

44 gill arches on each side of bodygill arches on each side of body 22 rows of gill filaments on each arch (demibranchs)rows of gill filaments on each arch (demibranchs) 100’s 100’s filaments per demibranch - closely spacedfilaments per demibranch - closely spaced1000’s1000’s lamellae per gill filamentlamellae per gill filament

gill area = 10 to 60 times that of body surface area, depending gill area = 10 to 60 times that of body surface area, depending on species!on species!

HUGE potential to extract Oxygen from water!HUGE potential to extract Oxygen from water!

Auxiliary Respiratory StructuresAuxiliary Respiratory Structures

• SkinSkin - diffusion of oxygen from water into dense network - diffusion of oxygen from water into dense network of capillaries in skin (eels), of capillaries in skin (eels), Thin skin (larval fish) supplies Thin skin (larval fish) supplies 50% of O50% of O22 needed. needed.

• Swim bladderSwim bladder - vascularized physostomous swim bladders - vascularized physostomous swim bladders (gars)(gars)

• LungsLungs - modified swim bladder (lungfishes) - modified swim bladder (lungfishes)• MouthMouth - vascularized region in roof of mouth (electric eel, - vascularized region in roof of mouth (electric eel,

mudsuckers)mudsuckers)• GutGut - vascularized stomach or intestinal wall (armored - vascularized stomach or intestinal wall (armored

catfish, loaches)catfish, loaches)

Branchial vs. Ram VentilationBranchial vs. Ram Ventilation

Branchial Branchial • MouthMouth• PharynxPharynx• OperculumOperculum• Branchiostegals (filaments, lamella)Branchiostegals (filaments, lamella)

RamRam• Uses same parts, but not the pumping energy required. Sharks Uses same parts, but not the pumping energy required. Sharks

primarily. Once swimming speed is achieved...no need to primarily. Once swimming speed is achieved...no need to actively vent buccal cavity. However, this can only be used actively vent buccal cavity. However, this can only be used consistently by strong swimmers (sharks, tuna).consistently by strong swimmers (sharks, tuna).

77

66

55

44

33

22

11

005 pm5 pm 10 pm10 pm 5 am5 am

Measured valuesMeasured values

Projected valuesProjected valuesDissolved ODissolved O22

mg/lmg/l

Practical Application of This Knowledge!Practical Application of This Knowledge!Projected Dissolved Oxygen LevelsProjected Dissolved Oxygen Levels

Time of DayTime of Day

Gas bladder of a porcupine fish.

Rete mirabile of a Queensland Groper, Epinephelus lanceolatus. © Geoff McPherson

How do you inflate a swim bladder?How do you inflate a swim bladder?

• Gas glandGas gland is location of action in wall of swim bladder is location of action in wall of swim bladder ((rete mirabilerete mirabile “wonderful net” and surrounding tissues) “wonderful net” and surrounding tissues)

• Need to pry ONeed to pry O22 molecules from Hb molecules in gas gland molecules from Hb molecules in gas gland

• Need to accumulate enough ONeed to accumulate enough O2 2 (>pO(>pO22) in solution in blood ) in solution in blood plasma to generate a diffusion gradient from distal end of plasma to generate a diffusion gradient from distal end of rete mirabile into lumen of swim bladderrete mirabile into lumen of swim bladder

• How???How???

Prying OPrying O22 from Hb from Hb

• Change of pHChange of pH in blood causes change in bond strength of Hb for O in blood causes change in bond strength of Hb for O22

• Bohr effectBohr effect--decrease in --decrease in affinityaffinity of Hb for O of Hb for O22 due to decreasing pH or due to decreasing pH or increasing pCOincreasing pCO22

affinity: affinity: strength of attractionstrength of attraction of Hb for O of Hb for O22

• RootRoot effecteffect--decrease in --decrease in capacitycapacity of Hb for O of Hb for O22 due to decreasing pH or due to decreasing pH or increasing pCOincreasing pCO2 2 (extreme Bohr effect)(extreme Bohr effect)

capacity:capacity: total quantitytotal quantity of O of O22 that Hb can carry that Hb can carry

• more active species tend to have greater Bohr & Root effectsmore active species tend to have greater Bohr & Root effects

00 8080 16016000

100100

5050

pOpO22 mm Mercury mm Mercury

% S

atur

atio

n of

Hb

% S

atur

atio

n of

Hb

pH 8.02pH 8.02

pH 7.47pH 7.47

Air saturationAir saturation

affinityaffinity

capacitycapacity

BohrBohr

RootRoot

Effect of pH on Hb*--2 components

*data for winter flounder*data for winter flounder

How to cause pH to drop in tissues of gas How to cause pH to drop in tissues of gas gland?gland?

• Regular metabolic processes result in release of HRegular metabolic processes result in release of H++, either , either from glycolysis (lactic acid) or COfrom glycolysis (lactic acid) or CO22 from aerobic from aerobic metabolismmetabolism

• Increase metabolic activity in tissues surrounding rete Increase metabolic activity in tissues surrounding rete mirabile = decrease of pHmirabile = decrease of pH

How to cause free OHow to cause free O22 to accumulate in to accumulate in distal end of rete?distal end of rete?

• Another Another counter-current exchange systemcounter-current exchange system::– long capillaries that fold back on selflong capillaries that fold back on self– afferentafferent (incoming) part of capillary experiences drop (incoming) part of capillary experiences drop

in pH, Hb loses Oin pH, Hb loses O22

– efferentefferent (outgoing part of capillary has higher partial (outgoing part of capillary has higher partial pressure (concentration) of dissolved Opressure (concentration) of dissolved O22 than afferent, than afferent, soso

– OO22 diffuses into afferent (incoming) arm, causing diffuses into afferent (incoming) arm, causing supersaturation of blood at distall end of rete with Osupersaturation of blood at distall end of rete with O22

Advantage of Bohr EffectAdvantage of Bohr Effect

TissuesGills

blood circulation

pH lowerpH higherpCO2 higherpCO2 lowerlactic acidno lactic acid

Buoyancy: Counter-current multiplication systemBuoyancy: Counter-current multiplication system

afferent blood

efferent blood

O2HbpO2

O2Hb O2

pO2

swim

bla

dder

O2Hb pO2

lactic acid

1

Diagram of basic functional unit

Buoyancy: Counter-current multiplication systemBuoyancy: Counter-current multiplication system

swim

bla

dder1

Diagram of basic functional unit

Function of Rete MirabileFunction of Rete Mirabile

1. Hemoglobin saturated with O1. Hemoglobin saturated with O2 2 ((OO22 HbHb))

Plasma OPlasma O2 2 low (low (p Op O22))

Counter-current multiplication systemCounter-current multiplication system

afferent blood

efferent blood

O2HbpO2

O2Hb pO2

pO2

swim

bla

dder

O2Hb pO2

lactic acid

1 2


2. Lactic Acid Secretions2. Lactic Acid Secretions HbHb dumps dumps OO22 to plasmato plasma pOpO22 diffuses into swim bladder to equilibrium.diffuses into swim bladder to equilibrium.


3. Multiplying effect: 3. Multiplying effect: pOpO22 diffuses from efferent (outgoing) diffuses from efferent (outgoing) capillary to afferent (incoming) capillary! Also, longer capillary to afferent (incoming) capillary! Also, longer capillaries yield more efficient exchange of oxygen, higher capillaries yield more efficient exchange of oxygen, higher pressures.pressures.

What about COWhat about CO22??

• Okay...we got the OOkay...we got the O22 inside...how do we get the CO inside...how do we get the CO2 2 outside?outside?

• Again, blood also is involved in COAgain, blood also is involved in CO22 transport. transport.

• Three mechanisms to move COThree mechanisms to move CO22 outside cell to be excreted. outside cell to be excreted.(1) (1) Simple dissoutionSimple dissoution in plasma in plasma(2) (2) BindingBinding to proteins/formation of carbamino groups. to proteins/formation of carbamino groups.(3) (3) DissociationDissociation into carbonic acid by pH change (greatest into carbonic acid by pH change (greatest

amount of COamount of CO22 transformed this way.) transformed this way.)

dissociation is slowdissociation is slow

HHbO2 + O2

O2

CO2 + HbO2

HbCO2 + O2

O2

“Chloride Shift”

OUCH!! Don’t worry! With quick action this fish can recover!

BouyancyBouyancy

Buoyancy strategiesBuoyancy strategies

1. Low density compounds1. Low density compounds2. Lift generated by swimming2. Lift generated by swimming3. Reduction of heavy tissues3. Reduction of heavy tissues4. Swim bladder (air bladder)4. Swim bladder (air bladder)

1. Low density compounds:1. Low density compounds:

Substance Specific GravityBone 2.0Muscle 1.05Cartilage 1.1Freshwater 1.002 @20CSaltwater 1.072 @20CLipids 0.9-0.92Squalene 0.86Advantages/disadvantages

2. Lift generated by swimming:2. Lift generated by swimming:

lift

lift

thrust

sharks Advantages/disadvantages

3. Reduction of heavy tissues3. Reduction of heavy tissues

umbrella mouth gulperumbrella mouth gulper Eurypharynx pelecanoides

deepwater fishes

Advantages/disadvantages

4. Swim bladder 4. Swim bladder

• low densitylow density• adjustableadjustable• most osteichthiansmost osteichthians• lost secondarily in some specieslost secondarily in some species

Two types of swim bladders:Two types of swim bladders:

• PhysostomousPhysostomous– pneumatic ductpneumatic duct– soft-rayed teleosts--herrings, salmonids, catfishes, soft-rayed teleosts--herrings, salmonids, catfishes,

cyprinids, eels, etc.cyprinids, eels, etc.• PhysoclistousPhysoclistous

– blood/circulatory systemblood/circulatory system– spiney-rayed teleosts--Acanthopterygii, sunfishes, perch, spiney-rayed teleosts--Acanthopterygii, sunfishes, perch,

most marine fishesmost marine fishes

Effects of depth on swim bladder volumeEffects of depth on swim bladder volume

• pressure increases 1 ATM/10mpressure increases 1 ATM/10m• swim bladder must be adjustableswim bladder must be adjustable• Physostomous fishes adjust volume by gulping or Physostomous fishes adjust volume by gulping or

spitting air.spitting air.– mostly shallow water speciesmostly shallow water species– gas-spitting reflexgas-spitting reflex– gulp air at surfacegulp air at surface

Physoclistous inflation/deflationPhysoclistous inflation/deflation

• circulatory system--source of gasescirculatory system--source of gases• rete mirabile (wonderful net) --inflationrete mirabile (wonderful net) --inflation• oval window--deflationoval window--deflation• Problem:Problem: fish need greater pressure in swim bladder fish need greater pressure in swim bladder

than is achieved by equilibrium with blood gasesthan is achieved by equilibrium with blood gases

Physoclistous swim bladderPhysoclistous swim bladder

• Pressures up to 300 ATM in some deep sea fishesPressures up to 300 ATM in some deep sea fishes

• Gases mostly OGases mostly O22, some CO, some CO22 and N and N22

• Guanine crystals in SB wall reduce permeabilityGuanine crystals in SB wall reduce permeability

• Deflation occurs at Deflation occurs at oval window*oval window**dense bed of capillaries on SB wall*dense bed of capillaries on SB wall

– gasses diffuse into bloodgasses diffuse into blood– mucus layer covers window during inflationmucus layer covers window during inflation

Summary:Summary:• Diffusion of ODiffusion of O22; controlled by structure & function; controlled by structure & function

• Relationship ORelationship O22 bound to Hb vs. O bound to Hb vs. O22 in plasma in plasma

• Effect of pH on affinity/capacity of Hb for OEffect of pH on affinity/capacity of Hb for O22

• Counter-current multiplierCounter-current multiplier– length of capillarieslength of capillaries– counter-current flow of bloodcounter-current flow of blood

Growth & Growth & MetabolismMetabolism

Growth:Growth:• LongevityLongevity

– unconfirmed reports of carp 200-400 yr.unconfirmed reports of carp 200-400 yr.– authenticated records for carp 50 yr.authenticated records for carp 50 yr.– large fish-few > 12-20 yr.large fish-few > 12-20 yr.– some marine spp > 100 yr. thornyspines, orange roughysome marine spp > 100 yr. thornyspines, orange roughy– many small spp-2 yr. or less (sardines, anchovies)many small spp-2 yr. or less (sardines, anchovies)

Note: aging with scales, bones, otolithsNote: aging with scales, bones, otoliths

Many Generalities:Many Generalities:• Sexual DimorphismSexual Dimorphism: females can be larger than males: females can be larger than males

• Growth rate a function of temperatureGrowth rate a function of temperature

• Longevity inversely proportional to temperatureLongevity inversely proportional to temperature

• Stress reduces growthStress reduces growth

• Dominance hierarchies - dominant get foodDominance hierarchies - dominant get food

• Overcrowding can lead to stuntingOvercrowding can lead to stunting

• Indeterminate growth - grow throughout lifeIndeterminate growth - grow throughout life

• Growth highly variable - decreased weight gainGrowth highly variable - decreased weight gain

Bioenergetics Bioenergetics continuedcontinued::

• Energy accumulation (Calories) vs. length or weightEnergy accumulation (Calories) vs. length or weight

• Energy Budget:Energy Budget:

I = M + G + Ewhere: I = ingested energyM = energy expended for metabolismG = energy stored as growthE = energy lost to environment

Bioenergetic Energy Budget:Bioenergetic Energy Budget:


I


I M


GI M

E


GI

E

M

heat


Ex: Ex: MM = = energy for body repairenergy for body repairmaintenancemaintenanceactivityactivitydigestiondigestion


Ex: Ex: EE = = energy in fecesenergy in fecesammonia, or ureaammonia, or ureamucusmucusepidermal cellsepidermal cells

Terms:Terms:

• Standard Metabolic RateStandard Metabolic Rate– maintenance met.; no growth, no activity

• Routine Metabolic RateRoutine Metabolic Rate– typical met.; routine growth & activity

• Active Metabolic RateActive Metabolic Rate– max. aerobic metabolism

Factors Affecting Growth: Factors Affecting Growth: TemperatureTemperature

Temperature

Met

abol

ic R

ate

standard

active routine

scopeactivity

growth{Where would

growth be best?


Temperature

Met

abol

ic R

ate

normal O2

reduced O2

reduced scopereduced growth

Factors Affecting Growth: Factors Affecting Growth: Dissolved oxygenDissolved oxygen

Dissolved Oxygen mg/LDissolved Oxygen mg/L

Rou

tine

Met

abol

ism

Rou

tine

Met

abol

ism

00 8844

OO22 regulator (most species) regulator (most species)

critical Ocritical O22 concentration concentration

OO22 conformer conformer


Temperature

Met

abol

ic R

ate

23

21 22

24

Where would

growth be best?

afferent blood

efferent blood

swim

bla

dder26 27

29

a. pO2 diffuses from efferent (outgoing) capillary to afferent (incoming) capillary. b. Lactic Acid Secretions cause Hb to dump O2 to plasma, c. pO2 diffuses into swim bladder to equilibrium.d. Hemoglobin saturated with O2 (O2 Hb), Plasma O2 low (p O2)e. Blood returns to gills

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Oxygen, Metabolism, Gas Transport

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